Postharvest Handling of Fruits and Vegetables

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Postharvest Handling of Fruits and Vegetables

  1. 1. 800-346-9140 POSTHARVEST HANDLING OF FRUITS AND VEGETABLES HORTICULTURE TECHNICAL NOTEAppr i e Technol Tr opr at ogy ansf f Rur Ar er or al eas ATTRA is the national sustainable agriculture information center funded by the USDA’s Rural Business -- Cooperative Service. Abstract: Appropriate production practices, careful harvesting, and proper packaging, storage, and transport all contribute to good produce quality. This publication covers postharvest practices suitable for small-scale operations, and points out the importance of production and harvesting techniques for improving quality and storability. Various methods for cooling fresh produce are discussed, and resources are listed for further information, equipment, and supplies.By Janet Bachmann and Richard EarlesNCAT Agriculture Specialists and have a longer shelf life than others. InAugust 2000 addition, environmental factors such as soil type, temperature, frost, andIntroduction rainy weather at harvest can have anYou have spent adverse effect onmonths working in storage life and quality.the fields, and now For example, carrotshave a bountiful grown on muck soilsharvest of beautiful do not hold up as wellfruits and in storage as carrotsvegetables. You grown on lighter,want to ensure that upland soils. Lettuceyour customers will harvested during aalso enjoy this period of rain does nothealthy harvest. ship well and productHow can you best losses are increased (1).maintain the qualityand safety of your produce as it travels from the Management practices can also affectfield to the table? How can produce be stored so postharvest quality. Produce that has beenthat it does not need to be sold immediately? stressed by too much or too little water, highHigh-quality, disease-free produce with a good rates of nitrogen, or mechanical injury (scrapes,shelf life is a result of sound production practices, bruises, abrasions) is particularly susceptible toproper handling during harvest, and appropriate postharvest diseases. Mold and decay on winterpostharvest handling and storage. squash, caused by the fungus Rhizoctonia, result from the fruits lying on the ground, and can beProduction Practices alleviated by using mulch. Contents: Broccoli heads areProduction practices have Production Practices....................................... 1 susceptible to postharvesta tremendous effect on the Harvest Handling........................................... 2 rot caused by the bacteriaquality of fruits and Postharvest & Storage .................................. 2 Erwinia if nitrogen is appliedvegetables at harvest and References .................................................... 8 as foliar feed—a groweron postharvest quality Enclosures ..................................................... 9 should feed the soil, not theand shelf life. To start Resources...................................................... 9 leaves. Beets and radishes Appendix I: Storage Conditions ......................... 13with, it is well known that are susceptible to soil-borne Appendix II: The Portacooler............................. 15some cultivars ship better diseases when the soil ATTRA // POSTHARVEST HANDLING OF FRUITS & VEGETABLES Page 1
  2. 2. temperature reaches 80º F; symptoms are black Harvest should be completed during the coolestspots on these root crops (2). time of the day, which is usually in the early morning, and produce should be kept shaded inFood safety also begins in the field, and should the field. Handle produce gently. Cropsbe of special concern, since a number of destined for storage should be as free as possibleoutbreaks of foodborne illnesses have been traced from skin breaks, bruises, spots, rots, decay, andto contamination of produce in the field. other deterioration. Bruises and otherCommon-sense prevention measures include a mechanical damage not only affect appearance,number of don’ts (3): but provide entrance to decay organisms as well.• Don’t apply raw dairy or chicken manure or Postharvest rots are more prevalent in fruits and slurries to a field where a vegetable crop such vegetables that are bruised or otherwise damaged. as leafy lettuce is growing. Mechanical damage also increases moisture loss.• Don’t apply manure to an area The rate of moisture loss may be increased by as immediately adjacent to a field nearing much as 400% by a single bad bruise on an apple, harvest maturity. and skinned potatoes may lose three to four times• Don’t forget to clean equipment that has been as much weight as non-skinned potatoes. Damage used to apply manure to one field before can be prevented by training harvest labor to moving it to another field in production. handle the crop gently; harvesting at proper• Don’t irrigate with water from a farm pond maturity; harvesting dry whenever possible; used by livestock. handling each fruit or vegetable no more than• Don’t harvest fruit from the orchard floor for necessary (field pack if possible); installing human consumption as whole fruit or padding inside bulk bins; and avoiding over or nonpasteurized juices, especially if manure under-packing of containers (4). has been spread or animals allowed to graze.• Don’t accumulate harvested product in areas Postharvest and Storage Considerations where birds roost. PackagingA grower should constantly evaluate water usedfor irrigation, and compost all animal manures Packaging should be designed to prevent physicalbefore applying them to fields. There are many damage to produce, and be easy to handle. Thegood sources of information on growing American Vegetable Grower magazine’s annualconditions and production practices that promote product guide is a good source of informationpostharvest quality. Consult textbooks, about suppliers (see Resources).Extension publications, and trade journals, andbecome involved with grower organizations to Temperaturefind out more. Temperature is the single most important factorHarvest Handling in maintaining quality after harvest. Refrigerated storage retards the following elements ofQuality cannot be improved after harvest, deterioration in perishable crops:only maintained; therefore it is important to • aging due to ripening, softening, and texturalharvest fruits, vegetables, and flowers at the and color changes;proper stage and size and at peak quality. • undesirable metabolic changes andImmature or overmature produce may not respiratory heat production;last as long in storage as that picked at proper • moisture loss and the wilting that results;maturity (4). Cooperative Extension Service • spoilage due to invasion by bacteria, fungi,publications are an excellent source of and yeasts;information on harvest maturity indicators • undesirable growth, such as sprouting offor vegetables and fruits. potatoes (5). ATTRA // POSTHARVEST HANDLING OF FRUITS & VEGETABLES Page 2
