No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Changes in biosynthesis of aroma volatile compounds during on-tree maturation of 'Pink Lady (R)' apples
Abstract
The production of aroma volatile compounds and standard quality attributes, in addition to lipoxygenase (LOX), hydroperoxide lyase (HPL), pyruvate decarboxylase (PDC), alcohol dehydrogenase (ADH) and alcohol o-acyltransferase (AAT) activities, were assessed during maturation of ‘Pink Lady®’ apples. Low production of aroma volatiles was observed in early harvested fruit, which gradually increased as ripeness approached. Hexyl acetate, hexyl 2-methylbutanoate, hexyl hexanoate, hexyl butanoate, 2-methylbutyl acetate and butyl acetate were prominent within the blend of volatiles produced by fruit throughout maturation. Multivariate analysis showed these compounds had the highest influence on differentiation of maturity stages, indicating that aroma volatile emission is an important factor for definition of fruit ripeness, which suggests production of these esters might be useful as an index of maturity. No large variations in AAT activity were found throughout the experimental period despite increasing ester emission, suggesting the enhancement of ester production by ‘Pink Lady®’ apples at ripening arises mainly from greater availability of substrates. Increased LOX activity was observed at later stages of fruit development, and the possible role of this enzyme activity on enhanced capacity for aroma volatile biosynthesis in more mature fruit is discussed.
... In vivo DI-SPME as a tool to characterize the metabolome of apples from different maturity stages. Biosynthesis of volatile metabolites is one of the key contributors to the final sensory quality of fruit produce 24,25 . The blend of volatiles produced by fruit is species-and cultivar-specific, as well as representative of its development stages, undergoing distinguishable changes throughout fruit growth and ripening 25,26 . ...
... In addition to its concentration, the contribution of each compound to the characteristic aroma profile of a given fruit is also modulated by other factors, such as the overall fruit composition, as well as the odor threshold above which the compound can be detected by smell [24][25][26] . Based on the odor thresholds cited in the literature, character impact odorants for apple fruit are ethyl butanoate, ethyl 2-methylbutanoate, 2-methylbutyl acetate, ethyl hexanoate, hexyl acetate, hexyl propanoate, and hexyl 2-methylbutanaote 27,35 . ...
... Straight chain esters such as ethyl hexanoate, ethyl butanoate, ethyl propanoate, 1-propylethanoate, butyl butanoate, propyl butanoate, butyl propanoate, propyl propanoate, butyl acetate (Supplementary Table 1) are synthesized by lipids via β-oxidation and lipoxygenase/hydroperoxide lyase (LOX/HPL) pathways 12,37 . Metabolism of fatty acids through β-oxidation, hydroxyacid cleavage, and lipoxygenase/hydroperoxide lyase pathways intensifies during fruit maturation, playing a key role in biosynthesis of precursors required for straight-chain ester formation [24][25][26]35,36 . At early maturity stages, enzymes and substrates of the LOX pathway are located in different subcellular sites; accordingly, lipid metabolism increases with respect to ripening as cell walls and membranes become more permeable to different substrates 24,25 . ...
An in vivo direct-immersion SPME sampling coupled to comprehensive two-dimensional gas chromatography – time-of-flight mass spectrometry (GCxGC-ToFMS) was employed to capture real-time changes in the metabolome of ‘Honeycrisp’ apples during ripening on the tree. This novel sampling approach was successful in acquiring a broad metabolic fingerprint, capturing unique metabolites and detecting changes in metabolic profiles associated with fruit maturation. Several metabolites and chemical classes, including volatile esters, phenylpropanoid metabolites, 1-octen-3-ol, hexanal, and (2E,4E)-2,4-hexadienal were found to be up-regulated in response to fruit maturation. For the first time, Amaryllidaceae alkaloids, metabolites with important biological activities, including anti-cancer, anti-viral, anti-parasitic, and acetylcholinesterase (AChE) inhibitory activity, were detected in apples. Considering the elimination of oxidative degradation mechanisms that adversely impact the representativeness of metabolome obtained ex vivo, and further evidence that lipoxygenase (LOX) pathway contributes to volatile production in intact fruit, in vivo DI-SPME represents an attractive approach for global plant metabolite studies.
... The minimum firmness of the samples is 35.38 N, and the mean firmness is 79.32 N. The first quartile for firmness is 60.96 N, the median is 81.01 N, and the third quartile is 96.52 N, suggesting that most apples have a firmness exceeding 80 N. The maximum firmness was 122.03 N. The variance in firmness was 370.34, and the standard deviation was 19.24 N, indicating significant data variability. According to the literature, the firmness of Pink Lady apples is generally 87-107 N [25]. The data show that the firmness of less than 25% of the samples falls within this range, with measurements deviating by ±20 N from this interval. ...
... In the literature, acidity in apples ranges from 3.00 to 7.00 g/L malic acid, which corresponds to an acidity of approximately 4.50 to 10.50 meq/100 mL [25][26][27]. The results show that 75% of samples fall within this standard range. ...
Apples are one of the most widely consumed fruits in the world and are available year- round. In France, Pink Lady production has increased despite stable global production in recent years. To meet consumer expectations in terms of quality, apples must be at optimum ripeness. Traditional destructive methods are currently used to measure physicochemical parameters. To avoid such destructive measurements, it has been shown in the literature that near-infrared (NIR) spectroscopy can predict fructose and glucose content in apple juice, as well as firmness, titratable acidity and sugar content in Fuji. The present study demonstrates the relevance of the MicroNIR spectrometer to address agricultural sustainability concerns. This compact device is easy to use in the field and allows non-destructive monitoring of the physicochemical characteristics of Pink Lady. The device acquires NIR spectra from different areas of apples, followed by standard analyses to assess these characteristics. Results indicate no impact on measurements across different quarters of the apple, though there is a slight impact between the median zone and the poles. Firmness is predictable with a 77 N threshold (using partial least square regression), and juiciness prediction is reliable, though a larger database could improve the model. Predictions for sugar content and acidity still need improvement, which would confirm the MicroNIR device’s potential for assessing Pink Lady apple ripeness in the field.
... As aroma is one of the most appreciated fruit properties, volatile flavor compounds may play a key role in determining the perception and acceptability of products by consumers [3,4]. Aroma, an important trait of fruit quality, has received increasing attention in recent years. ...
... Aroma, an important trait of fruit quality, has received increasing attention in recent years. To date, the aromas of various fresh fruits have been evaluated, including white pear [5], apple [3], watermelon [6], mango [7], melon [8], strawberry [9], peach [10] and tomato [11]. Aroma comprises more than eight classes, including amino acid-derived compounds, phenolic derivatives, esters, terpenoids, alcohols, aldehydes, ketones and Life 2023, 13, 1504 2 of 12 alkenes, of which esters are the most important volatiles of pear fruits [4,12,13]. ...
Aroma is an appreciated fruit property, and volatile flavor plays a key role in determining the perception and acceptability of fruit products by consumers. However, metabolite composition that contributes to the aroma in fruit quality is unclear. In this study, we detected 645 volatile organic compounds of ‘Panguxiang’ pear in total, including esters, alcohols, alkanes, acids, ketones, terpenes and aldehydes. In addition, the levels of sugars, organic acids and amino acids in ‘Panguxiang’ pear were investigated using high-performance liquid chromatography. In the aroma generation, glucose was the dominant sugar, followed by sucrose and fructose. At the development transferred storage stage, organic acids may not participate in aroma biosynthesis. The amino acids that may play potential roles in aroma substance synthesis are tyrosine and glycine. Through metabolomics analysis at different stages of ‘Panguxiang’ pear, we selected 65 key metabolites that were significantly related to glucose, sucrose, fructose, tyrosine and glycine, according to the trends of metabolite concentrations. Finally, we chose eight candidate metabolites (e.g., three esters, two aldehydes, one alcohol, one acid and one ketone) as the representative aroma substances of the ‘Panguxiang’ pear compared to the metabolome of the ‘Korla’ at stage Z5. Data and results from this study can help better understand the variations in aroma quality among pear varieties and assist in developing breeding programs for pear varieties.
... low, but increased sharply until approximately D200, possibly signalling the onset of the ripening process (Villatoro et al. 2008). Lu et al. (2016) also showed that the contents of aroma volatiles increased in Xinjiang apricot fruit until maturation. ...
... In the climacteric species pears, there were more esters providing a sweet and fruity odour and their levels were usually higher than those of the non-climacteric pears; thus, the mature fruits of climacteric pears smelled better. Fully ripe apples produced large amounts of hexyl esters, including hexyl acetate, hexyl-2-methylbutanoate and hexyl hexanoate (Villatoro et al. 2008). Esters are important volatiles of fully ripe bayberry fruit and contribute to the strong fruity and floral odour, and methyl benzoate is the dominant ester . ...
Bartlett, Hongnanguo, Korla Xiangli, Dangshansuli and Housui are representative cultivars from the five cultivated pear species that were chosen to identify aromatic compounds in fruit during developmental, mature and storage periods. We explored the expression levels of aroma formation-related genes during developmental and storage periods. The concentrations of the aromatic compounds first decreased, then increased in all five cultivars. For the climacteric pears, Bartlett and Hongnanguo, the increase continued to optimal sensory quality (OSQ), whereas those for the non-climacteric pears, Korla Xiangli, Dangshansuli and Housui decreased. Aldehydes contributing the 'green' odour and 1,4-benzoquinone were the primary components during early and middle developmental periods. Esters contributing the 'fruity' and 'sweet' odour, were the primary components in Bartlett, Hongnanguo and Korla Xiangli fruits during storage and at OSQ. Methyl- and ethyl-(E, Z)-2,4-decadienoate (pear-like odour), ethyl caproate (liquor odour), and hexyl acetate (fruity odour) were the key characteristic odorants in mature pear fruits of Bartlett, Hongnanguo and Korla Xiangli, respectively. Alcohol dehydrogenase (PbrADH-1 and PbrADH-2) and lipoxygenase (PbrLOX3) might participate in the formation of C6 and C9 volatile aldehydes and alcohols. The aroma content and volatiles of pear fruits during development and storage probably revealed a common pattern.
... It is well documented that female medflies lay eggs in ripening or ripe fruits ). Moreover, the most favorable hosts for the oviposition of the Mediterranean fruit fly, such as ripe apples, citrus, pears and stone fruits, include esters as major component of their aroma (Villatoro et al. 2008, El Hadi et al. 2013, Tabilio et al. 2013, Ladaniya 2008. There are numerous studies using electroantennography that report the response of C. capitata to esters. ...
... Ethyl hexanoate increased oviposition even in extremely low doses. This chemical and other esters contribute to the aroma of ripe fruits (Villatoro et al. 2008, El Hadi et al. 2013, Ladaniya 2008. Thus, even low quantities of esters in fruit volatiles must be detected as this may be crucial for female oviposition decisions. ...
The Mediterranean fruit fly, Ceratitis capitata (Wiedemann), is one of the most important pests of fruits worldwide. In the present study, we investigated the ovipositional response of C. capitata females to 37 compounds of fruit volatiles from various chemical groups and the dose response to five of them. Red plastic hollow hemispheres (domes) were used as oviposition substrates in all tests. Twenty of the compounds tested increased female egg laying compared to control substrates that contain no chemicals. With 16 compounds, similar number of eggs was deposited in treated and in control oviposition substrates. One terpene ((±)-linalool) reduced egg laying indicating a deterrent ovipositional effect. Both the esters and aldehydes tested increased the ovipositional responses in C. capitata. Most of the monoterpene hydrocarbons increased oviposition, while oxygenated monoterpenes, sesquiterpenes hydrocarbons, and oxygenated sesquiterpenes had mostly neutral effect. Ethyl hexanoate and R-(+)-limonene increased oviposition in the majority of doses tested. Different doses of (−)-linalool elicited differential female ovipositional responses. In contrast, valencene and citral, regardless of dose did not affect female oviposition. Practical implications of these findings are discussed.
... cultivar increasingly grown in many apple-producing areas of the world owing to its excellent flavor and sensory attributes. Commercial interest is thus focused on developing suitable criteria for harvest maturity as well as appropriate storage procedures in order to assure quality of final produce (Villatoro et al., 2008). Fruits of 'Pink Lady' apple cultivar has flesh and excellent flavor and it is firm, crisp and juicy (Corrigan, 1997). ...
... Acyl CoAs are reduced by acyl CoA reductase to produce aldehydes, which in turn are reduced by alcohol dehydrogenase (ADH) to form alcohols that are converted to esters via the action of aspartate amino transferase (AAT) (Song and Bangerth, 1994;Dixon and Hewett, 2000;Espino-Diaz, 2016). In the previous researches, it was explained that 2-methylbutyl acetate, butyl acetate, ethyl-2-methylbutanoate, hexyl-2-methylbutanoate were the main ester compounds in 'Royal Gala', 'Golden Delicious', 'Fuji', 'Mondial Gala' and 'Pink Lady' apple cultivars (Song et al., 1996;Young et al., 1996;Lara et al., 2007;Lopez et al., 2007;Echeverria et al., 2008;Salas et al., 2011;Gur, 2019). ...
