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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 main byproduct of apple agribusiness (apple bagasse) can represent 20-40% of the total apple quantity processed and is currently being used as animal feed or organic fertilizer [18]. Some terpenes are found on apples (i.e., limonene) [19,20], and other terpenes, such as ␣-pinene, -pinene and linalool, have been reported [21]. ...
... Other terpenes are present in many plant species and part of the main composition of many essential oils. Therefore, orange waste, apple pomace and pine substrates, terpenes, such as camphene, myrcene, p-cymene, terpinolene, cadinene, sabinene, longifolene, germacrene, linalool, terpinene, -phellandrene, 3carene, spathunelol, ␣-farnesene and citral have been found [8][9][10][13][14][15][19][20][21]. In addition to those previously mentioned, many of these terpenes have important biological properties and can be used as precursors to products of interest in various industrial fields. ...
... The apple pomace is expected to contain a small amount of monoterpenes. Limonene was found as the only terpene in Pink Lady apples but only at low concentrations [19], which is similar to this study where the limonene was the main monoterpene (3.42 g/100 g of extract). ␣-Pinene (0.64) and pinene (2.28) were also found at lower concentrations. ...
... 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). ...
... Aroma is a complex mixture product of aromatic volatile organic compounds, which has an important influence on the overall flavor of fruits and vegetables (Baldwin, 2002). As aroma is one of the most appreciated fruit characteristics, volatile organic compounds are likely to play a key role in determining the perception and acceptability of products by consumers (Villatoro et al., 2008). ...
... Different species of fruits have their unique aroma characteristics. For example, the mature apple fruits emits fruit odor (Villatoro et al., 2008), green grass is the primary aroma characteristic flavor in Asian pear (Li, 2012), tomato (Tadmor et al., 2002) and grape (Conde et al., 2007;Ruther, 2000;Watkins and Wijesundera, 2006), and aliphatic flavor is detected as the primary aroma flavor in P. ussuriensis pear (Qin et al., 2012). In this study, fruit, aliphatic and green were detected as the three primary aromas characteristics in the 12 Occidental pears. ...
Aroma is an appreciated fruit characteristic, and volatile flavor plays a key role in determining the perception and acceptability of fruit products by consumers. Occidental pear (Pyrus communis) is an aroma-dense fruit, and evaluation of the fruit aroma of different cultivars is meaningful to pear-breeding programs. In this study, we dissected the aroma composition and concentration of mature fruits from 12 Occidental pear cultivars. A total of 335 volatile organic compounds were identified, which were primarily esters, alcohols, alkanes, acids, ketones, terpenes and aldehydes. The concentration of total aroma was highest in ‘Alexandrine Douillard’ (18.73 μg/g), whereas the lowest total concentration was in ‘Bartlett-Max Red’ (0.33 μg/g). The principal aroma biosynthetic
pathway of ‘Bartlett-Max Red’, ‘Abate Fetel’ and ‘Butirra Rosata Morettini’ was the fatty acid pathway, whereas the amino acid pathway primarily functioned in ‘Bartlett’, ‘Yubileen Dar’, ‘Doctor Jules Guyot’ and ‘Alexandrine Douillard’. Based on the ABC's of Perfumery System, the 12 pear cultivars were divided into two groups, ‘La france’, ‘Abate Fetel’, ‘Bartlett’, ‘Beurre Bosc’, ‘Alexandrine Douillard’, ‘Doctor Jules Guyot’ and ‘Yubileen Dar’ as
the fruit scent type (Group one); and ‘Butirra Rosata Morettini’, ‘beurré Hardy’, ‘Bartlett-Max Red’, ‘Clapp Favorite’ and ‘Red Clapp Favorite’ as the aliphatic scent type (Group two).
... Hypothesis is not tested in this study. In climacteric fruit, the esters volatile compounds are prevalent in strawberries (Severo et al., 2011), apple (Villatoro et al., 2008) and melon (Obando-Ulloa et al., 2008). ...
