Fundamental aspects of postharvest heat treatments

Effects of delayed tuber cutting after catalytic infrared heat treatment on browning of fresh-cut potatoes and its potential mechanisms

Heat treatment, a form of thermal stress can confer anti-browning properties to potato tubers. However, the effect of delayed cutting after catalytic infrared heat treatment (DC-CIRHT) on browning inhibition remains unexplored. The study optimized catalytic infrared heat treatment conditions (55 °C for 10 min) and delayed cutting time (3 d). DC-CIRHT significantly inhibited the increase of browning index and browning degree and did not affect the quality of potato tubers. The mechanisms underlying browning inhibition involve two aspects: the reduction of phenolic-enzyme catalysis and the enhancement of the defense system. DC-CIRHT inhibits browning by suppressing polyphenol oxidase, peroxidase and phenylalanine ammonia lyase enzyme activity, reducing total phenol and flavonoid content, enhancing antioxidant activity, reducing membrane permeability and MDA, and balancing amino acid metabolism. This method offers a novel strategy for inhibiting browning during the post-harvest storage and processing of fruits and vegetables.

Transcriptome and metabolome analyses provide insights into the fruit softening disorder of papaya fruit under postharvest heat stress

Heat stress in summer causes softening disorder in papaya but the molecular mechanism is not clear. In this study, papaya fruit stored at 35 °C showed a softening disorder termed rubbery texture. Analysis of the transcriptome and metabolome identified numerous differentially expressed genes (DEGs) and differentially accumulated metabolites (DAMs) between the fruit stored at 25 °C and 35 °C. The DEGs and DAMs related to lignin biosynthesis were upregulated, while those related to ethylene biosynthesis, sucrose metabolism, and cell wall degradation were downregulated under heat stress. Co-expression network analysis highlighted the correlation between the DEGs and metabolites associated with lignin biosynthesis, ethylene biosynthesis, and cell wall degradation under heat stress. Finally, the correlation analysis identified the key factors regulating softening disorder under heat stress. The study's findings reveal that heat stress inhibited papaya cell wall degradation and ethylene production, delaying fruit ripening and softening and ultimately resulting in a rubbery texture.

Managing Postharvest Losses of Vegetables and Fruits: A Methodological Review

Vegetables and fruits are highly perishable agricultural commodities cultivated all over the world. However, inadequate handling practices have led to significant postharvest losses of these agricultural commodities, as well as the wastage of valuable resources, such as time and money. Hence, it can be observed that cultivators often experience significant financial setbacks as a result of inadequate comprehension regarding the nature and origins of these losses, insufficient preservation practices, and ineffective approaches to transportation and marketing. In addition, the utilization of suitable chemical agents during both the pre- and postharvest phases has the potential to prolong the shelf life of agricultural products. This preservation technique safeguards vegetables and fruits from pathogenic organisms and other forms of environmental harm, thereby enabling their availability for an extended duration. Therefore, this review proposes a methodology for managing fruits and vegetables postharvest to minimize losses and optimize returns.

Attenuating sugar spot and retaining quality of banana fruits by combined use of hot water and calcium lactate during storage

Combined use of hot water (HW) treatment and calcium lactate (CL) is a promising postharvest approach to preserve the food value and prolong the shelf life of fruits. The present experiment aims to determine the physiological loss in weight, firmness, respiration rate, ethylene and biochemical attributes of banana fruits treated with hot water (50 °C for 7 min) and aqueous CL dipping (1, 2, and 3% for 2 min). Treated fruits were stored under ambient conditions (22-25°C temperature and 60-65% of relative humidity) for up to 9 days. The study showed that combined use of HW and CL (3%) maintained higher hue angle, peel firmness (4.4 N), reduced decay loss (10.63%), respiration and ethylene evolution rate of stored fruits. Also, CL treatments (3%) with HW proved the best which reduced 6-fold sugar spot and 1.5-fold decay loss over untreated fruits. At the end of storage sensory parameters such as mouthfeel, peel colour and overall acceptability (score 6.9) were recorded higher in HW and CL 3% treated fruits. The findings indicated that pre-storage combined use of HW and CL has a great potential to preserve quality, delay ripening, and reduce sugar spots, and postharvest decay loss in banana fruit without any adverse effect on consumer appeal.