Objective: The aim of this research was to assess the profile of volatile compounds changes during the cold storage in ‘Pink Lady’ apples. Material and Methods: Six-year-old Cripps Pink (Pink Lady) fruits of apple trees grafted onto M9 rootstock were used as a plant material for this study. The trees were in a commercial orchard in Çanakkale-Turkey. Fruits were carefully picked up by hand at the commercial harvesting time. The fruits were dipped into calcium oxide solutions (concentrations of 2 and 4%) during three minutes. Control fruits were exposed to distilled water. Fruits were stored at 0° C and 90% relative humidity for 6 months. The aroma profiles of apples determined by GC/MS (Gas Chromatography/Mass Spectrometry) analysis followed by liquid-liquid extraction. Stored fruits were analyzed for their volatile contents at the 2nd, 4th and 6th months. Results: Fresh fruits at harvest period contained 15 volatile compounds in total. However, higher levels of aroma volatile compounds were detected in 6 months of cold storage. According to the chromatography results, control fruits had 24 volatile compounds, 2% CaO treated fruits had 25 volatiles and 4% CaO treated fruits had 27 volatile compounds at the end of the 6 months of cold storage. Apples at the initial stage produced an abundance of hexyl acetate (4.56%), butyl acetate (3.83%), and hexyl hexanoate (1.68%), which confer typical apple aroma characteristics. Mostly, ester production exhibited a fairly broad peak, declining as fruit aged. Isobutyric acid, allyl ester (initial 0.55%) was lower at the beginning of the storage compare to the end of storage (control fruits 0.06%, 2%CaO 0.13%, 4% CaO 0.20%). Conclusion: CaO applications especially 4% concentration had deformation effect on epidermal layer cells on fruit surface. As a result, CaO applications had a significant effect on aroma enhancement in Pink Lady apples during cold storage.
... HPL functions by breaking down fatty acid hydroperoxides, such as 13-hydroperoxide linolenic acid or 13-hydroperoxide linoleic acid, into short-chain volatile aldehydes (e.g., hexanal and (E)-2-hexenal) and ketones [60][61][62]. Our results corroborate these findings, revealing a strong correlation between HPL2 (LOC114819168) and (E)-2-heptenal in the pulp tissue. ...
We investigated the dynamic changes in volatile aroma compound profiles (types and concentrations) and associated gene expression patterns in both the peel and pulp tissues of apples during fruit maturation. This study aimed to elucidate the metabolic regulatory mechanisms underlying volatile aroma biosynthesis in Malus domestica “Ningqiu” apples, thereby providing theoretical support for the comprehensive utilization of aroma resources. Our methodological framework integrated headspace solid-phase microextraction gas chromatography–mass spectrometry (HS-SPME-GC-MS), ultra-high-performance liquid chromatography–orbitrap mass spectrometry (UHPLC-OE-MS), and Illumina high-throughput sequencing to generate comprehensive metabolomic and transcriptomic profiles of peel and pulp tissues. Critical differential aroma compound classes were identified, including esters, aldehydes, alcohols, terpenoids, and ketones, with their metabolic pathways systematically mapped through KEGG functional annotation. Our findings revealed substantial transcriptomic and metabolomic divergence across carotenoid, terpenoid, and fatty acid metabolic pathways. Integrative analysis of multi-omics data revealed 26 and 31 putative biologically significant hub genes in peel and pulp tissues, respectively, putatively associated with the observed metabolic signatures. Among these, five core genes—farnesyl diphosphate synthase (FDPS1.X1), alcohol acyltransferases (AAT1 and AAT3), alcohol dehydrogenase (ADH3), and carotenoid cleavage dioxygenase (CCD3)—were recognized as shared regulatory determinants between both tissue types. Furthermore, terpene synthase (TPS7) emerged as a peel-specific regulatory factor, while hydroperoxide lyase (HPL2), alcohol dehydrogenases (ADH2 and ADH4), and alcohol acyltransferase (AAT2) were identified as pulp-exclusive modulators of metabolic differentiation. The experimental findings provide foundational insights into the molecular basis of aroma profile variation in Malus domestica “Ningqiu” and establish a functional genomics framework for precision breeding initiatives targeting fruit quality optimization through transcriptional regulatory network manipulation.
... Fruit maturity plays a critical role in volatile productions; immature fruit produces less volatiles at harvest than mature fruits (Forney et al., 2000;Villatoro et al., 2008). The concentration of main sulfur volatiles (typical dialkyl polysulfides) increases with durian maturity (Moser et al., 1980). ...
Durian fruit (Durio sp.) is a tropical fruit native to Southeast Asian countries known for its strong and unique characteristic smell. This review provides comprehensive information on durian fruit aroma, which is characterized by various volatile compounds, with esters and sulfur compounds playing a key role. Additionally, the contribution of ketones, alcohols and aldehydes to its unique aroma cannot be overlooked. The important precursors for the generation of these volatiles are branched‐chain amino acids and polyunsaturated fatty acids. Moreover, the abundance and composition of aroma volatiles in durian fruit can be affected by various influencing factors, including genetic background, postharvest handling, and processing. This review also provides the common methods used to extract and analyze durian aroma components, with solid‐phase microextraction gas chromatography‐mass spectrometry emerging as a suitable and precise method to extract and analyze the complex aroma chemistry of the durian fruit.
... µg/kg), hexyl 2-methylbutanoate (382.45 µg/kg), hexyl hexanoate (187.67 µg/kg), hexyl butanoate (142.74 µg/kg), 2-methylbutyl acetate (255.15 µg/kg), and butyl acetate (196.75 µg/kg) were the prominent volatiles produced by the 'Pink Lady' fruit [28]. During the ripening period, 1-butanol-2-methyl-acetate, 2-hexenal, and 1-hexanol were the most abundant aroma components in the 'Starkrimson' apple [29]. ...
Aroma is an important characteristic of apples, contributing significantly to fruit flavor and consumer acceptance. The aroma profile in apple fruits results from the interaction of multiple volatiles, including esters, alcohols, aldehydes, terpenoids, and others, which are mainly derived from the fatty acid, amino acid, terpenoid, and phenylpropanoid metabolic pathways. With progress in omics technologies, it is of practical significance to uncover the biosynthetic pathway and regulatory mechanism underlying the formation of volatiles, not only for elucidating the apple molecular mechanisms underlying key genetic pathways and in advancing the development of novel apple varieties with optimized fragrance profiles through precision breeding techniques. In this review, the aroma composition in apple fruits and the biosynthesis pathways for volatile formation are summarized. Furthermore, the breeding strategies with molecular techniques and the regulation measures about application engineering on apple aroma are also discussed. This review provides valuable insights for the improvement of apple aroma quality in the future.
... Considering other fruits, ethyl butanoate is found in high concentrations in strawberries [27] and orange wine [28]. For the apple cultivar 'Pink Lady', butyl acetate remains prominent throughout maturation [29]. Strong floral, fruity, and sweet aromas have been detected at high concentrations of compounds like ethyl acetate, isobutyl acetate, and hexyl acetate, which are prominent straight-chain esters that contribute significantly to these sensory qualities [30]. ...
Korean melons (Cucumis melo var. makuwa), which have a short shelf life and are prone to browning, face challenges when exported over long-distance via maritime shipping. However, the high firmness and low suture browning rate of the ‘Eliteggul’ cultivar suggest its potential suitability for long-distance export. This study aimed to evaluate the export suitability of ‘Eliteggul’ by comparing it to the widely grown cultivar ‘Alchankkul’. Consumer preferences were assessed based on fragrance, sweetness, overall preference, appearance, and firmness. Both cultivars were grown and harvested in a commercial greenhouse in Seongju-gun, South Korea. After being treated with modified atmosphere film, the fruits were stored at 6 °C for 1 day, transported to Singapore in a shipping container at 7.4 °C for 13 days, and distributed at 22 °C for 3 days. After 14 days of storage, analysis in Singapore showed that ‘Eliteggul’ maintained a significantly higher firmness at 12.9 ± 0.3 kg·cm² compared to ‘Alchankkul’, which showed firmness at 8.1 ± 0.4 kg·cm². Additionally, ‘Eliteggul’ exhibited less browning on the white sutures at 1.3 ± 0.1, indicating better preservation of its quality than ‘Alchankkul’, at 2.0 ± 0.3. Even at 14 + 3 days, ‘Eliteggul’ maintained a firmness of 12.8 ± 0.2 kg·cm², which was significantly higher than that of ‘Alchankkul’, which showed a firmness of 7.7 ± 0.5 kg·cm². Consumer preference surveys (n = 78) conducted in the local market revealed that customers favored the fragrance and sweetness of ‘Alchankkul’. Correspondingly, an analysis of volatile organic compounds (VOCs) from melon juice using a Twister stir bar method showed that ‘Alchankkul’ had significantly higher levels of ethyl(methylthio)acetate, ethyl propanoate, and benzyl alcohol, known to contribute to a sweet flavor. Furthermore, a thermal desorption tube VOCs test indicated that hexyl acetate and 2-methylbutyl 2-methylbutyrate were also significantly higher in ‘Alchankkul’. Despite this result, there was no significant difference in the overall preference scores between the two cultivars. This study indicates that ‘Eliteggul’, with a superior firmness, reduced browning, and high consumer acceptance, is ideal for long-distance export, offering foundational data to bridge the research gap in export-oriented melons and support the broader distribution of Korean cultivars.
... This outcome can be attributed to the higher concentration of 1-hexanol in CA-stored pears, a precursor to hexyl acetate (Fig. 5F). Precursor availability is a critical factor in ester production, as seen in 'Pink Lady®' apples (Villatoro et al., 2008) and pears like 'Dangshansuli', 'Nanguoli' (Qin et al., 2014), and 'Doyenne du Comice' (Lara et al., 2003). Lower hexyl acetate concentrations were also observed in 'Bartlett' pears stored in ULO (0.8 kPa O 2 ) at 1.0 and − 1.0 • C (Zlatić et al., 2016) and 'Conference' pears stored in ULO (0.5 kPa O 2 ) at 0 • C (Saquet, 2016). ...
Pears (Pyrus communis) are climacteric fruit that require storage under appropriate conditions to extend availability and delay ripening. This study evaluated the production of volatile organic compounds (VOCs) and the physicochemical quality of ‘Santa Maria’ and ‘Rocha’ pears after storage in a controlled atmosphere (CA) or dynamic controlled atmosphere (DCA), monitored by respiratory quotient (RQ). The pears, harvested from an orchard in S˜ao Joaquim (Santa Catarina State), were stored at - 0.5 ◦C in CA (2.0 kPa O2) and DCA with RQ levels of 1.1, 1.2, 1.3, and 1.4, all under 1.0 kPa CO2. ‘Santa Maria’ pears were stored for four months, and ‘Rocha’ pears for six months, followed by seven days at 20 ◦C before quality analysis. Storage of ‘Santa Maria’ pears in CA resulted in fruit with a more yellow skin color, lower flesh firmness, and higher ethylene production, while ‘Rocha’ pears in CA retained higher flesh firmness and produced less ethylene at 4 and 7 days at 20 ◦C compared to DCA conditions. Storage conditions did not significantly affect soluble solids and acidity. In ‘Rocha’ pears, DCA, regardless of RQ, suppressed the production of butyl acetate, hexyl acetate, pentyl acetate, methyl acetate, and propyl acetate, while in ‘Santa Maria’ pears, esters such as butyl acetate and hexyl acetate were less affected. In conclusion, no significant differences were found between the DCA-RQ levels evaluated in this research in maintaining physicochemical quality and VOCs production. However, DCA suppressed VOCs production in both ‘Santa Maria’ and ‘Rocha’ pears compared with CA storage.
... Acetate esters (especially butyl acetate and 2-methylbutyl acetate) impart a fruity-sweet aroma, typical of 'Gala' apples, while ethyl esters (especially ethyl butanoate and ethyl 2-methylbutanoate) impart a fruity-fresh aroma, typical of 'McIntosh' apples (Panasiuk et al. 1980;Yahia 1991;Young et al. 1996). Hexyl and hexanoate esters (such as hexyl 2-methylbutanoate and butyl hexanoate) contribute "green-grassy" aromas characteristic of unripe bananas and 'Cripps Pink' apples (López et al. 2007;Villatoro et al. 2008). Additionally, C 6 alcohols and aldehydes such as hexanol and hexenal, respectively can impart these "green-grassy" aromas (Yan et al. 2020). ...
Flavor is a major component of the apple eating experience, along with taste, texture and appearance. Apples produce a wide array of volatile organic compounds that impart particular flavors. Cultivars producing increased or novel flavors may have more desirability for consumers and help to differentiate the fruit. Efficiently breeding more flavorful apples requires understanding the volatiles present in apple germplasm and their potential sensory impact. As an initial step towards the development of more flavorful apple cultivars, a New Zealand collection of germplasm was surveyed, and seventy-three volatiles were identified as being present in at least half the accessions. Substantial differences in the presence and relative abundance of specific volatiles were uncovered across the accessions and could sometimes be linked to an apple’s flavor profile. The large number of volatiles analyzed allowed relationships between and among molecule classes to be established. Esters were found to be the main drivers of volatile differentiation across accessions. Apples tended to produce either ethyl or acetate esters, suggesting there is different genetic control for these two ester types. Additionally, esters generally had larger broad-sense heritabilities, indicating they could be easier targets for modifying apple flavor. This volatile dataset is a valuable resource for apple breeding, and increases the understanding of an important consumer trait.
... These compounds included cyclohexanone, 2-hexanone, 3-hydroxy-2-butanone, 2,3-butanedione, acetone, 1-penten-3-one, and 2-butanone. Most of these ketones are produced through β-oxidation and degradation of fatty acids [39]. The short-chain ketones of C3-C6, such as cyclohexanone, 2-hexanone, 3-hydroxy-2-butanone, 2,3-butanedione, 1-penten-3-one, etc., are considered to have rich fruit flavours in fruits and green leafy plants. ...
