Fresh fruits and vegetables are inherently perishable. During the process of distribution and marketing, substantial losses are incurred which range from a slight loss of quality to total spoilage. Postharvest losses may occur at any point in the marketing process, from the initial harvest through assembly and distribution to the final consumer. The causes of losses are many: physical damage during handling and transport, physiological decay, water loss, or sometimes simply because there is a surplus in the marketplace and no buyer can be found!
Losses are high in many Asian countries, because of the inherent difficulty of collecting and transporting small quantities of produce from numerous small farms, and trying to collect these into a large enough quantity for efficient domestic marketing or for export. Even if large shipments can be collected together, the produce is often highly variable in size and quality, so that it is difficult to apply standardized grading and storage procedures. In tropical and subtropical countries, the warm, humid climate adds more stress and accelerates the decay of tropical produce. Postharvest losses of vegetables and fruit in most Asian countries are so high, and the causes of these losses are so diverse, that a great deal of research and training is needed if prevention measures are to be improved. . The need for improvement is shown by the fact that in developing countries where there is still a poor infrastructure and a lack of marketing facilities, postharvest losses of fresh produce range from 20 to 50 %.
A general picture of the rate of postharvest losses of horticulture crops in each country can be obtained from the Food Balance Sheet by calculating the difference between total production and total consumption. On this basis, losses of vegetable and fruit in Taiwan in 1992 were 10%, the same level as in Japan the same year, while in Korea in 1990 the rate of postharvest losses was 26 % for vegetables and 10% for fruit. However, this kind of average figure does not provide much practical information for planning and implementing programs at a local level for a specific commodity. For instance, the loss rate for Chinese cabbage is estimated to be around 30% in all countries in Asia, but the loss factors differ from country to country. It is more difficult to prevent losses in a warm humid climate than in a temperate one, but in a temperate climate high losses may occur during a single, short harvest period. Furthermore, the evaluation of losses is not uniform. The standards used to evaluate produce in Japan are very high. If if these were to be applied in the Philippines, estimated losses might be 40%.
What is needed is an assessment of the loss rate and identification of specific problems for specific commodities. For example, loss rates for mango vary from 2% to 95%. If loss rates are found to be very high in a specific area, it should be possible to find the cause and solve the problem.
Often the constraint is as much economic as technological. It is common in Asian countries for sophisticated postharvest procedures to be used for some export commodities by large commercial enterprises, alongside simple, low-cost methods used by smallholders who have access only to small local markets. There is also an increasing gap between the industrialized and less industrialized countries, in terms of the quality of their storage and marketing facilities and their food processing technology.
Little cross-country data for specific commodities is available, except for very common vegetables such as Chinese cabbage and onion. In the case of Chinese cabbage, postharvest losses (by weight) in Japan at a retailer level and in consumers' homes were 19.2% (1992), compared to 27.4% in Korea (1992) and 28.1% in ROC (1985). Comparable loss rates in the Philippines during the 1980s varied in different studies, but generally ranged between 20 and 34% (1980s).
Of the 17 million mt of vegetables produced in Japan in 1991, there was a 10% loss during handling and distribution. Most of these losses occurred at the retailer and home consumption level. For the vegetable items, postharvest losses ranged from 10 to 30%, with an average of around 20%. Since this figure includes the removal of non-edible parts of the vegetable, root vegetables had a higher loss rate than leafy ones. In Chinese cabbage, for example, there was only 2% loss at a retail level while the remaining 17% occurred in the consumer's home.
This result makes us realize how important are the losses at home when vegetables are prepared for cooking, although such losses do not generally appear in the Food Balance Sheet. It also reminds us that the total loss figure for a particular vegetable or fruit is only finally reached in the consumer's home when it has been prepared for eating.
The marketing chain in Japan is longer and more sophisticated than in most other countries. Many methods of preventing postharvest losses have been developed so that produce can meet the exacting standards of Japanese consumers. These include sophisticated and expensive methods such as vacuum pre-cooling, individual packing of items, and packing produce in plastic trays wrapped in film.