... In the same species, the profile of volatile compounds is different between climacteric and non-climacteric fruits (Obando-Ulloa et al., 2008). Villatoro et al. (2008) demonstrated that during the ripening of apples, there was increased esters production primarily by the accumulation of substrate for the action of the enzyme alcohol acyltransferase. This is due to the action of other enzymes such as precursor lipoxygenase (LOX), hydroperoxide lyase (HPL), pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH) that give rise to the substrates. ...
Melons are good models used for explaining the physiological and biochemical changes in postharvest ripening. In this study, transgenic melons expressing apple ACC oxidase gene when treated with ethylene (AS3) were evaluated. Cell wall expression (MPG1; MPG2), ethylene synthesis ACC oxidase (ACCO1), flavour synthesis AAT (alcohol acyltransferase) and physiochemical parameters such as pulp firmness, titratable acidity (TA), soluble solid content (SSC), volatile esters, ethylene productions, antioxidant assay capacity and ascorbic acid content were evaluated. In cell wall expression analysis, MPG1 increased when fruits of transgenic melons were exposed to ethylene; showing they are ethylene- dependent. MPG2 decreased gradually when fruits were subjected to ethylene application. Fruit firmness was modified in transgenic fruits when ethylene was applied. There was a great reduction similar to that of non- transgenic fruits. However, TA in transgenic fruits remained lower than in non- transgenic fruit. The ethylene applied in transgenic fruit made the titratable acid to increase during 48 h and after it, a reduction was observed. In relation to soluble solid contents, transgenic fruits treated with or without ethylene did not reduce gradually compared to the wild type melons in all the periods. Ethylene productions in transgenic fruits were reestablished when ethylene was applied, exhibiting the same behavior as transgenic fruits. Antioxidant assay levels were more active in transgenic fruits when ethylene was applied than in control fruits, and it was only in transgenic fruits without ethylene. Ascorbic acid was kept in transgenic fruits with or without the application of ethylene. Results obtained show that the application of ethylene in transgenic ACC oxidase melons is able to change the metabolism of the cell wall, flavors and antioxidant capacity levels in fruit during the ripening process. Keywords: Esters, antioxidant, solid soluble content, ascorbic acid African Journal of Biotechnology , Vol 13(31) 3252-3261
... 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 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 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
... In this context, several studies focused the chemical characteristics, volatile and microbiological aspects of vegetal matrices used in production of distilled beverages [20,[51][52][53][54]. The applied techniques in volatile compounds assessment are infrared spectroscopy [55], gas-chromatography coupled with mass-spectrometry [51,52,56,57] and gas-chromatography with flame ionisation detector [53,58]. ...
... In strawberry trees (Arbutus unedo L.), these compounds were found to have high concentrations, but the concentrations decreased as the fruit ripened (Oliveira et al. 2011). Additionally, (Z)-3-hexenyl acetate had relevant levels in raspberry (Rubus idaeus), which declined during the ripening process (Robertson et al. 1995), and hexyl acetate predominated in greater quantities in the final stages for the Pink Lady Ò apple (Villatoro et al. 2008). ...
Lulo (Solanum quitoense Lam.) is an exotic fruit cultivated in Colombia. During ripening and senescence, this climactic fruit undergoes biochemical processes that produce the volatiles responsible for its aroma. This study aimed to evaluate the changes in the volatile content during the ripening and senescence of lulo. Analysis of the volatile composition of lulo harvested in each of its five ripening stages and during its senescence time when stored at 18 ± 2 °C was performed using HS-SPME with GC–MS. Throughout ripening, the most notable change was the transformation of alcohols such as (Z)-3-hexen-1-ol and 1-penten-3-ol to afford esters such as (Z)-3-hexenyl acetate and ketones such as 1-penten-3-one. Some acids reacted with alcohols to produce acetate and hexanoate esters, concentrations which increased more than sixfold between stage one and five. Moreover, all the major compounds were C6 straight chain compounds related to the lipoxygenase pathway. During senescence, majority of compounds were methyl esters, which increased in concentration consistently until day eight. Remarkably, the content of methyl butanoate increased from 0.9% of the total amount of volatiles on day two up to 76.4% on day eight. Some of these volatiles are probably contributors to the “off flavor” during senescence.