Zangju (Citrus reticulata cv. Manau Gan) is the main citrus cultivar in Derong County, China, with unique aroma and flavour characteristics, but the use of Zangju peel (CRZP) is limited due to a lack of research on its peel. In this study, electronic nose, headspace-gas chromatography–ion mobility spectrometry (HS-GC–IMS), and partial least squares-discriminant analysis (PLS-DA) methods were used to rapidly and comprehensively evaluate the volatile compounds of dried CRZP and to analyse the role of dynamic changes at different maturation stages. The results showed that seventy-eight volatile compounds, mainly aldehydes (25.27%) and monoterpenes (55.88%), were found in the samples at four maturity stages. The contents of alcohols and aldehydes that produce unripe fruit aromas are relatively high in the immature stage (October to November), while the contents of monoterpenoids, ketones and esters in ripe fruit aromas are relatively high in the full ripening stage (January to February). The PLS-DA model results showed that the samples collected at different maturity stages could be effectively discriminated. The VIP method identified 12 key volatile compounds that could be used as flavour markers for CRZP samples collected at different maturity stages. Specifically, the relative volatile organic compounds (VOCs) content of CRZP harvested in October is the highest. This study provides a basis for a comprehensive understanding of the flavour characteristics of CRZP in the ripening process, the application of CRZP as a byproduct in industrial production (food, cosmetics, flavour and fragrance), and a reference for similar research on other C. reticulata varieties.
... The fingerprinting revealed 20 unique VOCs present in sweet orange juice and 9 unique VOCs present in mandarin juice, thus setting a basis for their identification and recognizing any possible adulteration by mixing these two juices. Villatoro et al. [17] monitored the change in aroma and the associated VOC biomarker blend of the "Pink Lady" apple variety during different stages of its ripening. It was found that VOC content was significantly low in unripe fruit, while the content of hexyl acetate, hexyl hexanoate, hexyl 2-methylbutanoate, hexyl butanoate, 2-methylbutyl acetate, and butyl acetate significantly increased as ripening advanced. ...
Food quality control is an important area to address, as it directly impacts the health of the whole population. To evaluate the food authenticity and quality, the organoleptic feature of the food aroma is very important, such that the composition of volatile organic compounds (VOC) is unique in each aroma, providing a basis to predict the food quality. Different types of analytical approaches have been used to assess the VOC biomarkers and other parameters in the food. The conventional approaches are based on targeted analyses using chromatography and spectroscopies coupled with chemometrics, which are highly sensitive, selective, and accurate to predict food authenticity, ageing, and geographical origin. However, these methods require passive sampling, are expensive, time-consuming, and lack real-time measurements. Alternately, gas sensor-based devices, such as the electronic nose (e-nose), bring a potential solution for the existing limitations of conventional methods, offering a real-time and cheaper point-of-care analysis of food quality assessment. Currently, research advancement in this field involves mainly metal oxide semiconductor-based chemiresistive gas sensors, which are highly sensitive, partially selective, have a short response time, and utilize diverse pattern recognition methods for the classification and identification of biomarkers. Further research interests are emerging in the use of organic nanomaterials in e-noses, which are cheaper and operable at room temperature.
... Aroma is an essential component of fruit quality. The aroma of many fruits has been studied in recent years, including the white pear [8], apple [9], watermelon [10], mango [11], melon [12], strawberry [13], peach [14], and tomato [15]. P. pyrifolia, in particular, contains more than 300 volatile compounds [16]. ...
Volatiles are essential substances that determine distinct fruit flavors and user preferences. However, the metabolic dynamic and molecular modulation models that regulate the overall flavor generation during fruit growth and ripening are still largely unclear for most fruit species. To comprehensively analyze the molecular mechanism and regulation mechanism of aroma accumulation and aroma component formation in Pyrus spp. ‘Panguxiang’ (‘Panguxiang’pear), this study compared pear phenotype, sugars, organic acid content, and the expression of related genes and metabolites amid pear growth and development in Pyrus spp. ‘Panguxiang’. A total of 417 VOCs (4 amines, 19 aromatics, 29 aldehydes, 31 alcohols, 38 ketones, 64 heterocyclic compounds, 89 terpenoids, 94 esters, and 49 others) were found. The potential gene expression patterns were explored by combining transcriptomics and metabolomics, and VOC-associated metabolism and transcriptome data from all samples were integrated during the growth and development period. On this basis, we constructed a colorful model depicting changes in the VOCs and genes throughout pear growth and development. Our findings reveal that terpenoid biosynthesis pathways are the main aroma production pathways during pear growth and development. In addition to providing novel insights into the metabolic control of fruit flavor during growth and development, this study also provides a new theoretical basis for studying aroma metabolites in pears.
... The C3-C6 short-chain ketones, such as cyclohexanone, cyclopentanone, 2-butanone, 2-methyl-tetrahydro-3-furanone, and 2-pentanone, are regarded as efficient aroma-producing compounds with rich sweet, mint and milk aroma properties in abundant of green leaf plants, fruits, and vegetables . Cyclohexanone is mainly formed by the degradation of fatty acids and the β-oxidation through the β-ketoacyl-Co A intermediate (Villatoro et al., 2008). CRP analysis also revealed 10 terpenes, including β-pinene, α-pinene, limonene, and γ-terpinene, which were analyzed in the CRP samples. ...
Citrus reticulatae pericarpium (CRP) is regarded as a valuable functional food in many countries due to its pharmacological activities and unique aroma. In this study, CRP was treated by different A. niger to accelerate aging. Headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS) fingerprinting was adopted to rapidly and comprehensively evaluate the flavor compounds of CRP and to identify their dynamic changes at different storage time. Results revealed that the hesperidin content of DOL groups reduced more clearly than other groups during storage. A total of 134 volatile flavor compounds were identified. The volatile organic compounds (VOCs) showed that the lemon, sweet with the musk aroma of CRP, changed to apple, pineapple, and coffee odors during storage. The principal component analysis (PCA) and fingerprint similarity analysis (FSA) results showed that the CRP was clearly distinguished at different storage time. DOL-3 and DOS-6 differ the most from the DOW-3,6, respectively. This work provided helpful information for accelerating the aging of CRP and has great potential for industrial application.
... Terpene β-cyclocitral and esters cis-3-hexenyl 2-methylbutanoate, hexyl isovalerate and hexyl acetate detected in higher concentrations in torenia cultivated in biocompost have low threshold perception, exerting important role in the odor of flowers (Villatoro et al., 2008;Sosa-Moguel, Pino, Sauri-Duch, & Cuevas-Glory, 2018;Guo et al., 2021;). These findings suggest that flowers cultivated in biocompost have greater odoriferous potential compared to flowers cultivated in traditional system. ...
Edible flowers have been widely consumed fresh in drinks, salads, desserts and salty dishes. This study evaluated the color parameters, chemical composition (phenolics, sugars, organic acids), volatiles compounds and microbiota (bacterial and fungal communities) in edible purple flowers (Torenia fournieri F. Lind.) cultivated in biocompost and traditional organic systems. Torenia flowers cultivated in biocompost had high (p < 0.05) contents of anthocyanins (cyanidin 3,5-diglucoside, delphinidin 3-glucoside), flavonols (quercitin 3-glycoside, myricetin and rutin), sugars (rhamnose and glucose), organic acids (citric and succinic), aldehydes (hexanal, cis-2-hexenal and trans-2-hexenal), and alcohols (trans-2-hexenol and 3-ethyl-4-methylpentan-1-ol). Flowers cultivated in biocompost showed higher (p < 0.05) abundance Cyanobacteria and Basidiomycota bacterial and fungal phyla, respectively, than flowers cultivated in traditional system. The high abundance of Oxyphotobacteria and Dothideomycetes classes, Acetobacterales and Cladosporiales orders, Oxyphotobacteriaceae and Cladosporiaceae families, and Raoultella and Cladosporium genera characterized torenia flowers cultivated in biocompost. The cultivation system influenced the torenia flowers microbiota and composition, primarily due to environmental response and enhanced uptake of nutrients. Our findings indicate that cultivation of torenia using the agroindustrial based-biocompost improves bioactive and volatiles contents in more purple and fruity flavored flowers, rendering flowers more attractive for consumption.
... Eight volatile compounds (E17 hexyl acetate, E26 butyl caproate, E27 hexyl butyrate, E28 hexyl 2-methylbutyrate, E40 hexyl hexanoate, A1 hexanal, A4 2-hexenal and O8 α-farnesene) were present in peels of all apple cultivars (Tables S1 and S2). As shown in Table 2, hexyl butyrate (E27), hexyl 2-methylbutyrate (E28), hexyl hexanoate (E40), and 2-hexenal (A4) and α-farnesene (O8) were the most abundant compounds (average content > 700 µg/kg FW) in the apple cultivars, which is in agreement with the results of previous studies [20][21][22]. Aroma is a complex mixture of many volatile compounds, and the amount and content of aroma substances showed different patterns among various apple cultivars [18,23]. In this study, differences were also observed in the total content of volatile compounds among the 40 apple cultivars, ranging from 2041.27 ± 120.36 µg/kg FW to 27,813.56 ± 2310.07 µg/kg FW ( . ...
Aroma is an important quality indicator for apples and has a great influence on the overall flavour and consumer acceptance. However, the information of the aroma volatile compounds in apple peels is largely unknown. In this study, evaluation of volatile compounds in peels of 40 apple cultivars was carried out using headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS). A total of 78 volatile compounds were identified, including 47 esters, 12 aldehydes, 5 alcohols, 3 ketones, 1 acid and 10 others. Eight volatile compounds were common in all apple cultivars. Cultivar Changfu No. 2 contained the highest number of volatile compounds (47), while Qinyue contained the least (20). Honey Crisps had the highest volatile content, at 27,813.56 ± 2310.07 μg/kg FW, while Huashuo had the lowest volatile content, at 2041.27 ± 120.36 μg/kg FW. Principal component analysis (PCA) clustered the 40 apple cultivars into five groups. Aroma is cultivar-specific, volatile compounds of hexyl butyrate, hexyl 2-methylbutyrate and hexyl hexanoate, together with hexanal, (E)-2-hexenal, 1-hexanol, estragole and α-farnesene could be proposed for apple cultivar classification in the future.
... The content of four soluble sugars in 'Orin' apples generally increased during the fruit ripening periods and reached the maximum at full ripening stage of 180 DAFB. From 60 DAFB to The total soluble solid (TSS) showed an upward trend during 'Orin' fruit ripening, which was consistent with the findings obtained on 'Pink Lady' apples in the previous study [21]. From 60 DAFB to 180 DAFB, the TSS significantly increased from 10.30 to 14.53 • Brix. ...
‘Orin’ is a popular apple cultivar, which has a yellow-green appearance, pleasant taste, and unique aroma. However, few studies on the fruit quality characteristics of ‘Orin’ apples have been reported before. In this study, changes of the physiological characteristics were measured at different ripening stages, and the soluble sugars and organic acids were determined by high-performance liquid chromatography (HPLC). Volatile compounds were identified using the headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS). During the fruit ripening, the ‘Orin’ apple fruit weight, size, and total soluble solid were gradually increased by contrast with the titratable acidity, and the firmness decreased. The content of four soluble sugars reached the maximum at the 180 days after full bloom (DAFB) stage. Malic acid was measured as the most abundant organic acid in ‘Orin’ apples. Ethyl butyrate, hexyl propanoate, hexyl acetate and butyl acetate belonging to esters with high odor activity values (OAVs) could be responsible for the typical aroma of ‘Orin’ apples. The aim of this work was to provide information on the flavor characteristics of ‘Orin’ apples and promote this apple cultivar for marketing and processing in the future.
... 23 All plants are able to emit volatile organic compounds and the content and composition of these molecules depens on genotic and phenotypic traits. 24 Is well known that volatile flavor compounds are likely to play a key role in determining the perception and acceptability of products by consumers. Identification of key volatile flavor metabolites that carry the unique character of the natural fruit is essential, as it provides the principal sensory identity and characteristic flavor of the fruit. ...
The kiwi is a fruit with a great agricultural, botanical, and economic interest. Originally from China, this species is currently widespread in practically all the world, due to the high nutritional value of the fruits, excellent organoleptic qualities besides therapeutic benefits in the health. The most common kiwifruit species grown commercially is Actinidia deliciosa even though many varieties of this fruit are produced by other cultivars or by another kind of plants, such as Actinidia chinensis and the Actinidia kolomikta or the Actinidia argute. Although there are many varieties in this species, the A. deliciosa Hayward cultivar is the most popular variety marketed commercially. Kiwifruits contain aromatic compounds able to attract consumers due to their palatability. The esters, ethyl butanoate and methyl benzoate and the aldehyde E-2-hexenal, were shown to increase “characteristic kiwifruit aroma and flavor”. All these characteristics are appreciated by the kiwi-consumers. Several preservation techniques have now been used to augment kiwi shelf life, including cold storage, chemical dipping, modified atmosphere packaging and edible coatings, making it possible for the consumers to enjoin the fruit all the year.
