CHAPTER 9: HANDLING AT DESTINATION

When handling produce at its destination, again it is important to avoid rough handling, minimize the number of handling steps, and maintain the lowest feasible temperature. If produce is to be stored before sale, then wholesale and retail markets need clean, well insulated storage rooms. Since a variety of commodities is usually being handled simultaneously at this point, it is important to remember not to mix those with different temperature requirements or store ethylene sensitive commodities near ethylene generating commodities. Stacking of non-uniform containers should be done with care to prevent collapse of weaker packages.

Before produce is sold to the consumer, the handler may wish to sort for quality, or at least to discard any damaged or decayed produce in order to give the product more market appeal. If ripeness or maturity is non-uniform, sorting at destination can provide the seller with a higher price for the better quality produce.

If the produce handled is a climacteric fruit crop that was harvested before it was ripe (bananas, tomatoes, avocadoes, mangoes), the handler at destination may want to ripen the produce before it is sold to the public. Sometimes commodities such as bananas are left at ambient temperatures and allowed to ripen naturally. Covering the bananas with a plastic sheet will help ripening be more uniform throughout the lot (PHTRC, 1984). Placing a simple air vent (a pipe or a tube of some sort) into the center of the pile of ripening fruit can help reduce overheating during ripening and increase subsequent shelf life. The introduction of ethylene gas or ethylene-releasing compounds into a special storage environment (known as a ripening room or cabinet, depending upon size) is a more effective way to ensure uniform ripening.

Temperatures of the display tables or refrigerated supermarket displays should be suited to the commodity on sale. For example, while peppers and tomatoes look pleasing when displayed with lettuce, peppers and tomatoes are chilling sensitive, while lettuce is not. Misting commodities that can tolerate surface water (lettuce, broccoli, green onions) with cool clean water can help maintain a high relative humidity around the product.

Outdoor marketplaces suffer from a lack of temperature control and high air circulation, which can lead to desiccation of crops, which will be seen as shriveling and wilting. These marketplaces can often benefit by the increased use of shading and protection from prevailing winds.

Finally, the handler at destination can help reduce losses in the future by maintaining good records of the sources of losses suffered at the wholesale or retail level (Kasmire & Ahrens in Kader, 1992). Identifying whether losses were due to mechanical damage, decay/disease, immaturity or over-ripeness allows the handler to provide better quality feedback to produce suppliers.

Unloading

A loading dock can ease the work associated with handling horticultural produce at destination. Containers can be transferred more rapidly and with less bending and lifting.

For large trucks, a loading dock 117 to 122 cm high (46 to 48 inches) functions well, while for small trucks or pickups a height of 66 to 81 cm (26 to 32 inches) is recommended.

Source: Selders, A.W. et al. 1992. Facilities for Roadside Markets. Northeast Regional Agricultural Engineering Service/ Cornell University Cooperative Extension.

A simple device for easing the work of unloading transport vehicles can be constructed using a two pulleys and a strong rope. One pulley can be mounted inside the truck at the front of the bed, the second outside on a portable post or on a stationary object like the side of a building. Containers can be hung directly by their handles or placed into a sling.

Source: Pantastico, Er. B. 1980. FAO/UNEP Expert Consultation on Reduction of Food Losses in Perishable Products of Plant Origin. Working Document 2: Fruits and Vegetables. (6-9 May, Rome : FAO)

A simple set of stairs can be constructed to ease the work of loading and unloading produce. The stairs illustrated here can be folded and pushed back under the back of the truck when the vehicle is in motion. The steps can be made of wood or steel matting and steel bars can be used for supports.

Using a ramp is a simple and safe method for unloading produce. The ramp should be wide enough to prevent accidents and strong enough to carry the full weight of the handler plus the package she/he is carrying. Providing hand-trucks or small carts can also ease the work associated with unloading.

Source: Pantastico, Er. B. 1980. FAO/UNEP Expert Consultation on Reduction of Food Losses in Perishable Products of Plant Origin. Working Document 2: Fruits and Vegetables. (6-9 May, Rome : FAO)

Temporary storage temperatures

When produce is held at destination for a short time before marketing, the handler can help maintain quality and reduce losses by storing commodities at their most suitable temperature. However, if the storage period is seven days or less, relative humidity is maintained between 85 and 95%, and the ethylene level is kept below 1 ppm, by ventilating or using a scrubber, most commodities can be grouped into the following three temperature-based groups.

* Products marked with an asterisk are sensitive to ethylene damage.

Source: Thompson, J.F., Kader, A.A. and Sylva, K. 1995. Compatibility Chart for Fruits and Vegetables in Short-term transport or Storage. University of California DANR Publication 21560 (poster).

