Reducing postharvest losses of tomato in traditional and modern supply chains in Cambodia

Traditional and modern supply chains for tomato in Cambodia were assessed and possible handling improvements were introduced. Traditional chain involved farmers and collectors in Kandal Province, and wholesalers and retailers in wet markets in the capital of Phnom Penh, about 35 km apart. In the modern chain, only one intermediary between farmers and supermarkets in Phnom Penh was involved; collector-wholesaler in Kandal Province or a development organization in Kampong Speu Province (65 km away from Phnom Penh) which consolidated farmers’ produce through its packinghouse facility. Postharvest losses in the traditional and modern chains were about 23% and 22.5%, respectively, but the modern chain had more stringent quality requirements and offered higher prices than the traditional chain. Farmers’ losses were mainly due to preharvest damage by insect pests and diseases and immaturity while losses during subsequent handling were due to physical damage, rotting, weight loss and/or over-ripening. Improved packaging, precooling and sanitizing treatments as individual handling improvements were tried in the traditional chain. Use of 20 kg capacity plastic crate with 50 μm-thick low density polyethylene (LDPE) bagging and 20 kg capacity bamboo basket lined with newsprint reduced fruit damage at the wholesale and retail stages relative to the conventional packaging of using 20 kg capacity 50 μm-thick high density PE (HDPE). More dramatic effect on weight loss reduction was obtained with both conventional HDPE and plastic crate-LDPE packaging methods. Precooling (5 min dip in 5oC water) and chlorine wash (2 min dip in 200 ppm chlorine solution) combined with LDPE packaging had no pronounced effect on the incidence of fruit damage but reduced weight loss at the retail stage by about two-fold compared to that of fruit conventionally packed in HDPE bag without precooling or chlorine treatment. For the modern chain, modified atmosphere packaging (MAP) comparing LDPE and 11 μm-thick film overwrap was tried under simulated supermarket conditions (15oC). Fruit weight loss and ripening were inhibited relative to that at ambient (24-33°C, 65-92% RH). MAP had no appreciable effect on weight loss at 15°C but further retarded ripening based on colorimetric a* values (red color), soluble solids and citric acid contents. Film overwrap was more effective than LDPE. The results indicate that the handling techniques introduced could be applied in tomato supply chains to reduce postharvest losses.