The Impact of Different Withering Approaches on the Metabolism of Flavor Compounds in Oolong Tea Leaves

In this study, complementary metabolomic and proteomic analyses were conducted on the solar- and indoor-withered oolong tea leaves, and freshly plucked leaves as the control, for the purpose to reveal the mechanisms underlying the initial formation of some flavor determinants during the early stage of oolong tea processing. As a result, a total of 978 non-volatile compounds and 152 volatile compounds were identified, the flavonoids and several esters were differently accumulated in various tea samples. In total, 7048 proteins were qualitatively and quantitatively determined, the analysis on pathway enrichment showed that phenylpropanoid, flavonoid metabolisms, and protein processing in endoplasmic reticulum were the major pathways discriminating the different tea samples. The joint protein-metabolite analysis showed that the multiple stresses such as dehydration, heat, and ultra-violet irradiation occurred during the withering step induced the dynamic and distinct changes in the biochemical network in the treated leaves compared to fresh leaves. The significant decreases in flavonoids, xanthine alkaloids, and several amino acids contributed to the alleviation of bitter or astringent taste of withered leaves, although the decomposition of L-theanine resulted in the loss of umami flavor over the solar-withering step. Moreover, the fruity or floral aromas, especially volatile terpenoids and phenylpropanoids/benzenoids, were retained or accumulated in the solar withered leaves, potentially aiding the formation of a better characteristic flavor of oolong tea made by indoor withered tea leaves. Distinct effects of solar- and indoor-withering methods on the flavor determinant formation provide a novel insight into the relationship between the metabolite accumulation and flavor formation during the withering step of oolong tea production.

Metabolic changes associated with chilling injury tolerance in tomato fruit with hot water pretreatment

Hot water treatment (HWT) of tomato (Solanum lycopersicum L.) fruit reduces the symptoms of chilling injury (CI). The aim of this study was to identify metabolites associated with HWT-induced CI tolerance in tomato fruit cv. Imperial. Mature green tomatoes with HWT (42°C/5 min) and control were stored under chilling conditions (5°C/20 days) and then ripened (21°C/7 days). Methanol extracts from pericarp were analyzed for total phenolics (TP), antioxidant activity (AoxA), and metabolic profiling by UPLC-DAD-MS and GC-MS. After cold storage and ripening, HWT fruit showed less CI, higher TP, and AoxA than control. It also showed an increased accumulation of phenolics, sugars, and some alkaloids that may be mediated by azelaic acid, glutamine, and tryptophan. The levels of N-feruloyl putrescine, esculeoside AII, and hydroxy-α-tomatine II were reduced. The better metabolic performance of HWT fruit under cold storage was associated with a higher accumulation of several metabolites (e.g., antioxidants and osmolytes) in ripening fruit. PRACTICAL APPLICATION: The identification of metabolites associated with the reduction of chilling injury (CI) symptoms in HWT tomato fruit extends the understanding of the mechanisms involved in CI tolerance. This information provides targets that could be used to develop strategies for preventing CI (e.g., genetic improvement of tomato, direct application of key metabolites). The application of such strategies will increase the economic value and decrease postharvest losses.

Orbitides and free polyamines have similarly limited fungicidal activity against three common pathogens of flax in vitro