Sorting/repacking

Some produce may require washing, trimming, bunching or sorting at the wholesale or retail market level. The layout of the work station used for handling produce at destination should be organized to minimize non-productive movement. In the illustration below, a dump table is located next to a sink for washing produce, and the drain board is positioned directly next to the sink. Once produce has dried, cartons can be packed and placed onto a cart located right next to the repacking table. With this layout, a single operator could easily perform all the handling steps or several handlers could work side by side.

Source: Selders, A.W. et al. 1992. Facilities for Roadside Markets. Northeast Regional Agricultural Engineering Service/ Cornell University Cooperative Extension.

Some produce may have to be repacked by the wholesaler or retailer due to changes in quality or uneven ripening. The tomato sorting table illustrated below has work stations for up to five who select either ripes, pinks or breakers and allow the green tomatoes to run off to the end of the line. Rejects (culls) are placed in pails under the
table.

Source: USDA. No date. Tomato repacking methods and equipment. USDA Marketing Service, Transportation and Facilities Research Division, Marketing Research Report No. 597

Ripening

Ripening is the process by which fruits attain their desirable flavor, color and textural properties. Climactericfruits can ripen off the plant once they have reached physiological maturity.

Climacteric fruits include apples, avocado, banana, blueberries, breadfruit, cherimoya, durian, feijoa, fig, guava, kiwifruit, mango, muskmelon, papaya, passion fruit, pears, persimmon, plantain, quince, sapodilla, sapote, soursop, stone fruits (apricots, nectarines, peaches, plums) and tomato. Some of these these fruits if harvested "mature-green", can be ripened after harvest and short term storage. Pears and bananas are unusual in that they develop the best flavor and texture characteristics when harvested mature-green and ripened off the tree. Avocadoes do not ripen on the tree.

Some climacteric fruits give off large quantities of ethylene during ripening. These include apples, apricots, avocadoes, cantaloupe, kiwifruit, nectarines, peaches, pears, plums and passion fruit. A small dose of ethylene gas will stimulate other climacteric fruits to begin the ripening process. A few climacteric fruits, such as muskmelons, will not increase in sugar content during ripening, but will soften.

Non-climacteric fruits must ripen on the plant if you want a fully ripe fruit, since once they have been harvested, no further ripening will occur. Flavor and texture will be of low quality if fruits are picked before fully ripe.

Some non-climacteric fruits include berries, cherries, citrus fruits (lemons, limes, oranges, grapefruits, mandarins, tangerines), cucumber, dates, eggplant, grapes, lychee, okra, peas, peppers, pineapple, pomegranates, strawberry, summer squash, tamarillo and watermelon.

Non-climacteric fruits will not respond to attempts to ripen them with ethylene gas. A partially red strawberry, for example, will not develop any more color or sweetness after being picked, and will deteriorate faster if exposed to ethylene. Watermelons develop most of their sweetness during the week before they reach full maturity, making early harvest very undesirable.

Sometimes ripening commodities before sale at the wholesale or retail level will improve their value. Ripening rooms are often used for tomatoes, citrus fruits and bananas. The use of diluted ethylene gas mixtures is safer than using pure ethylene which is explosive and flammable at concentrations of 3% or higher.

For tomatoes, technical grade ethylene gas is introduced into the room at a concentration of about 100 ppm for about 48 hours. Approximately 0.25 cubic feet/hr of ethylene gas is required for each 1000 cubic feet of ripening room volume. A small fan can be used to ensure a uniform continuous flow of ethylene into and through the room. Forced-air ripening is increasingly being used to provide more uniform temperatures and ethylene concentrations throughout the ripening room.

Continuous flow gassing:

Source: Kasmire, R.F. 1981. Continuous flow ethylene gassing of tomatoes. California Tomatorama. Fresh Market Tomato Advisory Board Information Bulletin No. 29.

For more information about ethylene generators, see the Internet site of American Ripener Co., Inc. at http://www.ripening.com or Catalytic Generators, Inc. (International Ripening Company) at http://www.Qasupplies.com

Ripening can also be initiated by using ethylene generated by passing ethanol over a bed of activated alumina. This method is safer than using pure ethylene gas.

Ethylene-releasing compounds such as ethephon {(2-chloroethyl) phosphoric acid} are sometimes used to ripen tomatoes destined for processing. When using ethephon as a spray, the amount of ethylene released will increase as pH and/or relative humidity increase.

Source: Kays, S.J. and Beaudry, R.M. 1987. Techniques for inducing ethylene effects. Acta Horticulturae 201:77-115.

