Postharvest heat treatments lead to an alteration of gene expression and fruit ripening can sometimes be either delayed or disrupted. The extent of the alternation of fruit ripening is a function of the exposure temperature and duration and how quickly the commodity is cooled following the heat treatment.
Full Answer
How does heat treatment affect the color of fruits and vegetables?
Such metabolic processes are enzyme-mediated, and depending on the effect of heat treatment on the activity of such enzymes, fruits and vegetables show their response to heat treatment in the form of enhanced or lowered color formation.
How does heat affect fruit ripening?
The most commonly measured components of fruit ripening affected by heat treatments include fruit softening, membrane and flavor changes, respiration rate, ethylene production, and volatile production.
How can we overcome heat stress in fruit crops?
The success in overcoming heat stress is limited owing to poor knowledge of heat stress during critical stages of fruit crops. There is urgent need to improve heat stress tolerance by using traditional breeding and transgenic approach.
What is postharvest heat treatment for fruit?
Postharvest heat treatments of fruit are used for insect disinfesta- tion, disease control, to modify fruit responses to other stresses and maintain fruit quality during storage (Armstrong et al., 1989; Couey, 1989; Klein and Lurie, 1990; Paull, 1994; Paull and McDonald, 1994; Lurie, 1998; McDonald et al., 1999).
What temperature should I use for a fruit softener?
What are the factors that influence postharvest ripening behavior of fruits?
What temperature to rinse satsuma?
Why are fruits and vegetables considered biological?
How to treat post harvest decay?
How to use hot water for fungus?
What causes post harvest rot?
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What are the changes or alterations that occur as a result of heat in the fruits and vegetables?
As temperatures increase, pollen production decreases leading to reduced fruit set, reduced seed set, smaller pods, and split sets. Heat injury in plants includes scalding and scorching of leaves and stems, sunburn on fruits and stems, leaf drop, rapid leaf death, and reduction in growth.
How does heat treatment for food work?
14.4. Heat treatment is a pesticide-free method to care for texture quality during storage. This method is conducted using hot air, hot water dips, or vapor heat, and is an alternative to cut down the need to use chemical products to assure the quality of fruits or vegetables.
What is the effect of temperature on fruit?
For fruit cultivation, the ambient temperature during fruit development is an important factor that affects fruit quality. High temperatures during fruit development suppress fruit color development. For example, poor coloration caused by high temperature has been reported for grapes (Tomana et al.
What is heat treatment in food preservation?
Pasteurization is the application of heat to a food product in order to destroy pathogenic (disease-producing) microorganisms, to inactivate spoilage-causing enzymes, and to reduce or destroy spoilage microorganisms.
What is heat treatment process?
Heat treatment is the process of heating metal without letting it reach its molten, or melting, stage, and then cooling the metal in a controlled way to select desired mechanical properties. Heat treatment is used to either make metal stronger or more malleable, more resistant to abrasion or more ductile.
How does heat preservation work?
Processes that employ heat to make food safe for consumption and/or extend shelf-life by reducing or eliminating microbiological contamination (pathogens or spoilage) and enzymatic activity of the food. These processes could also affect texture and flavor of food products.
How does temperature affect ethylene?
An increase in storage temperatures between 14 and 30°C enhances the rate of ripening and the fruit softens at a faster rate (Smith, 1989). The respiration rate and ethylene production were also shown to increase with an increase of temperature (Weixin et al., 1993).
How does temperature affects the postharvest life of a produce?
Temperature is the single biggest factor in postharvest quality of vegetables. The temperature of produce drives water loss, changes in metabolic activity, loss of flavour, texture and nutrients and the development of rots.
How are plants affected by high temperature?
High temperatures are unfavorable for the growth of many plant species because the rate of photosynthesis (the basic process plants use to make sugar) begins to decline rapidly after a critical high temperature is reached.
What type of low temperature preservation method is applicable to fruits?