Fusarium oxysporum f. sp. lini and Septoria linicola are causes of fusarium wilt and pasmo in flax ( Linum usitatissimum). Members of a third fungal genus, Alternaria spp., have also been found in fiber and linseed varieties of flax, and are a source of post-harvest spoilage and mycotoxins in a wide range of crops. We performed a microdilution assay and calculated the median effective concentration (EC50) to compare the potency of cyclolinopeptides (CLPs), two polyamines (spermidine and spermine), and the fungicide carbendazimin in the control of three fungi that have potential pathogenic activity ( F. oxysporum, S. linicola, and Alternaria spp), of which the first two are particulary significant causes of disease in flax. For carbendazim, all EC50 values were <0.6 μg/mL. The observed EC50 ranged from 111 to 340 μg/mL for a mixture of six unique CLPs, 109 to 778 μg/mL for spermine, and 21 to 272 μg/mL for spermidine. Spermidine was most effective against Alternaria sp., with an EC50 of 21 μg/mL. The results presented here showed that polyamines and CLPs possess limited antifungal activities against several fungi, with spermidines the most effective naturally occurring compound tested. Our findings do not support the hypothesis that CLPs act as potent antifungals against the three species of pathogens tested.

Hot Water Treatment for Post-Harvest Disinfestation of Bactrocera dorsalis (Diptera: Tephritidae) and Its Effect on cv. Tommy Atkins Mango

Simple Summary

The oriental fruit fly Bactrocera dorsalis is a major quarantine pest in sub-Saharan Africa that threatens mango production and international trade. In this study, we developed a hot water treatment (HWT) protocol for the post-harvest disinfestation of B. dorsalis and assessed its impact on cv. Tommy Atkins mango quality parameters after treatment. First, we established the rate of development of the immature stages of B. dorsalis in cv. Tommy Atkins mango and then determined their heat tolerance. The third-instar larva was found to be the most heat tolerant of the immature stages. The study demonstrates that a hot water treatment schedule of 46.1 °C for 72.63 min can lead to complete mortality of the most heat-tolerant stage of B. dorsalis in cv. Tommy Atkins mango. Furthermore, we carried out large-scale confirmatory trials to validate our hot water treatment schedule, and none of the 59,120 most heat-tolerant larvae treated survived. Our protocol guarantees effective quarantine security with no adverse effect on the quality of cv. Tommy Atkins mango fruit and can be commercially adopted to promote and increase mango exports to lucrative markets abroad.

Abstract

Mango production and trade in sub-Saharan Africa is hampered by direct damage and the high quarantine status of B. dorsalis and the paucity of effective post-harvest phytosanitary treatments. The current study reports the development of a quarantine treatment protocol using hot water to disinfest B. dorsalis and assess its effect on cv. Tommy Atkins mango quality. We first determined the development of the eggs and all larval stages of B. dorsalis in cv. Tommy Atkins mango and used the information to establish a time–mortality relationship of the immature stages after subjecting infested fruits to a regimen of eight, time instances of hot water at 46.1 °C. Using probit analysis, we estimated the minimum time required to achieve 99.9968% mortality of each stage. Our results indicate that the egg was the least heat tolerant, followed by the first, second, and third instar. The time required to achieve 99.9968% control of the third instar in cv. Tommy Atkins mango (400–600 g) was determined to be 72.63 min (95% Cl: 70.32–74.95). In the confirmatory trials, the hot water treatment schedule of 46.1 °C/72.63 min was validated, and none of the 59,120 most heat-tolerant individuals treated survived. Further, there were no significant differences between hot water-treated and untreated mangoes recorded in weight loss, fruit firmness, pH, total soluble solids, moisture content, and titratable acidity eleven days post-treatment. These findings demonstrate an effectively optimum post-harvest disinfestation treatment against B. dorsalis in cv. Tommy Atkins mango that should be adopted commercially to facilitate access to profitable but strict export markets globally.

The Effect of Hydrothermal Treatment on Metabolite Composition of Hass Avocados Stored in a Controlled Atmosphere