... Aroma is a complex mixture of volatile organic compounds, which has an important impact on the overall flavor of fruits (Baldwin, 2002) and play a major role in determining the perception and acceptability of foods by consumers (Garcia et al., 2012;Villatoro et al., 2008). Overall, aroma is basically comprised of volatile compounds in fruits, and volatile profile in fruits is essentially determined by fruit genotype and cultivation conditions (Liu et al., 2018). ...
In this study, the properties of nutritional, color and volatile organic compounds of currant varieties (Ribes spp.) in Turkey were investigated. A total of 125 different volatile organic compounds were identified with GC-QTOF/MS. The levels of protein, sugar fractions, dietary fibre, ascorbic acid and minerals of the currant fruits were found to be different between varieties. Ascorbic acid content ranged from 169.33 to 725.52 mg/100 g dry weight. The K, Ca and Mg minerals were found to be in high amount in all varieties. Total dietary fibre levels were found between 7.17 (Red Lake) and 9.90 g/100 g dw (Rosenthal). The common volatiles found in all cultivars were ocimene, carene, alpha-phellandrene, alpha-terpinene, benzaldehyde and piperonal. ‘Rosenthal’ and ‘Goliath’ displayed large differences in the volatile fraction which allow for their discrimination in the PCA (principal component analysis) plot.
... Ester production was reduced more than 90% in apples with suppressed ACC-oxidase or ACC-synthase activity or when treated with the ethylene action inhibitor 1-methylcyclopropene (1-MCP) (Defilippi et al., 2005) due to ethylene regulation of alcohol acyl-CoA transferase (AAT), a key enzyme in ester biosynthesis. Increase of ethyl esters in CA for "Fuji" (Echeverrıa et al., 2004;Lara et al., 2006) and "Pink Lady" (Villatoro et al., 2008) apples as well as in pear (Lara et al., 2003) was associated with the availability of alcohol precursors. A MA of low O 2 and high CO 2 retarded blackcurrant fruit from synthesizing terpenes over 3 weeks of storage and changed the terpene profile (Harb et al., 2008). ...
... All fruits emit volatile compounds. However, the content and composition of these molecules vary with species, variety, location, the composition of soils, usage of fertilizer, climate, and temperature Maffei (2010). The aroma is a complex mixture of a large number of volatile compounds, T whose composition is specific to species and often to the variety of fruit (Sanz et al., 1997;Schwab (2008). ...
This study aimed to compare fatty acid and volatile compound compositions of Viburnum opulus fruits grown at various locations at different altitudes of Turkey (Ardahan/Center, Sivas/Gemerk, Kayseri/Develi, Gumushane/ Kelkit). The total lipid contents in fruits varied from 9.34 % (Ardahan) to 12.35 % (Gümüşhane). A total of ten fatty acids (lauric acid (C12:0), myristic acid (C14:0), oleic acid (C 18:1), palmitic acid (C16:0), linoleic acid (C18:2), α-Linolenic acid(C18:3), arachidic acid (C20:0), gondoic acid (C20:1), behenic acid (C22:0), stearic acid (C18:0)) have been identified and quantified. The major fatty acids in all the samples were oleic acid, linoleic acid, and palmitic acid. The highest saturated fatty acid (SFA) content was found in Gümüşhane sample (18.14 %), while the lowest content was detected in Sivas (13.46 %). Unlike SFA, the highest unsaturated faty acid (UFA) content was determined in Sivas sample (87.01 %), while the lowest content was identified in Gümüşhane sample (82.26 %). We used headspace and immersion solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME/GC-MS and Im-SPME/GC-MS) techniques to identify the volatiles. 23 and 35 compounds were identified by the HS-SPME/GC-MS technique at 28 and 40 ̊ C, however, 44 and 38 compounds were detected by the Im-SPME/GC-MS technique at 28 and 40 ̊ C. Thirty volatile components of V.opulus fruits have been detected for the first time in this study. 3-methylbutanoic acid in Ardahan, Kayseri, Sivas samples, ethyl acetate in Sivas sample, 2-octanol in Gümüşhane sample, phenol in Ardahan sample are the main volatile compounds. Im-SPME/GC-MS technique allowed identification of a larger number of volatile compounds and thus is more efficient than the HS-SPME/GC-MS technique.
... odor, produced by volatile compounds, which vary due to genotypic and phenotypic plasticity. [20] As an important trait of fruit quality, aroma and flavor have gained increasing attention. The perception of metabolomics-assisted breeding is a novel and powerful approach leading to new targets for breeding programs for the improvement of metabolite-based quality traits. ...
The hexane soluble non-polar metabolites in pericarp and seeds of Capsicum chinense (cv. ghee smelling group), C. frutescens (cv. erect upward bird’s eye chili group and cv. upward tobasco group), and C. annuum (cv. clustered pendent downward group, cv. cherry group, cv. pendent – anaheim group, cv. small hot pendent solitary group, cv. glossum of green, red and yellow bell pepper and cv. long waxy group) were identified at different stages of ripening. The hexane soluble metabolites were chemically characterized using GC-MS (Gas Chromatogrphy Mass Spectrometry)-based metabolomics. The non-polar metabolites of Capsicum species and their varieties were correlated with their progressive ripening stages, many of which may contribute to their aroma and flavor. Chemometric analyses showed distinct changes during ripening based on the metabolite profiles.
... Molecules 2019, 24, 974 2 of 20 most important esters contributing to the characteristic apple aroma [6][7][8][9]. In pear fruit, esters were also the most significant contributors to aroma [10], being methyl and hexyl esters of decadienoate, the character imparting compounds of the European pear [11]. ...
In the current study, a comprehensive approach based on headspace solid-phase microextraction (HS-SPME), combined with gas chromatography-quadrupole mass spectrometry (GC-qMS), was used to establish the volatile signature of fresh and processed fruit juices, obtained from the same batch of grapes, red fruits, orange, pear, and apple. This is a powerful tool for evaluating the impact of the production process on the volatomic pattern of fruit juice. A total of 169 volatile organic compounds (VOCs) belonging to different chemical groups were identified. Esters, carbonyl compounds, terpenoids, and alcohols are the major chemical groups in the investigated fruit juices. However, their contribution to the total volatile profile varied. Special attention should be paid to processed fruit juices to avoid the possible deleterious effects associated with the formation of furanic compounds (e.g., heat treatment), since their furanic content was significantly higher in comparison to that of fresh fruit juices. The knowledge obtained in the current study will allow for the introduction of modifications to the process involved in processing juice, which will improve the organoleptic characteristics of processed juices, contributing to a better acceptance by consumers. Furthermore, more assays should be performed to assess the effect of harvests, geography, and agronomy on the volatile profile of juices.
... 23 All plants are able to emit volatile organic compounds and the content and composition of these molecules depens on genotic and phenotypic traits. 24 Is well known that volatile flavor compounds are likely to play a key role in determining the perception and acceptability of products by consumers. Identification of key volatile flavor metabolites that carry the unique character of the natural fruit is essential, as it provides the principal sensory identity and characteristic flavor of the fruit. ...
Abstract
The kiwi is a fruit with a great agricultural, botanical, and economic interest. Originally from China, this species is currently widespread in practically all the world, due to the high nutritional value of the fruits, excellent organoleptic qualities besides therapeutic benefits in the health. The most common kiwifruit species grown commercially is Actinidia deliciosa even though many varieties of this fruit are produced by other cultivars or by another kind of plants, such as Actinidia chinensis and the Actinidia kolomikta or the Actinidia argute. Although there are many varieties in this species, the A. deliciosa Hayward cultivar is the most popular variety marketed commercially. Kiwifruits contain aromatic compounds able to attract consumers due to their palatability. The esters, ethyl butanoate and methyl benzoate and the aldehyde E-2-hexenal, were shown to increase “characteristic kiwifruit aroma and flavor”. All these characteristics are appreciated by the kiwi-consumers. Several preservation techniques have now been used to augment kiwi shelf life, including cold storage, chemical dipping, modified atmosphere packaging and edible coatings, making it possible for the consumers to enjoin the fruit all the year.
Keywords: ki
During the post-ripening process of ‘Docteur Jules Guyot’ pear, the aroma of the fruit gradually becomes richer with increasing maturity. In this study, the volatile substances in ‘Docteur Jules Guyot’ pear fruits stored at room temperature (RT), low temperature (LT), and low temperature to room temperature (LT-RT) were identified and analyzed using solid-phase microextraction (SPME) with gas chromatography–mass spectrometry (GC–MS) at different ripening stages. The results showed that the volatile substances were mainly alcohols, aldehydes, esters, acids, ketones, alkanes, and terpenes. Esters are the main substances of fruit aroma; with an increase in fruit maturity, the ester content increases gradually. Ethyl acetate, hexyl acetate, heptyl acetate, and amyl acetate were the main volatile components of the fruit. The aroma content under LT was lower than that under RT, and after transferring from LT-RT, the ripening of the fruit was accelerated, and the aroma content increased rapidly. Among the genes involved in the lox pathway, the expression of PcHPL1, PcADH1, PcGLIP1, PcGLIP-like, PcLOX2, PcLIP2, and PcFAD2 were the most contributing to the changes of esters in ‘Docteur Jules Guyot’ pear. These results are helpful to provide basic data for the study of volatile in ‘Docteur Jules Guyot’ pear fruit under LT and RT storage.
Abscisic acid (ABA) is a key hormone in plant growth and development, playing a central role in responses to various biotic and abiotic stresses as well as in fruit ripening. The present study examined the impact of ABA and nordihydroguaiaretic acid (NDGA) on various postharvest ‘Docteur Jules Guyot’ pear fruit characteristics, including firmness, pectinase activity, pectin content, volatile aromatic substances, and the expression of correlated genes. The results showed that ABA quickly reduced fruit firmness, increasing the activity of pectin degradation-related enzymes. The contents of water-soluble pectin (WSP) and ionic-soluble pectin (ISP) increased, and covalent binding pectin (CBP) decreased under ABA treatment. Among the detected volatile aromatic substances, the highest-level substance of the fruit was ester, and the ABA treatment significantly promoted the amount of ester substances. The cell wall disassembly-related genes PcPME3, PcPG1, PcPG2, PcPL, PcARF2, and PcGAL1, as well as ABA biosynthesis-related genes PcNCED1 and PcNCED2, were also significantly induced by ABA. Conversely, all these genes were repressed in the NDGA treatment group. Therefore, it was speculated that ABA may promote the softening of postharvest European pear fruit by affecting the activity of pectin degradation enzymes in fruit cell walls.
Cucumber is a widely consumed vegetable crop known for its rich nutrient composition and distinctive flavor,
influenced by both volatile and non-volatile compounds. Grafting and delayed harvesting are crucial strategies
for increasing cucumber yield. The present study investigates the impact of delayed harvesting at different
developmental stages and grafting on the metabolic profile, flavor, and overall quality of cucumber fruits Yuxiu 2
(YX) using UPLC-MS/MS and GC-MS/MS techniques. The results indicate that delayed harvesting of YX led to
significant increases in length, diameter, and weight from 12 to 24 days after pollination (DAP), with minimal
growth beyond 24 DAP. However, grafting did not affect these physical parameters compared to self-rooted
plants. Furthermore, metabolic profiling reveals that delayed harvesting enhances the concentration of certain
non-volatile metabolites, including alkaloids, organic acids, and phenolic acids, while leading to a reduction in
flavonoid contents. Overall, 140 non-volatile and 26 volatile differential metabolites were screened at three
developmental stages. Notably, four new organic acids (6-amino hexanoic acid, 5-amino valeric acid, 1-hydroxy-
2-naphthoic acid, and succinic semialdehyde) and three novel alkaloids (3-indole acetonitrile, epinephrine, and
serotonin) were identified. Volatile compounds, such as aldehydes, esters, terpenes, alcohols, and ketones,
exhibit a peak in concentration at 24 DAP, followed by a decline. The characteristic cucumber flavor compound,
(E,Z)-2,6-nonadienal, remains consistent across all developmental stages. In grafted cucumber fruits, a total of
113 non-volatile and 11 volatile differential metabolites were screened, and among them, ten unique non-volatile
metabolites were detected in grafted fruits, contributing to the sour and bitter taste of cucumbers. Moreover,
some of the metabolites like (1S,4S,4aR)-1-isopropyl-4-methyl-7-methylene-1,2,3,4,4a,5,6,7-octahydronaph
thalene with pentylenetetrazol contribute to an undesirable camphor-like odor. The study concludes that while
delayed harvesting and grafting practices can increase cucumber yield, they also significantly alter the fruit’s
metabolic profile, impacting taste and flavor.
