Chinese cabbage management before and after harvest.
Klieber, A.; Porter, K.; Collins, G.;
Postharvest handling of fresh vegetables. Proceedings of a workshop held in Beijing, China, 9-11 May 2001
2001
บทคัดย่อ
Chinese cabbage (Brassica rapa var. pekinensis [Brassica pekinensis]) cv. Yuki was grown, harvested and stored under various conditions to optimize postharvest quality. Transient water stress, achieved by rewatering when tensiometer readings declined to -35 to -40 kPa (no stress), -55 to -60 kPa (medium stress) or -75 to -80 kPa (high stress), had no effect on water status, trimming loss, quality or sugar levels; neither did the time of day at which harvesting occurred, from dawn to dusk, influence these parameters. This was because of the protection provided by the wrapper and coarse outer leaves; temperature fluctuations were 150% higher in those leaves than the insulated head. Minor cooling delays of 0.5 h in the field did not affect quality. Postharvest changes in heads stored for up to 3 weeks at 20 deg C or up to 9 weeks at 0 deg C or 2 deg C were mainly a result of water loss and microbial infections on outer leaves, the base, and wound sites, resulting in trimming losses. Chlorophyll breakdown was a minor issue, as inner leaves contain little and outer leaves also generally showed other deteriorative symptoms as well. Postharvest disorders occurred, especially patchy papery necrosis (PPN). PPN was identified as a form of chilling injury; its incidence was most severe during storage at 0 deg C, little was found at 2 deg C, and none at 20 deg C. Injury induced through compression (under 3 kg for 42-48 h), dropping (twice from 50 cm), and repeated trimming, compared with unhandled heads, induced little product failure such as splitting and did not produce any observable physiological differences. The only exception was that repeatedly trimmed heads produced much less ethylene, as senescing and rotting outer leaves were not present. However, this did not result in different quality or reduced trimming losses at the end of a 9-week storage period.