... As reported by Mattheis et al. (1991), the balance of ethyl ester production is a key metabolic aspect in apples stored under low oxygen conditions with consequences on sensory properties of the fruit. In fact, these compounds have been described as potent odorants that are important contributors to the aroma of apple due to their low organoleptic threshold (Dixon and Hewett, 2000;Echeverria et al., 2004;López et al., 2007;Villatoro et al., 2008;Ferreira et al., 2009;Ortiz et al., 2011). Alcohols and some esters, such as ethyl acetate, are generally produced at high levels but, since they have a high organoleptic threshold they likely have less impact on fruit flavour and are rarely reported to be impact compounds in fruit aroma; these molecules confer background notes to the characteristic flavour of each fruit (Buttery, 1993;Iglesias et al., 2012). ...
Keywords: Hypoxic metabolism Ultra low oxygen (ULO) Dynamic controlled atmosphere (DCA) Malus domestica Postharvest Metabolic profiling A B S T R A C T The response of apple fruit to storage conditions based on low oxygen protocols depends on their genetic background. In order to elucidate common and divergent processes characterizing the metabolic changes under hypoxia, fruit of two apple (Malus domestica) varieties ('Granny Smith', GS, and 'Red Delicious', RD) were stored under two different low oxygen protocols (Ultra Low Oxygen, ULO, at 0.9 kPa oxygen, and Dynamic Controlled Atmosphere based on chlorophyll fluorescence, DCA-CF, between 0.2 and 0.55 kPa oxygen) for up to 200 and 214 days of storage for GS and RD samples, respectively. Through an integrated metabolomics approach (1 H NMR, GC–MS, HS-SPME-GC–MS analyses) a total of 130 metabolites (volatiles and non-volatiles) were identified. Most of them (117) were common to both cultivars; 95 were significantly different between both cultivars when comparing the whole set of data (ULO + DCA-CF), whereas 13 volatile compounds, identified via HS-SPME-GC–MS, were specific for either GS or RD. Multivariate analyses (PCA and PLS) of the whole dataset allowed to clearly discriminate between GS and RD samples. When storage condition was used as a categorical response variable, a lower percentage explained variance was obtained as this effect was overshadowed by the large effect of storage time. After 4 months of storage, RD underwent more pronounced metabolic compositional changes of the cortex, possibly associated with the evolution of ripening. Based on the accumulation pattern of pyruvate-derived metabolites (ethanol, acetaldehyde, lactate, alanine) it can be hypothesized that there are two main metabolic reconfiguration strategies in GS and RD to regenerate NAD + and cope with energy crisis under hypoxia. GS showed more pronounced responses through changes in the nitrogen metabolism and limited induction of the ethanol fermentation while the latter was highly induced in RD under both ULO and DCA-CF. Marked differences were detected between the VOC profiles of the two cultivars regardless storage conditions. Ethyl esters and 2-methylbutyl derivatives appeared finely modulated by the oxygen level in GS and RD apples, respectively.
... In the case of RA apples, ester production did not show to be dependent on AAT enzyme activity. Echeverría et al. (2004a) and Villatoro et al. (2008) noted that modifications in AAT specific activity could not explain the observed behavior in the production of esters. Figure 4 shows ADH specific activity in apples stored under CA and RA (P < 0.05). ...