Such methods inevitably mean high marketing costs, and therefore high prices for the consumer. Recent research in Japan tends to emphasize cost management efficiency, such as reducing the labor cost of harvesting and sorting, increasing the efficiency of pre-cooling, improved packaging to extend the shelf-life, and greater efficiency in transportation and the market information system.
The Food Balance Sheet indicates a high level of vegetable losses in Korea - 26.2% in 1988. This represents a marked increase from the level of 14.8% in 1970, although fruit losses remained stable at 10% during the same period. The reason for the high and rising rate of vegetable losses is because the production of vegetable increased sharply in the 1980s, stimulated by the growing demand, while the market capacity was not able to absorb these huge harvests. This shows that over-production and market failure can contribute greatly to postharvest losses.
Chinese cabbage and radish, both of which are highly perishable crops, are the basic materials with which Korean people make kimchi (salted, fermented vegetables which are a staple part of the Korean diet, particularly over the winter). Losses of Chinese cabbage were estimated as 32% in 1980 and as 27% in 1993. This high rate of loss seems to be inevitable in the present situation. The major vegetables used for kimchi (Chinese cabbage and radish, with the addition of red pepper, garlic and Welsh onion for flavoring) all share the same short harvest season in autumn. There are not enough storage facilities to extend the period during which they can be consumed fresh.
Loss assessment should not just involve total losses by weight, but should give some idea of lost market value. However this approach tends to magnify losses at the retail stage compared to the farm level, and losses in years with bumper crops are smaller than when yields are low. Estimating losses on the basis of lost income also reflects the market price of a particular commodity at a particular time, so that losses of cheaper commodities are counted as smaller losses than high-value ones,. even if the loss per unit of volume or weight is the same. A study was made in 1990 of the extent of lost market value as a component of the total marketing cost in Korea. The loss as a percentage of total marketing costs was estimated to be 11% for Chinese cabbage, 14% for sweet potato and onion as 14%, and 11% for apple.
A study of another important source of loss, the discarding by consumers of the less edible or less appetizing parts of fruit and vegetables, found that less Chinese cabbage was discarded in consumers' homes in Korea than in Japan - only 8%, compared to Japan's 17%, with similar figures for Welsh onion and garlic. Loss rates in the home were much higher for fruit. This is to be expected if we consider how much of a whole fruit is inedible peel. Levels of home losses in Korea for fruit were 42% for watermelon, 29% for grape and 25% for mandarin orange.
Horicultural crops are an important part of agricultural production in the Philippines, accounting for 44% of the total volume of food crops. These make a major contribution to the economy, and are an important source of export earnings. Average postharvest losses are 42% for vegetables and 28% for fruit.
Transport of produce from the field to the market is difficult due to the poor condition of masny rural roads, especially in remote areas where only narrow and unpaved feeder roads exist. Carts, sleds, horses or people carry products to collection points. High transit temperature during daytime aggravates this problem.
For transport to market, vegetables such as cabbage, potatoes, carrots or snap beans are placed in polyethylene bags or plastic mesh bags. Larger commodities like squash are put directly into trucks.
Even though export commodities have a relatively high value, studies have generally shown high rates of loss. Fruits such as mango, banana, papaya, citrus and pineapple have postharvest losses ranging from 15 to 35%. Losses are highest for pineapple (30-40%) and banana (25-35%). These general estimates are supported by a few studies of specific commodities. For one trial shipment of `Saba' cooking bananas from Tupto to Manila, a loss of 20% was reported. Most postharvest mango losses are the result of disease, but there was also a general weight loss of 6-10% from dehydration, while the comparable weight loss for papaya was 13%. Common causes of postharvest losses are diverse, but the most common are overripening, disease, harvesting when the fruit is too immature, and mechanical damage.