Avocado cv. Hass consumption has expanded worldwide given its nutritional, sensory, and functional attributes. In this work, avocado fruit from two harvests was subjected to hydrothermal treatment (38 °C for 1 h) or left untreated (control) and then stored for 30 and 50 days in a controlled atmosphere (4 kPa O₂ and 6 kPa CO₂ at 7 °C) (HTCA and CA, respectively) with subsequent ripening at ~20 °C. The fruit was evaluated for primary and secondary metabolites at harvest, after storage, and after reaching edible ripeness. A decrease from harvest to edible ripeness in mannoheptulose and perseitol was observed while β-sitosterol, hydrophilic and lipophilic antioxidant activity (H-AOX, L-AOX), abscisic acid, and total phenolics (composed of p-coumaric and caffeic acids such as aglycones or their derivatives) increased. HTCA fruit at edible ripeness displayed higher contents of mannoheptulose, perseitol, β-sitosterol, L-AOX, caffeic acid, and p-coumaric acid derivatives, while CA fruit presented higher contents of α-tocopherol, H-AOX, and syringic acid glycoside for both harvests and storage times. The results indicate that a hydrothermal treatment prior to CA enables fruit of high nutritional value characterized by enhanced content of phenolic compounds at edible ripeness to reach distant markets.

Influence of Harvest Date and Postharvest Treatment on Carotenoid and Flavonoid Composition in French Marigold Flowers

The aim of this study was to characterize carotenoids and flavonoids present in French marigold flowers (Tagetes patula "Durango Red") as well as to assess the effects of harvest dates and postharvest treatments on these compounds. Carotenoids and flavonoids were quantified using their respective standards or semiquantified using relevant related standards. Lutein and its derivatives largely dominated the flower carotenoids, while the flavonoids were diverse with patuletin leading the list. Of the different postharvest treatments, ensilage leads to the highest content of carotenoids (from 5.0 to 7.8 g kg^-1 dw) and flavonoids (from 19 to 50 g kg^-1 dw). The composition of individual flavonoids was greatly influenced by different postharvest treatments, while the influence of harvest dates was secondary. Ensilage and drying induced separate metabolic pathways leading to degradation of high-molecular glycosidic compounds, converting the compounds either to their aglycones or into the intermediate flavonoid glycosides. We conclude that according to the intended industrial application, different postharvest techniques can be employed to acquire desired flavonoids on a large scale.

The Effect of Different Cooking Methods on The Nutritional Composition f Tilapia (Oreochromis Sp.)

Tilapia (Oreochromis sp.) is a fish that is gaining ground in cultivation and sales because of its nutritional properties: high protein content, vitamins, and minerals with few unhealthy saturated fats as in red meats. This work aimed to evaluate the effect of cooking on the chemical composition, Aw, and pH, in addition to the electrophoretic, and fatty acid profile of the Tilapia using an electric oven, microwave and steaming as cooking methods. The results showed that the nutritional components of Tilapia changed significantly (p<0.05) at two temperatures and at two potencies used. Microwave and steaming preserved better the proteins in the Tilapia after its cooking. Electrophoresis results showed a decrease in intensity and number of bands depending on the type of treatment to which the meat was subjected. On the other hand, the electric oven method at 2 temperatures resulted with the highest increase in essential fatty acids (45% and 36%), with a slight decrease in the ω-6 family, because of a probable hydrolysis or oxidation of the same. The steam cooking showed a slight increase in essential fatty acids, but microwave oven preserved better the proteins, indicating that this could be a good method for cooking Tilapia.

Generation of fruit postharvest gene datasets and a novel motif analysis tool for functional studies: uncovering links between peach fruit heat treatment and cold storage responses

A survey of developed fruit gene-specific datasets and the implementation of a novel cis-element analysis tool indicate specific transcription factors as novel regulatory actors under HT response and CI protection. Heat treatment (HT) prior to cold storage (CS) has been successfully applied to ameliorate fruit chilling injury (CI) disorders. Molecular studies have identified several HT-driven benefits and putative CI-protective molecules and mechanisms. However, bioinformatic tools and analyses able to integrate fruit-specific information are necessary to begin functional studies and breeding projects. In this work, a HT-responsive gene dataset (HTds) and four fruit expression datasets (FEds), containing gene-specific information from several species and postharvest conditions, were developed and characterized. FEds provided information about HT-responsive genes, not only validating their sensitivity to HT in different systems but also revealing most of them as CS-responsive. A special focus was given to peach heat treatment-sensitive transcriptional regulation by the development of a novel Perl motif analysis software (cisAnalyzer) and a curated plant cis-elements dataset (PASPds). cisAnalyzer is able to assess sequence motifs presence, localization, enrichment and discovery on biological sequences. Its implementation for the enrichment analysis of PASPds motifs on the promoters of HTds genes rendered particular cis-elements that indicate certain transcription factor (TF) families as responsible of fruit HT-sensitive transcription regulation. Phylogenetic and postharvest expression data of these TFs showed a functional diversity of TF families, with members able to fulfil roles under HT, CS and/or both treatments. All integrated datasets and cisAnalyzer tool were deposited in FruitGeneDB (https://www.cefobi-conicet.gov.ar/FruitGeneDB/search1.php), a new available database with a great potential for fruit gene functional studies, including the markers of HT and CS responses whose study will contribute to unravel HT-driven CI-protection and select tolerant cultivars.

