Negative geotropic curvature of fresh asparagus spears after harvest was prevented by a brief heat treatment. The heat treatment was immersion in heated water at 47.5 degrees C for 2-5 min and cooling to storage temperature as soon as possible after heat treatment. The heat treatment can be varied from 45 degrees C for longer than 5 min to 50 degrees C for 2.5 min or less to avoid significant loss of spear appearance. The treatment temperature and time needed to be adjusted for spear diameter, small diameter spears required a shorter exposure time or lower temperature.
Quality is a term that is frequently used in postharvest studies but rarely defined. What is more disturbing is that most researchers, producers, users, consultants and decision makers interested in fruit and vegetable quality have a reasonably clear concept of the term, but there are as many different concepts as there are different perspectives in postharvest handling and distribution. A lack of appreciation for different perspectives on quality may be the most limiting factor in improving the quality of fresh fruits and vegetables as delivered to the consumer. The primary dividing line between differing concepts of quality is orientation. Most postharvest researchers, producers and handlers are product-oriented in that quality is described by specific attributes of the fruit or vegetable itself such as sugar content, color or firmness. Consumers, marketers and economists are more likely to be consumer-oriented in that quality is described by consumer wants and needs. A continuation of the product orientation to quality will lead to continued advances in postharvest technology in academic research. It is likely that when major producers/distributors start to adopt a consumer orientation to quality of fresh fruits and vegetables, competitors will either follow or suffer the economic consequences. At this point then research scientists may need to reorient to remain relevant to commercial needs.
Continuous ozone exposure at 0.3 ppm (v/v) (US-OSHA Threshold Limit Value for short term exposure) inhibited aerial mycelial growth and sporulation on ‘Elegant Lady’ peaches wound inoculated with Monilinia fructicola, Botrytis cinerea, Mucor piriformis, or Penicillium expansum and stored for 4 weeks at 5 °C and 90% relative humidity (RH). Aerial growth and sporulation, however, resumed afterward in ambient atmospheres. Ozone exposure did not significantly reduce the incidence and severity of decay caused by these fungi with the exception of brown rot. Gray mold nesting among ‘Thompson Seedless’ table grapes was completely inhibited under 0.3 ppm ozone when fruit were stored for 7 weeks at 5 °C. Gray mold incidence, however, was not significantly reduced in spray inoculated fruit. Continuous ozone exposure at 0.3 ppm increased water loss after 5 weeks of storage at 5 °C and 90% RH in ‘Zee Lady’ peaches but not after 4 weeks of storage in ‘Flame Seedless’ grapes. Respiration and ethylene production rates of ‘O'Henry’ peaches were not affected by previous exposure to 0.3 ppm ozone. In every test, no phytotoxic injuries of fruit tissues were observed in ozonated or ambient atmosphere treatments.
The effect of pretreatment with 20% CO2 plus 20% O2 for 3 days was studied with regard to its effectiveness on natural postharvest decay control and its possible induction of specific PR genes in table grapes. Full-length cDNAs encoding a class I chitinase (Vcchit1b) and β-1,3-glucanase (Vcgns1) were isolated from table grapes (Vitis vinifera L. cv. ‘Cardinal’). Our results indicate that this short-term high CO2 treatment had a residual effect and significantly reduced decay incidence of table grapes during low temperature storage and upon transfer to 20 °C. Our results indicate that during low temperature storage the expression pattern differed between the two tested PR genes. So, while the abundance of Vcgns1 transcript increased sharply at the beginning of storage at 0 °C, the increase in Vcchit1b mRNA levels was paralleled by the change in total decay. High CO2 pretreatment restrained the up-regulation of Vcgns1 gene expression and delayed the accumulation of Vcchit1b transcript as compared with non-treated grapes. Upon transfer to 20 °C after 33 days of cold storage, when attainment of maximum total decay was observed, there was a sharp increase in the accumulation of Vcchit1b mRNA in both treated and non-treated grapes, which was higher in the non-treated ones. Our results point out that the expression of class I chitinase and β-1,3-glucanase genes is not enhanced in CO2-treated grapes which control total fungal decay. These results suggest, then, that the efficacy of high CO2 pretreatment in reducing total fungal decay is not mediated by induction of the above-mentioned PR genes.