Dehydro freezing of fruits and vegeta-bles is the drying of the food to about 50 percent of its original weight and volume and then freezing the food to preserve it. The quality of dehydro frozen fruits and vegetables is equal to that of fruits and vegetables which are frozen without pre-liminary drying.
Why is heat used in preserving food?
Heating food is an effective way of preserving it because the great majority of harmful pathogens are killed at temperatures close to the boiling point of water. In this respect, heating foods is a form of food preservation comparable to that of freezing but much superior to it in its effectiveness.
What food can be preserved by heating?
Heat preserved foods are foods that have been treated using a thermal process to extend their shelf life. Examples include canned fruit and vegetable products, aseptically processed fruit juices in cartons and pasteurised ready meals.
What is mild heat treatment for food?
Pasteurization is a relatively mild heat treatment in which food or beverages are heated to less than 100°C to eliminate pathogens or to reduce the number of spoilage organisms in a product.
What is the minimum temperature when reheating food?
*All parts of the food must reach a temperature of at least 165°F for 15 seconds. Reheating must be done rapidly, within 2 hours after being removed from refrigeration. Foods reheated in a microwave oven must be reheated so that all parts of the food reach a temperature of at least 165°F.
What is the result of thermal processing on nutritional quality?
These findings indicate thermal processing enhanced the nutritional value of tomatoes by increasing the bioaccessible lycopene content and total antioxidant activity and are against the notion that processed fruits and vegetables have lower nutritional value than fresh produce.
Abstract
Postharvest heat treatments lead to an alteration of gene expression and fruit ripening can sometimes be either delayed or disrupted. The extent of the alternation of fruit ripening is a function of the exposure temperature and duration and how quickly the commodity is cooled following the heat treatment.
1. Introduction
Heat treatments (thermotherapy) have been used for over a century to free plant materials from pathogens, the temperature and exposure duration having been determined empirically ( Grondeau and Samson, 1994 ).
3. Temperature stress
The transfer of plants to an elevated temperature produces stress. The severity of stress is primarily determined by the temperature differential and the duration of exposure ( Lurie, 1998 ). Other factors such as rapidity of the change in temperature and the previous growing conditions are also important.
4. Response to heat treatment
The gross cytological changes that follow high temperature exposure (>45°C) have been described ( Belehradek, 1957) and include coagulation of the cytoplasm, cytolysis, nuclear changes and altered mitosis. Protoplasmic streaming is inhibited, and there is increased protoplasmic viscosity and a loss of membrane permeability ( Alexandrov, 1977 ).
5. Mechanism of responses to high temperature
HSPs produced in response to high temperature are believed to prevent irreversible protein denaturation that would be detrimental to the cell ( Parsell and Linquist, 1993) and this activity may be enhanced in plants by small HSPs ( Lee and Vierling, 2000 ).
6. Conclusions
Changes in fruit ripening during and following heat treatments can be divided broadly into two types ( Table 3 ). The first type of response is the normal stress cellular responses that lead to modification of chilling sensitivity, delayed or slowed ripening and some slight modification of quality.
Acknowledgements
We thank Mrs Gail Uruu and Dr Ching Cheng Chen for technical help. This is the College of Tropical Agriculture and Human Resource, Journal Series ♯4490.
What is the result of heat treatment?
The result of the treatments is to maintain fruit and vegetable quality following the heat treatment. Examples will be presented of the use of high temperature treatments in postharvest production systems and their effect on the quality of fruits and vegetables.
How does cold storage affect peach?