  3. 3. One of the most important functions of produce. Likewise, most refrigerated storagerefrigeration is to control the crop’s respiration rooms have neither the refrigeration capacity norrate. Respiration generates heat as sugars, fats, the air movement needed for rapid cooling.and proteins in the cells of the crop are Therefore, pre-cooling is generally a separateoxidized. The loss of these stored food reserves operation requiring special equipment and/orthrough respiration means decreased food rooms (4, 5).value, loss of flavor, loss of salable weight, andmore rapid deterioration. The respiration rate Rapid pre-cooling to the product’s lowest safeof a product strongly determines its transit and temperature is most critical for crops withpostharvest life. The higher the storage inherently high respiration rates. These includetemperature, the higher the respiration rate artichokes, brussels sprouts, cut flowers, greenwill be (4). onions, snap beans, asparagus, broccoli, mushrooms, peas, and sweet corn. Crops withFor refrigeration to be effective in postponing low respiration rates include nuts, apples, grapes,deterioration, it is important that the temperature garlic, onions, potatoes (mature), and sweetin cold storage rooms be kept as constant as potatoes (4).possible. Appendix I charts the optimumtemperature ranges for various crops. Exposure Appropriate pre-cooling methods as well asto alternating cold and warm temperatures may appropriate storage temperature and humidityresult in moisture accumulation on the surface of for a number of fruits and vegetables are shownproduce (sweating), which may hasten decay. in Appendix I. The following methods are theStorage rooms should be well insulated and most commonly used:adequately refrigerated, and should allow for aircirculation to prevent temperature variation. Be • Room cooling: Produce is placed in ansure that thermometers, thermostats, and manual insulated room equipped with refrigerationtemperature controls are of high quality, and units. This method can be used with mostcheck them periodically for accuracy (5). commodities, but is slow compared with other options. A room used only to storeOn-farm cooling facilities are a valuable asset for previously cooled produce requires aany produce operation. A grower who can cool relatively small refrigeration unit. However,and store produce has greater market flexibility if it is used to cool produce, a larger unit isbecause the need to market immediately after needed. Containers should be stacked so thatharvest is eliminated. The challenge, especially cold air can move around them, andfor small-scale producers, is the set-up cost. constructed so that it can move through them.Innovative farmers and researchers have created Used refrigerated truck bodies make excellenta number of designs for low-cost structures. small cooling rooms (4).Some of these ideas are detailed in Appendix IIand in the enclosures attached to this document. • Forced-air cooling: Fans are used inAdditional designs are available in publications conjunction with a cooling room to pull cool airlisted in the Resources section. through packages of produce. Although the cooling rate depends on the air temperaturePre-cooling and the rate of air flow, this method is usually 75–90% faster than room cooling. Fans shouldPre-cooling is the first step in good temperature be equipped with a thermostat thatmanagement. The field heat of a freshly harvested automatically shuts them off as soon as thecrop—heat the product holds from the sun and desired product temperature is reached.ambient temperature—is usually high, andshould be removed as quickly as possible before To avoid over-cooling and dehydration of produce,shipping, processing, or storage. Refrigerated pro do not operate forced-air fans after the producetrucks are not designed to cool fresh commodities tem has been cooled to its optimum temperature (4).but only maintain the temperature of pre-cooled ATTRA // POSTHARVEST HANDLING OF FRUITS & VEGETABLES Page 3
  4. 4. • Hydro-cooling: Dumping produce into cold water cooling followed by refrigerated water, or running cold water over produce, storage appeared to offer no advantage over is an efficient way to remove heat, and can refrigerated storage immediately after serve as a means of cleaning at the same harvest (6). time. In addition, hydro-cooling reduces water loss and wilting. Use of a disinfectant • Top or liquid icing: Icing is particularly in the water is recommended to reduce the effective on dense products and palletized spread of diseases. Hydro-cooling is not packages that are difficult to cool with forced appropriate for berries, potatoes to be air. In top icing, crushed ice is added to the stored, sweet potatoes, bulb onions, container over the top of the produce by hand garlic, or other commodities that cannot or machine. For liquid icing, a slurry of water tolerate wetting. and ice is injected into produce packages through vents or handholds without Water removes heat about five times faster removing the packages from pallets and than air, but is less energy-efficient. Well opening their tops. Icing methods work well water is a good option, as it usually comes with high-respiration commodities such as out of the ground with temperatures in the sweet corn and broccoli. One pound of ice 50–60º F range. Mechanical refrigeration is will cool about three pounds of produce from the most efficient method for cooling water. 