BIOLOGY AND TECHNOLOGY 39

Losses in quantity and quality affect horticultural between har- vest and consumption. The magnitude of postharvest losses in fresh and vegetables is an estimated 5 to 25% in developed countries and 20 to 50% in developing countries, depending upon the com- modity, cultivar, and handling conditions. To reduce these losses, pro- ducers and handlers must first understand the biological and environ- mental factors involved in deterioration, and second, use postharvest techniques that delay senescence and maintain the best possible qual- ity. This chapter briefly discusses the first item and introduces the Postharvest second, which is covered in detail in subsequent chapters. Fresh fruits, vegetables, and ornamentals are living tissues that are Biology and subject to continuous change after . While some changes are desirable, most-from the consumer's standpoint-are not. Posthar- Technology: An vest changes in fresh produce cannot be stopped, but they can be slowed within certain limits. Senescence is the final stage in the devel- Overview opment of organs, during which a series of irreversible events leads to breakdown and death of the plant cells. Fresh horticultural crops are diverse in morphological structure' (roots, stems, leaves, flowers, fruits, and so on), in composition, arid Adel A. Kader in general physiology. Thus, commodity requirements and recommen- dations for maximum postharvest life vary among the commodities. All fresh horticultural crops are high in water content and are subject to desiccation (wilting, shriveling) and to mechanical injury. They are also susceptible to attack by bacteria and fungi, with pathological breakdown the result.

BIOLOGICAL FACTORS INVOLVED IN DETERIORATION

RESPIRATION Respiration is the process by which stored organic materials (carbohy- drates, proteins, fats) are broken down into simple end products with a release of energy. Oxygen (02) is used in this process, and carbon dioxide (CO2) is produced. The loss of stored reserves in the commodity during respiration means the hastening of senescence as the reserves that provide energy to maintain the commodity's living status are exhausted; reduced food value (energy value) for the con- sumer; loss of flavor quality, especially sweetness; and loss of salable dry weight, which is especially important for commodities destined for dehydration. The energy released as heat, known as vital heat, affects postharvest technology considerations, such as estimations of refrigeration and ventilation requirements. The rate of deterioration (perishability) of harvested commodities is generally proportional to the respiration rate. Horticultural com- modities are classified according to their respiration rates in table 4.l. Based on their respiration and ethylene (C2H4) production patterns during maturation and , fruits are either climacteric or non- climacteric (table 4.2). Climacteric fruits show a large increase in CO2 and C2H4 production rates coincident with ripening, while nonclimac- teric fruits show no change in their generally low CO2 and C2H4 pro- duction rates during ripening.

ETHYLENE PRODUCTION Ethylene (C2H4), the simplest of the organic compounds affecting the physiological processes of , is a natural product of plant 40 CHAPTER 4

Table 4.1. Horticulturalcommoditiesclassifiedaccordingto respiration Generally, C2H4 production rates increase rates with maturity at harvest and with physical Rangeat soC(41°F) injuries, disease incidence, increased temper- Class (mg COz/kg-hr)* Commodities atures up to 30°C (86°F), and water stress. - nn --- - Verylow <5 Dates,driedfruits andvegetables,nuts On the other hand, C2H4 production rates by fresh horticultural crops are reduced by stor- Low 5-10 ,beet,celery,citrusfruits,cranberry, garlic,grape,honeydewmelon,kiwifruit, age at low temperature, by reduced O2 levels onion,papaya,persimmon,pineapple, (less than 8%), and elevated CO2 levels pomegranate,potato(mature),pumpkin, (more than 2%) around the commodity. sweetpotato,watermelon,winter squash COMPOSITIONAL CHANGES Moderate 10-20 Apricot,banana,blueberry,cabbage,can- taloupe,carrot(topped),celeriac,cherry, Many changes in pigments take place during cucumber,fig, gooseberry,lettuce(head), development and maturation of the commod- mango,nectarine,olive,peach,pear,plum, ity on the plant; some may continue after potato (immature),radish(topped),sum- harvest