Cold storage is extensively used to slow the rapid deterioration of peach (Prunus persica L. Batsch) fruit after harvest. However, peach fruit subjected to long periods of cold storage develop chilling injury (CI) symptoms. Post-harvest heat treatment (HT) of peach fruit prior to cold storage is effective in reducing some CI symptoms, maintaining fruit quality, preventing softening and controlling post-harvest diseases. To identify the molecular changes induced by HT, which may be associated to CI protection, the differential transcriptome of peach fruit subjected to HT was characterized by the differential display technique. A total of 127 differentially expressed unigenes (DEUs), with a presence-absence pattern, were identified comparing peach fruit ripening at 20°C with those exposed to a 39°C-HT for 3 days. The 127 DEUs were divided into four expression profile clusters, among which the heat-induced (47%) and heat-repressed (36%) groups resulted the most represented, including genes with unknown function, or involved in protein modification, transcription or RNA metabolism. Considering the CI-protection induced by HT, 23-heat-responsive genes were selected and analyzed during and after short-term cold storage of peach fruit. More than 90% of the genes selected resulted modified by cold, from which nearly 60% followed the same and nearly 40% opposite response to heat and cold. Moreover, by using available Arabidopsis microarray data, it was found that nearly 70% of the peach-heat responsive genes also respond to cold in Arabidopsis, either following the same trend or showing an opposite response. Overall, the high number of common responsive genes to heat and cold identified in the present work indicates that HT of peach fruit after harvest induces a cold response involving complex cellular processes; identifying genes that are involved in the better preparation of peach fruit for cold-storage and unraveling the basis for the CI protection induced by HT.
What is the role of glutathione peroxidase in ripening?
Glutathione peroxidases (GPXs) are central members in the antioxidant system and play an important role in response to oxidant stress. To understand the role of the major molecular players in peach fruit ripening, the GPX gene family was investigated in this study. Eight Glutathione peroxidase genes (PpaGPX1-8) in peach fruit were isolated from genome databases and characterized using bioinformatics analysis. The expression patterns of GPX genes were analyzed in peach fruit harvested at three different maturity classes and treated with heat + 1-MCP (HM). The unripe fruit were found to have both higher enzymatic and transcriptional capacity compared with the more mature fruit, and the ripe fruit were more sensitive to HM treatment. PpaGPX6 and PpaGPX8 were the most abundantly expressed genes at all three maturity classes of peach fruit. All the PpaGPX genes (except PpaGPX1) showed up-regulated expression in the late stage of ripening (after the peak of respiratory climacteric). Moreover, HM treatment dramatically delayed the postharvest ripening process of peach fruit, by postponing the climacteric peak in respiration, enhancing firmness, increasing GPX activity and up-regulating PpaGPXs expression. These data indicated that PpaGPXs had a more important regulating function in the late stage of peach fruit ripening.
What is tomato preservation?
Fresh tomato (Solanum lycopersicum) is one of the most consumed fruits and the preservation of its quality and shelf-life extension is a continuous challenge. An understanding of fruit deterioration factors allows the investigation of new approaches to reach this objective. Fruit preservation is achieved by destroying enzymes and micro-organisms, and reducing physiological disorders, using treatments such as chlorinated water (HIPO), ozone, low or high temperatures, ultrasounds, UV-C radiation, modified atmosphere packaging, edible coatings and 1-methylcyclopropene. In this review, a description of action, advantages and disadvantages of each preservation treatment, and corresponding effects on tomato quality and safety are presented. The development of a green technology for tomato has advantages for all fresh chain interventions, with direct or indirect impacts on human health.
What do phytochromes do in plants?
Higher plants use light as an information source for optimizing their growth and development. Among the photoreceptors sensing ambient light environment, phytochromes are most intensively characterized and mediate plethora of developmental responses ranging from seed germination, chloroplast development, flowering to senescence. Available evidences indicate that fruit-localized phytochromes in tomato regulate the accumulation of lycopene which is the major carotenoid pigments of fruits. Consistent with this view, fruits of hp1 and hp2 mutants of tomato, which encode negative regulators of phytochrome signal transduction, show higher accumulation of carotenoids. Currently there is limited information about the role of different phytochrome species in regulation of carotenoid formation during fruit ripening. In tomato phytochromes are encoded by a multigene family, namely PHYA, PHYB1, PHYB2, PHYE and PHYF. In this study, we compared pigment accumulation in on-vine ripened fruits of three different phytochrome mutants, phyA, phyB1 and phyB2 with fruits that were harvested at Mature Green stage and ripened off-vine under darkness, or red light, or farred light. We show that light is not mandatory for carotenoid accumulation in these fruits and even dark grown fruits show significant accumulation of carotenoids. The analysis of single, double and triple mutants of phytochromes revealed a complex relationship between carotenoid accumulation and putative roles of different phytochrome species in fruit ripening. Our results indicate that fruitlocalized phytochromes are not the master regulators of carotenoid accumulation during tomato fruit ripening.