An integrated metabolomic and gene expression analysis identifies heat and calcium metabolic networks underlying postharvest sweet cherry fruit senescence

Ηeat and calcium treatments reprogram sweet cherry fruit metabolism during postharvest senescence as evidenced by changes in respiration, amino acid metabolism, sugars, and secondary metabolites shift. Heat and calcium treatments are used to improve postharvest fruit longevity; however, the exact mechanism remains poorly understood. To characterize the impact of these treatments on sweet cherries metabolism, 'Lapins' fruits were treated with heat or CaCl₂ solutions and their combination and subsequently were exposed at room temperature, for up to 4 days, defined as senescence period. Single and combined heat and calcium treatments partially delayed fruit senescence, as evidenced by changes in fruit colour darkening, skin penetration force, and respiration activity. Calcium content was noticeably increased by heat in Ca-treated fruit. Several primary metabolites, including amino acids, organic acids, and alcohols, were decreased in response to both treatments, while many soluble sugars and secondary metabolites were increased within 1 day post-treatment. Changes of several metabolites in heat-treated fruits, especially esculetin, peonidin 3-O-glucoside and peonidin 3-O-galactoside, ribose, pyroglutamate, and isorhamnetin-3-O-rutinoside, were detected. The metabolome of fruit exposed to calcium also displayed substantial modulations, particularly in the levels of galactose, glycerate, aspartate, tryptophan, phospharate rutin, and peonidin 3-O-glucoside. The expression of several genes involved in TCA cycle (MDH1, IDH1, OGDH, SUCLA2, and SDH1-1), pectin degradation (ADPG1) as well as secondary (SK1, 4CL1, HCT, and BAN), amino acids (ALDH18A1, ALDH4A1, GS, GAD, GOT2, OPLAH, HSDH, and SDS), and sugar (PDHA1 and DLAT) metabolism were affected by both treatments. Pathway-specific analysis further revealed the regulation of fruit metabolic programming by heat and calcium. This work provides a comprehensive understanding of metabolic regulation in response to heat and calcium during fruit senescence.

Significance of Temperature and Humidity Control for Agricultural Products Storage: Overview of Conventional and Advanced Options

The agricultural products are perishable in nature and possesses short shelf/storage life under ambient conditions. The temperature and humidity control systems are required to enhance to storage life of the products with optimum quality, quantity and nutritive attributes. In this regard, the significance of air-conditioning in storage application is highlighted along with the conventional storage options. The implications of compressor-based refrigeration and air-conditioning systems regarding low-cost and energy efficient air-conditioning systems are discussed in detailed. It is concluded that thermally driven air-conditioning systems can be used on top priority for the short-term storage of fresh agricultural products. Moreover, the long-term storage of products at freezing temperature can be made through hybrid systems instead of standalone conventional compressor based vapor compression refrigeration and/or air-conditioning systems. Finally, the air-conditioning systems are proposed for the optimum storage of different categorize of the food products.