85º F to 40º F (7, 8). A thermal storage immersion hydro-cooler system can be fabricated economically to suit • Vacuum cooling: Produce is enclosed in a various volume requirements. Used chamber in which a vacuum is created. stainless-steel bulk farm milk coolers may be As the vacuum pressure increases, water an option. If hydro-cooling water is within the plant evaporates and removes recirculated, it should be chlorinated to heat from the tissues. This system works minimize disease problems (4). best for leafy crops, such as lettuce, which have a high surface-to-volume ratio. To A study compared sweet corn quality after reduce water loss, water is sometimes hydro-cooling with ice water, well water sprayed on the produce prior to placing it cooling, and refrigerated air cooling, and in the chamber. This process is called subsequent refrigerated storage. Hydro- hydrovac cooling. The primary drawback cooling with ice water lowered the to this method is the cost of the vacuum temperature of the ears most quickly. Well chamber system (9). These products can be iced: Artichokes Asparagus Beets Broccoli Cantaloupes Carrots Cauliflower Endive Green onions Leafy greens Radishes Spinach Sweet corn Watermelon ATTRA // POSTHARVEST HANDLING OF FRUITS & VEGETABLES Page 4
  5. 5. These items are damaged by direct contact with ice: Strawberries Blueberries Raspberries Tomatoes Squash Green beans Cucumbers Garlic Okra Bulb onions Romaine lettuce HerbsChilling injury is also important. The relative humidity of the storage unit directly influences water loss inMany vegetables and fruits store best at produce. Water loss can severely degradetemperatures just above freezing, while others quality—for instance, wilted greens may requireare injured by low temperatures and will store excessive trimming, and grapes may shatter loosebest at 45 to 55 degrees F. Both time and from clusters if their stems dry out. Water losstemperature are involved in chilling injury. means salable weight loss and reduced profit (4).Damage may occur in a short time iftemperatures are considerably below the danger Most fruit and vegetable crops retain betterthreshold, but some crops can withstand quality at high relative humidity (80 to 95%), buttemperatures a few degrees into the danger zone at this humidity, disease growth is encouraged.for a longer time. The effects of chilling injury are The cool temperatures in storage rooms help tocumulative in some crops. Low temperatures in reduce disease growth, but sanitation and othertransit, or even in the field shortly before harvest, preventative methods are also required.add to the total effects of chilling that might occur Maintaining high relative humidity in storage isin storage (7). complicated by the fact that refrigeration removes moisture. Humidification devices suchCrops such as basil, cucumbers, eggplants, as spinning disc aspirators may be used. Evenpumpkins, summer squash, okra, and sweet buckets of water will increase humidity as thepotatoes are highly sensitive to chilling injury. fans blow air across the water’s surface andModerately sensitive crops are snap beans, increase evaporation (10). Keeping the floor wetmuskmelons, peppers, winter squash, tomatoes, is helpful, though messy and potentially hazardous to two-legged creatures; frequentand watermelons (8). These crops may look cleansing with a weak chlorine solution will besound when removed from low temperature needed to prevent harboring of diseasestorage, but after a few days of warmer organisms in water and produce scraps on thetemperatures, chilling symptoms become floor. Crops that can tolerate direct contact withevident: pitting or other skin blemishes, internal water may be sprinkled to promote high relativediscoloration, or failure to ripen. Tomatoes, humidity (4).squash, and peppers that have been over-chilledmay be particularly susceptible to decay such as When it comes to maintaining appropriateAlternaria rot (7). humidity levels, “the biggest thing for small growers is going to be monitoring equipment,”Preventing moisture loss says Kansas State University Extension Specialist Karen Gast. Humidity is measured by anWhile temperature is the primary concern in the instrument called a hygrometer. Severalstorage of fruits and vegetables, relative humidity companies offer small, low-priced hygrometers ATTRA // POSTHARVEST HANDLING OF FRUITS & VEGETABLES Page 5
  6. 6. suitable for small-scale producers (10). See Organic growers must use chlorine withResources for more information. caution, as it is classified as a restricted material. The California Certified OrganicSanitation Farmers regulations permit a maximum of 4 ppm residual chlorine, measured downstreamSanitation is of great concern to produce of the product wash (3). Growers certified byhandlers, not only to protect produce against other agencies should check with theirpostharvest diseases, but also to protect certifying agent.consumers from foodborne illnesses. E. coli0157:H7, Salmonella, Chryptosporidium, Hepatitis, Ozonation is another technology that can be usedand Cyclospera are among the disease-causing to sanitize produce. A naturally occurringorganisms that have been transferred via fresh molecule, ozone is a powerful disinfectant.fruits and vegetables (3, 11). Use of a Ozone has long been used to sanitize drinkingdisinfectant in wash water can help to prevent water, swimming pools, and industrialboth postharvest diseases and foodborne wastewater. Fruit and vegetable growers haveillnesses. begun using it in dump tanks as well, where it can be thousands of times more effective thanChlorine in the form of a sodium hypochlorite chlorine. Ozone not only kills whateversolution (for example, Clorox™) or as a dry, foodborne pathogens might be present, it alsopowdered calcium hypochlorite