What is edible coating?
The decrease in fruit quality between harvest and consumption is an important area in agriculture. Edible coatings are harmless compounds used for covering the crops after harvest to reduce the metabolism intensity. γ-aminobutyric acid (GABA) is a good candidate because it is a natural substance produced by plants at stress conditions. Pomegranate (Punica granatum L.) is a perishable fruit because it has a high content of water and nutritional compounds and also relatively soft texture. In this study the effect of GABA on extending the pomegranate shelf life at 4 ± 1 °C was studied. The treatments included control (distilled water), GABA (5, 10 and 15 mM) and the storage periods (45 and 90 days) with four replications. The results showed that GABA treatments had some positive effects on improving peel (skin) and aril (edible part of seeds) firmness, antioxidant activity, phenolic compounds content, scent and taste, freshness of texture and aril color indicators and they reduced ion leakage, chilling injury signs and malondialdehyde formation. However, GABA did not have a positive effect on weight loss. Total acidity in control and treated samples was reduced until 45 days but increased at day 90. GABA had the ability to maintain the fruit pH stable. Total soluble solids and vitamin C content were not affected by storage and GABA, and the effects on anthocyanin content were varied among treatments. Totally, the results suggested that postharvest application of GABA has the potential to extend the storage life of pomegranate fruits by maintaining some fruit qualities.
What is tomato ripening?
Tomato fruit ripening is a complex metabolic process regulated by a genetical hierarchy. A subset of this process is also modulated by light-signaling, as mutants encoding negative regulators of phytochrome signal transduction, show higher accumulation of carotenoids. In tomato phytochromes are encoded by a multi-gene family, namely PhyA, PhyB1, PhyB2, PhyE and PhyF, however, their contribution to fruit development and ripening has not been examined. Using single phytochrome mutants- phyA, phyB1 and phyB2 and multiple mutants- phyAB1, phyB1B2 and phyAB1B2, we compared the on-vine transitory phases of ripening till fruit abscission. The phyAB1B2 mutant showed accelerated transitions during ripening with shortest time to fruit abscission. Comparison of transition intervals in mutants indicated a phase-specific influence of different phytochrome species either singly or in combination on the ripening process. Examination of off-vine ripened fruits indicated that ripening specific carotenoid accumulation was not obligatorily dependent on light and even dark incubated fruits accumulated carotenoids. The accumulation of transcripts and carotenoids in off-vine and on-vine ripened mutant fruits indicated a complex and shifting phase-dependent modulation by phytochromes (s). Our results indicate that in addition to regulating carotenoid levels in tomato fruits, phytochrome (s) also regulate the time required for phase transitions during ripening.
How to preserve nutrient in food?
While most forms of fruits and vegetables will provide a variety of nutrients, the Oregon State University Extension program recommends some strategies for maximum nutrient preservation. Refrigerate raw vegetables and use them as soon as possible. Buy local produce to prevent nutrient loss in shipping, and cook raw vegetables in a small amount of water. Canned foods should be stored in a cool dark place, and the brine or syrup should also be consumed. Frozen foods should be kept from temperature fluctuations and packaged properly.
How long does vitamin C last in canned food?
In canned foods, the remaining vitamin C is stable for two years. And thiamine, another heat-sensitive B vitamin found in beans, also survives the canning process well. Advertisement.
