Assessment of postharvest handling systems for vegetables in Beijing.
Zheng ShuFang; Li Wu; Gao LiPu; Wu Ping;
Postharvest handling of fresh vegetables. Proceedings of a workshop held in Beijing, China, 9-11 May 2001
2001
บทคัดย่อ
The postharvest handling systems for Chinese cabbage, broccoli and oriental bunching onion were evaluated from harvest to market. For Chinese cabbage there are three kinds of distribution: fresh, storage, and export. For fresh Chinese cabbage, for which no packaging was applied, losses (about 10-15%) were the result of trimming off of old leaves. Pit storage and ventilated storage were used to store Chinese cabbage. Before storage, Chinese cabbage must be trimmed several times and sun-basked to remove excess water. During storage, energy consumption and abscission caused 20-30% loss depending upon the length of storage. No pre-cooling was applied to either fresh or stored Chinese cabbage. Chinese cabbage destined for export has strict handling requirements. First, the product must be trimmed to the degree specified by the purchaser. The cabbages are then pre-cooled in the cold room and packed. Trimming before pre-cooling caused losses of 30-45%. The harvest time for broccoli is usually in the hot season. For the domestic market, no cold chain was available to transported, pre-cooled, and stored broccoli. Also, the vehicles used to transport the crop provided poor conditions. After more than two hours transportation in a hot environment, the quality of broccoli had obviously declined. For export broccoli, on the other hand, every available facility was provided to maintain the commodity, from coldroom through to high quality packaging. However, when coldroom pre-cooling was applied, water loss and efficiency were compromised. Oriental bunching onion is popular as a spice and fresh vegetable. Harvest time is usually at the end of October. The only packaging used was to wrap the onion bunches in straw sheaves. Bunching onion is not very sensitive to mechanical damage. The main losses after harvest were from water loss and broken leaves. Bunching onion can also be backyard-stored during winter, but with high losses. During storage the leaves become dry, but the stem remains fresh with the protection of outer leaves. For the domestic market, none of the vegetables was provided with good packaging and pre-cooling because these are too costly. For export, all available cold resources were exploited to maintain the quality of produce, though not with any great expertise. At most times in Beijing, China the humidity is not high (about 40-60%). Thus, vegetables left without protection in the marketplace are inclined to lose water and become unattractive.