can be used in destroys microbes responsible for spoilage. Ahydro-cooling or wash water as a disinfectant. basic system consists of an ozone generator, aSome pathogens such as Chryptosporidium, monitor to gauge and adjust the levels of ozonehowever, arevery resistant to Amounts of hypochlorite to add to clear, clean water for disinfestation.chlorine, andeven sensitive target ppm ounces/5 gallons cup/50 gallonsones such as Sodium hypochlorite 50 .55 .5Salmonella and (5.25%) 75 .8 .75E. coli may be 100 1.1 1.0located in 125 1.4 1.25inaccessible 150 1.7 1.5sites on theplant surface. Sodium hypochlorite 50 .12 .1For the majority (12.7%) 75 .17 .15of vegetables, 100 .23 .2chlorine in 125 .29 .25wash water 150 .35 .3should bemaintained in the range of 75–150 ppm (parts per being produced, and a device to dissolve themillion.) The antimicrobial form, hypochlorous ozone gas into the water. Systems cost anywhereacid, is most available in water with a neutral pH from $10,000 to $100,000, and should be installed(6.5 to 7.5). by an ozone sanitation company experienced in produce industry applications (12).The effectiveness of chlorine concentrations arereduced by temperature, light, and interaction Hydrogen peroxide can also be used as awith soil and organic debris. The wash water disinfectant. Concentrations of 0.5% or lessshould be tested periodically with a monitoring are effective for inhibiting development ofkit, indicator strips, or a swimming pool-type postharvest decay caused by a number of fungi.indicator kit. Concentrations above 200 ppm Hydrogen peroxide has a low toxicity rating andcan injure some vegetables (such as leafy greens is generally recognized as having little potentialand celery) or leave undesirable off-flavors. for environmental damage. The ATTRA ATTRA // POSTHARVEST HANDLING OF FRUITS & VEGETABLES Page 6
  7. 7. publication Sources for Organic Fertilizers and at 33º F; carry to market in a portable cooler,Amendments lists several sources of food-grade either refrigerated or with ice, and keep in thehydrogen peroxide. cooler until ready to display. If displaying unwrapped heads at a farmers’ market, mistCreative growers can customize their produce- occasionally with cold water.washing system to promote sanitation andincrease efficiency and ease of operation. At EthyleneDrumlin Community Farm in Madison,Wisconsin, the crew “used to wash greens and Ethylene, a natural hormone produced by somesmall crops by the handfuls in wash tubs and air fruits as they ripen, promotes additionaldry them on screen tables. Now they line harvest ripening of produce exposed to it. The oldcontainers with a mesh produce bag, dunk the adage that one bad apple spoils the wholewhole bagful at once, and dry two bagfuls at a bushel is true. Damaged or diseased applestime in an old washing machine set to spin produce high levels of ethylene and stimulatecycle.” At another farm, loose greens are the other apples to ripen too quickly. As thedumped into a 500-gallon bulk milk tank. The fruits ripen, they become more susceptible towater in the tank is agitated with bubbling air diseases.from a jacuzzi motor. The washed greens arescooped out of the tank with a mesh bag-lined Ethylene “producers” should not be stored withlaundry basket, and the bags of greens are then fruits, vegetables, or flowers that are sensitive tospun dry in a washing machine. The grower it. The result could be loss of quality, reducedremoved the washer’s agitator to make more shelf life, and specific symptoms of injury. Someroom for the produce (13). examples of ethylene effects include:This type of system has several advantages—it • russet spotting of lettuce along the midrib ofreduces handling (and potential damage) of the the leaves;crop; it makes the washing process more time • loss of green color in snap beans;and labor efficient; and it enhances postharvest • increased toughness in turnips and asparagusquality by getting the crop cooled down, spears;washed, dried, and in cold storage much more • bitterness in carrots and parsnips;quickly. Perhaps most importantly, washing • yellowing and abscission of leaves in broccoli,greens in large batches rather than one-by-one cabbage, Chinese cabbage, and cauliflower;reduces physical stress on the worker’s back and • accelerated softening of cucumbers, acornarms. and summer squash; • softening and development of off-flavor inAt a cost of $2–8 each, woven polyester or nylon watermelons;bags are durable, lightweight, water-permeable, • browning and discoloration in eggplant pulpand fast-drying. Suitable mesh laundry bags may and seed;be found at hardware or discount stores (13). The • discoloration and off-flavor in sweet potatoes;Resources section lists two companies that sell • sprouting of potatoes;mesh bags by mail order. Spin-drying can be • increased ripening and softening of maturedone with a washing machine, honey extractor, green tomatoes (8); andor commercial salad spinner. A restaurant or • shattering of raspberries and blackberries (2).industrial-scale salad spinner is an efficientmachine for both washing and drying greens Ethylene producers include apples, apricots,(available from restaurant supply stores; prices avocados, ripening bananas, cantaloupes,range from $650 to $1500). honeydew melons, ripe kiwifruit, nectarines, papayas, passionfruit, peaches, pears,Some further tips for postharvest handling of persimmons, plantains, plums, prunes, quinces,lettuce and other leafy greens: package in and tomatoes (14). Produce that is sensitive tobreathable or perforated plastic bags; refrigerate ethylene is indicated in Appendix I. ATTRA // POSTHARVEST HANDLING OF FRUITS & VEGETABLES Page 7