and can be desirable or undesirable: mersquash, Loss of chlorophyll (green color) is desir- High 20-40 Avocado,blackberry,carrot(with tops), . able in fruits but not in vegetables. cauliflower,leek,lettuce(leaf),limabean, radish(with tops),raspberry,strawberry . Development of carotenoids (yellow and Veryhigh 40-60 Artichoke,beansprouts,broccoli,Brus- orange colors) is desirable in fruits such as selssprouts,cherimoya,cutflowers, apricots, peaches, and citrus. Red color endive,greenonions,kale,okra,passion development in tomatoes and pink grape- , snapbean,watercress fruit is due to a specific carotenoid Extremely high >60 Asparagus, mushroom, parsley, peas, (lycopene); beta-carotene is provitamin A spinach, sweet corn and thus is important in nutritional quality. ------Note: *Vital heat (Btu/ton/24 hrs) = mg COz/kg-hrx 220. . Development of anthocyanins (red and Vital heat (kcal/1,000 kg/24 hrs) = mg COz/kg-hrx 61.2. blue colors) is desirable in fruits such as (red cultivars), cherries, strawber- metabolism and is produced by all tissues of ries, cane berries, and red-flesh oranges. higher plants and by some microorganisms- These water-soluble pigments are much As a , C2H4regulates many less stable than carotenoids. aspects of growth, development, and senes- Changes in anthocyanins and other phe- cence and is physiologically active in trace . nolic compounds may result in tissue amounts (less than 0.1 ppm). It also plays a browning, which is undesirable for major role in the abscission of plant organs. appearance quality. On the other hand, The amino acid methionine is converted these constituents contribute to the total to S-adenosylmethionine (SAM), which is the antioxidant capacity of the commodity, precursor of l-aminocyclopropane-l-car- which is beneficial to human health. boxylic acid (ACC), the immediate precursor of C2H+ ACC synthase, which converts SAM Changes in carbohydrates include starch- to ACe, is the main site of control of ethylene to- conversion (undesirable in pota- biosynthesis. The conversion of ACC into toes, desirable in apple, banana, and other ethylene is mediated by ACC oxidase. The fruits); sugar-to-starch conversion (undesir- synthesis and activities of ACC synthase and able in peas and sweet corn; desirable in ACC oxidase are influenced by genetic factors potatoes); and conversion of starch and sug- and environmental conditions, including ars to CO2 and water through respiration. temperature and concentrations of oxygen Breakdown of pectins and other polysaccha- and carbon dioxide. rides results in softening of fruits and a con- Horticultural commodities are classified sequent increase in susceptibility to mechan- according to their C2H4 production rates in ical injuries. Increased lignin content is table 4.3. There is no consistent relationship responsible for toughening of asparagus between the C2H4 production capacity of a spears and root vegetables. given commodity and its perishability; how- Changes in organic acids, proteins, amitlO ever, exposure of most commodities to C2H4 acids, and lipids can influence flavor quality accelerates their senescence. of the commodity. Loss in vitamin content, POSTHARVEST BIOLOGY AND TECHNOLOGY 41

especially ascorbic acid (vitamin C) is detri- onions and root crops is also undesirable. mental to nutritional quality. Production of Asparagus spears continue to grow after har- flavor volatiles associated with ripening of vest; elongation and curvature (if the spears fruits is very important to their eating quality. are held horizontally) are accompanied by increased toughness and decreased palatabil- GROWTH AND DEVELOPMENT ity. Similar geotropic responses occur in cut Sprouting of potatoes, onions, garlic, and gladiolus and snapdragon flowers stored root crops greatly reduces their food value horizontally. Seed germination inside fruits and accelerates deterioration. Rooting of such as tomatoes, peppers, and lemons is an undesirable change. Table 4.2. Fruitsclassifiedaccordingto respiratorybehavior during ripening TRANSPIRATION OR WATER lOSS ------..------Climacteric fruits Nonclimacteric fruits Water loss is a main cause of deterioration ------..