Treatment with diphenylamine (DPA), sometimes in combination with storage under low (≤1.5%) O2 atmosphere, is the major commercial means of limiting superficial scald in apple fruit. Synthesis and oxidation of the sesquiterpene α-farnesene are thought to be directly involved in induction of this storage disorder. Control of scald by DPA has been ascribed to its ability to block both in vitro and in vivo oxidation of α-farnesene to conjugated trienes (CTs), but a number of reports have indicated that DPA has multiple effects, including reduction of α-farnesene synthesis, ethylene production, and respiration. The time course and levels of α-farnesene and CT accumulation in peel tissue were compared in ‘Empire’ apples that were either DPA-treated or untreated and stored for up to 28 weeks at 0°C in air or under 1.5% O2 atmosphere. Also, it was found that the HPLC-UV method previously developed to quantify α-farnesene and CTs could be used to simultaneously measure the concentration of DPA residue. In air-stored fruit, DPA treatment protracted rather than diminished α-farnesene synthesis; a similar maximum level of α-farnesene was reached at 15 and 28 weeks in untreated and DPA-treated fruit, respectively. DPA treatment delayed the onset of CT production by ∼5 weeks and reduced CT accumulation more than 2.5-fold. The low O2 atmosphere was overall more effective than DPA treatment in reducing synthesis and oxidation of α-farnesene. In combination, however, DPA and low O2 had a synergistic effect, resulting in a ninefold reduction in α-farnesene and virtual elimination of CT production over 28 weeks. In both air and 1.5% O2, DPA residue in the peel tissue declined rapidly during the first 15 weeks of storage and more gradually thereafter, with an overall drop from ∼11 to 1.1 μg g−1.
A large-scale transcriptome analysis was conducted using an oligo-based microarray (14,562 probes) on skins of wine grape (Vitis vinifera L.) berries dehydrated at different rates (slow, S and rapid, R) after harvest up to 10 and 30% of weight loss (WL). At 10% WL, a total of 84 and 68 probes were differentially expressed following S and R dehydration, respectively. At 30% WL, 309 and 262 differentially expressed probes were detected in S and R samples, respectively, indicating that grape berries are still reactive at advanced stages of postharvest dehydration. Bioinformatic analysis revealed that about 70% of the differentially expressed probes could be annotated and putative functions were assigned. Functional characterization highlighted that, independently of the rate and intensity of dehydration, differential expression occurred in particular for genes associated with general metabolism, regulatory processes, and responses to biotic and abiotic stimuli. A total of 16 (induced) and 10 (repressed) probes, common to all four dehydrated samples, were associated with hormone (ethylene) metabolism, transcription factors, carbohydrate and secondary (polyphenols) metabolism, transport and stress responses. Together with the total number of differentially expressed probes, enhancing the dehydration level from 10 to 30% WL also affected the distribution of genes within functional categories: this behaviour was observed in particular for R samples. A higher level of water stress in grapes appears to be associated with modification to the expression of genes mainly involved in hormone and sugar metabolism, and defence mechanisms. Besides the intensity of dehydration, a significant effect on gene expression was also associated with rate of water loss: an increase in the percentage incidence of differentially expressed probes was present for categories involved in defence and environmental stress when comparing R and S samples. The microarray data, validated by RT-PCR analyses, represent robust evidence for the marked effects of postharvest water loss on metabolic processes in fruit tissues.