Biosynthesis of volatile compounds (VC), as well as activity of related en-zymes (lipoxygenase LOX, alcohol acyltransferase AAT, and alcohol dehydro-genase ADH), and fatty acids (palmitic, stearic, oleic, linoleic and linolenic ac-ids) were assessed in Golden Delicious fruit apples (Malus domestica Borkh.) during 1 ºC storage at different atmosphere conditions. Three atmosphere conditions were used: 21 % O2 and > 1 % CO2 (Regular Atmosphere, RA), 3 % CO2 and 2 % O2 (Controlled Atmosphere, CA), and CA, with 7 d under RA conditions (CA + RA), to evaluate the effect of shorts periods under air stor-age. CA conditions inhibited the production of butyl acetate and hexyl acetate esters, and increased hexanol concentration. Production of the branched ester 2-methyl butyl acetate did not decrease under CA conditions. As a result of 7 d under RA, butyl acetate and hexyl acetate in CA + RA increased, mainly after one month of storage. Storage under CA conditions inhibited LOX and AAT ac-tivity at some stages whereas ADH activity increased during CA storage. LOX activity showed high correlation with production of aldehydes (r2 = 0.85) and cis-2-hexenal (r2 = 0.94), during storage of apples under CA conditions. Good correlation was found between AAT activity and total esters and butyl acetate content under CA storage of apples (r2 = 0.92 and r2 = 0.93, respectively). While most fatty acids increased in concentration during RA and CA storage, linolenic acid content decreased. No correlation between volatile compounds content and fatty acid production was found.
... In addition, the aroma components are an important quality factor in apples. A low production of volatile aromas was observed in early harvested fruit, which gradually increased as ripeness was approached [18]. ...
"Starkrimson" is a traditional apple cultivar that was developed a long time ago and was widely cultivated in the arid region of the northern Wei River of China. However, little information regarding the quality characteristics of "Starkrimson" fruit has been reported in this area. To elucidate these characteristics, the color, soluble sugars, organic acids, anthocyanins and aroma components were measured during the ripening period through the use of high performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS). The results indicated that the changes in anthocyanin contents took place later than the changes in the Commission International Eclairage (CIE) parameters. Meanwhile, cyanidin 3-galactoside (cy3-gal), fructose, sucrose, glucose and malic acid were the primary organic compounds, and 1-butanol-2-methyl-acetate, 2-hexenal and 1-hexanol were the most abundant aroma components in the skin. Furthermore, rapidly changing soluble sugars and organic acid synchronization took place in the early ripening period, while rapidly changing aroma components occurred later, on the basis of fresh weight. This result suggested that the production of aroma components might be a useful index of apple maturity.
... 6) The ethylene silenced apples synthesize much lower amounts of both the hexyl and butyl esters, whereas aldehyde and alcohol precursors were inhibited by only 12-38 kPa; the significant change in the ratio of hexanal/(2E)-hexenal suggested that ethylene may regulate either lipoxygenase or hydroperoxide (Dandekar et al., 2004). 7) Villatoro et al. (2007) found no large variations in the activity of AAT with 'Pink Lady ® ' apple throughout the experimental period, although ester emission increased substantially, and LOX activity was increased at later stages of fruit development; researchers suggested that the enhancement of ester production at ripening arises mainly from greater availability of substrates. ...
Odour volatiles represent a major quality parameter for fresh produce. Consequently, improving the emission of volatiles in fruit has become an important challenge. A series of experiments were conducted in our laboratories in the last 20 years that aimed to elucidate the development of volatiles of various fruit types, but with an emphasis on apples. The major findings of these experiments are the following: 1) Early harvested apples had a poorer ability to produce volatiles, and that was coupled with lower respiration and less fatty acids (FA) levels. This may be related to the insensitivity of immature fruit to ethylene, since treatment with high concentrations of ethylene stimulated respiration, and increased the levels of FA and volatiles. 2) The biosynthesis of volatiles is highly reduced by apple fruit following ultra low oxygen (ULO) storage, and also after treatments with aminoethoxyvinyl glycine and 1-methylcyclopropene; the reduction became severe after an extended storage period. 3) Feeding apple fruit with volatile precursors (alcohols and aldehydes) stimulated the biosynthesis of the corresponding volatiles, mainly esters. Moreover, feeding AVG-treated fruit with precursors also led to a marked increase in the production of the corresponding volatiles. However, this effect was transitory with both ULO stored as well as with AVG-treated fruit.