‘Binzi’ (BZ) (Malus domestica subsp. chinensis var. binzi Li Y.N.) and ‘Xiangguo’ (XG) (Malus domestica subsp. chinensis var. xiangguo Li Y.N.) are the ancient cultivars in China. The BZ fruits have a low-fragrant flavor on harvest day but a high-fragrant flavor after storage at room temperature, while the XG fruits have a stronger flavor when mature. ‘Starking’ (SK) and ‘Golden Delicious’ (GD) fruits have a rich flavor and are recognized by all countries in the world. However, information on the differences between ancient Chinese cultivars and Western apple cultivars in aroma compounds remains unknown. The apple fruits were collected for continuous two years. Aroma compounds in the skin and pulp of the fruits were detected at room temperature (20 ± 1 °C) during storage. The dynamics of VOCs in BZ and SK fruits were more similarly reflected in esters, while those of XG and GD fruits were reflected in aldehydes and alcohols. Ethyl 2-methylbutyrate, with an extremely low odor threshold, was the main source of typical apple flavor in SK, BZ, and XG fruits, while hexyl acetate was the source of the banana flavor in GD fruits. 6-methyl-5-hepten-2-one and β-damascenone were the important ketones produced in the later stage of storage, derived from the carotenoid metabolism pathway and providing a citrus and rose flavor to the four apple cultivars. SK had the highest number of characteristic aroma components, which were mainly derived from the amino acid metabolism pathway, providing fruits with a sweet and fruity flavor. Although the characteristic aroma components of GD were derived from the fatty acid metabolic pathway, the number of volatile esters was lower. Ethyl butyrate, derived from the saturated fatty acid metabolism, had the highest content in BZ, providing a pineapple flavor; the flavor of XG was mainly derived from ethyl 2-methylbutyrate, 6-methyl-5-hepten-2-one, and β-damascenone. Therefore, we suggest BZ and XG apples as the aroma-breeding material with which to enrich new cultivars’ aroma components, derived from the fatty acid metabolism and carotenoid metabolism pathways, respectively.
Based on the concept of circular economy, citrus peel was considered a valuable source of bioactive compounds for high-value foods. Electrohydrodynamic (EHD) drying is a novel technology appropriated for the dehydration of heat-sensitive products such as citrus peel. In current work, EHD drying of citrus peel was performed based on alternating current (AC) or direct current (DC) sources at various voltage levels (9, 18, 27, 36, and 45 kV). The effect of EHD on drying characteristics, water retention capacity, enzyme inactivation, phytochemical contents (phenolic compounds and carotenoids), and volatile compounds of citrus peel were evaluated and compared. Results showed that the drying time in the AC electric field was shorter compared to DC electric field at the same applied voltages due to the polarization layer formed by unipolar charges. The applied voltage determined electric field strength as well as the degree of tissue collapse and cell membrane rupture. EHD elucidated the transformation and degradation of phytochemicals including phenolic compounds, carotenoids, and volatile composition in proportion to the applied voltage. The findings indicate that EHD drying with AC improves drying behaviors, inactivates enzymes, and retains the phytochemical properties of citrus peel.
Volatile esters are major aromas contributing to the organoleptic quality of apple fruit. However, the molecular mechanisms underlying the regulation of volatile ester biosynthesis in apple remain elusive. This study investigated the volatile profiles and transcriptomes of 'Qinguan' (QG) apple fruit during development and/or postharvest storage. Although the constitution of volatiles varied widely between the peel and flesh, the volatile profiles of the peel and flesh of ripening QG fruit were dominated by volatile esters. WGCNA results suggested that 19 genes belonging to ester biosynthesis pathways and 11 hub transcription factor genes potentially participated in the biosynthesis and regulation of esters. To figure out key regulators of ester biosynthesis, correlation network analysis, dual-luciferase assays, and yeast one-hybrid assay were conducted and suggested that MdMYB94 trans-activated the MdAAT2 promoter and participated in the regulation of ester biosynthesis. This study provides a framework for understanding ester biosynthesis and regulation in apple.
In this study; quality characteristics and volatile compounds of Starking Delicious, Amasya, Granny Smith, and Golden Delicious apple cultivars were determined. Granny Smith has the highest titratable acidity and the lowest pH value, while the Amasya apple has the highest dry matter and water-soluble solids. Aroma is an important quality criterion for apples and its has a big role in consumer taste. The aroma composition of apples was determined in gas chromatography-mass spectrometry (GC-MS) using the headspace method. Forty different volatile compounds, including 24 esters, 5 higher alcohols, 1 aldehyde, 1 terpene and 9 unidentified volatile compounds, were detected in apples. Esters, which make up 80.00% of Starking Delicious, 76.55% of Amasya and 62.82% of Golden Delicious are the main flavor group in apples and esters generally impart aroma compounds preferred by consumers. Butyl acetate, 2-methyl butyl acetate, hexyl acetate, (E,E)-α-farnecene, ethanol and ethyl 2-methyl butyrate were the aroma components determined at the highest rates in apples. These compounds contribute to the aroma of apples such as banana, fruity, strawberry, sweet, pear, grass and alcohol.
Anastrepha obliqua Macquart (Diptera: Tephritidae) is a polyphagous species with hog plums (Spondias spp.) (Sapindales: Anacardiaceae) and mangoes (Mangifera indica L.) (Sapindales: Anacardiaceae) as primary host fruits. In this study, the olfactory preference of A. obliqua for three stages of ripeness of two mango cultivars (‘Coche’ and ‘Ataulfo’) was investigated. The female flies were more attracted to ripe ‘Coche’ fruits compared to those ripe ‘Ataulfo’. Further, they were more attracted to the ‘Coche’ half-ripe and ripe fruits than to the unripe ones, but they did not discriminate among the stages of ripeness of ‘Ataulfo’ fruits. The male flies did not show preference for any specific mango cultivars or ripeness stage tested. Four compounds from ripe ‘Coche’ mangoes, and two from ripe ‘Ataulfo’ fruits were identified using coupled gas chromatography-electroantennographic (GC-EAD) recording and gas chromatography-mass spectrometry (GC-MS) analysis. ‘Coche’ mango volatiles eliciting responses from the female antennae were ethyl butyrate, ethyl hexanoate, ethyl heptanoate, and ethyl octanoate. The two ‘Ataulfo’ mango volatiles were identified as 3-carene and ethyl octanoate. These compounds were absent in unripe mangoes of both cultivars. Synthetic blends of these compounds were attractive to females as mango extracts in field cage tests. Our results suggest that the olfactory preference of A. obliqua for attractive hosts is based on the presence or absence of the compounds associated with fruit maturity.
Citrus reticulata ‘Chachi’ is a commercially important and predominantly cultivated tangerine cultivar in Xinhui County, Guangdong, China. The dried C. reticulata ‘Chachi’ pericarp (CRCP), known as “Guangchenpi” in Mandarin has unique flavor properties, and has been used as a highly valuable nutritional food source and in traditional medicine for centuries. In this study, headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS) and partial least squares-discriminant analysis (PLS-DA) were adopted to rapidly and comprehensively evaluate the flavor compounds of dried CRCP, and to identify their dynamic changes at different fruit picking stages. Results revealed a total of 71 volatile compound in the samples at six different fruit picking stages. The C6–C9 alcohols and aldehydes with aromatic green grass profiles had higher concentrations in the early fruit picking stages (from July to October), while most terpenes, ketones, and esters with typical aromas of mature flowers and fruits were highly accumulated in the late fruit picking stages (from November to December). PLS-DA results showed that samples picked in different stages could effectively be divided into relatively independent clusters, and the variable importance in projection (VIP) models identified 12 representative flavor compounds, which could be used as flavor markers for distinguishing CRCP samples picked at different stages.
This study evaluated the effects of delayed storage followed by storage under static controlled atmosphere (CA) and dynamic controlled atmosphere established by respiratory quotient (DCA‐RQ) with and without 1‐methylcyclopropene (1‐MCP) application on quality and volatile profile of “Cripps Pink” apple. A fruit batch was immediately stored at 1.5 ± 0.1°C, and another remained for 7 days at 20°C (delay) until storage. The storage conditions were: (1) CA (1.0 kPa O 2 + 1.0 kPa CO 2 ); (2) DCA‐RQ 1.3; (3) DCA‐RQ 1.5. Additionally, for each storage condition and delay strategy, a batch of fruit was treated with 1‐MCP, and another batch was left untreated.
Practical applications
DCA‐RQ 1.3 maintened flesh firmness even without 1‐MCP and with delayed storage. 1‐MCP application reduced all esters. Delayed storage increased the esters concentration and when associated with DCA‐RQ 1.3 and 1.5 should be recommended to reduce decay, increase the healthy fruit amount, and improve the aroma emission of “Cripps Pink” apple.
Fruits have different aromatic profiles according to their stage of ripeness, therefore, volatile compounds profile is an important quality attribute, which also determines flavor and aroma characteristics, making this profile a perfect option to guide the optimization of postharvest treatment of fruits. In this context, the objective was to discuss the effects of postharvest treatments, associating them with the biosynthesis of volatile compounds in fruits. There are three major groups of fruit flavor precursors: carbohydrates, amino acids, and fatty acids. The biosynthesis of volatile compounds is directly related to metabolic changes that occur according to the fruit ripening stage. This process occurs under the regulation of hormones, which have ethylene as one of the main agents. Several hormones are also part of this complex mechanism and interact by regulating ethylene levels positively or negatively to form a fine adjustment. Therefore, hormonal treatments have an impact on the biosynthesis of volatile compounds in different ways. Other postharvest treatments such as cold storage, controlled atmosphere, and UV radiation can also impact the volatile compounds biosynthesis, but are generally used synergistically, which circumvents the negative effects on the aromatic profile of the fruits.
With the aim of gaining insights into the evolution of quality characteristics of banana (Musa ABB Pisang Awak) during postharvest ripening, the cultivar 'Guangefen 1' was used to investigate the changes in physiological quality, the changes in volatile aroma components with maturity and the changes in the expression patterns of the gene related to aroma synthesis during postharvest storage at room temperature (25 ℃). The results showed that fruit firmness decreased sharply within 2 days after harvest, and the contents of total soluble solids (TSS) and soluble sugar increased significantly. Full ripening was reached on the 6 th day of storage. On the 8 th day, fruit firmness was reduced to a very low level, and the contents of TSS, and total aroma substances were maximized while the maximum contents of TSS and amino acid occurred on the 6 th day. A smaller number of volatile compounds were detected in immature bananas at lower levels, consisting mainly of C6-C9 aldehydes and alcohols along with a lesser amount of esters. The content of volatile compounds increased significantly with fruit ripening, including isoamyl isobutyrate, hexyl acetate, isoamyl acetate as esters, contributing to the unique aroma of Pisang Awak bananas. Expression analysis of the key genes involved in fruit aroma synthesis revealed that the expression of LOX (lipoxygenase), AAT (alcohol acyltransferase), ADH (alcohol dehydrogenase), BCAT (branched chain
Apples are one of the most widely planted fruits in the world, with an extremely high annual production. Several issues should be addressed to avoid the damaging of samples during the quality grading process of apples (e.g., the long detection period and the inability to detect the internal quality of apples). In this study, an electronic nose (e-nose) detection system for apple quality grading based on the K-nearest neighbor support vector machine (KNN-SVM) was designed, and the nasal cavity structure of the e-nose was optimized by computational fluid dynamics (CFD) simulation. A KNN-SVM classifier was also proposed to overcome the shortcomings of the traditional SVMs. The performance of the developed device was experimentally verified in the following steps. The apples were divided into three groups according to their external and internal quality. The e-nose data were pre-processed before features extraction, and then Principal Component Analysis (PCA) and Linear Discriminant Analysis (LDA) were used to reduce the dimension of the datasets. The recognition accuracy of the PCA–KNN-SVM classifier was 96.45%, and the LDA–KNN-SVM classifier achieved 97.78%. Compared with other commonly used classifiers, (traditional KNN, SVM, Decision Tree, and Random Forest), KNN-SVM is more efficient in terms of training time and accuracy of classification. Generally, the apple grading system can be used to evaluate the quality of apples during storage.
Volatile organic compounds (VOCs) emitted by plants consist of a broad range of gasses which serve purposes such as protecting against herbivores, communicating with insects and neighboring plants, or increasing the tolerance to environmental stresses. Evidence is accumulating that the composition of VOC blends plays an important role in fulfilling these purposes. Constitutional emissions give insight into species-specific stress tolerance potentials and are an important first step in linking metabolism and function of co-occurring VOCs. Here, we investigate the blend composition and interrelations among co-emitted VOCs in unstressed seedlings of four broad-leaved tree species, Quercus robur, Fagus sylvatica, Betula pendula, and Carpinus betulus. VOCs of Q. robur and F. sylvatica mainly emitted isoprene and monoterpenes, respectively. B. pendula had relatively high sesquiterpene emission; however, it made up only 1.7% of its total emissions while the VOC spectrum was dominated by methanol (∼72%). C. betulus was emitting methanol and monoterpenes in similar amounts compared to other species, casting doubt on its frequent classification as a close-to-zero VOC emitter. Beside these major VOCs, a total of 22 VOCs could be identified, with emission rates and blend compositions varying drastically between species. A principal component analysis among species revealed co-release of multiple compounds. In particular, new links between pathways and catabolites were indicated, e.g., correlated emission rates of methanol, sesquiterpenes (mevalonate pathway), and green leaf volatiles (hexanal, hexenyl acetate, and hexenal; lipoxygenase pathway). Furthermore, acetone emissions correlated with eugenol from the Shikimate pathway, a relationship that has not been described before. Our results thus indicate that certain VOC emissions are highly interrelated, pointing toward the importance to improve our understanding of VOC blends rather than targeting dominant VOCs only.
Plants emit various volatile organic compounds (VOCs) during the developmental stages of growth, and as responses to the various abiotic and biotic stresses. During postharvest storage, horticultural commodities can undergo its natural metabolisms like senescence, sprouting, ripening, and may be infected with various groups of microorganisms. These commodities may undergo various temperatures, relative humidity, water, and other abiotic stress conditions during preharvest and post-harvest conditions, and will behave differently than the normal crop, and follow a separate biochemical pathway, leading to change in the VOC profile. These VOCs can act as the signature of a particular state of storage material; therefore classified as the biomarkers in postharvest storage management. The biotic or abiotic stresses are completely responsible for the stimulation of specific VOC emission and are the attributing factors for the uncertainty in the case of VOC release during storage. This review focused mainly on the grouping of VOCs emanating from horticultural commodities during post-harvest storage, their classification linked to various abiotic and biotic factors, and their application in e-sensing for non-destructive quality monitoring. This will justify the implementation of the VOC-biomarker method as a technique to detect the quality of horticulture crops in commercial storage.