------because it results not only in direct quantita- Muskmelon Apple Blackberry Lychee tive losses (loss of salable weight), but also Apricot Nectarine Cacao Okra in losses in appearance (wilting and shrivel- Avocado Papaya Carambola Olive ing), textural quality (softening, flaccidity, limpness, loss of crispness and juiciness), Banana Passionfruit Cashewapple Orange and nutritional quality. Biriba Peach Cherry Pea The commodity's dermal system (outer -- Pear Blueberry Cranberry Pepper protective coverings) governs the regulation Breadfruit Persimmon Cucumber Pineapple of water loss. It includes the cuticle, epider- Cherimoya Plantain Date Pomegranate mal cells, stomata, lenticles, and trichomes. (hairs). The cuticle is composed of surface Durian Plum Eggplant Pricklypear waxes, cutin embedded in wax, and a layer Feijoa Quince Grape Raspberry of mixtures of cutin, wax, and carbohydrate Fig Rambutan Grapefruit Strawberry polymers. The thickness, structure, and Guava Sapodilla Jujube Summersquash chemical composition of the cuticle vary Jackfruit Sapote Lemon greatly among commodities and among. developmental stages of a given commoditt. Kiwifruit Soursop Lime Tangerineand mandarin The transpiration rate (evaporation of Mango Sweetsop Longan water from the plant tissues) is influenced by Mangosteen Tomato Loquat Watermelon ------internal, or commodity, factors (morphologi- cal and anatomical characteristics, surface-to- Table4.3. Classificationof horticultural commodities accordingto eth- volume ratio, surface injuries, and maturity ylene (CZH4)production rates stage) and by external, or environmental, fac------Rangeat 20°C(68°F) tors (temperature, relative humidity [RH], air Class (IJLCzH4/kg-hr) Commodities movement, and atmospheric pressure). Tran------__OM ------spiration is a physical process that can be con- Verylow Lessthan 0.1 Artichoke,asparagus,cauliflower,cherry, trolled by applying treatments to the com- citrusfruits,grape,jujube,strawberry, pomegranate,leafyvegetables,root veg- modity (e.g., waxes and other surface coatings etables,potato,mostcutflowers or wrapping with plastic films) or by manipu- lating the environment (e.g., maintaining high Low 0.1-1.0 Blackberry,blueberry,casabamelon, cranberry,cucumber,eggplant,okra, RH and controlling air circulation). olive,pepper(sweetand chili),persim- PHYSIOLOGICAL BREAKDOWN mon,pineapple,pumpkin,raspberry, tamarillo,watermelon Exposure of the commodity to undesirable temperatures can result in physiological dis- Moderate 1.0":10.0 Banana,fig, guava,honeydewmelon, orders: Iychee,mango,plantain,tomato High 10.0-100.0 Apple,apricot,avocado,cantaloupe,fei- Freezing injury results when commodities joa, kiwifruit (ripe),nectarine,papaya, . are held below their freezing temperatures. peach,pear,plum The disruption caused by freezing usually. Veryhigh Morethan 100.0 Cherimoya,mammeeapple,passion results in immediate collapse of the tissues fruit, sapote ------and total loss of the commodity. 42 CHAPTER 4

Chilling injury occurs in some commodi- . accelerate water loss, provide sites for fun- ties (mainly those of tropical and subtrop- gal infection, and stimulate CO2 and C2H4 ical origin) held at temperatures above production by the commodity. their freezing point and below 5° to 1S0C (41 ° to S9°F), depending on the commod- PATHOLOGICAL BREAKDOWN ity. Chilling injury symptoms become One of the most common and obvious more noticeable upon transfer to higher symptoms of deterioration results from the (nonchilling) temperatures. The most activity of bacteria and fungi. Attack by most common symptoms are surface and inter- organisms follows physical injury or physio- nal discoloration (browning), pitting, logical breakdown of the commodity. In a watersoaked areas, uneven ripening or few cases, pathogens can infect apparently failure to ripen, off-flavor development, and accelerated incidence of surface healthy tissues and become the primary cause of deterioration. In general, fruits and molds and decay (especially the incidence vegetables exhibit considerable resistance to of organisms not usually found growing potential pathogens during most of their on healthy tissue). postharvest life. The onset of ripening in . Heat injury is induced by exposure to fruits, and senescence in all commodities, direct sunlight or excessively high temper- renders them susceptible to infection by atures. Its symptoms include bleaching, pathogens. Stresses such as mechanical surface burning or scalding, uneven ripen- injuries, chilling, and sunscald lower the' ing, excessive softening, and desiccation. resistance to pathogens.