... They are acceptors in an alcohol acyltransferase reaction that links an acetyl moiety from coenzyme A to the alcohol. The activity of alcohol acyltransferase is a key limiting factor in the formation of esters (Perez et al., 1996;Shalit et al., 2001;Defilippi et al., 2005;Li et al., 2006;Lara et al., 2007;Villatoro et al., 2008a;Zhu et al., 2008). 1-Hexanol, the precursor of hexyl acetate, was found in many of the cultivars, and hexyl acetate itself was an important ester in many of the cultivars. ...
... Esters, mainly ethyl butanoate, ethyl 2-methylbutanoate, 2-methylbutylbutanoate, 2-methylbutyl acetate, hexyl acetate, hexyl hexanoate, and hexyl 2-methylbutanoate, are main contributors to the apple aroma for the Pink Lady variety (Lopez et al. 2007). Of the two pathways of processing fatty acids precursors-β-oxidation and LOX-the first one prevails in fruits; however, LOX pathway can become active (Villatoro et al. 2008) with high LOX and HPL activities in skin and flesh during ripening of apples. ...
Lipid-derived volatile compounds form one of main groups of food flavors. Lipid oxidation, which influences food acceptability by consumers, results in formation of volatile compounds responsible for rancid off-odors as a result of autooxidation reactions. Lipid oxidation mediated by enzymes that takes place in plant tissues during growth, maturation, or tissue disruption is responsible for the characteristic flavor of many fruits and vegetables.
... In this stage, the presence of butanoic acid, hexanoic acid, and g-butyrolactone could be related to the fermented odor note, which is characteristic of this stage. The production of these volatile compounds could indicate the beginning of the fermentative stages and the loss of sensory fruit quality, process in which some esters could act as precursors (25). Thus, new volatile compounds appeared during soursoup ripening process and others, which were already present in the unripe fruits, were transformed. ...
Fruits of soursop (Annona muricata L. c v. Elita) were evaluated at different ripening stages to determine the changes in their physicochemical characteristics: total soluble solid content, percentage of acidity, pH, and ripeness index. The change in volatile compounds were determined through Headspace-Solid Phase Microextraction and subsequent Gas Chromatography-Mass Spectrometry analyses. The volatile compounds were identified through the comparison of their chromatographic and spectral properties against the ones exhibited by reference substances. The sensorial quality factors showed values that changed according to the ripening stage. It was established that the ester levels, particularly those from C6, C4, and C8 saturated and unsaturated aliphatic acids, increased with ripening. C6 aliphatic compounds, such as (Z)-3-hexenol and (Z)-3-hexenal, were observed to be the major volatile constituents in the green stage. In contrast, methyl hexanoate and methyl (E)-2-hexenoate were the main volatile in ripe, overripe and half ripe fruits. The overripe stage was characterized by an increase in the ethyl acetate, methyl butanoate and ethyl butanoate levels, and the appearance of butanoic and hexanoic aliphatic acids. These facts could be used as an indicator of the beginning of the fermentation stage and the loss of fruit sensory quality.
... Lopez et al. (2007) have reported that the soluble solids, TA, background color, and emission of hexyl 2-methylbutanoate, hexyl hexanoate, hexyl propanoate, butyl 2-methylbutanoate, 2-methylbutyl acetate, and butyl propanoate contents positively influenced the acceptability of "Pink Lady" apples during 25 days of cold storage. In another study on the same variety of apple, Villatoro et al. (2008) had observed low production of aroma volatiles in the early harvested fruit, but the volatiles gradually increased as the ripeness approached. Ong et al. (2006) have evaluated the chemical composition (i.e., TA, moisture content, crude fiber, color, pH, soluble solids, sugars, organic acids) and flavor changes during the 5-day ripening of jackfruit (Artocarpus heterophyllus L.). ...