Aureobasidium pullulans strains Ach 1-1 and 1113-5 are two effective biocontrol agents against Botrytis cinerea and Penicillium expansum on stored apples. In the present work, a monitoring system allowing their identification and quantification was developed. The methodology used consisted of the development of both molecular markers and a semi-selective medium. The random amplified polymorphic DNA (RAPD) technique was applied to a collection of 15 strains of A. pullulans, including Ach 1-1 and 1113-5. Five specific RAPD fragments were amplified for strain Ach 1-1 and three others for strain 1113-5. Among them, a fragment of 528 bp specific to strain Ach 1-1 (generated with the OPR-13 RAPD primer) and another one of 431 bp specific to strain 1113-5 (amplified with the OPQ-03 RAPD primer) were selected, cloned, sequenced, and used to design sequence-characterized amplified region (SCAR) primers. Three different SCAR markers were amplified: two specific to strain Ach 1-1 (189 bp and 387 bp) and one specific to strain 1113-5 (431 bp). These SCAR primers can clearly identify strains Ach 1-1 and 1113-5 among 14 strains of A. pullulans and among eight yeast strains commonly present on apple fruit surfaces. Their selectivity was also tested using DNA extracted from epiphytic microflora of the apple surface. As a semi-selective medium, PDA medium supplemented with 0.5 mg L−1 euparen, 1 mg L−1 sumico, 2.5 mg L−1 hygromycin B, 30 mg L−1 streptomycin sulphate, and 1 mg L−1 cycloheximide was selected. It inhibited the development of the air microflora and appeared highly toxic for the epiphytic microflora of apple surface without altering the growth of the targeted strains Ach 1-1 and 1113-5. The combination of the semi-selective medium and SCAR markers provides a valuable monitoring tool to specifically identify and quantify A. pullulans strain Ach 1-1 and strain 1113-5 and could be used in future studies to evaluate their population dynamics under various laboratory and practical conditions.
Extracts of the cap, gill and stipe of the fruiting body of the mushroom (Agaricus bisporus) were studied by 13C-NMR spectroscopy. This technique enables changes in the main metabolite pools to be studied simultaneously as a function of storage time, temperature and postharvest development. An earlier reported reduction in dry weight of the stipe could be explained by a decrease in mannitol content. At 1 °C storage temperature, no postharvest development occurred, yet mannitol content decreased. It is concluded that mannitol is probably used as a respiratory substrate in gill tissue. Proteolytic breakdown was apparent, even during storage at 1 °C, but occurred preferentially in the stipe. The products are most probably used by the gill and to a lesser extent by the cap to maintain metabolic activity as demonstrated by urea-cycle activity. Changes in the content of four amino acid pools (glutamate, glutamine, alanine and aspartate) proved to be tissue-specific, as were changes in the content of mannitol, fumarate and malate.
A treatment of hot water brushing and prochloraz followed by 2,4-dichlorophenoxyacetic acid (2,4-D) diluted in wax, reduced postharvest diseases by 50–70% and improved fruit quality during prolonged storage. Alternaria alternata, Phomopsis spp. and Lasiodiplodia spp. were the main causal organisms of stem end decay. The best control was obtained by concentrations of 2,4-D ranging from 75 to 175 μg ml−1, which could efficiently control side rots caused by A. alternata and the stem end rot-causing pathogens. The combination of hot water brushing, prochloraz application and 2,4-D treatment reduced the incidence of stem end rot after 4 weeks of storage at 14°C and 7 days of shelf life at 20°C from 86 to 10% in cv. Tommy Atkins and from 63 to 12% in cv. Keith. At 175 μg ml−1 2,4-D did not affect fruit firmness or colour development but ensured high quality and fewer rotten fruits.
The aim of this study was to evaluate the effects of 2,4-dichlorophenoxyacetic acid (2,4-D) on chilling injury (CI) in mango fruit. 2,4-D treatment at 150 mg L−1 could significantly alleviate CI or disease incidence of mango fruit during 7 days storage at 4 °C and an additional 14 days at 20 °C (P < 0.05). Fruit quality, including increased soluble solids, soluble sugar, fruit firmness, and peel chlorophyll level, was strongly improved by 2,4-D treatment. These results indicate that 2,4-D could be used as an effective method to preserve the postharvest life of mango fruit.Endogenous H2O2 levels in the fruit were increased by 2,4-D treatment and decreased by exogenous H2O2 treatment. The activities of catalase, superoxide dismutase, ascorbate peroxidase (APX) and glutathione reductase (GR) in the 2,4-D-treated fruit were much higher than those in control fruit. However, exogenous H2O2-treated fruit showed higher CI and lower activities of APX and GR. In addition, the results showed that 2,4-D treatment could significantly enhance levels of the endogenous ABA and GA3, and reduce IAA and zeatin riboside levels in the fruit. These results suggest that 2,4-D could regulate chilling resistance by changing the balance of endogenous hormones levels.