Certain types of physiological disorders orig- ENVIRONMENTAL FACTORS inate from pre harvest nutritional imbalances. INFLUENCING For example, blossom end rot of tomatoes DETERIORATION and bitter pit of apples result from calcium deficiency. Increasing calcium content by Temperature. Temperature is the environ- preharvest or postharvest treatments can mental factor that most influences the deteri- reduce the susceptibility to physiological dis- oration rate of harvested commodities. Fer orders. Calcium content also influences the each increase of lOOC (lSOF) above optirrlum, textural quality and senescence rate of fruits the rate of deterioration increases by two- to and vegetables; increased calcium content threefold (table 4.4). Exposure to undesirable has been associated with improved firmness temperatures results in many physiological retention, reduced CO2 and C2H4 production disorders, as mentioned above. Temperature rates, and decreased decay incidence. also influences the effect of C2H4, reduced Very low °2( d %) and high CO2 (>20%) °2, and elevated CO2, The spore germination atmospheres can cause physiological break- and growth rate of pathogens are greatly down of most fresh horticultural commodi- influenced by temperature; for instance, cool- ties, and C2H4 can induce physiological ing commodities below SOC (41°F) immedi- disorders in certain commodities. The inter- ately after harvest can greatly reduce the inci- actions among °2, CO2, and C2H4 concentra- dence of Rhizopus rot. Temperature effects tions, temperature, and duration of storage on postharvest responses of chilling-sensitive influence the incidence and severity of physi- and nonchilling-sensitive horticultural crops ological disorders related to atmospheric are compared in table 4.5. composition. Relative humidity. The rate of water loss from fruits and vegetables depends on the PHYSICAL DAMAGE vapor pressure deficit between the commodi- Various types of physical damage (surface ty and the surrounding ambient air, which injuries, impact bruising, vibration bruising, is influenced by temperature and RH. At a and so on) are major contributors to deteri- given temperature and rate of air movement, oration. Browning of damaged tissues the rate of water loss from the commodity results from membrane disruption, which depends on the RH. At a given RH, water loss exposes phenolic compounds to the increases with the increase in temperature.. polyphenol oxidase enzyme. Mechanical Atmospheric composition. Reduction of injuries not only are unsightly but also O2 and elevation of CO2, whether intentional POSTHARVEST BIOLOGY AND TECHNOLOGY 43

Table 4.4. Effectoftemperature on deteriorationrate of a non-chilling-sensitive (modified or controlled atmosphere storage) commodity ------or unintentional (restricted ventilation within Relative a shipping container or transport vehicle), can Temperature velocity of Relative loss per day either delay or accelerate the deterioration of (OF) (°C) Assumed Q1O' deterioration shelf life (%) ------fresh horticultural crops. The magnitude of 32 0 1.0 100 1 these effects depends on the commodity, culti- 50 10 3.0 3.0 33 3 var, physiological age, O2 and CO2 levels, 68 20 2.5 7.5 13 8 temperature, and duration of holding. 86 30 2.0 15.0 7 14 Ethylene. Because the effects of C2H4 on 104 40 1.5 22.5 4 25 ------harvested horticultural commodities can be Note: 'Q1O = Rate of deterioration at temperature (T) + 10°C desirable or undesirable, C2H4 is of major Rate of deterioration at T concern to all produce handlers. Ethylene can be used to promote faster and more uni- Table 4.5.Fruits and vegetables classified according to sensitivity to form ripening of fruits picked at the mature- chillinginjury green stage. On the other hand, exposure to C2H4 can be detrimental to the quality of GROUPI GROUPII most nonfruit vegetables and ornamentals. Non-chilling-sensitive of 'C Chilling-sensitive commodities 122 50 commodities Light. Exposure of potatoes to light should 113 45 be avoided because it results in greening due to formation of chlorophyll and solanine High-temperature injury -1 104 40 1- High-temperature injury , 95 35, (toxic to humans). Light-induced greening of .;.. 