  8. 8. Mixed loads The two structural options for storage of these crops are coolers and root cellars. ByczynskiWhen different commodities are stored or provides an example of a farm using both: “Thetransported together, it is important to combine Seelys have a bank barn, which has the bottomonly those products that are compatible with floor built into a hillside…They have built bothrespect to their requirements for temperature, coolers and a dry storage room into the lowerrelative humidity, atmosphere (oxygen and floor to provide different combinations ofcarbon dioxide), protection from odors, and temperature and humidity for the vegetables theyprotection from ethylene (4). store.” Coolers used for root crop storage will require water added to the air and regularIn regard to cross-transfer of odors, combinations monitoring of the humidity level (see discussionthat should be avoided in storage rooms include: under Preventing moisture loss above.) Someapples or pears with celery, cabbage, carrots, growers have used concrete basements of houses,potatoes, or onions; celery with onions or carrots; closed off from heat and with ventilation to let inand citrus with any of the strongly scented cold winter air, as root cellars. Another idea is tovegetables. Odors from apples and citrus are bury a big piece of culvert under a hillside (10).readily absorbed by meat, eggs, and dairyproducts. Pears and apples acquire an Whatever the method, only “perfect” produce isunpleasant, earthy taste and odor when stored suitable for long-term storage, so carefulwith potatoes. It is recommended that onions, inspection is critical. Any damaged produce isnuts, citrus, and potatoes each be stored going to spoil and induce spoilage in the rest ofseparately (4). the crop. Byczynski advises growers to “either rub off soil and leave the crops somewhat dirty,Storage crops or wash them and let them dry thoroughly before putting them in storage. With onions, garlic,What about the crops that will not be transported winter squash, pumpkins and sweet potatoes, it’sand marketed fresh after harvest? Growers can important that they be cured thoroughly beforeextend their selling season into the winter storage” (10).months by growing root crops and othervegetables and fruits suited for long-term storage. ConclusionThe challenge is in keeping quality high bycreating and maintaining the correct storage Postharvest handling is the final stage in theenvironment. As Growing for Market editor Lynn process of producing high quality fresh produce.Byczynski notes, Being able to maintain a level of freshness from the field to the dinner table presents many Most storage crops require low temperatures challenges. A grower who can meet these and high humidity, two factors that don’t challenges, will be able to expand his or her come together easily. Several others require marketing opportunities and be better able to low humidity and low temperatures. And compete in the marketplace. This document is then there are a few that fall in between…Root intended to serve as an introduction to the topic crops such as beets, carrots, turnips, rutabagas, and a resource pointer; the grower is advised to and leeks store best at 32º F and 90% seek out more complete information from humidity. Potatoes prefer temperatures of 40– Extension and other sources. 60º F and 90% humidity. Onions and garlic like it cool—32º—but require less humidity— about 65–75%. Winter squash prefer temperatures of 50–60º F, but dry. That’s four References: different types of storage for vegetables that will hold a month or more: cold and humid; 1) Herner, Robert C. 1989. Sources of loss cited cold and dry; cool and humid; cool and during post harvest handling. Great Lakes dry (10). Vegetable Growers News. May. p. 16. ATTRA // POSTHARVEST HANDLING OF FRUITS & VEGETABLES Page 8
  9. 9. 2) Andersen, Craig. 1998. Postharvest handling Enclosures: workshop. Huntsville, AR. February 22. Joyce, Daryl and Michael Reid. 1992. Postharvest3) Suslow, Trevor. 1997. Microbial food safety: handling of fresh culinary herbs. Herbal an emerging challenge for small-scale growers. Connection. Vol. 2, No. 5. p. 7–9. Small Farm News. June–July. p. 7–10. Brun, Charles A. 1994. On-farm refrigeration.4) Wilson, L.G., M.D. Boyette, and E.A. Estes. Pacific Northwest Sustainable Agriculture. 1995. Postharvest Handling and Cooling of June. p. 4–5. Fresh Fruits, Vegetables and Flowers for Small Farms. Leaflets 800–804. North Carolina Nagangast, Dan. 1995. Low-cost cooler uses old Cooperative Extension Service. 17 p. air conditioner. Growing for Market. Accessed on-line at: November. p. 14. http://www.foodsafety.org/nc/nc1055.htm5) Hardenburg, Robert, et al. 1986. The Resources: Commercial Storage of Fruits, Vegetables, and Florist and Nursery Stocks. USDA Handbook Further Information No. 66. United States Department of Agriculture, Agricultural Research Commercial Cooling of Fruits, Vegetables, and Flowers. Service. 136 p. By James Thompson, et al. 1998. 65 p. University of California, ANR6) Wilhelm, Luther R. et al. 1992. Effect of Publications # 21567 cooling treatment on the quality of sweet corn. Detailed descriptions of proper temperature Tennessee Farm and Home Science. Winter. management for perishables and commercial p. 30–35. cooling methods. Complete discussion of design for hydro-cooler and forced-air cooler systems, the two7) Anon. 1992. Put it on ice. American most commonly used cooling methods. 25 graphs Vegetable Grower. June. p. 17–18. and illustrations, 11 color plates, and 15 tables. Available for $10 plus $3.50 s/h. Make check8) Howell, John C., editor. 1993. Postharvest payable to UC Regents and specify pub. #21567. handling. Vegetable Notes: Growing and University of California Marketing Information for Massachusetts ANR Communication Services Commercial Growers. p. 1–5 6701 San Pablo Avenue Oakland, CA 94608-12399) Sasseville, David N. 1988. Harvesting and (800) 994-8849 handling produce: Plan now for high quality. http://anrcatalog.ucdavis.edu Missouri Farm. May–June. p. 19–21. UC-Davis Produce Facts website10) Byczynski, Lynn. 1997. Storage crops extend http://postharvest.ucdavis.edu/Produce/ProduceFac the season. Growing for Market. September. ts/index.html p. 1, 4–5. Separate postharvest fact sheets for a great variety of fruit, vegetable, and ornamental crops. Each fact11) Melnick, Rick. 1998. Safety sets the table. sheet includes information about maturity and American Vegetable Grower. February. p. 9– quality indices, optimum temperature and relative 11, 13, 15. humidity, rates of respiration and ethylene production rates, responses to ethylene and controlled atmospheres, physiological and12) Gooch, Jamie. 1998. Getting into the ‘o’zone. pathological disorders: causes and control, and Fruit Grower. January. p. 10–11. other relevant information. Periodic updates of these fact sheets will be published as new13) Newenhouse, Astrid. 1998. Line harvest information becomes available. The goal is to containers with mesh bags for washing. eventually post fact sheets for all major perishable Growing for Market. December. p. 8. crops.14) Aylesworth, Jean. 1992. Deliver quality. American Vegetable Grower. June. p. 19–20. ATTRA // POSTHARVEST HANDLING OF FRUITS & VEGETABLES Page 9