Effects of the synthetic auxin 2,4-dichlorophenoxy-propionic acid (2,4-DP) on 1-aminocyclopropane-1-carboxylate (ACC) synthase and oxidase gene expression in ‘La France’ and aroma production in ‘Bartlett’ pears (Pyrus communis L.) were investigated. In non-stored, non-treated ‘La France’ fruit, the accumulation of ACC synthase (ACS) and ACC oxidase (ACO) transcripts was not observed. In 2,4-DP treated ‘La France’ fruit, the level of mRNAs hybridized with ACS4 probe increased strongly while ACS1, ACS3, and ACO1 mRNA levels were similar between 2,4-DP treated fruit and stored non-treated fruit. The result indicates that ACS4 may be an ACC synthase gene which is induced by auxin in pears. Thirty-eight volatile compounds were detected from ‘Bartlett’ pears. The composition and amount of aroma volatiles were similar between 2,4-DP treated fruit and stored non-treated fruit. Esters were the most prevalent compounds and butyl-, ethyl-, and hexyl acetate were produced in the largest amounts. In non-stored, non-treated fruit, aldehydes constituted a high percentage of the total volatiles detected, although the amount of total volatiles detected was relatively low. Internal browning in 2,4-DP treated ‘Bartlett’ fruit developed on the tree within 30 days of application. Possible effects of pre-harvest ethylene, carbon dioxide, and temperatures, are discussed.
Advanced maturity nectarines cv. Caldesi 2000 [Prunus persica var. nectarina (Ait.) Maxim.] and peaches cv. Royal Glory [Prunus persica (L.) Batch] were treated in 46 °C hot water containing 200 mM NaCl for 25 min, sealed in low thickness PE bags and stored at 0 °C for 1 and 2 weeks. Quality was evaluated initially and after each storage period plus 1 day shelf life. Hot water treatment (an acceptable treatment to reduce spoilage from fungi) did not cause any fruit damage based on external observations, specific conductivity and total phenol content evaluations, but reduced firmness loss (possibly in combination with MA packaging) especially in the white-flesh nectarines and kept the cellular membranes functioning better. PE bags were of low thickness and MA conditions inside the bags were found inadequate (O2 levels >15%, CO2 levels <5%) to significantly affect the ripening process during cold storage, but could be harmful after 10 h at room temperature (O2 levels <3%, CO2 levels >13%). Mass losses were kept low in PE bags. Juice soluble solids concentration, pH and acidity were not affected by the hot water treatment before and after cold storage. Hot water combined with MA packaging during storage resulted in good quality fruit after 1 week duration for postharvest handling.
During postharvest ripening and softening of kiwifruit (Actinidia deliciosa (A. Chev.) C.F. Liang and A.R. Ferguson cv. Bruno) at 20 °C, the levels of salicylic acid (SA) in fruit tissues declined. Concurrently, lipoxygenase (LOX) activity increased, and this was associated with climacteric ethylene release. In fruit stored at 0 °C with a reduced rate of softening, SA concentrations remained at relatively high levels. Application of acetylsalicylic acid (ASA) to ripening kiwifruit resulted in substantially higher SA levels than in control fruit. ASA treatment slowed down the increase in LOX activity and superoxide free radical production, and suppressed ACC synthase and ACC oxidase activities and biosynthesis of ethylene, and hence retarded the climacteric rise in ethylene production. Fruit ripening and senescence were also delayed. A close relationship was found to exist between change in SA levels in the fruit tissues and the extent of fruit ripening and softening.
