Postharvest Technology for Horticultural Crops
In October, FFTC held a training course for extension specialists and technical staff
This training course was conducted for extension specialists and technical staff, to enhance their knowledge of both the principles and practices of postharvest handling of horticultural crops. The trainees are expected to disseminate this information to growers, to help them reduce postharvest losses and improve the quality of their produce.
Packaging
The packaging of fruits and vegetables should protect them from injury and water loss, and be convenient for handling and marketing. Packages should also provide information about the product, including the grade, handling instructions, and appropriate storage temperatures when the product is on display. The cost of the packaging is important, including whether the container can be recycled or reused.
Transport
Fresh horticultural products should be cooled after harvest and during transport. It is very important that the cold chain is continuous. Once fruit and vegetables have been cooled, they must stay cool. Trucks for road transport may be refrigerated, or may sometimes just be insulated. It is difficult to control the temperature of air shipments, but produce shipped by air should be covered and precooled.
Quality Considerations
Several factors are important in determining the quality of fruits and vegetables: the appearance, the flavor, the texture, the nutritional value and the safety. Only the first three can be easily identified by consumers.
Successful postharvest handling depends partly on the initial quality of the crop at harvest, including the degree of maturity. It also depends on careful handling to minimize mechanical damage, proper management of the environmental conditions, and good sanitation.
Diseases
On average, economic losses from diseases after harvest are even higher than disease losses in growing crops!! A major cause of postharvest losses is fungus diseases, including anthracnose and stem-end rot. Preharvest treatment is the best method of control. This should include the use of healthy seedlings, as well as proper disease control in the field and good field sanitation.
Tropical fruits are susceptible to many postharvest diseases. They are sensitive to chilling injury, and cannot be kept at low temperatures. It is very important to harvest tropical fruits at the right stage of maturity. Treatments with sulfur dioxide, fungicides and antioxidants help to reduce losses of tropical fruits from postharvest diseases, as does careful attention to humidity and temperature. Most important is careful handling to minimize injuries. Bruised fruit, or fruit with a damaged skin, is more vulnerable to diseases, spoils more quickly and sells more slowly.
Many kinds of cut flowers are also sensitive to chilling injury, causing the flowers to discolor and decay. Diseases such as anthracnose and grey mold may also occur on cut flowers, especially in conditions of high humidity.
Imports and Exports
Countries in the Asian and Pacific region play a major role both as exporters of horticultural crops, and as importers. A major concern is to prevent the accidental invasions of alien pests and diseases. Japan is the largest importer of agricultural and forestry products in the world. Strict implementation of plant quarantine measures through fumigation is being conducted, to prevent the invasion of pests.
Fumigation with Methyl Bromide
The fumigant methyl bromide is generally preferred for the disinfection of both durable and perishable agricultural commodities. This is because of its low phytotoxicity and its wide-ranging action against a large number of pests. Furthermore, large, bulky shipments can be rapidly and easily treated. However, methyl bromide has now been identified as one of the chemicals that are damaging the world's ozone layer. Efforts are being made to develop alternatives, and treatment systems which recycle methyl bromide.
VHT (Vapor Heat Treatment)
Fruitfly is a major problem in the import and export of tropical fruits and vegetables. VHT is an effective, non-chemical method of treatment, widely used to treat mangoes and other tropical fruits grown for export. VHT treatment maintains produce at a certain temperature for a fixed period of time, using a hot water/steam vapor system. This destroys any larvae of the fruitfly which might be present inside the fruit, as well as the eggs and pupae.
The FFTC Training Course
As well as country reports and lectures on important aspects of postharvest technology, trainees carried out laboratory exercises. These included ethylene production, respiration rate, respiration heat, the effect of ethylene, chilling injury, precooling and quality evaluation.
Index of Images
Figure 1 FFTC Training Course on Postharvest Technology for Horticultural Crops: Trainees Evaluate the Quality of Vegetables after Chilling Treatment.
Figure 2 Trainees Watch Workers at a Cooperative Warehouse in Taiwan. the Workers Are Packing Bottle Gourd.