‘Honeycrisp’ is a popular apple cultivar because of its superior appearance and flavor. We investigated its aroma profiles and characteristic aroma. Whereas the aroma profiles of developing fruits were dominated by aldehydes, postharvest fruit accumulated abundant esters, alcohols, and sesquiterpenoids. Most of these components showed maxima at the fruit’s climacteric peak. There were more types and higher contents of sesquiterpenoids, aldehydes, and esters in the fruit skin than in the pulp, while alcohol contents and types were comparable between the pulp and skin. Aroma extract dilution and gas chromatography−olfactometry analyses revealed that hexyl 2-methylbutyrate, α-farnesene, 1,3-octanediol, hexanal, (E)-2-hexenal, hexanol, butanol, and 2-methyl-butanol are the most potent odor compounds in ‘Honeycrisp’ apple. Aroma reconstruction and omission tests combined with sensory analyses suggested that hexyl 2-methylbutyrate is responsible for the strong fruity note of ‘Honeycrisp’ apple, and that other alcohols, aldehydes, and α-farnesene are essential for its background aroma notes.
The postharvest development of greasiness in apple skin has negative effects on fruit appearance and market quality and causes significant economic losses. The fluid wax constituents responsible for skin greasiness comprise mainly oleate and linoleate esters of (E,E)-farnesol and short-chain alcohols (C3-C5). Butyl esters are also key components. It is believed that accumulations of volatile alcohols affect the development of skin greasiness by offering substrates for the biosynthesis of the greasy esters. To demonstrate the putative role of volatile alcohols on apple skin greasiness, ‘Cripps Pink’ apples were treated with either 10 or 25 μL L⁻¹ n-butanol (NBA) and then stored at 20 °C. The composition of each cuticular wax was analyzed, and the expression levels of the related genes were recorded. There was no significant difference in the time course of fruit ripening or senescence among the two NBA treatments and the control. As expected, accumulations of the fluid wax constituents were indeed promoted in the NBA-treated fruit. On day 42, compared with the control, the butyl ester contents of the skins of the 10 and 25 μL L⁻¹ NBA-treated fruits were 1.7 and 2.9 times higher, respectively. Moreover, the 25 μL L⁻¹ NBA-treated fruit showed higher greasiness levels and looked shinier than the fruit exposed to the lower NBA treatment or the control. Several genes were more highly expressed in the NBA-treated fruit than in the control. These included MdKASIII, MdSAD6, MdWSD1 (related to wax biosynthesis) and MdLTPG1 (related to wax export). We conclude that NBA had no significant effects on fruit ripening or senescence but promoted the development of skin greasiness.
Apple quality and the storage potential likely depend on a range of physiological and biochemical events occurring throughout fruit development and ripening. In this study, we investigated the major physiological (ethylene production and respiration) and biochemical changes (related to sugar and malic acid content as well as antioxidant metabolism) occurring during growth and on-tree ripening of two apple varieties (‘Granny Smith’ (GS) and ‘Early Red One’ (ERO)) with known differences in their postharvest behaviour, mainly firmness loss and susceptibility to superficial scald. Our results demonstrate that the higher storability and the limited loss of firmness of ‘GS’ fruit was associated to a higher acid content, mainly malic acid, that seemed to be regulated already at fruit set (20 DAFB). The reduced loss of firmness during storage in ‘GS’ was also associated to the fruit inability to produce ethylene upon harvest resulting from very low 1-aminocyclopropane-1-carboxylic acid oxidase (ACO) activity. Sugar accumulation, on the other hand, was similar among both varieties as was also observed for the rate of fruit growth or the fruit respiration pattern. In addition, the higher susceptibility of ‘GS’ if compared to ‘ERO’ to superficial scald was not associated to peroxidative damage (malondialdehyde accumulation) nor to higher levels of the sesquiterpene α-farnesene but rather mediated by a fruit antioxidant imbalance resulting from higher H2O2 levels and lower antioxidant (peroxidase) enzymatic capacity. The interplay between ethylene, respiration and antioxidants or sugars and organic acids during apple growth and development is further discussed.
The metabolic origin and emission by the leaves of the tropospheric trace gas acetaldehyde were examined in 4-month-old poplar
trees (Populus tremula × P. alba) cultivated under controlled environmental conditions in a greenhouse. Treatments which resulted in increased ethanol concentration
of the xylem sap caused significantly enhanced rates of acetaldehyde and ethanol emission by the leaves. Leaves fed [14C]-ethanol via the transpiration stream emitted [14C]-acetaldehyde. These findings suggest that acetaldehyde in the leaves is synthesized by a metabolic pathway that operates
in the opposite direction of alcoholic fermentation and results in oxidation of ethanol. Enzymatic studies showed that this
pathway is mediated either by alcohol dehydrogenase (ADH; EC 1.1.1.1) or catalase (CAT; EC 1.11.1.6), both constitutively
present in the leaves of poplar trees. Labelling experiments with [14C]-glucose indicated that the ethanol delivered to the leaves by the transpiration stream is produced in anaerobic zones of
submersed roots by alcoholic fermentation. Anoxic conditions in the rhizosphere caused by flooding of the root system resulted
in an activation of alcoholic fermentation and led to significantly increased ethanol concentrations in the xylem sap. These
results support the hypothesis that acetaldehyde emitted by the leaves of trees is derived from xylem transported ethanol
which is synthesized during alcoholic fermentation in the roots.
The temporal relationship between changes in ethylene production, respiration, skin color, chlorophyll fluorescence, volatile ester biosynthesis, and expression of ACC oxidase (ACO) and alcohol acyl-CoA transferase (AAT) in ripening banana (Musa L. spp., AAA group, Cavendish subgroup. 'Valery') fruit was investigated at 22°C. Ethylene production rose to a peak a few hours after the onset of its logarithmic phase; the peak in production coincided with maximal ACO expression. The respiratory rise began as ethylene production increased, reaching its maximum ≈30 to 40 hours after ethylene production had peaked. Green skin coloration and photochemical efficiency, as measured by chlorophyll fluorescence, declined simultaneously after the peak in ethylene biosynthesis. Natural ester biosynthesis began 40 to 50 hours after the peak in ethylene biosynthesis, reaching maximal levels 3 to 4 days later. While AAT expression was detected throughout, the maximum level of expression was detected at the onset of natural ester biosynthesis. The synthesis of unsaturated esters began 100 hours after the peak in ethylene and increased with time, suggesting the lipoxygenase pathway be a source of ester substrates late in ripening. Incorporation of exogenously supplied ester precursors (1-butanol, butyric acid, and 3-methyl-1-butanol) in the vapor phase into esters was maturity-dependent. The pattern of induced esters and expression data for AAT suggested that banana fruit have the capacity to synthesize esters over 100 hours before the onset of natural ester biosynthesis. We hypothesize the primary limiting factor in ester biosynthesis before natural production is precursor availability, but, as ester biosynthesis is engaged, the activity of alcohol acyl-CoA transferase the enzyme responsible for ester biosynthesis, exerts a major influence.
Changes in the concentration of free fatty acids (FA) and FA as constituents of neutral and polar lipids were determined during the course of ripening in the peel of ‘Golden Delicious’ apple fruit. The concentration of these FA was then related to previously examined volatile aroma substances in order to evaluate a possible quantitative relationship between both variables. In particular, the concentrations of the C18:1 and C18:2 FA in the free FA fraction were low in pre-climacteric fruit but rapidly increased three- to fourfold during the climacteric rise. Changes in FA concentrations during maturation were less pronounced in the neutral lipid fraction and almost absent in the polar lipid fraction. Treatment of immature fruit (harvested almost 5 weeks before the climacteric rise) with 100 μl l−1 ethylene increased the concentration of FA in the free and neutral lipid fraction but not in polar lipids. The increase in the free and ‘neutral lipid’ 18:2 FA after ethylene treatment in immature apples exceeded the concentration of this FA found in mature climacteric fruit. A hypothesis is discussed linking the examined dynamic changes of FA with previous results of ATP and aroma volatiles in an attempt to explain deficiencies in aroma volatile production in unripe and long-term stored apple fruit.
The volatiles of Asian pear (Seuri cultivar) were studied by high-resolution gas chromatography and combined gas chromatography/mass spectrometry (GC/MS) using vacuum simultaneous distillation-extraction of blended fruit and dynamic headspace sampling of intact and enzymatically inhibited blended fruit. Esters were the dominant constituents in all of the samples. A total of 72 components were identified in the headspace of intact fruit, including 39 constituents reported for the first time in pear. Odor unit values calculated from concentration and odor threshold data indicate that the following compounds are important contributors to pear aroma: ethyl 2-methylbutanoate, ethyl hexanoate, ethyl butanoate, ethyl 2-methylpropanoate, hexyl acetate, ethyl heptanoate, hexanal, ethyl pentanoate, and ethyl propanoate.
Fruit flavor is a result of a complex mixture of numerous compounds. The formation of these compounds is closely correlated with the metabolic changes occurring during fruit maturation. Here, we describe the use of DNA microarrays and appropriate statistical analyses to dissect a complex developmental process. In doing so, we have identified a novel strawberry alcohol acyltransferase (SAAT) gene that plays a crucial role in flavor biogenesis in ripening fruit. Volatile esters are quantitatively and qualitatively the most important compounds providing fruity odors. Biochemical evidence for involvement of the SAAT gene in formation of fruity esters is provided by characterizing the recombinant protein expressed in Escherichia coli. The SAAT enzyme showed maximum activity with aliphatic medium-chain alcohols, whose corresponding esters are major components of strawberry volatiles. The enzyme was capable of utilizing short- and medium-chain, branched, and aromatic acyl-CoA molecules as cosubstrates. The results suggest that the formation of volatile esters in fruit is subject to the availability of acyl-CoA molecules and alcohol substrates and is dictated by the temporal expression pattern of the SAAT gene(s) and substrate specificity of the SAAT enzyme(s).
Golden Delicious' apples (Malus domestica Borkh.) harvested at the preclimacteric and climacteric stages of ripening were stored for up to 8 months at 1C in air and under various controlled atmosphere(s) (CA), including ultralow oxygen (ULO) storage conditions. Aroma volatiles were measured at 2-month intervals in fruit ripened for 10 days at 20C. Fruits harvested at the climacteric stage produced more volatiles during all storage conditions than preclimacteric fruit. All CA storage treatments suppressed aroma production compared to cold storage. The greatest reduction was found under ULO (1% O 2 ) and high CO 2 (3%) conditions. A partial recovery of aroma production was observed when CA fruits were subsequently stored for 14 days under cold storage conditions. Suppression of aroma production under ULO conditions seems to be related to low fatty acid synthesis and/or degradation, and is restricted to volatiles having a straight C chain. Production of branched C-chain aroma compounds was suppressed by high CO 2 concentrations. The reduced capacity of aroma production during shelf life after ULO storage is confined to apple cultivars producing mainly ester compounds with a straight C-chain, e.g., `Golden Delicious'.
A protein determination method which involves the binding of Coomassie Brilliant Blue G-250 to protein is described. The binding of the dye to protein causes a shift in the absorption maximum of the dye from 465 to 595 nm, and it is the increase in absorption at 595 nm which is monitored. This assay is very reproducible and rapid with the dye binding process virtually complete in approximately 2 min with good color stability for 1 hr. There is little or no interference from cations such as sodium or potassium nor from carbohydrates such as sucrose. A small amount of color is developed in the presence of strongly alkaline buffering agents, but the assay may be run accurately by the use of proper buffer controls. The only components found to give excessive interfering color in the assay are relatively large amounts of detergents such as sodium dodecyl sulfate, Triton X-100, and commercial glassware detergents. Interference by small amounts of detergent may be eliminated by the use of proper controls.
Aroma and flavor characters of 'Gala' apples [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Manse 'Gala'] were identified by 10 trained panelists. A vocabulary of 13 aroma descriptors and 16 flavor descriptors were used to characterize changes in controlled atmosphere (CA) and air, or regular atmosphere (RA) storage over 20 weeks. When compared with RA storage, the intensity of fruity (pear, banana, and strawberry) and floral descriptors decreased after 10 weeks in CA for whole and cut fruit aroma and flavor. During the entire storage period under CA, aroma of cut apples retained high vegetative and citrus characters but had a less intense anise aroma. Sourness and astringency were significantly higher for CA-stored apples, and sweetness was significantly lower. A musty note was perceived in whole apples stored in CA for 20 weeks. Aroma of whole fruit stored for 16 weeks in CA followed by 4 weeks in RA was higher in fruitiness, banana, floral, and anise characters when compared with apples stored 20 weeks in CA. There was no difference between fruit stored in CA followed by RA versus CA stored apples for flavor and aroma of cut fruit. Changes in descriptor ratings during storage are discussed in relation to gas chromatography and olfactometry data obtained with the Osme method.