Quality of fresh-cut products as affected by harvest and postharvest operations

There is a rising demand for fresh-cut convenience products with high quality and nutritional standards that needs to be met by the fresh-cut industry. It is well known that harvest and postharvest handling of fresh produce has a paramount impact on its quality and storage, although most of the existing literature has focused on these impacts related only to fresh produce that is destined for the final consumers. Indeed, current harvest methods and postharvest technologies have improved fruit and vegetable handling and distribution processes by slowing down physiological processes and senescence. Nonetheless, these technologies and methods may influence the quality of fresh produce as raw material for fresh-cut processing as a result of the dynamic responses of fresh produce to handling procedures and treatments. Here, we review the existing literature on the challenges facing the fresh-cut industry, focusing on the impact of harvest, maturity, and handling of fruit and vegetables on the quality of raw materials, as well as the implications for fresh-cut products. The review also highlights areas for further research with the aim of enhancing the sensorial, nutritional and biochemical quality of such products. © 2018 Society of Chemical Industry.

Evaluation of Low-Temperature Phosphine Fumigation for Control of Oriental Fruit Fly in Loquat Fruit

Oriental fruit fly, Bactrocera dorsalis (Hendel; Diptera: Tephritidae), is recognized as a quarantine pest and a threat to Chinese loquat (Eriobotrya japonica Lindl.) fruit exports. Since loquat fruit is very sensitive to methyl bromide (MB) fumigation and cold treatment, in this study, low-temperature phosphine (PH3) fumigation was investigated to develop an alternative phytosanitary treatment method. Tolerance tests showed that the third instar was the most tolerant of all life stages of B dorsalis to PH3 gas at 8°C. Toxicity assay with 500-3000 ppm PH3 and subsequent probit analysis showed that 2000 ppm PH3 was optimal for fumigation and 152.75 h of treatment duration were required to achieve 99.9968% mortality. In the verification test, 144 and 168 h of treatment duration with 2000 ppm PH3 completely killed 35,277 and 35,134 B. dorsalis third instars, respectively. However, 13 live larvae were found after 120 h of treatment. Furthermore, these treatments reduced fruit respiration rates while causing no adverse effects on other fruit quality parameters, including firmness, soluble solid content, and titratable acidity over 192 h storage at 8°C. The results strongly suggest that low-temperature PH3 fumigation could be used for the postharvest control of B. dorsalis in loquat fruit.

The influence of antioxidant postharvest treatment on content of biologically active substances during storage of cucumbers

The influence of heat treatment with antioxidant compositions on the content of biologically active substances during storage of cucumbers is investigated. It was found that the use of the proposed treatment inhibits the activity of ascorbate oxidase by 15–18%, which allows to slow down the decomposition of ascorbic acid by 1.5 times. The content of ascorbic acid in the experimental fruit after storage for 28 days is 1.4 times higher than in the control after 21 days of storage. It was found that in the cucumbers 11–14 sm long, the synthesis of polyphenols continued in the period of storage.  The intensity of accumulation of phenolic substances proved to be different in the treated and control groups. It was shown that thermal treatment with antioxidants slowed the growth rate of total polyphenols by 20% relative to control, indicating inhibition of maturation processes. It was revealed that the activity o polyphenol oxidase during the storage of treated fruits was slowing down. It has been established that the application of said treatment substantially inhibits the degradation of chlorophylls. Rapid loss of chlorophyll caused yellowing and loss of consumer properties in the control groups after 2 weeks of storage. In processed cucumbers only 21 days of storage revealed a decrease in the concentration of chlorophyll in relation to the moment of laying. At day 28 the amount of chlorophylls in the experimental fruit is at the same level as in the control after a week of storage. It has been found that the use of the proposed treatment slows the degradation of carotenoids. The quantity of carotenoids in experimental cucumbers at the end of storage is 21–23% higher than in the control ones. The compensatory function of ascorbic acid, carotenoids and phenolic substances during storage of cucumber fruits is proved.

To disinfect or not to disinfect in postharvest research on the fungal decay of apple?