Ethephon is also approved for a variety of ripening and de-greening uses as shown in the following table:

Approved uses for ethephon (2-chloroethane phosphonic acid) in US agriculture.

Source: Reid, M.S. 2002. Ethylene in Postharvest Technology pp.149-162. In: Kader, A.A. (ed). Postharvest Technology of Horticultural Crops. Univ. of California , Div. of Agriculture and Natural Resources, Publication 3311.

The following table shows typical produce storage and ripening temperatures for some of the commodities that can be ripened.

¹Multiply by 220 to obtain heat to respiration (BTU/ton/24 hours)

Source: Thompson, J.F. 1994. Ripening facilities. Perishables Handling Newsletter, Nov. 1994. Special Issue No. 80: 5-8.

The following illustration is a de-greening room designed for use with citrus in pallet boxes. The ceiling of the room is relatively high, allowing boxes to be stacked at least four high. A false ceiling is added to provide for adequate air movement throughout the room. For more detailed information on room construction, temperature and relative humidity management and air circulation, refer to the article entitled "Ripening Facilities" (Thompson, 1994) in the reference section of the manual.

Source: USDA. No date. Modernizing Handling Systems for Florida Citrus from Picking to Packing Line. Agricultural Research Service, Marketing Research Report No. 914.

Several small ripening rooms may be more useful than a single large room for small scale handlers, since the amount of product handled at destination may vary from time to time. In this case, flow through systems can be designed to allow the use of one or more rooms at the same time.

Flowmeters can be located in one place for ease of monitoring, or can be strung out in a line. Locating all the flowmeters in one place requires the use of more tubing than if flowmeters are located in each ripening room. For more information and details on how to set up a flow through system for ripening fruit, see Sherman and Gull (1981).

Flowmeters in one location

Flowmeters located in each ripening room

Source: Sherman , M. and Gull, D.D. 1981. A flow through system for introducing ethylene in tomato ripening rooms. University of Florida/IFAS , Vegetable Crops Fact Sheet 30.

Small-scale handlers can now lease portable ripening facilities from a variety of companies in the United States . The self-contained, portable system illustrated below features a 20 pallet capacity, high capacity air flow and is simple to operate. All that is needed is a loading dock and a supply of 220V electricity.

Source: Modular Ripening Company, Inc. 1994. Norfolk Virginia

Small-scale wholesalers and retailers can ripen fruits in bins or large cartons by placing a small quantity of ethylene-generating produce such as ripe bananas in with the produce to be ripened. Cover the bin or carton with a plastic sheet for 24 hours, then remove the plastic cover.

A simple way to ripen fruits at home in small amounts is to use a ripening bowl. Fruits that require ripening should be placed into the bowl with a ripe apple or ripe banana (or any other high ethylene-generating product). The bowl shown below is made of clear molded plastic and has ventilation holes around the top. Using this method, ripening will take from one to four days.

Home ripening is also possible using another, extremely low-tech practice-- place fruits to be ripened into a paper bag with a ripe piece of fruit, close loosely and check in a few days.

Display

This wooden display table is designed to be used for commodities such as cruciferous crops or leafy green vegetables that tolerate cooling with ice. The table can be used in the horizontal position or as a tilted display. For more complete design specifications, contact the Cornell University Extension Service, 304 Riley-Robb Hall, Ithaca , New York , 14853 .

Four to five lbs of crushed ice per square foot of display space are required for cooling per day. A catch pail should be provided for melt water. To minimize ice needs, the display tray should be insulated and kept out of the direct sun.

When displaying horticultural crops, single or double layers of produce are most likely to protect the commodities from compression damage and over-handling by the consumers.

Source: Bartsch, J.A. et al. No date. Construction and management of an iced produce display. Cornell University , Agricultural Engineering Extension Bull. 438.

High relative humidity can be maintained during display by misting leafy vegetables and water tolerant crops with clean, cold water. A simple sprinkler device can be constructed by perforating a pipe with tiny holes and connecting it to a hose. If this display is used outdoors, shade should be provided.

Displays and storage areas must be cleaned and sanitized on a regular basis. Trimmings, waste, and bruised product remaining in displays are unsightly and can be sources of decay, odor and ethylene.

Produce that benefits from misting while being displayed:

A simple semi-circular display table can be constructed from one four foot by eight foot sheet of plywood. Plans for the table illustrated below and for other market stands are available from Cornell University Extension, 304 Riley-Robb Hall, Ithaca , New York 14853 .

Source: Agricultural and Biological Engineering. No date. Description and Price List of Plans for Storages and Market Stands for Fruit and Vegetables. Cornell University Extension Bulletin 851-S.