86 30 .;.. Belgian endive is also undesirable. Optimumripening 77 25 Optimumripening Other factors. Various kinds of chemicals temperatureforran~efruits--{ 68 20}- fortemperaturefruits range 59 15 (e.g., , growth regulators) may be } Ideal temperature range 50 10 l~ for transit and storage applied to the commodity to affect one or Idealtemperature range 41 5 Chillinginjury more of the biological deterioration factors. for transit and storage ---{ 32 0 r Freezinginjury--- 23 -5 - Freezinginjury POSTHARVEST r 1 TECHNOLOGY PROCEDURES GROUPI GROUPII t ------,------Fruits Vegetables Fruits Vegetables TEMPERATURE MANAGEMENT ,------Apple' Artichoke Avocado Beans,snap PROCEDURES Apricot Asparagus Banana Cassava Temperature management is the most effec- Blackberry Beans,lima Breadfruit Cucumber tive tool for extending the shelf life of fresh Blueberry Beet Carambola Eggplant Cherry Broccoli Cherimoya Ginger horticultural commodities. It begins with the Currant Brusselssprouts Citrus Muskmelon rapid removal of field heat by using one of Date Cabbage Cranberry Okra the following cooling methods: hydrocool- Durian Fig Carrot Peppers ing, in-package icing, top-icing, evaporative Grape Cauliflower Feijoa Potato Kiwifruit Celery Guava Pumpkin cooling, room cooling, forced-air cooling, Loquat Corn,sweet Jackfruit Squash serpentine forced-air cooling, vacuum cool- Nectarine' Endive Jujube Sweet potato ing, or hydro-vacuum cooling. Peach' Garlic Taro Longan Cold storage facilities should be well-engi- Pear Lettuce Lychee Tomato Persimmon' Mushrooms Mango Watermelon neered and adequately equipped. They Plum' Onion Mangosteen Yam should have good construction and insula- Prune Parsley Olive tion, including a complete vapor barrier on Raspberry Parsnip Papaya the warm side of the insulation; strong Strawberry Peas Passion fruit Radish Pepino floors; adequate and well-positioned doors Spinach Pineapple for loading and unloading; effective distribu- Turnip Plantain tion of refrigerated air; sensitive and properly Pomegranate located controls; enough refrigerated coil Pricklypear Rambutan surface to minimize the difference between Sapodilla the coil and air temperatures; and adequate Sapote capacity for expected needs. Commodities Tamarillo should be stacked in the cold room with air Note: 'Some cultivars are chillingsensitive. spaces between pallets and room walls to 44 CHAPTER 4

ensure good air circulation. Storage rooms perature and RH, but they can help extend should not be loaded beyond their limit for the shelf life of harvested produce beyond proper cooling. In monitoring temperatures, what is possible using refrigeration alone commodity temperature rather than air tem- (table 4.6). perature should be measured. Treatments applied to commodities include Transit vehicles must be cooled before . curing of certain root, bulb, and tuber loading the commodity. Delays between cool- vegetables ing after harvest and loading into transit . cleaning followed by removal of excess vehicles should be avoided. Proper tempera- surface moisture ture maintenance should be ensured . sorting to eliminate defects throughout the handling system. . waxing and other surface coatings, includ- ing film wrapping CONTROL OF RELATIVE HUMIDITY . heat treatments (hot water or air, vapor Relative humidity can influence water loss, heat) decay development, incidence of some phys- . treatment with postharvest fungicides iological disorders, and uniformity of fruit . sprout inhibitors ripening. Condensation of moisture on the . special chemical treatments (scald commodity (sweating) over long periods of inhibitors, calcium, growth regulators, time is probably more important in enhanc- anti-ethylene chemicals for ornamentals) ing decay than is the RH of ambient air. . fumigation for insect control Proper relative humidity is 85 to 95% for . ethylene treatment (de-greening, ripening) fruits and 90 to 98% for vegetables except dry onions and pumpkins (70 to 75%). Treatments to manipulate the enviro~- Some root vegetables can best be held at 95 ment include to 100% RH. . packaging Relative humidity can be controlled by . control of air movement and circulation one or more of the following procedures: . control of air exchange or ventilation . adding moisture (water mist or spray, . exclusion or removal of C2H4 steam) to air by humidifiers . controlled or modified atmospheres .(CA . regulating air movement and ventilation or MA) i in relation to the produce load in the cold . sanitation storage room . maintaining the refrigeration coils within RECENT TRENDS IN about 1DC (2DF) of the air temperature PERISHABLES HANDLING . providing moisture barriers that insulate storage room and transit vehicle walls; SELECTION OF CULTIVARS adding polyethylene liners in containers For many commodities, producers are using and plastic films for packaging cultivars with superior quality and/or long . wetting floors in storage rooms postharvest life, such as "super-sweet" sweet . adding crushed ice in shipping containers corn, long-shelf-life tomatoes, and sweeter or in retail displays for commodities that melons. Plant geneticists in public and pri- are not injured by the practice vate institutions are using molecular biology . sprinkling produce with water during methods along with proce- retail marketing (use on leafy vegetables, dures to produce new genotypes that taste cool-season root vegetables, and immature better, maintain firmness better, are more fruit vegetables such as snap beans, peas, disease resistant, have less browning poten- sweet corn, summer squash tial, and have other desirable characteristics.