Pretreatments at moderate temperatures applied immediately prior to the high or low temperature treatments can reduce skin damage to avocados. These temperature tolerance-inducing pretreatments have generally been applied immediately prior to the high or low temperature. We examined whether a delay between the pretreatment and potentially damaging high and low temperatures may cause a loss in the induced tolerance. A hot air pretreatment (38 °C for 6 h) applied prior to storage at 0 °C for 3 weeks with intervening delays of 1–4 days at 20 °C, showed a large reduction in chilling injury as a result of the pretreatment but that this was progressively lost with increasing delay to storage. Hot water pretreatments (38 °C for 0, 5, 20 and 60 min) increasingly reduced chilling damage at 0 °C, and heat damage from a hot water treatment (HWT) at 50 °C/10 min. With delays of up to 3–24 h prior to the HWT, heat damage was reduced for the 5 and 20 min pretreatments. However, delays up to 5 days between pretreatment and HWT, loss of heat tolerance was observed. For delays of between 1 and 5 days there was a clear loss of chilling tolerance which was more rapid than the increase in chilling injury in control treatments for the same delays. However, the effect of delays <24 h was less clear for the 5 and 20 min treatments. Heat shock protein (hsp) 17 and 70 homologous RNA levels were induced by heat pretreatments and delays lead to first an increase in RNA levels (maximum induction at 6 h), which paralleled the induced tolerance, and then a decline which was less closely associated with loss in tolerance. Thus, delayed time between thermotolerance inducing pretreatments and high or low temperatures can lead to a general reduction in tolerance, and should be considered and exploited in the application of temperature treatments. A dose response/decay model for induced tolerance fits the pattern of temperature damage and hsp expression.
Fresh carrots were treated with or without a continuous atmosphere of 50 ± 10 nL L−1 ozone during storage for up to 6 months at 0.5 °C and >95% relative humidity to determine the effect on decay caused by Sclerotinia sclerotiorum and Botrytis cinerea and quality attributes. Lesions on carrots inoculated with S. sclerotiorum at the beginning of the storage period were reduced in length but the subsequent rate of lesion expansion over time was similar for both treatments. Lesion size and rate of expansion on carrots inoculated with B. cinerea were reduced by ozone. Aerial mycelium of both pathogens was markedly reduced in the ozone treatment, but sporulation of B. cinerea was stimulated, characterized by dense mats of short conidiophores on the lesions. Susceptibility to S. sclerotiorum increased with storage time while susceptibility to B. cinerea peaked at 4 months and then decreased possibly related to carrot moisture loss. The incidence of carrots harboring visible saprophytic mold on the crown was substantially reduced in the ozone treatment. Ozone-induced injury, appearing as blotches of brownish discolored periderm, was slight, but increased with time whereas carrots in the control treatment did not become discolored. Ozone treatment had no effect on fresh weight loss, sprouting of carrot crowns, nor on concentrations of glucose, fructose, sucrose or galactose. Levels of isocoumarin (3-methyl-6-methoxy-8-hydroxy-3,4-dihydroisocoumarin) were slightly elevated and averaged 17.8 mg kg−1 compared with 12.1 mg kg−1 in the controls and may have been associated with reduced lesion growth by B. cinerea. The ozone treatment may be useful for reducing nesting caused by S. sclerotiorum and B. cinerea in carrots destined for the processing market where any ozone-induced discoloration would be removed during peeling.
Sweet cherries (Prunus avium L.) were treated by 915 MHz microwaves in a pilot-scale multimode microwave system with an auxiliary hot air heater to determine heating characteristics and the effect of treatments on insect mortality and fruit quality. Quality parameters of the microwave-treated ‘Bing’ cherries were compared with control fruit and those subjected to methyl bromide fumigation. When heating cherries to average pit temperatures of 45, 50 and 55°C, the cherry pits heated faster than the surface, and larger cherries heated more quickly than smaller ones. Cherry temperature increased linearly with time with heating rates dependent on the microwave power, sample weight, cherry size and radial location inside the cherry. With a 2 min holding and 5 min hydrocooling protocol after microwave treatments, adjusted percentage 3rd instar codling moth (Cydia pomonella L.) mortality ranged from 5 to 62% and 39 to 98% without and with 1–2 days cold storage, respectively. A higher mortality rate was obtained for insects in ‘Bing’ than ‘Rainier’ fruit. Firmness, percentage soluble solids content, titratable acidity, fruit weight, and objective fruit colour of microwave-treated ‘Bing’ fruit were comparable with these properties of control fruit and to those of cherries fumigated with methyl bromide. Stem greenness colour was reduced after the microwave and dry hot air combined treatments. Microwave energy may provide an alternative non-chemical quarantine treatment against codling moth in export cherries, but further study is needed to optimize the treatment protocol for insect control and fruit quality.