Postharvest losses of fruit and vegetables can reach up to 30%, the main cause being microbial decay. For apple fruit, mostly fungal pathogens, such as Penicillium expansum, Colletotrichum spp., Neofabraea spp. and Botrytis cinerea, are important. As such losses are unsustainable in many ways, it is necessary that research is conducted to prevent them. Generally, for plants and fruit grown under non-sterile field conditions, disinfection is carried out prior to the start of a phytopathological experiment. The motivation for this practice is the removal of background contamination so that it will not affect the experimental outcome and its interpretation. In literature, a plethora of disinfection methods exists, differing in disinfectant, strength and duration. The following two disinfectants are commonly used: sodium hypochlorite (NaOCl) and ethanol. This article presents a targeted investigation into the effects of these two disinfectants on apple fruit surface and physiology. The results clearly demonstrate that both were affected by both disinfectants. NaOCl caused oxidative damage to the apple's wax layer, causing it to crack. Ethanol affected a redistribution of the wax on the fruit surface and altered the wax composition and/or metabolism. Both NaOCl and ethanol treatment resulted in an increased respiration rate. Therefore, apple and possibly other fruit should not be disinfected in phytopathological studies. A negative control, as is typically used, is not solving this issue, as we clearly demonstrate that the living tissue shows metabolic effects following disinfection, and hence the study objects are changed, hampering a clear interpretation of the experimental outcomes. Moreover, fungal inoculation during experiments is typically taking place at rather large levels in wounded tissue (as infection success is the exception), outnumbering the variable levels of background population, if present.

The impact of the postharvest environment on the viability and virulence of decay fungi

Postharvest decay of fruits, vegetables, and grains by fungal pathogens causes significant economic losses. Infected produce presents a potential health risk since some decay fungi produce mycotoxins that are hazardous to human health. Infections are the result of the interplay between host resistance and pathogen virulence. Both of these processes, however, are significantly impacted by environmental factors, such as temperature, UV, oxidative stress, and water activity. In the present review, the impact of various physical postharvest treatments (e.g., heat and UV) on the viability and virulence of postharvest pathogens is reviewed and discussed. Oxidative injury, protein impairment, and cell wall degradation have all been proposed as the mechanisms by which these abiotic stresses reduce fungal viability and pathogenicity. The response of decay fungi to pH and the ability of pathogens to modulate the pH of the host environment also affect pathogenicity. The effects of the manipulation of the postharvest environment by ethylene, natural edible coatings, and controlled atmosphere storage on fungal viability are also discussed. Lastly, avenues of future research are proposed.

Combined Treatments Reduce Chilling Injury and Maintain Fruit Quality in Avocado Fruit during Cold Quarantine

Quarantine treatment enables export of avocado fruit (Persea americana) to parts of the world that enforce quarantine against fruit fly. The recommended cold-based quarantine treatment (storage at 1.1°C for 14 days) was studied with two commercial avocado cultivars 'Hass' and 'Ettinger' for 2 years. Chilling injuries (CIs) are prevalent in the avocado fruit after cold-quarantine treatment. Hence, we examined the effect of integrating several treatments: modified atmosphere (MA; fruit covered with perforated polyethylene bags), methyl jasmonate (MJ; fruit dipped in 2.5 μM MJ for Hass or 10 μM MJ for Ettinger for 30 s), 1-methylcyclopropene (1-MCP; fruit treated with 300 ppb 1-MCP for 18 h) and low-temperature conditioning (LTC; a gradual decrease in temperature over 3 days) on CI reduction during cold quarantine. Avocado fruit stored at 1°C suffered from severe CI, lipid peroxidation, and increased expression of chilling-responsive genes of fruit peel. The combined therapeutic treatments alleviated CI in cold-quarantined fruit to the level in fruit stored at commercial temperature (5°C). A successful therapeutic treatment was developed to protect 'Hass' and 'Ettinger' avocado fruit during cold quarantine against fruit fly, while maintaining fruit quality. Subsequently, treated fruit stored at 1°C had a longer shelf life and less decay than the fruit stored at 5°C. This therapeutic treatment could potentially enable the export of avocado fruit to all quarantine-enforcing countries. Similar methods might be applicable to other types of fruit that require cold quarantine.