... Production of volatile compounds derived from fatty acids could also help explain the lower lipid levels in LH apples. Villatoro et al. (2008) observed higher levels of lipoxygenase activity and volatile biosynthesis in apples harvested in October compared with those harvested in September, and it has been described that fatty acids are major precursors of aroma volatiles in many apple varieties, including 'Golden Delicious'. Even though no reports have been published about the effects of controlled atmosphere storage on total protein content, several studies have shown a decrease in the biosynthesis of many enzymes associated with quality loss (Galvis Sanchez & Morais 2002) which could have an effect on the total protein content in the fruit. ...
The chemical composition, sugars profile, total phenolic compounds, phenolic profile and antioxidant activity of ‘Golden Delicious’ apples during storage under controlled atmospheres were evaluated. Total lipids and proteins slightly decreased during storage, while total carbohydrate and mineral content remained constant. The content of total phenolic compounds ranged from 564–748 mg gallic acid equivalents per 100 g of dry apple. Epicatechin, chlorogenic acid, catechin, phloridzin, cyanidin-3-galactoside, quercetin-3-galactoside and quercetin-3-glucoside were the seven major phenolic compounds identified in all samples. Their content was modified by harvest date and in late harvested apples was increased by controlled atmosphere storage. Antioxidant activity, evaluated by ferric reducing antioxidant power (FRAP), radical 2,2-diphenyl-1-picrylhydrazyl scavenger capacity (DPPH) and TROLOX equivalent antioxidant capacity (TEAC), remained unchanged during the whole storage for both harvest dates. The concentration of sucrose decreased, while glucose increased and fructose remained unchanged during the storage time for both harvest dates. The present results suggest that, under the storage conditions used, nutrients and bioactive compounds of apples were maintained for at least 8 months and phenolic profile was modified by harvest date and storage.
... On the hand, more than 300 volatile organic compounds (VOCs) have been reported in fresh apples (Dixon and Hewett, 2000). Although the chemical group, total number and concentration VOCs identified is dependent on maturity of the apple and are cultivar specific (Holland et al., 2005;Villatoro et al., 2008). In pear fruit more than 300 VOCs have been characterized, with decadienoate methyl-and hexyl esters identified as the predominant impact-compounds ( Rapparini and Predieri, 2003;Kahle et al., 2005). ...
Composition, concentration and combination of volatile fractions in fresh and fresh-cut fruit and vegetables are essential in conferring the unique aroma characteristics of the product. The volatile organic compounds (VOCs) present are directly responsible for the taste and odour and, hence, the unique identities of fresh and fresh-cut produce. Flavour quality plays a crucial role in consumer preference and liking of pomegranate cultivars and products. This review discusses the volatile composition of pomegranate fruit, including a critical evaluation of the role played by various preharvest and postharvest factors on the flavour life of pomegranates. Future prospects and potential application of VOCs in smart/intelligent packaging and storage of horticultural crops are highlighted. This review provides some critical information for the entire role players along pomegranate value chain.
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 seven days at 20 °C (delay) until storage. The storage conditions were : [1] CA (1.0 kPa O2 + 1.0 kPa CO2); [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.
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.
As an exotic highly perishable tropical fruit commercially grown in Colombia, soursop (Annona muricata L.) is currently in need of postharvest handling studies. Thus, the present research was conducted to characterize the volatile compounds of soursop cv. Elita during postharvest. For this purpose, fruit ripeness was evaluated, for one thing, by a volatile compound measuring system known as electronic nose (EN), and for another thing, by headspace solid phase microextraction and gas chromatography mass spectrometry (HS-SPME/GC-MS). The profile of volatile substances in fruits is one of the main indicators of the sensory attributes that typify the organoleptic quality of these products. The EN constitutes an economical, relatively simple, fast and innovative alternative to determine groups of volatile compounds in whole or fractionated samples from fruits of commercial interest. In contrast, and despite its being a highly selective technique, the use of SPME/CG-MS might be limited by its elevated cost. Based on EN assessment, fruit ripening stages were classified as unripe, half ripe, ripe and overripe. The most active EN sensors were numbers 2 sensitive to nitrogen oxides), 6 (sensitive to methane) and 8 (sensitive to alcohols and partially aromatic compounds). HS-SPME/GC-MS analysis allowed establishing that during postharvest, the major proportion of volatile compounds corresponded to esters, predominantly Methyl hexanoate. Particularly in overripe fruits, the presence of alcoholic compounds coincides with the EN assessment, which, for its part, detected mainly alcohols and a wide range of aromatic substances. The study contributes to the characterization of postharvest volatiles, which are one of the major sensory attributes of tropical fruits.