The role of phospholipase A2 (PLA2) activity in development of postharvest peel pitting in mature ‘Fallglo’ tangerines [Bower citrus hybrid (Citrus reticulata Blanco × C. reticulata Blanco × C. paradisi Macf.) × Temple (C. reticulata Blanco × Citrus sinensis L.)] and ‘Navel’ oranges (Citrus sinensis L. Osbeck) was investigated. Changes in RH from 30% to 90% followed by fruit waxing increased electrolyte leakage and PLA2 activity in flavedo, and induced pitting. Treatment with an aqueous dip of aristolochic acid (AT), a specific inhibitor of secretory phospholipase A2 (sPLA2) activity, immediately before transfer from 30% to 90% RH storage, markedly reduced peel pitting symptoms. Five genes encoding various phospholipase As isolated from citrus (three patatin-like and two sPLA2-like sequences) differentially accumulated in healthy areas, areas with developing lesions and necrotic lesions of disordered fruit. Other PLA2, phospholipase C, and phospholipase D inhibitors also reduced peel pitting; however, PLA2 inhibitors were the most effective in preventing the disorder. In addition, phospholipase inhibitors promoted fruit decay, suggesting that innate resistance is impacted by phospholipase action. Together, the results provide evidence for involvement of phospholipase activity in development of postharvest peel pitting symptoms in citrus fruit.
Postharvest rind disorders of citrus fruit may be caused by chilling but also by other stress conditions at non-chilling temperatures. The mechanisms involved in the tolerance of citrus fruit to these postharvest physiological disorders and how they are related to each other are not well understood. In the present work, we have examined changes in the activities of the antioxidant enzymes, superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR), and of phenylalanine ammonia-lyase (PAL), the initial rate-controlling enzyme in phenolic synthesis, in ‘Navelate’ oranges and in its yellow abscisic acid-deficient mutant ‘Pinalate’ in relation to their susceptibility to chilling injury (CI) and to non-chilling peel pitting. ‘Navelate’ oranges developed CI during storage at 2 °C and very slight postharvest non-chilling peel pitting at 12 °C. By contrast, ‘Pinalate’ fruit did not show CI and were more susceptible to non-chilling peel pitting than ‘Navelate’ fruit. No important differences in the activities of the enzymes GR and APX were found in fruit of both phenotypes when stored at 2 °C or 12 °C. By contrast, ‘Pinalate’ fruit, the chilling-tolerant cultivar, had higher CAT activity than ‘Navelate’ oranges during storage at 2 °C, while it was lower at the temperature causing non-chilling peel pitting. PAL activity barely changed in response to cold stress in the mutant but increased in the chilling-susceptible ‘Navelate’ fruit. On the other hand, the increase in PAL occurring in ‘Pinalate’ fruit at 12 °C might be associated with their greater development of non-chilling peel pitting. The overall results indicate that the enzyme PAL might be a good biochemical marker for both chilling-induced superficial scald and non-chilling peel pitting and that CAT may play a role protecting ‘Navelate’ and ‘Pinalate’ fruit from conditions favoring both physiological disorders. In addition, SOD could be involved in the higher tolerance of ‘Navelate’ oranges to develop non-chilling peel pitting.