Typical apple (Malus domestica Borkh.) flavour develops during ripening. Maximum endogenous volatile concentration occurs at the climacteric peak but it is not known whether the volatile biosynthetic enzymes are constitutive or induced during the climacteric. Exposing apples to hypoxic conditions induces accumulation of high concentrations of acetaldehyde and ethanol; after return to air ethyl esters are enhanced and non‐ethyl esters decrease. There are differences in degree of ethyl ester enhancement among cultivars. These may be because of: differential activity or synthesis of alcohol acyl CoA transferase (AAT) or alcohol dehydrogenase (ADH); separate iso‐forms of AAT and ADH each with their own substrate specificity; variation in alcohol precursors in different cultivars; or a combination of all three. Volatile production is greater at higher temperatures in the range from 0 to 30°C but exposure to low temperatures (
Fruit flavor is a result of a complex mixture of numerous compounds. The formation of these compounds is closely correlated with the metabolic changes occurring during fruit maturation. Here, we describe the use of DNA microarrays and appropriate statistical analyses to dissect a complex developmental process. In doing so, we have identified a novel strawberry alcohol acyltransferase (SAAT) gene that plays a crucial role in flavor biogenesis in ripening fruit. Volatile esters are quantitatively and qualitatively the most important compounds providing fruity odors. Biochemical evidence for involvement of the SAAT gene in formation of fruity esters is provided by characterizing the recombinant protein expressed in Escherichia coli. The SAAT enzyme showed maximum activity with aliphatic medium-chain alcohols, whose corresponding esters are major components of strawberry volatiles. The enzyme was capable of utilizing short- and medium-chain, branched, and aromatic acyl-CoA molecules as cosubstrates. The results suggest that the formation of volatile esters in fruit is subject to the availability of acyl-CoA molecules and alcohol substrates and is dictated by the temporal expression pattern of the SAAT gene(s) and substrate specificity of the SAAT enzyme(s).
Changes in the odor-active volatile compounds produced by 'Gala' apples [Malus xsylvestris (L.) Mill. var. domestica (Borkh.) Mansf. 'Gala'] were measured after 4, 10, and 20 weeks storage at 1 °C in regular atmosphere (RA) or controlled atmosphere (CA), and 16 weeks in CA followed by 4 weeks in RA. Aroma was evaluated using the gas chromatography-olfactometry method Osme. Production of volatile esters decreased along with corresponding fruity aromas during CA storage. Hexyl acetate, butyl acetate, and 2-methylbutyl acetate were emitted in the largest amounts and perceived with the strongest intensities from RA-stored fruit. While hexyl acetate and butyl acetate concentrations and aroma intensities decreased during CA storage, 2-methylbutyl acetate remained at the RA concentration until apples had been stored 16 weeks in CA. Perception intensities of methylbutyrate esters with apple or berrylike odors decreased less than straight chain esters in CA-stored fruit. 4-Allylanisole, β-damascenone, and 1-octen-3-ol, as well as an unknown compound with a watermelon descriptor, were perceived more in RA-stored fruit than in CA-stored apples. Factor analysis indicated the importance of these compounds in 'Gala' apples stored 4 weeks in RA. Even though these compounds do not have an apple odor, they contribute to fresh 'Gala' aroma.
The quality of scab-resistant apple cv. ´Golden Orange`, as influenced by harvest time, was evaluated in comparison with the scab-susceptible cv. ´Golden Delicious` (clone B) (Golden B). Fruits from both cultivars were harvested on three different dates and ripened at 20°C. Quality parameters at harvest [fruit mass, flesh firmness, starch hydrolysis, soluble solids content (SSC), titratable acidity (TA)], colour, ethylene production (EP), development of headspace volatiles during post-harvest ripening, and sugar and organic acid compositions at the end of ripening were measured. At harvest, firmness, SSC, TA, starch hydrolysis and Streif Index indicated that ´Golden Orange` apples were less mature than ´Golden B` apples, even if their skin colour was more yellow. Generally, during post-harvest ripening, ´Golden Orange` apples showed lower EP, lower total volatile production, and their skin turned as yellow as ´Golden B`. ´Golden Orange` apples differed from ´Golden B` in their sugar, organic acid and volatile compound compositions. These differences were independent of harvest date and could explain the different sensory descriptions peculiar to this cultivar. Compounds that contributed most to the characteristic aroma were ethyl 2-methylbutanoate and hexyl and 2-methylbutyl acetate in ´Golden B` apples, and ethyl and hexyl 2-methylbutanoate, ethyl hexanoate and hexyl acetate in ´Golden Orange` fruit, at all harvest times. The concentrations of these volatiles were largely dependent on harvest date and on the length of post-harvest ripening.
This work determined the effects of harvest date and storage conditions on fruit quality and aroma production in `Fuji' apples over two years. Fruits were harvested on two dates and stored in different atmospheres: AIR (21% O2 + 0.03% CO2); SCA (3% O2 + 2% CO2); ULO1 (1% O 2 + 1% CO2) and ULO2 (1% O2 + 2% CO2). After 3, 5 and 7 months of storage (plus 1, 5 and 10 days at 20 °C) fruit firmness, titratable acidity, soluble solids, skin colour, physiological disorders and aroma production were measured. `Fuji' apple quality was maintained during the harvest and storage periods, however fruit quality was better in controlled than AIR atmospheres. ULO1 was more effective in maintaining firmness during storage than other treatments, especially in earlier-harvested apples. Differences in soluble solids and titratable acidity were not always significant. The incidence of physiological disorders was low. Maximum aroma production was reached in fruits stored in AIR atmosphere (after 5 days at 20 °C) for early-harvested fruits in 2000/2001 season. In general, aroma levels decreased over time in different storage treatments. Fruits stored in ultra low oxygen atmospheres showed low aroma production, especially after long storage periods (7 months) in ULO2 atmosphere. ULO1 (1% O 2 + 1% CO2) was a good atmosphere for maintaining quality and aroma production in `Fuji' apples during storage and shelf-life periods.
The relationship between acetate ester-forming activity of acetyl CoA alcohol transferase (ACAT), non-ethylene volatile emission, and flesh volatile content of “Rome” apples (Malus domestica Borkh.) after removal from 9 months storage in low-oxygen environments was investigated. Apple samples held at 0–1°C were removed from refrigerated air (RA) or controlled-atmosphere (CA) storage at 1.0 or 0.5% v/v O2/1% CO2 and placed in ambient laboratory conditions. Every three days fruit flesh and headspace were analyzed for volatile compounds using capillary gas chromatography. Acetate ester forming activity was assayed spectrophotometrically on partially-purified extracts of cortical tissue. Patterns of acetate ester formation depended upon storage environment and alcohol moiety precursor. Ethyl acetate content was always higher in the headspace and flesh of RA fruit, regardless of time after storage. Propyl acetate concentrations in CA stored apple flesh were higher until post-storage day 12 when they decreased. Headspace propyl acetate levels were higher in RA controls until days 9–15 when more emanated from CA fruit. Butyl acetate concentrations were lower in flesh and headspace of CA fruit until day 15, when RA fruit headspace levels decreased. Headspace and flesh concentrations of 2-methyl-1-butyl acetate were higher in CA apples. Acetate ester-forming activity was detectable at day 0 in 1.0% oxygen-stored fruits, but not in 0.5% oxygen-stored fruits. By post-storage day 9, ACAT activity in CA apples reached maximal levels, only to decrease by day 15. RA-stored apples had more ACAT activity at day 0, but did not substantially increase in activity like the 0.5% oxygen-stored apples removed from CA storage. It is unknown whether the ACAT protein is reactivated by exposure to ambient oxygen or synthesized de novo.
Little change was observed in the concentration of sitosterol, the principal free sterol of apple, during ripening of the fruit in air at 12°. Phospholipid increased by ca 10% during the first 15–18 days and thereafter showed little change. Phosphatidylcholine increased during ripening whilst phosphatidylethanolamine exhibited a transitory increase in the first 7–18 days. Incorporation of [14C]acetate into free sterol by apple cortical discs showed little change during ripening but incorporation into phospholipids increased substantially between days 1 and 15 with a 27-fold increase in incorporation into phosphatidylcholine and an 8-fold increase into phosphatidylethanolamine and phosphatidylinositol.
Changes in fermentation volatiles and enzymes were studied in preclimacteric and postclimacteric Bartlett pears (Pyrus communis L.) kept in air, 0.25% O[sub 2], 20% O[sub 2] + 80% CO[sub 2], or 0.25% O[sub 2] + 80% CO[sub 2] at 20 C for 1, 2, or 3 days. All three atmospheres resulted in accumulation of acetaldehyde, ethanol, and ethyl acetate. The postclimacteric pears had higher activity of pyruvate decarboxylase (PDC) and higher concentrations of fermentation volatiles than those of the preclimacteric fruit. For the preclimacteric pears, the 0.25% O[sub 2] treatment dramatically increased alcohol dehydrogenase (ADH) activity, which was largely due to the enhancement of one ADH isozyme. Exposure to 20% O[sub 2] + 80% CO[sub 2] slightly increased ADH activity, but the combination of 0.25% O[sub 2] + 80% CO[sub 2] resulted in lower ADH activity than 0.25% O[sub 2] alone. Ethanolic fermentation in Bartlett pears could be induced by low O[sub 2] and/or high CO[sub 2] via (1) increased amounts of PDC and ADH; (2) PDC and ADH activation caused by decreased cytoplasmic pH; or (3) PDC and ADH activation or more rapid fermentation due to increased concentrations of their substrates (pyruvate, acetaldehyde, or NADH).
A series of straight chain and branched esters (ethyl acetate to 2-nonyl acetate) were purified by preparative gas chromatography and their odour thresholds were determined using sensory panel methods. Pentyl acetate and 2-butyl acetate had the lowest odour thresholds of the straight chain and branched acetates, respectively. Addition of a methyl group at the 1-position of the alcohol did not have a consistent effect on the odour threshold. For ethyl acetate, propyl acetate, butyl acetate and heptyl acetate the addition of a methyl group in the 1-position caused a decrease in the odour threshold; whereas for pentyl acetate, hexyl acetate and octyl acetate the addition of a methyl group in the 1-position caused an increase in the odour threshold.
Melon varieties (Cucumis melo L.) differ in a range of physical and chemical attributes. Sweetness and aroma are two of the most important factors in fruit quality and consumer preference. Volatile acetates are major components of the headspace of ripening cv. Arava fruits, a commercially important climacteric melon. In contrast, volatile aldehydes and alcohols are most abundant in cv. Rochet fruits, a nonclimacteric melon. The formation of volatile acetates is catalyzed by alcohol acetyltransferases (AAT), which utilize acetyl-CoA to acetylate several alcohols. Cell-free extract derived from Arava ripe melons exhibited substantial levels of AAT activity with a variety of alcohol substrates, whereas similar extracts derived from Rochet ripe melons had negligible activity. The levels of AAT activity in unripe Arava melons were also low but steadily increased during ripening. In contrast, similar extracts from Rochet fruits displayed low AAT activity during all stages of maturation. In addition, the benzyl- and 2-phenylethyl-dependent AAT activity levels seem well correlated with the total soluble solid content in Arava fruits. Keywords: Aroma; volatile acetates; biosynthesis; alcohol acetyltransferase; melons (Cucumis melo. L)
Volatile constituents of fresh apricots (Prunus armeniaca) of the Blenheim variety were analyzed by capillary gas chromatography and gas chromatography-mass spectrometry. The fruit was sampled by simultaneous vacuum steam distillation-extraction. A total of 49 components were identified in the extract, including 25 constituents reported for the first time in apricot. Linalool, lactones, and C6 lipid peroxidation products were the major constituents in the extract. Odor unit values, calculated from concentration and odor threshold data, indicate that the following compounds are major contributors to blended apricot aroma: β-ionone, linalool, γ-decalactone, hexanal, (E)-2-hexenal, (E,E)-2,4-decadienal, (E)-2-nonenal, and γ-dodecalactone. Headspace analyses of the intact fruit led to the identification of 83 components, 60 of which had not been previously reported in apricot. Esters were the dominant constituents in the headspace samples.
Bisbee Delicious apples were stored for 6 months in controlled atmosphere (CA) where oxygen concentration was increased from 1 to 2% after 3, 4, or 5 months. Volatile emission after storage was highest in late-harvest apples. Increasing the oxygen concentration during storage did not increase loss of firmness, soluble solids content, or titratable acidity, and volatile emission was not enhanced. All CA treatments reduced volatile emission compared to that of air-stored fruit. Esters were the majority of volatiles detected. Emission of lipid-derived esters was inhibited more by CA treatments than were esters resulting from amino acid metabolism.
The enzymes acylhydrolase, lipoxygenase, and fatty acid hydroperoxide lyase were found in cell-free extract of olive fruit. Triacylglycerols and phospholipids are hydrolyzed to free fatty acid, mainly polyunsaturated, by acylhydrolase. From linoleic and linolenic acids 9- and 13-hydroperoxides were formed by lipoxygenase. The lyase cleaves the 13-hydroperoxides of linoleic and linolenic acids to form the volatile aldehydes hexanal and cis-3-hexenal, respectively; the enzyme does not act on 9-hydroperoxides of these acids. Incubation of ripe olive fruit tissue disks resulted in biological conversion of hexanal and trans-2-hexenal to corresponding alcohols. Hexyl alcohols were converted to their acetate esters during the incubation with olive fruit tissue. A sequential enzymatic pathway for the formation of green odor compounds in virgin olive oil is proposed.