SUPPLEMENT TEMPERATURE PACKING AND PACKAGING MANAGEMENT The produce industry is increasingly using Many technological procedures are used plastic containers that can be reused and commercially as supplements to temperature recycled in order to reduce waste disposal management. None of these procedures, problems. For example, standard-sized (4,8 alone or in their various combinations, can by 40 in., about 120 by 100 cm) stacking substitute for maintenance of optimal tem- (returnable) pallets are becoming more POSTHARVEST BIOLOGY AND TECHNOLOGY 45

widely used. There is continued increase in cooling facility within O.5°C (about 1°F) of use of modified atmosphere and controlled the optimal storage temperature. Periodic atmosphere packaging (MAP and CAP) sys- ventilation of storage facilities is effective in tems at the pallet, shipping container (fiber- maintaining CZH4 concentrations below 1 board box liner), and consumer package lev- ppm, which permits mixing of temperature- els. Also, the use of absorbers of CZH4' COz, compatible, ethylene-producing, and ethyl- Oz', and/or water vapor as part of MAP and ene-sensitive commodities. CAP is increasing. POSTHARVEST INTEGRATED PEST COOLING AND STORAGE MANAGEMENT (I PM) The current trend is towards increased pre- Controlled atmosphere (CA) conditions cision in temperature and relative humidity delay senescence, including fruit ripening, (RH) management to provide the optimal and consequently reduce the susceptibility of environment for fresh fruits and vegetables fruits to pathogens. On the other hand, CA during cooling and storage. Precision tem- conditions unfavorable to a given commodi- perature management (PTM) tools are ty can induce physiological breakdown and becoming more common in cooling and render it more susceptible to pathogens. storage facilities. Forced-air cooling contin- Calcium treatments have been shown to ues to be the predominant cooling method reduce decay incidence and severity; wound for horticultural perishables. Operators can healing following physical injury has been. ensure that all produce shipments leave the observed in some fruits and has reduced their susceptibility to decay Biological con- Table 4.6. Freshhorticultural crops classifiedaccordingto relative per- trol agents are being used alone or in comQi- ishability and potential storage life in air at near-optimal temperature nation with reduced concentrations of and RH postharvest fungicides, heat treatments, Potential and/or fungistatic CA for control of posthar- Relative storage life vest diseases. perishability (weeks) Commodities Chemical fumigants, especially methyl ~~---~ ~.-~--- ~~--~-~ ~---~-_. ~--~--- - - Veryhigh <2 Apricot,blackberry,blueberry,cherry,fig, bromide, are still the primary method used. for insect control in harvested fruits when. raspberry,strawberry;asparagus,bean sprouts,broccoli,cauliflower,cantaloupe, such treatment is required by quarantine greenonion,leaflettuce,mushroom,pea, authorities in importing countries. Many spinach,sweetcorn,tomato(ripe);most studies are under way to develop alternative cut flowersandfoliage;fresh-cut(mini- methods of insect control that are effective, mallyprocessed)fruits andvegetables not phytotoxic to the fruits, and present no health hazard to the consumer. These alter- High 2-4 Avocado,banana,grape(without 502 treatment),guava,loquat,mandarin, natives include cold treatments, hot water or mango,melons(honeydew,crenshaw, air treatments, ionizing radiation (0.15-0.30 Persian),nectarine,papaya,peach, kilo gray) and exposure to reduced (less than pepino,plum;artichoke,greenbeans, 0.5%) Oz and/or elevated CO2 (40-60%) Brusselssprouts,cabbage,celery,egg- atmospheres. This is a high-priority research plant,headlettuce,okra,pepper,summer and development area because of the possi- squash,tomato(partiallyripe) ble loss of methyl bromide as an option for insect control. Moderate 4-8 Appleand pear(somecultivars),grape (504-treated),orange,grapefruit,lime, kiwifruit, persimmon,pomegranate, USE OF CONTROLLED AND MODIFIED pummelo;tablebeet,carrot,radish,pota- ATMOSPHERES to (immature) The use of CA during transport and/or stor- Low 8-16 Appleandpear(somecultivars),lemon, age of fresh fruits and vegetables (marketed potato (mature),dryonion,garlic,pump- intact or lightly processed) continues to kin,winter squash,sweetpotato,taro, expand because of improvements in nitro- yam;bulbsand otherpropagulesof orna- gen-generation equipment and in instru- mentalplants ments for monitoring and maintaining desired concentrations of oxygen and carbon Verylow >16 Treenuts,driedfruits andvegetables dioxide. Controlled atmosphere is a useful 46 CHAPTER 4