Avocado fruit are highly variable, and even those graded for similar size and appearance do not behave in the same manner after harvest. This is particularly problematical for those involved in sales to the “ready-ripe” market. These operations are faced with a high variation in the rate of ripening within a consignment, causing logistical difficulties. Fruit water content (or its complement dry matter) has a major impact on-line ripening and has hence been used as the maturity marker in the South African avocado industry. Presently, fruit water content is destructively measured using a representative sample as an indicator of when to post-harvest. In order to investigate if fruit water content and/or abscisic acid triggers fruit ripening, water or ABA was infused into commercially mature, but non-ripe avocado fruit. The fruit ripening, mass, CO2 and ethylene production patterns were determined over the ripening period. By infusing water through the pedicle, the variation in days to ripening was decreased without any effect on the number of days to ripening. ABA infusion hastened ripening but did not affect the variation in days to ripening. It is therefore suggested that the fruit water content at harvest forms the baseline condition from which the trigger for ripening is determined, while post-harvest water loss and ABA modulate and stimulate ripening, respectively. Furthermore, an equation was developed using Near Infrared Spectroscopy (NIRS) to measure mesocarp water content (R2 = 0.92, SE = 1.8% MC). It is postulated that on line sorting of fruit using NIRS, based on time to ripen, would result in consignments of fruit with less ripening variation, thereby solving the industry's logistical problem of fruit which have a wide spread of ripening being packed into one carton.
Softening during ripening in climacteric fruit is generally attributed to degradation in cell wall assembly, particularly the solublization of pectin. These changes could involve increased activities of various cell wall hydrolases. Their activity is believed to be regulated by ripening-related hormones and/or other signal molecules. Activities of pectin methyl esterase (PME), polygalacturonase (PG), pectate lyase (PL) and cellulase in banana cv. dwarf cavendish fruit were measured over a period of 7 days after ripening was initiated with ethylene. Effects of treatments with 1-methylcyclopropene (1-MCP), abscisic acid (ABA) and indole acetic acid (IAA) on activities of these hydrolases were measured in order to help elucidate their roles during banana ripening. Ethylene stimulated activities of all four enzymes, at best differentially. 1-MCP and IAA suppressed the ethylene effects. ABA stimulated activities of all hydrolases except polygalacturonase. ABA stimulation was most evident for pectate lyase. Thus ethylene plays a major role in up-regulating the activities of various cell wall hydrolases. In contrast IAA suppresses their activity. ABA can enhance softening with or without ethylene.
Fruit products certified by quality labels should guarantee high levels of consumer acceptance, despite the unavoidable variability arising from growing conditions and postharvest responses. The quality of ‘Abate Fetel’ pear (Pyrus communis L.) fruit was studied, after short or long cold storage, by analysis of physicochemical, texture and flavour traits, to investigate factors affecting consumer acceptance. Fruit from three orchards differing in location and design, monitored during 10 d of ripening at 20 °C, softened progressively to reach and exceed firmness adequate for consumption. Change in colour, in particular hue angle, paralleled softening. Sensory traits were investigated by evaluating fruit of three different firmness levels within the range of acceptable eating quality. Firmness differences were clearly perceived both by expert judges and by consumers, but did not influence the degree of liking. ‘Abate Fetel’ pear can maintain acceptable eating quality at 20 °C for 4–8 d after 13 weeks storage at −1 °C, or 2–6 d after 23 weeks storage at −1 °C. Changing texture parameters were perceived at eating, without compromising overall quality. Production system affected intrinsic quality parameters such as total soluble solids concentration, but did not influence consumer acceptance. In consumer tests conducted after 13 weeks of cold storage, high scores were recorded, with a 86% acceptance frequency and more than 40% of scores reflecting “like very much” or “like extremely”. After 23 weeks of cold storage a decrease in degree of liking was observed. The overall value of ‘Abate Fetel IGP Emilia-Romagna’ quality label was confirmed by consumer evaluations. However, the decrease in consumer acceptance after 23 weeks of cold storage indicates that caution should be used in using long storage durations.
Abiotic stress potential has a significant impact on quality and nutritional status of fresh cut fruits and vegetables. However, very little work has been directed to defining and documenting the abiotic stresses that occur during fresh cut processing, packaging and storage. Many indicators can be used to infer impact of abiotic stress such as discolouration (e.g. browning of fresh-cut surfaces), increased respiration and ethylene evolution, loss of flavour and texture, weight loss, decline in levels of ascorbate, development of off-odours, membrane breakdown, and tissue softening. Using these indicators, a case is made from existing literature for the importance of abiotic stress in determining quality of fresh cut products. Impact of preharvest stress, genetic variation and stress response, injuries incurred after harvest, and storage regimes will be discussed in detail. From this literature review, it becomes clear that current understanding of abiotic stress levels and mechanisms is relatively sparse. Further research is required to better document this issue as well as to develop effective strategies to modulate stress responses such that quality and nutritive value of fresh cut fruits and vegetables can be improved.
