Introduction the manual

Postharvest handling steps for a typical commodity
Principal causes of postharvest losses and poor quality
Resources for quality assurance and export marketing

The two main objectives of applying postharvest technology to harvested fruits and vegetables are to maintain quality (appearance, texture, flavor, nutritive value and safety) and to reduce losses between harvest and consumption. Effective management during the postharvest period, rather than the level of sophistication of any given technology, is the key in reaching the desired objectives. While large scale operations may benefit from investing in costly handling machinery and high-tech postharvest treatments, often these options are not available to small-scale handlers for the simple reason of economies of scale. Instead, simple, low cost technologies can be more appropriate for small volume, limited resource commercial operations, farmers involved in direct marketing, for home gardeners, as well as for handlers in developing countries.

Many recent innovations in postharvest technology in developed countries have been in response to the desire to avoid the use of costly labor and the desire for cosmetically "perfect" produce. These methods may not be sustainable over the long term, due to socioeconomic, cultural and/or environmental concerns. For example, the use of postharvest pesticides can be costly both in terms of money and environmental consequences. Local conditions for small-scale handlers may include labor surpluses, lack of credit for investments in postharvest technology, unreliable electric power supply, lack of transport, storage facilities and/or packaging materials, as well as a host of other constraints. Fortunately, there is a wide range of simple postharvest technologies from which to choose, and many have the potential of meeting the special needs of small-scale food handlers and marketers. Many of the practices included in the manual have been successfully used in various parts of the world for handling horticultural crops for many years.

There are many interacting steps involved in any postharvest system Produce is often handled, transported and stored repeatedly between harvest and consumption (Figure 1; FAO, 1986). While particular practices and the sequence of operations will vary for each crop, there is a general series of steps in postharvest handling systems that will be followed for the purposes of the manual.

Postharvest handling steps for a typical commodity

FIGURE 1: Postharvest Handling Steps for a Typical Commodity

Section 1 presents some harvesting practices and methods of preparation for market. Section 2 provides selected examples of how to cure root, tuber and bulb crops before further handling or storage. Section 3 illustrates simple technologies that can be used in the packinghouse, be it a simple shed in the field or a separate structure with cooling and storage facilities.

Section 4 presents a variety of packing methods and packaging materials that can help to maintain product quality and reduce mechanical damage during handling and storage. Section 5 describes pest control methods and offers suggestions for alternatives to chemical treatments for insect and disease control.

The most common causes of postharvest losses in developing countries include rough handling and inadequate cooling and temperature maintenance (Table 1). The lack of sorting to eliminate defects before storage and the use of inadequate packaging materials further add to the problem. In general, minimizing rough handling, sorting to remove damaged and diseased produce and effective temperature management will help considerably toward maintaining a quality product and reducing storage losses. If the temperature during the postharvest period is kept as close to the optimum as feasible for a given commodity, storage life will be enhanced. Simple methods for cooling are described in Section 6. Storage structures, methods for ensuring adequate ventilation, and simple technologies for modified atmosphere storage are presented in Section 7. Transport practices that can reduce losses are described in Section 8, and methods for handling at destination (wholesale or retail markets) are illustrated in Section 9. Finally, Section 10 presents some simple methods for processing fresh produce such as drying, canning and juice extraction.

Principal causes of postharvest losses and poor quality

Table 1: Principal Causes of Postharvest Losses and Poor Quality for Various Groups of Fruits and Vegetables

GROUP	EXAMPLES	PRINCIPAL CAUSES OF POSTHARVEST LOSSES AND POOR QUALITY (IN ORDER OF IMPORTANCE)
Root vegetables	Carrots	Mechanical injuries
	Beets	Improper curing
	Onions	Sprouting and roving
	Garlic	Water loss (shriveling)
	Potato	Decay
	Sweet Potato	Chilling injury (subtropical and tropical root crops)
Leafy vegetables	Lettuce	Water loss (wining)
	Chard	Loss of green color (yellowing)
	Spinach	Mechanical injuries
	Cabbage	Relatively high respiration rates
	Green onions	Decay
Flower vegetables	Artichokes	Mechanical injuries
	Broccoli	Yellowing and other discolorations
	Cauliflower	Abscission of florets
Immature-fruit vegetables	Cucumbers	Decay
	Squash	Overmaturity at harvest
	Eggplant	Water loss (shriveling)
	Peppers	Bruising and other mechanical injuries
	Okra	Chilling injury
	Snap beans	Decay
Mature-fruit vegetables and fruits	Tomato	Bruising
	Melons	Over-ripeness and excessive softening at harvest
	Citrus	Water loss
	Bananas	Chilling injury (chilling sensitive fruits)
	Mangoes	Compositional changes
	Apples	Decay
	Grapes
	Stone fruits

Each of the practices presented in the manual are briefly described and illustrated. For further information on any particular practice, users can refer to the source listed or write directly to the authors of the manual. The practices described in this manual are not meant to be a comprehensive list of postharvest handling practices, but a starting point for low-input and/or small-scale handlers of horticultural commodities. It is hoped that users of the manual will send to the authors any information about simple, low cost technologies currently in use which were not covered in this edition. Such information would be very useful since we plan to update the manual on an annual basis.

Appendix A contains a list of manufacturers and suppliers of appropriate postharvest technologies, and handlers can contact these businesses directly. Suggestions for additions to this list are welcomed by the authors. We believe that application of some of the practices illustrated in the manual will enable small-scale handlers to reduce produce losses and help maintain quality of fruits vegetables and ornamental crops.

Resources for quality assurance and export marketing

For handlers who desire more detailed information on requirements for export, the Natural Resources Institute (1994) has published a comprehensive Manual for Horticultural Export Quality Assurance. NRI's manual provides practical guidelines for the total quality management of the postharvest process, including inspections, hygiene, pesticide residue analysis, standardization of instruments for temperature checking, and records maintenance. This manual is highly recommended to anyone involved in the business of exporting horticultural commodities to countries of the European Union. (Available for sale from NRI, Central Avenue, Chatham Maritime, Kent ME4 4TB, UK).

Standards for U. S. Grades are available for a wide range of fruits and vegetables for fresh market or processing. For a single free copy of U.S. Grades for a particular commodity, write to Fresh Products Branch, USDA-AMS, FV, Room 2056-S, Washington, D.C., 20250. U.S. Inspection Instructions are also available at a small fee from this address.

The Organization of Economic Cooperation and Development (OECD) publishes booklets on "International Standards of Fruits and Vegetables". In North America, write to: OECD Publications and Information Center, 2001 L Street, N.W., Suite 700, Washington, D.C., 20036-4910. From countries outside North America, contact OECD Publications Service, 2 Rue André-Pascal, 75775 PARIS Cedex 16, France.

Protrade advises and promotes businesses in Latin America, Africa, Asia and Eastern Europe by providing marketing expertise for products that are competitive in European markets. Handbooks on general trade and marketing are available for fresh fruit and dried fruit. Export manuals (in English and Spanish) are available for asparagus, mangoes, avocados, papaya and pineapple. These publications are available from Deutsche Gesellschaft für Technische Zusammenarbeit (GTZ), Gmb H/ Protrade, P.O. Box 5180, D-65726 Eschborn, Germany.

Publications on the harvesting, postharvest handling and marketing of banana, mango, rambutan, papaya and durian are available from the ASEAN Food Handling Bureau, as a part of its series on "Fruit Development, Postharvest Physiology, Handling and Marketing in ASEAN". Each book is available for sale from ASEAN Food Handling Bureau, Level 3, G14/G15, Pusat Bandar Damansara, 50490 Kuala Lumpur, Malaysia.