supplement to the proper maintenance of allowing all shipments to be continuously optimal temperature and RH during trans- monitored. Some new trucks have air ride port and storage of many fresh fruits and suspension, which can eliminate transport vegetables. It allows use of marine transport vibration damage. As the industry realizes the instead of air transport of some commodities. value of air ride, its popularity will increase. Several refinements in CA storage have been made in recent years to improve quality HANDLING AT WHOLESALE AND RETAIL maintenance. These include creating nitro- Wholesale and retail markets have been gen by separation from compressed air using increasingly using automated ripening, in molecular sieve beds or membrane systems; which the gas composition of the ripening low O2 (1.0-1.5%) storage; low ethylene CA atmosphere, the room temperature, and fruit storage; rapid CA (rapid establishment of the color are continuously monitored and modu- optimal levels of O2 and CO2); and pro- lated to meet desired ripening characteristics. grammed (or sequential) CA storage (e.g., Improved ripening systems will lead to storage in 1% O2 for 2 to 6 weeks followed greater use of ripening technology to deliver by storage in 2 to 3% O2 for the remainder of products that are ripened to the ideal eating the storage period). Other developments, stage. Better-refrigerated display units, with which may expand use of MA during trans- improved temperature and RH monitoring port and distribution, include using edible and control systems, are being used in retail coatings or polymeric films with appropriate markets, especially for fresh-cut fruit and veg- gas permeabilities to create a desired MA etable products. Many retail and food service around and within the commodity. Modified operators are using Hazard Analysis Critical atmosphere packaging is widely used in mar- Control Points (HACCP) Programs to a~sure keting fresh-cut fruits and vegetables. consumers that food products are safe. Successful application of atmospheric modification depends on the commodity, FOOD SAFETY ASSURANCE cultivar, maturity stage at harvest, and a posi- During the past few years, food safety became tive return on investment (benefit-cost ratio). and continues to be the number-one concern Commercial use of CA storage is greatest of the fresh produce industry. U.S. trade worldwide on apples and pears; less on organizations such as the International Presh- kiwifruits, avocados, persimmons, pomegran- Cut Produce Association (IFPA), Produce ates, nuts, and dried fruits and vegetables. Marketing Association (PMA), United Fresh Atmospheric modification during long-dis- Fruit and Vegetable Association (UFFVA), tance transport is used on apples, asparagus, and Western Growers Association (WGA) avocados, bananas, broccoli, cane berries, have taken an active role in developing vol- cherries, figs, kiwifruits, mangoes, melons, untary food safety guidelines for producers nectarines, peaches, pears, plums, and straw- and handlers of fresh fruits and vegetables. berries. Continued technological develop- The U.S. Food and Drug Administration ments in the future to provide CA during (FDA) published in October 1998 the Guide transport and storage at a reasonable cost are to Minimize Microbial Food Safety Hazards for essential to greater CA applications on fresh Fresh Fruits and Vegetables. This guide should fruits and vegetables. be used by all handlers of fresh produce to develop the most appropriate agricultural and TRANSPORTATION management practices for their operations. Improvements are continually being made in The FDA guide is based on the following attaining and maintaining the optimal envi- basic principles and practices associated with ronmental conditions (temperature, RH, and minimizing microbial food safety hazards concentrations of O2, CO2, and C2H4) in from the field through distribution of fresh transport vehicles. Produce is commonly fruits and vegetables. cooled before loading and is loaded with an Principle 1. Prevention of microbial conta- air space between the palletized produce and mination of fresh produce is favored over the walls of the transport vehicles to improve reliance on corrective actions once contami- temperature maintenance. In some cases, nation has occurred. , vehicle and produce temperature data are Principle 2. To minimize microbial food transmitted by satellite to a control center, safety hazards in fresh produce, growers, POSTHARVEST BIOLOGY AND TECHNOLOGY 47