The present study aimed at characterising the flavour composition of apple cultivars grown in the Northeast Italy through different cultivation methods, by combining Head Space-Solid Phase Micro Extraction/Gas Chromatography Mass Spectrometry (HS-SPME/GC-MS) analysis of volatile fraction with chemometric tools for class modeling. In order to represent the overall production in the target area, the investigation included 42 apples varieties consisting of ancient, non-native and new hybrid cultivars grown in Friuli Venezia Giulia and Alto Adige-South Tyrol, respectively. Moreover, apple samples from both conventional and organic agricultural practices were considered. Overall 118 volatile compounds were identified in the samples and Partial Least Squares-Discriminant Analysis (PLS-DA) was used to classify apples based on their different geographical origin or growing conditions. Models highlighted good classification results both in calibration (over 91%) and cross-validation (over 87%), enabling to obtain a good separation between apple categories with high prediction accuracy (over 90%). In addition, the Variable Importance in Projection (VIP) scores of the PLS-DA models were calculated, allowing to identify a reduced number of volatiles (e.g., ethanol, ethyl acetate, isobutyl acetate, propyl propanoate, 1-hexanol, d-limonene, (Z)-2-hexen-1-ol acetate and others) which are relevant for the discrimination of different apple groups. The proposed approach may represent a powerful tool for fruit traceability.
The types and amounts of volatiles in denucleated fruit of 30 Chinese dwarf cherry germplasms were determined by headspace solid-phase microextraction and gas chromatography–mass spectrometry to assess the genotypic variation. Eighty-five volatiles were identified; hexyl acetate, 4-penten-1-yl acetate, prenyl acetate, (Z)-pent-2-enyl hexanoate, geranyl acetate, n-butyl acetate, (3Z)-3,7-dimethylocta-1,3,6-triene, geraniol, pent-2-enyl butanoate, ethyl caprylate, butyl hexanoate, and linalool were the main volatiles. The type and content of volatile varied with genotype. Red fruits had the most abundant aroma and vinicolor fruits exhibited the least. Principal component analysis clustered the 30 Chinese dwarf cherry germplasms into four groups: (1) 2 germplasms (NM2 and HN3) had high ester content, (2) 24 germplasms (BJ1–BJ6, HB1, HB2, HN1, HN2, NM1, NM3, SX1, SX2, SX4–SX6, SX8–SX10, SX12, SX13, SX15, and SX16) contained mainly esters, lactones, and terpenes, (3) 2 germplasms (SX11 and SX14) had high ester and lactone content, and (4) 2 germplasms (SX3 and SX7) had high ester and terpene content.
Flavor is a key quality attribute of apples defined by aroma volatile compounds. Biosynthesis of aroma compounds involves metabolic pathways where the main precursors are fatty acids and amino acids, and the main products are aldehydes, alcohols and esters. Some enzymes are crucial in the production of volatile compounds, such as lipoxygenase (LOX), alcohol dehydrogenase (ADH), and alcohol acyltransferase (AAT). Composition and concentration of volatiles in apples may be altered by pre-, and post-harvest factors that cause a decline in apple flavor. Addition of biosynthetic precursors of volatile compounds may be a strategy to promote aroma production of apples. The present manuscript compiles information regarding the biosynthesis of aroma volatile compounds, metabolic pathways, enzymes and substrates involved, and factors that may affect production of aroma volatile compounds. This manuscript also includes a wide number of studies focused on the addition of biosynthetic precursors for the production of aroma volatile compounds.