  10. 10. Perishables Handling North Carolina Cooperative Extension Service.Editor: Pam Moyer Leaflets 800–804.Postharvest Technology Five-part series: Quality Maintenance; Cooling;Dept. of Pomology Handling; Mixed Loads; References. Available on-One Shields Ave. line at:Univ. of California http://www.ces.ncsu.edu/depts/hort/hil/Davis, CA 95616-8683 post-index.html(530) 752-6941 Perishables Handling, a quarterly publication North Carolina State University also offers the from the UC-Davis Postharvest Outreach following fact sheets on postharvest cooling and Program, reports research in progress, recent handling, at: publications, and brief reviews of various aspects of www5.bae.ncsu.edu/programs/extension/ postharvest technology of horticultural crops. A publicat/postharv/index.html one-year subscription costs $25. Back issues are available for $8 each. Tables of contents of back Apples AG-413-1 issues may be reviewed on-line at: Strawberries AG-413-2 http://postharvest.ucdavis.edu/Pubs/ Peppers AG-413-3 POSTPhn.html Sweet Corn AG-413-4 Cabbage and Leafy Greens AG-413-5Produce Handling for Direct Marketing Onions AG-413-6Natural Resource, Agriculture, and Engineering Blueberries AG-413-7Service (NRAES) Greenbeans and Field Peas AG-413-81992. 26 p. NRAES-51. Tomatoes AG-413-9 For growers selling seasonal produce at farmers’ Proper Postharvest Cooling and Handling markets and roadside stands. Describes Methods AG-414-1 postharvest physiology, food safety, produce Design of Room Cooling Facilities AG-414-2 handling from harvest to storage, refrigeration, Forced-Air Cooling AG-414-3 produce displays, and specific handling Hydrocooling AG-414-4 recommendations for over 40 fruits and vegetables. Crushed and Liquid Ice Cooling AG-414-5 Includes eleven tables and eight figures. Chlorination and Postharvest Disease Control AG-414-6Refrigeration and Controlled Atmosphere Storage for Cool and Ship: Low Cost Portable Forced AirHorticultural Crops Cool Unit AG-414-71990. 44 p. NRAES-22 Packaging Requirements for Fresh Fruits and General construction procedures for storage Vegetables AG-414-8 facilities: structural considerations, site selection, thermal insulation, vapor barriers, and attic For information on ordering print copies of these ventilation. Explanations of various refrigeration publications, contact: systems, with descriptions of equipment and operating procedures. Controlled atmosphere North Carolina State University storage construction, testing, and operation, Dept. of Communication Services especially in relation to apple storage. Box 7603 Raleigh, NC 27695-7603 Both of these NRAES publications are available, for $8 each plus a total of $3.75 s/h, from: (919) 515-2861 NRAES Cooperative Extension Kansas State University offers the following publications on postharvest management of commercial horticultural 152 Riley-Robb Hall crops. All are available on-line at: Ithaca, NY 14853-5701 http://www.oznet.ksu.edu/library (607) 255-7654 http://www.nraes.org Containers and Packaging—Fruits and Vegetables MF979Postharvest Handling & Cooling of Fresh Fruits,Vegetables, and Flowers for Small Farms Fruits and Vegetables—Precooling ProduceBy L.G. Wilson, M.D. Boyette, and E.A. Estes. MF10021995. 17 p. Harvest Maturity Indicators for Fruits and Vegetables MF1175 ATTRA // POSTHARVEST HANDLING OF FRUITS & VEGETABLES Page 10
  11. 11. Storage Conditions—Fruits and Vegetables Cooperative Extension Publishing MF978 Rm. 170, 630 W. Mifflin St. Storage Construction MF1039 Madison, WI 53703 Storage Operations MF1033 (608) 262-3346 Storage Options MF1030 http://www.uwex.edu/ces/pubs/ For information on ordering print copies, contact: Sydney Postharvest Lab Production Services http://www.postharvest.com.au Kansas State University This Australian website offers postharvest handling 24 Umberger Hall and storage information, with extensive links to Manhattan, KS 66506-3402 other postharvest sites. (785) 532-5830 e-mail: orderpub@oz.oznet.ksu.edu Growing for Market Editor: Lynn ByczynskiThe University of Wisconsin has produced a very helpful P.O. Box 3747set of “Work Efficiency Tip Sheets” for fresh-market Lawrence, KS 66046vegetable growers. These materials were developed by the (800) 307-8949Healthy Farmers, Healthy Profits Project, with the goal This monthly newsletter is a great resource forof sharing labor-efficiency practices that maintain farmers’ small-scale growers. Lots of good, practicalhealth and safety while increasing profits. Topics in the information from other producers, with frequentseries include: coverage of postharvest topics. Subscriptions cost $30. for one year, or $55. for two years. A Specialized Harvest Cart for Greens A3704-1 Stooping or kneeling and crawling to Manufacturers & Suppliers harvest salad greens requires a lot of time and energy. An alternative is to build a NOTE: This list is intended to be neither simple cart that allows you to sit and roll comprehensive nor exclusive. Endorsement of any while you harvest. The cart also holds particular product or company is not implied. your harvest container, so it rolls along with you. Parts for the cart will cost American Vegetable Grower about $150. Meister Publishing Company Mesh Produce Bags: Easy Batch Processing 37733 Euclid Ave. A3704-2 Willougby, OH 44094 Elements and benefits of the batch method (440) 942-2000 for washing greens, as discussed above The annual “Source Book” issue (July) is a under the heading “Sanitation.” comprehensive listing of manufacturers and Standard Containers A3704-3 suppliers of every type of product for farmers, Standard containers for carrying and including postharvest equipment and supplies. 