packers, or shippers should use good agricul- duce. Paris: International Institute of Refrigera- tural and management practices in those tion. 219 pp areas over which they have control. Kader, A. A. 1983. Postharvest quality maintenance Principle 3. Fresh produce can become of fruits and vegetables in developing countries. microbiologically contaminated at any point In M. Lieberman, ed., Postharvest physiology along the farm-to-table food chain. The and preservation. New York: Plenum. major source of microbial contamination of 520-536. fresh produce i5 associated with human or Kantor, L S., K. Lipton, A. Manchester. and V animal feces. Oliveira. 1997. Estimating and addressing Amer- Principle 4. Whenever water comes in ica's food losses. Food Review 20:3-11. contact with produce, the quality of the Kitinoja, L, and A. A. Kader 1995. Small-scale water dictates the potential for contamina- postharvest handling practices: A manual for tion. Minimize the potential of microbial horticultural crops. 3rd ed. Davis: Univ. Calif. contamination from water used with fresh Postharv. Hort. SeT 8. 231 pp. fruits and vegetables. Kitinoja, L, andj. R. Gorny. 1999. Postharvest tech- Principle 5. Practices using animal nology for small-scale produce marketers: Eco- manure or municipal biosolid wastes should nomic opportunities, quality and food safety. be managed closely to minimize the potential Davis: Univ. Calif. Postharv. Hort. SeT 21. for microbial contamination of fresh produce. Lidster, PD., P D. Hilderbrand, L S. Berard, and S. Principle 6. Worker hygiene and sanita- W Porritt. 1988. Commercial storage of fruits tion practices during production, harvesting, and vegetables. Can. Dept. Agric. PubI. 1532. sorting, packing, and transport playa critical 88 pp. role in minimizing the potential for micro- Lipton, W j. 1987. Senescence in leafy vegetables. bial contamination of fresh produce. HortScience 22:854-859. Principle 7. Follow all applicable local, Mayak, S. 1987. Senescence in cut flowers. state, and federal laws and regulations or HortScience 22:863-865. corresponding or similar laws, regulations, or National Academy of Sciences. 1978. Postharvest standards for operators outside the United food losses in developing countries (Science and States, for agricultural practices. Technology for International Development). Washington, D.c.: Natl. Acad. Sci. 202 pp. REFERENCES Rhodes, M. j. C. 1980a. The maturation and ripening of fruits. In K. V Thimann, ed., Senescence in Brady, C. j. 1987. Fruit ripening. Annu. Rev. Plant plants. Boca Raton, FL: CRC Press. 157-205. Physiol. 38:155-178. -. 1980b. The physiological basis for the con- Cappellini, R. A., and M.j. Ceponis. 1984. Posthar- servation of food crops. Prog. Food NUlr Sci. vest losses in fresh fruits and vegetables. In H. E. 4(3-4): 11-20. Moline, ed., Postharvest pathology of fruits and Romani, R. j. 1987. Senescence and homeostasis in vegetables: Postharvest losses in perishable postharvest research. HortScience 22:865-868. crops. Oakland: Univ. Calif. Bull. 1914.24-30. Shewfelt, R. L 1986. Postharvest treatment for Giovannoni, j. 2001. Molecular biology of fruit matu- extending the shelf-life of fruits and vegetables. ration and ripening. Annu. Rev. Plant Physiol. Food Technol. 40(5): 70-89. Plant Mol. BioI. 52:725-749. Tindall, H. D., and F j. Proctor 1980. Loss preven- Grierson, D. 1987. Senescence in fruits. HortScience tion of horticultural crops in the tropics. Prog. 22:859-862. Food Nutr Sci. 4(3-4): 25-40. Harvey, j. M. 1978. Reduction oflosses in fresh mar- United Nations Food and Organization ket fruits and vegetables. Annu. Rev. Phy- (FAO) 1981. Food loss prevention in perishable topathol. 16:321-341. crops. FAO Agric. Serv. Bull. 43. 72 pp. International Institute of Refrigeration. 2000. Recom- Wang, C. Y, ed. 1990. Chilling injury of horticultural mendations for chilled storage of perishable pro- crops. Boca Raton, FL: CRC Press. 313 pp.