Studies of postharvest losses of vegetables identified losses in the range of 20 to 40%. Cabbage losses were amongst the highest, at 20 to 30%. Most of this was from trimming and transportation losses. Loss of garlic in the Philippines was 20 to 42%, which is high compared to most other countries. A study of varietal differences in postharvest losses of tomato found interesting differences between varieties. This implies that plant breeding may be a useful approach to loss prevention. Breeders should always keep in mind the storage life after harvest, as well as performance in the field. Some tomato varieties such as BPI-TMz, although they are agronomically successful, are becoming less popular among growers in the Philippines because of their greater susceptibility to postharvest damage.
Vegetables and fruit occupy 26% and 22%, respectively, of Taiwan's total cultivated land area, compared to comparable figures of 15% and 7% in Korea. Taiwan has a mild climate, allowing the production of fresh fruit and vegetables throughout the year. More than 130 different kinds of vegetable are grown. At the same time, because the climate tends to be warm and humid, it has taken great efforts to reduce postharvest losses to their present level of 10% for both vegetables and fruit, according to the Food Balance Sheet. Selective studies of particular commodities have found some loss rates to be much higher than this average figure, for example up to 30% for Chinese cabbage and 16% for radish.
It is interesting that overall, it was the wholesale market where major losses of most commodities occurred. However, during transportation vegetables such as cucumber, green bean, green pepper and watermelon suffer fairly high rates of loss. For papaya, starfruit, banana and Ponkan orange, heavy losses tend to take place at the retail stage. To reduce postharvest losses, research and extension in Taiwan are emphasizing improved handling (including the precooling of fresh produce), individual packing for longer shelf-life, research on the maturity and ripening of fruit, and training for market operators.
Since 1987, the production of fruit in Thailand has increased by 31%, while vegetable production has risen by 69%. Thailand is a tropical country, and tropical produce tends to have a high water content and a high high respiration rate. There are serious levels of postharvest losses, mainly as a result of physical damage, physiological changes and disease. Fruit rot is a major cause of fruit losses, and can be as high as 60% in mango.
The postharvest losses of vegetables shipped by truck from production sites around Chiang Mai, in northern Thailand, to packing stations can be high as 60% for cabbage and tomato, 50% for head lettuce and cauliflower, 30% for bell pepper and 17% for Chinese cabbage. The percentage losses vary according to season, but can all be reduced significantly by improved containers and packaging material. Physical damage to head lettuce shipped from Chiang Mai to Bangkok was reduced from 35.8% to 12.6% when rigid plastic crates were used in place of conventional bamboo baskets.
Although there have been many programs to reduce postharvest losses of horticultural crops, progress has been slow. This is partly because the cooperative system has not grown as rapidly as hoped, and partly because Thai farmers, like Asian farmers everywhere, tend to focus on production and overlook the role of postharvest technology.
This meeting was convened in Taipei on December 20-24, 1994. The specialists attending this meeting included plant physiologists as well as economists, and provided the information given in this report. The purpose of the meeting was so that they could exchange information of the current situation in each country with regard to postharvest losses of fruit and vegetables, and discuss the preventative measures being used or under development.
In their final discussion, the specialists recommended that two topics in particular be included on the research agenda. Firstly, the concepts and methodology for studying postharvest losses need to be refined and standardized, so that different studies can give comparable data. Secondly, policy makers need to know more about the costs and benefits of investment for loss reduction. Sometimes technology is available for reducing losses which does not give an economic return, such as a cold storage system. It was also agreed that postharvest studies should include losses from the seasonal over-production of some commodities.
The survey covered Japan, Korea, Philippines, Thailand, and Taiwan
Figure 1 Simple on-Farm Washing of Fruit
Figure 2 Fruit Washing and Packing Station Operated by Farmersâ€™ Association
Figure 3 Traditional Asian Rope and Bamboo Basket Used to Market Vegetables. I.
Figure 4 Traditional Asian Bamboo Basket Used to Market Vegetables. II
Figure 5 Traditional Asian Bamboo Basket Used to Market Vegetables. III.
Figure 6 Packaging of Mandarins by Farmersâ€™ Cooperatives in Korea