Is vitamin C heat sensitive?
Image Credit: Bob Ingelhart/iStock/Getty Images. However, some vitamins and nutrients are heat-sensitive. The University of Michigan says that when fruits or vegetables are cooked at high temperatures or for long periods of time, heat-sensitiv e nutrients such as B vitamins, vitamin C and folate are more likely to be destroyed.
What temperature is a citrus fruit susceptible to?
Citrus fruits are susceptible to chilling injury when exposed to temperatures lower than 2–5 °C. High temperature treatments using HAT 28 and HWT 29, 30 can delay the appearance of chilling injury and inhibit fungal infection. Sala and Lafuente 28 found a correlation between catalase (CAT) activity and resistance to chilling injury when mandarins were stored at 2 °C following a 3 min HWT at 53 °C or 3-day HAT at 38 °C hot air. They did not find induction of ascorbate peroxidase (APX), glutathione reductase or superoxide dismutase (SOD) in the heated fruit. This treatment of HAT can also increase polyamine concentration and the increase correlated with lower chilling sensitivity of mandarins. 31
How does temperature affect plant growth?
Temperature is one of the most important environmental factors that regulate plant growth and development. Plants have evolved signaling pathways to sense changes in ambient temperature and adjust their metabolism and cell function to prevent heat-related damage. Many features of the heat stress response pathway are conserved among both prokaryotic and eukaryotic organisms. 7 Because plants are sessile organisms that cannot escape stress conditions, they invest valuable resources in modifying their metabolism to prevent damage caused by heat, in a process referred to as acclimation, or acquired thermotolerance. 7, 8 The accumulation of HSPs, under the control of heat stress transcription factors (HSFs), plays a central role in the heat stress response and in acquired thermotolerance in plants and other organisms.
What changes occur after heat stress?
In the case of short times of exposure to high temperature, the molecular changes may actually occur after the heat stress has ended. The changes involve accumulation of stress and defense proteins, including HSPs, PRs, dehydrins, and antioxidant enzymes and compounds (polyphenols).
What happens when you get high temperature?
A high temperature will affect most macromolecules and will cause changes such as increased membrane fluidity, partial melting of DNA and RNA strands, protein subunit disassociation and exposure of hydrophobic cores.
How hot is the temperature of postharvest storage?
The treatment times and temperature range vary widely, from days at 35 °C to 39 °C in hot air, to up to 63 °C for less than a minute in hot water. Much of the research has been performed to develop solutions to a particular problem, and less investigation has been conducted on the responses of the commodity to the treatment. However, since the turn of the century, a number of groups have been active in examining the molecular responses and changes that occur in commodities during and after the heat treatment. This review examines the changes at the level of transcriptome, proteome and metabolome that occur in response to the different heat treatments.
What is post harvest heat treatment?
Postharvest heat treatments of fruit are used for insect disinfestation, disease control, to modify fruit responses to cold stress and maintain fruit quality during storage. 1 – 5 The temperature and exposure duration for a particular crop for a particular purpose are usually determined empirically. Conditioning treatments at temperatures from 30 °C to 40 °C in hot air (HAT) for times ranging from hours to days have been developed to affect commodity quality and storability. 1 Higher temperatures are normally used for either insect or microorganism control. Some treatments which have commercial approval for insect control involve either vapor heat or hot water immersion of the fruit until the core temperature reaches 47 °C, which takes a number of hours unless radiofrequency is involved. 5 Other treatments, involving hot water dips (HWT), are for a few minutes at temperatures of 50–56 °C to control fungal pathogens. In addition, there is a short (10–25 s) treatment of hot water rinsing and brushing (HWB) which may involve temperatures of up to 63 °C. 4
Why are commodities exposed to low temperature?
Harvested commodities are invariably exposed to low temperature in order to retard product respiration and delay ripening and senescence. Many commodities will develop chilling injury if the temperature is too low or if the cold conditions are maintained for too long.
How does heat affect plants?