The postharvest development of Botrytis blight in rose flowers (Rosa × hybrida cv. Mercedes) was suppressed when flower buds were sprayed with 1 mM solution of gibberellic acid (GA3). The development of the disease was promoted by application of abscisic acid (ABA) and the suppressive effect of GA3 was reduced when GA3 solution was supplemented with ABA. The GA3-imposed suppression of Botrytis blight was enhanced by addition of paclobutrazol (PBZ) to the GA3 solution, but the development of the disease was not affected by PBZ alone. Germination of conidia and germ-tube elongation of Botrytis cinerea in vitro were unaffected by ABA and PBZ, whereas linear growth of fungal colonies was promoted by ABA but was inhibited by PBZ.
‘Navelina’ (Citrus sinensis L. Osbeck) oranges are prone to develop postharvest rindstaining during storage at a non-chilling temperature (22 °C). This physiological disorder is manifest as extensive collapsed and dry areas of the flavedo (outer coloured part of the peel), and part of the albedo (inner part of the peel), that becomes dark with time. In the present study we have examined the effect of humidity, temperature and applying ethylene to harvested fruit on the abscisic acid (ABA) content in the flavedo and on their susceptibility to develop rindstaining. The incidence of this physiological disorder was considerably reduced by treating the fruit with ethylene or by keeping them at low temperature (2 °C) but was enhanced by increasing the relative humidity (RH) during storage at 22 °C. Fruit treated with air and kept at 22 °C under low RH (55–60%) had higher ABA contents than fruit kept under high RH (85–90%) at the beginning of the storage period. However, after 14 days storage little difference in ABA content between fruit held under both treatments was found and the rindstaining index of fruit was different. The beneficial effect of keeping the fruit at 2 °C appeared to be more related to the influence of low temperature on delaying the mechanism of peel pitting than to the changes occurring in ABA content in the flavedo of fruit. Ethylene induced a sharp increase in ABA content in the flavedo and considerably reduced rindstaining. However, no differences in ethylene-induced ABA levels were found despite the efficacy of ethylene in controlling rindstaining increasing with concentration of gas applied and duration of the treatment. The overall results indicate that ethylene, but not ABA, may be an important factor protecting ‘Navelina’ fruit from the development of rindstaining.
Onion bulbs (Allium cepa L.) of cultivars with long-, medium- and short-storage lives, viz. Renate, Ailsa Craig and SS1, respectively, were stored in controlled atmosphere (CA) conditions (3.03 kPa CO2; 5.05 kPa O2; 2 °C). Bulb abscisic acid (ABA) concentration, pyruvate, fructans, total soluble solids (TSS) and firmness were measured throughout storage.In all cultivars, bulb ABA concentration declined exponentially during storage. The greatest decrease in ABA concentration occurred during the first 80 days of storage. Although the pattern of decline was similar for the long-, medium- and short-storing onion bulbs, onion cv. SS1 bulbs had the lowest initial ABA concentration. Onion bulb ABA concentration at harvest (measured on a fresh weight basis) may prove to be a better indicator of storage life. The ABA concentration at harvest (DW) may be indicative of a greater difference in sprouting during storage between cv. SS1 and the other cultivars than between cvs. Renate and Ailsa Craig.It is hypothesised that the storage potential of bulbs of different onion cultivars is inversely related to the time at which they reach a minimal ABA content. Thus, the storage life of short-storing cultivars (e.g. cv. SS1) might be prolonged by slowing the decline in ABA concentration. This could help extend the period for supplying these onions from temperate regions. Onion bulbs of cvs. Renate, Ailsa Craig and SS1 were characterised by high, intermediate and low concentrations of pyruvate, fructan and total soluble solids, respectively.