For the first time, an in vivo sampling mode of direct immersion - solid phase microextraction (DI-SPME) was employed to capture the metabolome of living plant specimens, using apple (Malus ×domestica Borkh.) as a model system. Metabolites were extracted from apple tissues and introduced by thermal desorption into a comprehensive two-dimensional gas chromatography - time-of-flight mass spectrometry (GCxGC-ToFMS) instrument. The feasibility of this sampling approach, based on exploitation of microextraction principles, including negligible depletion of free analyte concentrations, solventless sampling and sample preparation and on-site compatibility was determined in global metabolite analysis. Rather than adopting an approach of traditional sample preparation, requiring metabolism quenching and laborious sample preparation, the objective of the study was to capture metabolome in vivo, evaluate the feasibility of approach to provide unbiased extraction coverage and compare analytical precision when different SPME sampling modes are employed. The potential of in vivo DI-SPME in quantitative plant metabolomics was assessed by evaluating changes in metabolic fingerprints in response to fruit maturation. The in vivo SPME sampling approach has been demonstrated as capable of sampling living systems with high reproducibility, considering that nearly 50% of hundreds of evaluated compounds included in the determination of analytical performance met the 15% RSD FDA criterion. Esters were extracted with high repeatability (% RSD for hexyl butanoate and butyl butanoate 16.5 and 5.9, respectively, 9 determinations in 3 apples) and found to be up-regulated in response to apple fruit maturation.
Solid-phase microextraction (SPME) is a rapid sample preparation in volatile analysis. The aromatic volatile compositions of ‘Kuerle’ were analyzed using SPME and gas chromatography-mass spectrometry (GC-MS). The effect of different types of fibers, extraction time, and extraction temperature on the volatile results were compared and discussed. The results were as followed. Results showed that 65μm PDMS/DVB fiber had the best effect of extraction. The optimum factors such as extraction time and temperature were 45 min and 40˚C.
Sensory and physicochemical changes of three apple cultivars ('Golden Delicious', 'Idared' and 'Gloster') were monitored during 14 weeks of storage at 6 degrees C and 70% relative humidity in three following years. The aim was to investigate physicochemical parameters that were best correlated with sensory evaluation of apples during their storage. Sensory quality was assessed using a category point scale and the sensory profile was evaluated using a graphical unstructured scale. Physicochemical changes, such as weight, soluble solids, titratable acidity, and dry matter content, were monitored. All the examined parameters changed during the observed period, with the greatest changes occurring in weight, texture, and taste. There were also differences between the tested cultivars. Statistically significant correlations between sensory and physicochemical data were observed between texture characteristics and weight changes. In case of sweet taste, only a weak correlation between the intensity of sweet flavour and soluble solid content values was found. No statistically significant correlation between the intensity of sour taste and titratable acidity was observed.
Fruits produce a wide range of volatile organic compounds that impart their characteristically distinct aromas and contribute to unique flavor characteristics. Fruit aroma and flavor characteristics are of key importance in determining consumer acceptance in commercial fruit markets based on individual preference. Fruit producers, suppliers and retailers traditionally utilize and rely on human testers or panels to evaluate fruit quality and aroma characters for assessing fruit salability in fresh markets. We explore the current and potential utilization of electronic-nose devices (with specialized sensor arrays), instruments that are very effective in discriminating complex mixtures of fruit volatiles, as new effective tools for more efficient fruit aroma analyses to replace conventional expensive methods used in fruit aroma assessments. We review the chemical nature of fruit volatiles during all stages of the agro-fruit production process, describe some of the more important applications that electronic nose (e-nose) technologies have provided for fruit aroma characterizations, and summarize recent research providing e-nose data on the effectiveness of these specialized gas-sensing instruments for fruit identifications, cultivar discriminations, ripeness assessments and fruit grading for assuring fruit quality in commercial markets.
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.