12 moving produce are made of molded issues/$15.95. Single issue/$2.75. plastic, have sturdy handles, and are stackable. They’re easier to use and more Cady Industries efficient than bushel baskets, buckets or P.O. Box 2087 wooden crates. Memphis, TN 38101 Narrow Pallet System A3704-4 (800) 622-3695 If you currently carry boxes of produce by Sells a 32” x 27” McKnit nylon bag with 1/8” hand, switching to a narrow pallet system mesh for $6 each, with a minimum order of 10. may save you time and money. With a hand pallet truck you can move up to 16 The Nylon Net Co. half-bushel boxes at a time. This system 845 North Main St. can cut your time spent moving boxes by Memphis, TN 38107 more than 60% and will dramatically (800) 238-7529 reduce the stress put on your body. Sells a ¼”nylon mesh “diver’s bag” with drawstring, 24” x 34”, for $8.28 each. These tipsheets may be ordered from the following address, or accessed on-line at: http://www.bse.wisc.edu/hfhp/ ATTRA // POSTHARVEST HANDLING OF FRUITS & VEGETABLES Page 11
  12. 12. Delta Track Cool Care Consulting, Inc.P.O. Box 398 4020 Thor Dr.Pleasanton, CA 94566 Boynton Beach, FL 33426(800) 962-6776 (561) 364-5711 Sells “Hygro Thermometers”: about the size of a e-mail: ron.roberts@coolcareinc.com deck of cards, battery operated, digital display of http://www.coolcareinc.com temperature and humidity, records daily min./max. Sells postharvest pre-cooling and refrigeration of each. equipment, including forced air, ice, hydro, vacuum, modular, and mobile cooling units.Spectrum Technologies23839 W. Andrews Rd. Bio Safe SystemsPlainfield, IL 60544 80 Commerce St.(800) 248-8873 Glastonbury, CT 06033 Sells humidity monitors. (888) 273-3088 e-mail: Rob@biosafesystems.comBarr, Inc. http://www.biosafesystems.com1423 Planeview Dr. Sells organic-approved, eco-friendly washwaterOshkosh, WI 54904 treatments/disinfectants.(920) 231-1711e-mail: info@barrinc.comhttp://www.barrinc.com Distributor of used coolers, freezers, and The electronic version of Postharvest Handling of Fruit & Vegetables is located refrigeration systems. at: http://www.attra.org/attra- pub/postharvest.html By Janet Bachmann and Richard Earles NCAT Agriculture Specialists August 2000 The ATTRA Project is operated by the National Center for Appropriate Technology under a grant from the Rural Business-Cooperative Service, U.S. Department of Agriculture. These organizations do not recommend or endorse products, companies, or individuals. ATTRA is located in the Ozark Mountains at the University of Arkansas in Fayetteville at P.O. Box 3657, Fayetteville, AR 72702. ATTRA staff members prefer to receive requests for information about sustainable agriculture via the toll-free number 800-346-9140. ATTRA // POSTHARVEST HANDLING OF FRUITS & VEGETABLES Page 12
  13. 13. APPENDIX I Storage Conditions for Vegetables and Fruits Temperature % Relative Precooling Storage life Ethylene F humidity method Days sensitiveApples 30-40 90-95 R, F, H 90-240 YApricots 32 90-95 R, H 7-14 YAsparagus 32-35 95-100 H, I 14-21 YAvocados 40-55 85-90 14-28 YBananas 56-58 90-95 7-28 YBeans, snap 40-45 95 R, F, H 10-14 YBeans, lima 37-41 95 7-10Beets, roots 32 98-100 R 90-150Blackberries 31-32 90-95 R, F 2-3Blueberries 31-32 90-95 R, F 10-18Broccoli 32 95-100 I, F, H 10-14 YBrussel sprouts 32 95-100 H, V, I 21-35 YCabbage 32 98-100 R, F 90-180 YCantaloupe 36-41 95 H, F 10-14 YCarrots, topped 32 98-100 I, R 28-180 YCauliflower 32 90-98 H, V 20-30Celery 32 98-100 I 14-28 YCherries, sweet 30-31 90-95 H, F 14-21Corn, sweet 32 95-98 H, I, V 4-6Cranberries 36-40 90-95 60-120Cucumbers 50-55 95 F, H 10-14 YEggplant 46-54 90-95 R, F 10-14 YEndive 32 90-95 H, I 14-21 YGarlic 32-34 65-75 N 90-210Grapefruit 50-60 85-90 28-42Grapes 32 85 F 56-180Kiwifruit 32 95-100 28-84 YLeeks 32 95-100 H, I 60-90 YLemons 50-55 85-90 30-180Lettuce 32 85-90 H, I 14-21 YLimes 48-50 85-90 21-35Mushrooms 32 95 12-17Nectarines 31-32 95 F, H 14-18 YOkra 45-50 90-95 7-14 YOnions, bulb 32 65-70 N 30-180Onions, green 32 95-100 H, I 7-10Oranges 32-48 85-90 21-56Peaches 31-32 90-95 F, H 14-28 Y ATTRA // POSTHARVEST HANDLING OF FRUITS & VEGETABLES Page 13
  14. 14. Temperature % Relative Precooling Storage life Ethylene F humidity method Days sensitivePears 32 90-95 F, R, H 60-90 YPeas, in pods 32 95098 F, H, I 7-10 YPeppers, bell 45-55 90-95 R, F 12-18 YPeppers, hot 45-50 60-70 R, F 14-21 YPineapple 45-55 85-90 14-36Plums 32 90-95 F, H 14-28 YPotatoes, early 50-60 90 R, F 56-140Potatoes, late 40-50 90 R, F 56-140 YPumpkins 50-60 50-75 N 84-160Radishes 32 95-100 I 21-28Raspberries 32 90-95 R, F 2-3 YRutabagas 32 98-100 R 120-180Spinach 32 95-100 H, I 10-14 YSquash, summer 41-50 95 R, F 7-14 YSquash, winter 50-55 50-70 N 84-150Strawberries 32 90-95 R, F 5-10Sweet potatoes 55-60 85-90 N 120-210 YTangerines 40 90-95 14-28Tomatoes 62-68 90-95 R, F 7-28 YTurnips 32 95 R, H, V, I 120-150Watermelon 50-60 90 N 14-21F = forced-air cooling, H = hydrocooling, I = package icing, R = room cooling, V = vacuumcooling, N = no precooling needed. Sources: USDA Agricultural Marketing Service, Kansas StateUniversity Cooperative Extension Service ATTRA // POSTHARVEST HANDLING OF FRUITS & VEGETABLES Page 14