As heat stress becomes more severe a series of event occurs in plants starting with a decrease in photosynthesis and increase in respiration. As stress increases, photosynthesis shuts down due to the closure of stomates which slows or stops CO 2 capture and increases photo-respiration. This will cause growth inhibition. There will be a major slow-down in transpiration leading to reduced plant cooling and internal temperature increase. At the cellular level, as stress becomes more severe there will be membrane integrity loss, cell membrane leakage and protein breakdown. Toxins generated through cell membrane releases will cause damage to cellular processes. Finally, if stress is severe enough there can be plant starvation through rapid use of food reserves, inefficient food use, and inability to call on reserves when and where needed.
How to reduce heat stress?
The major method to reduce heat stress is by meeting evapotranspiration demand with irrigation. Use of overhead watering, sprinkling, and misting can reduce of tissue temperature and lessen water vapor pressure deficit. Mulches can also help greatly. You can increase reflection and dissipation of radiative heat using reflective mulches or use low density, organic mulches such as straw to reduce surface radiation and conserve moisture. In very hot areas of the world, shade cloth is used for partial shading to reduce advected heat and total incoming radiation.
Why do plants lose water?
Very hot, dry winds are a major factor in heat buildup in plants. Such conditions cause rapid water loss because leaves will be losing water more quickly than roots can take up water, leading to heat injury. Therefore, heat damage is most prevalent in hot, sunny, windy days from 11 a.m. to 4 p.m. when transpiration has been reduced. As the plants close stomates to reduce water loss, leaf temperatures will rise even more. In addition, wind can decrease leaf boundary layer resistance to water movement and cause quick dehydration. Wind can also carry large amounts of advected heat.
What are the signs of heat damage in plants?
Heat injury in plants includes scalding and scorching of leaves and stems, sunburn on fruits and stems, leaf drop, rapid leaf death, and reduction in growth. Wilting is the major sign of water loss which can lead to heat damage.
What happens when a plant's roots are dry?
Dry soil conditions start a process that can also lead to excess heating in plants. In dry soils, roots produce Abscisic Acid (ABA). This is transported to leaves and signals to stomate guard cells to close. As stomates close, transpiration is reduced. Without water available for transpiration, plants cannot dissipate much of the heat in their tissues. This will cause internal leaf temperatures to rise.
Why do plants' internal leaf temperatures rise?
As stomates close, transpiration is reduced. Without water available for transpiration, plants cannot dissipate much of the heat in their tissues. This will cause internal leaf temperatures to rise. Vegetables can dissipate a large amount of heat if they are functioning normally.
What happens when a plant dies?
Plants often will drop leaves or, in severe cases, will “dry in place” where death is so rapid, abscission layers have not had time to form. There are three types of sunburn which may have effects on fruits and fruiting vegetables.
What temperature should I use for a fruit softener?
Fruits and vegetables subjected to HAT of 38–40°C exhibit slower softening as compared to those that are nonheated. However, extended disinfestations treatment for mangoes and papaya of hot forced air for 4 h at 50°C resulted in faster softening ( Shellie and Mangan, 1994 ). Slower rate of softening as a result of heat treatment at temperatures between 30°C and 40°C has been reported in the case of pears ( Maxie et al., 1974 ), plums ( Tsuji et al., 1984 ), avocadoes ( Eaks, 1978 ), and tomatoes ( Biggs et al., 1988 ). Prestorage heat-treated apple fruits were firmer by 10 N than nonheated fruits even after 6 months of storage at 0°C and subsequent shelf life for 7 days at 20°C ( Conway et al., 1994; Sams et al., 1993 ). Chàvez-Sanchez et al. (2013) found that the use of antifungal HWT at 55°C for 3 min did not affect softening process in papaya since the cell wall enzyme activity pectinmethylesterase [PME and polygalacturonase (PG)] was not altered by the treatment.
What are the factors that influence postharvest ripening behavior of fruits?