Volatile compounds produced by Delicious apple fruit during the 8-week transition period from pre- to postclimacteric were identified using headspace sampling of intact fruit and GC-MS. As apple development progressed, concentrations of butanal, pentanal, (E)-2-hexenal, and heptanal declined. Concentrations of most alcohols were variable throughout the same period, but 2-methyl-1-butanol was present only in samples from the late harvests. Ketones lacked a discernible pattern, while some esters, most notably 2-methylbutyl acetate, appeared in samples before the onset of ethylene production. Acetic acid was present in the samples throughout the harvest period, indicating alcohol substrate availability may be the limiting factor in ester formation. Production of several acetate esters preceded the increased ethylene levels associated with the onset of apple ripening.
‘Golden Delicious’ apples were stored in semicommercial chambers in normal atmosphere and in various controlled atmospheres (CAs) in which oxygen and carbon dioxide contents were held at 10, 20 or 30 l m−3 for 3, 5 or 7 months. Following storage, fruits were kept at 20 °C for 1, 5 or 10 days, after which quality parameters were determined and aroma components were obtained and analysed by the dynamic headspace method and quantified by gas chromatography–mass spectrometry. The highest emission of volatile components was obtained after 5 months of storage. Esters were the main compounds released after cold storage in all conditions. Normal cold storage gave the highest amounts of straight-chain esters, while low-oxygen atmospheres gave the highest amounts of branched-chain esters. After 3 and 7 months there were no significant differences in volatiles on comparing fruits from different storage conditions. Low-oxygen atmospheres had beneficial effects on fruit firmness, titratable acidity and colour. Apples coming from low-oxygen atmospheres gave the highest sensory score after 5 months of cold storage.© 2000 Society of Chemical Industry
The effect of exogenous short-chain n-alcohols on the concentrations of main aroma components in mature intact Red Delicious apples and aged apple tissue discs has been studied. Storage of intact apples in an atmosphere containing ethanol vapours for 24 h resulted in a more than threefold increase in the sum of ethyl ester concentrations. The simplified model of tissue discs was applied to examine the influence of various ethanol concentrations on rate and time course of ester formation. On supplying a range of n-alkan-1-ols and 2-keto valeric acid in equimolar amounts to the discs, maximum conversion into esters was found with butanol and pentanol. The possibility of an in vivo aroma enrichment before processing of fruits is discussed.
Ester synthesis by apples supplied with alcohols (C2–C8) and methyl esters of short chain fatty acids (C4–C8) was studied using gas chromatographic analysis of the products. The substrates were supplied as vapours to whole fruits stored in 2% O2 at 3°C. The alcohols were converted to the corresponding acetate ester; butanol, pentanol and hexanol were converted most rapidly. The methyl esters of short chain fatty acids (Cn) were converted to esters with an alkyl group (Cn-2, Cn-4) confirming the presence in whole fruits of an active β-oxidation pathway for fatty acids. Ester synthesis was stimulated when apples were supplied with methyl octanoate at different periods during long term storage in 2% O2. Treatment of the fruit immediately postharvest did not enhance ethylene synthesis.
Recently, there has been increased attention in the literature on the use of ensemble methods in multivariate regression and classification. These methods have been shown to have interesting properties for both regression and classification. In particular, they can improve the accuracy of unstable predictors. Ensemble methods have so far been little studied in situations that are common for calibration and prediction in chemistry, i.e. situations with a large number of collinear x-variables and few samples. These situations are often approached by data compression methods such as principal component regression (PCR) or partial least squares regression (PLSR). The present paper is an investigation of the properties of different types of ensemble methods used with PLSR in situations with highly collinear x-data. Bagging and data augmentation by simulated noise are studied. The focus is on the robustness of the calibrations. Real and simulated data are used. The results show that ensembles trained on data with added noise can make PLSR robust against the type of noise added. In particular, the effects of sample temperature variations can be eliminated. Bagging does not seem to give any improvement over PLSR for small and intermediate numbers of components. It is, however, less sensitive to overfitting. Copyright © 2005 John Wiley & Sons, Ltd.
Spectrophotometric assays for hydroperoxide lyase have traditionally measured the loss in absorption at 234 nm due to the
disruption of conjugated diene in the fatty acid hydroperoxide. However, that assay does not distinguish between hydroperoxide
lyase and hydroperoxide dehydrase activities, both of which cause a loss of conjugation in the substrate hydroperoxide. A
new assay has been developed which is specific for hydroperoxide lyase. It is based on the ability of hydroperoxide lyase
products, aldehydes and ω-oxoacids, to serve as substrates for yeast alcohol dehydrogenase. Thus, the new hydroperoxide lyase
assay is a coupled enzyme assay, which is conducted spectrophotometrically at 340 nm and measures the oxidation of nicotinamide
adenenine dinucleotide, reduced form (NADH). In addition to its specificity for hydroperoxide lyase, the coupled assay allows
higher concentrations of both fatty acid hydroperoxide substrate and crude enzyme extracts than the assay conducted at 234
nm.
The maturity of apple fruit at harvest was examined as a factor affecting later flavour development. Respiration, ethylene production and aroma compound emanation at 20 °C from ripening ‘Golden Delicious’ apple fruit harvested at different stages of maturity and their changes during ripening were studied. Volatile compound production was highly maturity-dependent and closely related to the changes in the respiratory rate and ethylene production. Earlier-harvested fruit (4 weeks ahead of the climacteric rise) had reduced respiration, and ethylene production, with lower and later total aroma synthesis than that for optimal-harvested fruit. Among the 36 aroma compounds identified by GC-MS, four flavour and character impact compounds were examined in detail. The onset of production and rates of synthesis of butylacetate, hexylacetate, 2-methylbutylacetate and ethyl-2-methylbutanoate during maturation and ripening were determined. The production trends of straight-chain (butylacetate and hexylacetate) and branched-chain (2-methylbutylacetate and ethyl-2-methylbutanoate) volatile compounds were similar to that of total aromas, except for a later increase in ethyl-2-methylbutanoate. As fruit development approached optimal harvest date for fruit quality, respiration, ethylene- and aroma production occurred with less of a delay reaching greater maximum levels. It is suggested that fundamental physiological processes such as respiration and ethylene production may be limiting factors for volatile production in earlier-harvested fruit.
Production of volatile aroma compounds, and quality parameters, were monitored in relation to the activity of lipoxygenase, pyruvate decarboxylase, alcohol dehydrogenase and alcohol o-acyltransferase during maturation of ‘Fuji’ apples. Acetate esters increased during maturation and were quantitatively the most significant compounds contributing to ‘Fuji’ aroma. Increase in acetate ester production was associated with the availability of the necessary alcohol precursors. Principal component analysis revealed a clear separation according to sampling date, which accounted for up to 67% of total variance, and allowed ‘Fuji’ apples used in this study to be classified into three ripeness stages. Overall the results suggest that precursor availability for the related enzymes is a more significant factor than enzyme activity for the development of aroma during on-tree maturation of ‘Fuji’ apples.
Standard quality parameters, consumer acceptance, and volatile compound emission of ‘Pink Lady®’ apples (Malus × domestica Borkh.) were measured at harvest and after 14 and 25 weeks of cold storage in three different atmospheres. After storage, fruit were left to ripen for 1 and 7 days at 20 °C before instrumental and sensory measurements were performed. Data were subjected to principal component analysis (PCA) and partial least square regression (PLSR). PLSR results indicated that the parameters positively influencing acceptability were soluble solid content, titratable acidity, background colour, and emission of hexyl 2-methylbutanoate, hexyl hexanoate, hexyl propanoate, butyl 2-methylbutanoate, 2-methylbutyl acetate and butyl propanoate. Results of sensory analyses revealed the treatments considered in this work could be split into two levels of acceptability.
Emission of aroma volatile compounds and some related enzyme activities (LOX, PDC, ADH, and AAT) were assessed in ‘Fuji’ apples (Malus × domestica Borkh.) during shelf life at 20 °C following cold storage under air or under three different CA conditions (3 kPa O2:2 kPa CO2; 1 kPa O2:1 kPa CO2; or 1 kPa O2:2 kPa CO2). Data were used for principal component analysis (PCA) and partial least-square regression (PLSR) analysis of results. LOX activity was partly inhibited by hypoxic conditions, and thus could have contributed to differentiation between air- and CA-stored fruit. Accordingly, emission of straight-chain esters was also higher in air- than in CA-stored fruit. In contrast, PDC activity was responsible for part of the differences between low (3 kPa) and ultra-low (1 kPa) O2 storage conditions, probably by providing substrates for AAT action. AAT activity afforded no satisfactory differentiation between samples, and therefore it is suggested that substrate availability is a more decisive factor than enzyme activity for volatile production after storage. The PCA and PLSR models developed in this work were not useful for discrimination between the two studied ultra-low O2 conditions.
The production of butyl and hexyl acetates and the contents of ethanol and acetaldehyde in relation to the activity of some related enzymes (lipoxygenase, pyruvate decarboxylase, alcohol dehydrogenase and alcohol o-acyltransferase) was studied in ‘Doyenne du Comice’ pears during ripening at 20 °C, following long-term cold storage under different conditions: air, or CA in 2 kPa O2 with various CO2 partial pressures (0.7, 2 or 5 kPa). A decrease in volatile production was found for fruit stored under low O2 upon return to ambient conditions. Results suggest that inhibition of volatile biosynthesis by CA storage is caused mainly by limited precursor/substrate supply to the related enzymes rather than by enzyme degradation or inactivation. Ethanol production by the fruit did not correlate well with ADH activity. The possibilities of a feedback inhibition of enzyme activity by excess product and of oxidation into acetaldehyde upon return to air are discussed. Hypoxic conditions caused a decrease in LOX activity after 5 months storage, possibly leading to shortage of lipid precursors for ester biosynthesis.
A protein determination method which involves the binding of Coomassie Brilliant Blue G-250 to protein is described. The binding of the dye to protein causes a shift in the absorption maximum of the dye from 465 to 595 nm, and it is the increase in absorption at 595 nm which is monitored. This assay is very reproducible and rapid with the dye binding process virtually complete in approximately 2 min with good color stability for 1 hr. There is little or no interference from cations such as sodium or potassium nor from carbohydrates such as sucrose. A small amount of color is developed in the presence of strongly alkaline buffering agents, but the assay may be run accurately by the use of proper buffer controls. The only components found to give excessive interfering color in the assay are relatively large amounts of detergents such as sodium dodecyl sulfate, Triton X-100, and commercial glassware detergents. Interference by small amounts of detergent may be eliminated by the use of proper controls.
Starking Delicious apples were cold-stored in semicommercial chambers in normal atmosphere and in different controlled atmospheres in which oxygen and carbon dioxide were held at 1%, 2%, and 3% for 3, 5, and 7 months. After storage, fruit was kept at ambient temperature (20 degrees C) for 1, 5, and 10 days. The volatile emission was collected and analyzed. After all storage periods and conditions, the total aromatic volatile emission was higher than at commercial harvest. The highest emission of volatile components was obtained after 5 months of storage, in which controlled-atmosphere conditions gave a lower concentration than normal cold storage. Esters were the main volatiles detected (>98%). Acetate ester concentrations after all storage periods assayed were higher at 3% and 2% O(2)/CO(2). The components that contributed most to the characteristic aroma of Starking Delicious were ethyl 2-methylbutyrate, ethyl butyrate, and ethyl hexanoate. Their concentrations were higher after 5 months of storage and also during poststorage at ambient temperature (20 degrees C).
Expression of the yeast Delta9 desaturase gene in tomato (Lycopersicon esculentum Mill.) resulted in changes in the profiles of fatty acids in tomato leaves. Transgenic leaves displayed a dramatic increase in cis-Delta9 16:1, which only existed in a small quantity in control leaves. Also higher, but not as dramatic, were 18:1 and 16:3 fatty acids. Several fatty acids, viz. 16:0, 18:0, and 18:3 declined in transgenic leaves. Changes in fatty acids were accompanied by changes in certain volatile compounds derived from fatty acids. On a percentage basis, most notable increases (>3-fold) were 1-hydroxy-2-butanone, 1-penten-3-ol, heptanal, 3-hexen-1-ol, 2-octanol,cis-3-hexenal, hexanal and 2-nonenal. Several flavor compounds not known to be biochemically derived from fatty acids, viz. 2-ethyl-furan, 5-ethyl-2-[5H]-furanone, eugenol, and 2-ethylthiophene also showed sharp increases in transgenic leaves.
Regulation of ethylene biosynthesis or action has a major effect on volatiles production in apples. To understand the biochemical processes involved, we used Greensleeves apples from a transgenic line with a high suppression of ethylene biosynthesis. The study was focused at the level of the aroma volatile-related enzymes, including alcohol acyltransferase (AAT), alcohol dehydrogenase (ADH), and lipoxygenase (LOX) and at the level of amino acids and fatty acids as aroma volatile precursors in peel and flesh tissues. In general, volatile production, enzyme activity levels, and precursor availability were higher in the peel than the flesh and were differentially affected by ethylene regulation. AAT enzyme activity showed a clear pattern concomitant with ethylene regulation. Contrarily, ADH and LOX seem to be independent of ethylene modulation. Isoleucine, an important precursor of aroma compounds including 2-methylbutanoate esters, showed a major increase in the peel during ripening and responded significantly to ethylene regulation. Other important aroma volatiles precursors, like linoleic and linolenic acid, showed an accumulation during ripening associated with increases in aldehydes. The significance of these changes in relation to aroma volatile production is discussed.