  15. 15. APPENDIX IIThe Portacooler heaters using copper wire so that they contact the cooling coils of the airA portable precooler designed by USDA conditioner. Mount the blower on the frontresearchers can be built with readily inside wall, centered above the airavailable materials at a cost of around conditioner so that the blower$1,200. The most expensive component discharge is 12 inches below the insideis an airconditioner. If a used ceiling.airconditioner is available, the initialinvestment will be decreased. The All electrical components should be properlyPortacooler can be towed to the field and grounded, and wiring should comply withused to reduce field heat of berries, national and local electrical codes. Consult avegetables, and other high-value crops licensed electrician for more informationimmediately after picking. about how to install any components of the electrical system.The structure of the Portacooler is a basicwood frame and plywood panel The Portacooler can be powered fromconstruction (see diagram). The outside either an electrical wall outlet or adimensions of the cooler are 4 feet high by gasoline-powered generator. The main4 feet wide by 8 feet long. The frame is electrical connection from the powermade of 2 by 3s spaced 2 feet on center, source is split to the individual switches.excluding the doorway and the air From the switches, the power travels to theconditioner space. The frames are blower and to the air conditioner. Thesheathed with 1/2 inch plywood. The strip heaters and the thermostat are wiredprecooler is insulated with 2-inch thick from the timer. The timer creates a defrostplastic foam that fits firmly between the cycle by alternating power from theframe studs. compressor to the strip heaters. (An interval of compressor shutdown timeAfter the frame and sheathing are should be approximately 2.5 minutescompleted, the electrical components can during every 10 minutes.)be installed (see diagram). The standardjunction box, power switches, daily cycle Once the cooler is assembled, and thetimer, and industrial thermostat control electrical components hooked up, mount thebox should be mounted on the outside of air flow bulkhead. Mount the bulkhead withthe front wall near the air conditioner. An blower discharge hoe flush with the edge ofadjustable, industrial thermostat control the blower discharge, allowing a 6-inch-highbox should be mounted on the outside of return-air gap along the floor.the front wall near the air conditioner. Anadjustable, industrial thermostat must be All wood surfaces should be coated withconnected to the air conditioner to replace polyurethane and an all-weather sealer tothe existing thermostat. Mount strip prolong the useful equipment life. ATTRA // POSTHARVEST HANDLING OF FRUITS & VEGETABLES Page 15
  16. 16. General Material List• air conditioner, 12,000 Btu, 115 V......................................................................................................1• centrifugal blower, 1/3 hp, 1210 c.f.m. ............................................................................................1• 20-amp wall switch, with boxes and covers ...................................................................................2• 4 by 8 ft, exterior AC, 1/4-in plywood.............................................................................................11• lumber, 2 by 3 in, 8 ft long..................................................................................................................30• lumber, 2 by 4 in, 12 ft long................................................................................................................3• lumber, 2 by 6 in, 8 ft long..................................................................................................................1• industrial wheels, 5-in diameter........................................................................................................2• industrial wheels, 5-in diameter, swivel..........................................................................................2• dry wall screws, 2 1/2-in long...........................................................................................................5 lb• dry wall screws, 1-in long ..................................................................................................................1 lb• water sealer...........................................................................................................................................1 gal• polyurethane coating ..........................................................................................................................1 gal• weather stripping, 1-in wide roll ......................................................................................................1• insulation, 2 in, 4 by 8 ft sheets..........................................................................................................5• 1/4-in plywood, 4-in wide strips ......................................................................................................12 ft• door latch, sliding bolt ........................................................................................................................1• thermostat, 115 B, 16 amp, remote bulb ..........................................................................................1• strap hinges, screw fastened, 3-in long ............................................................................................4• lumber, 2 by 10 in, 4 ft long................................................................................................................1• standard junction box .........................................................................................................................1• strip heaters, 150 watt, 8 in, 115 B .....................................................................................................2• insulated wire.......................................................................................................................................30 ft• cycle timer, SPDT, 115 B, 20 amp, 1 hour ........................................................................................1The design, construction, and research of the Portacooler was conducted by Joseph Anthony,Gerald Berney, William Craig, and Daniel P. Schofer. For further information, contact DanielSchofer, Room 1211 South Bldg., 12 & Independence, Box 96456, Washington, D.C. 20090-6456. ATTRA // POSTHARVEST HANDLING OF FRUITS & VEGETABLES Page 16
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