The factors include level of field-induced thermotolerance ( Woolf and Ferguson, 2000 ), cultivar ( Miller and McDonald, 1991; Paull, 1995 ), fruit size and morphological characteristics, physiological stage of the commodity or the stage of ripeness, heat transfer rate and energy balance, final temperature, and the duration of exposure at different temperatures.
What temperature to rinse satsuma?
Hot water rinsing and brushing (HWRB) at 55°C for 15 s significantly reduced decay development in P. expansum -inoculated Golden Delicious apples after 4 weeks at 20°C, or in naturally infected fruit after prolonged storage of 4 months at 1°C ( Fallik et al., 2001 ). The VHT of Sultanina grapes at 55°C for 18–21 min reduced the infection levels of B. cinerea by 72%–95% on the ninth day of the storage ( Lydakis and Aked, 2003 ).
Why are fruits and vegetables considered biological?
Fruits and vegetables, being biological entities, continue to respire and undergo metabolic processes even after being detached from the plant. Exposure to unfavorable storage regimes, insect pests, and disease pathogens not only cut short their postharvest life but also reduces quality and consumer acceptability. While the use of synthetic chemicals to control insect pests, diseases, and physiological disorders is still rampant, consumers are increasingly aware of the potential health hazards posed by these chemicals. There is a growing demand, the world over, for reducing the postharvest use of chemicals against pathogens and insects. Thus, over the recent years, researchers have felt the urgent need to develop safe, effective, and nondamaging physical treatments for disinfection and disinfestation of horticultural produce—a research area that still continues unabated.
How to treat post harvest decay?
Heat/thermal treatment of fruits and vegetables is an efficient, easy, safe, and cost-effective means for postharvest decay control as well as for the maintenance of proper postharvest quality. Over the years, heat treatments have been employed for achieving postharvest solutions such as insect disinfestations, control of decay and diseases, alleviation of chilling injury, and maintenance of fruit quality during storage. Temperature-time combination for different heat treatments ranges from 35°C to 39°C in hot air for days to up to 63°C in hot water for less than a minute. Normally, higher temperatures are employed for insect disinfestation and control of microorganisms. Thermotherapy has been used for more than a century to free plant materials from pathogens. Postharvest heat treatments are used for insect disinfestations, disease and decay control of fruits and vegetables, to modify commodity responses to other stresses and to maintain fruit quality during storage. Heat treatment has been successfully employed to maintain firmness of tomatoes, potatoes, carrots, and strawberries; preserve color in broccoli, kiwifruit, lettuce, celery, and asparagus; prevent overripening in melons and cantaloupe; and improve shelf life in grapes, peaches, plums, etc.
How to use hot water for fungus?
Water is an efficient medium of heat transfer owing to its high heat capacity. Hot water treatment (HWT) is accomplished either through dipping or spraying. As stated earlier, HWT is usually used for fungal disinfection. Postharvest dips are done at comparatively lower temperature and for shorter duration lasting few minutes. This milder treatment is done because only the surface of the commodity requires heating. Fruits and vegetables can generally tolerate water temperatures of 50–60°C for up to 10 min, while shorter exposure at these temperatures can effectively control many postharvest plant pathogens ( Barkai-Golan and Phillips, 1991 ). Generally, for insect disinfestation, the time of dipping/immersion can last up to 1 h or more at temperatures < 50°C, while antifungal treatments are usually done for minutes at temperatures above 50°C.
What causes post harvest rot?
Spoilage caused by decay pathogens is a primary cause of huge postharvest losses in horticultural produce handling. Heat treatment as an effective and safe method of postharvest decay control is well documented. Heat treatment minimizes rots, either directly, by killing the germinating spores or slowing down the germ tube elongation, or indirectly by affecting the physiological responses of the fruit tissue through the induction of antifungal substances, PR proteins such as chitinase and β-1,3 glucanase, or by inhibiting the synthesis of cell wall hydrolyzing enzymes.
