Influence of Impact Stress on the Postharvest Physiological and Chemical Properties of Cabbage Heads

Because the mechanical damage caused by postharvest handling (including bulk storage and transport) plays an important role in the yield and the postharvest quality of fresh produce, the effect of postharvest impact stress on the physiological and chemical properties of cabbage (Brassica oleracea var. Capitata L.) was investigated in this study. To simulate the impact stress occurrence during the bulk handling practice, cabbage picked at commercial harvest stage was dropped from different heights (10, 20, 40, and 80cm) onto a flat, rigid concrete floor. The effects of the dropping treatment on the respiration rate and on the content of various sugars (sucrose, glucose, and fructose) were evaluated during storage at 20℃ for 6 days. Shortly after the dropping treatment, an increased rate of respiration correlated with a higher dropping height. However, a decreased respiration rate was observed after one day of storage. The sugar content of all samples changed slightly at days 1 and 3. At day 6, cabbages dropped from 80 and 40cm showed the lowest content of fructose and total sugar (the sum of sucrose, glucose, and fructose). The major effects of impact stress on cabbage heads include increases in the respiration rate and a loss of sugar content. In addition, tests of controlled atmosphere (CA) treatment on dropped cabbages showed that CA likely inhibited the severe damage caused by impact stress on cabbages because it reduced the rise in respiration rate and slowed the loss of sugar content in dropped cabbages during storage at 20℃. Overall, impact stress obviously affects the postharvest physicochemical properties of cabbage just after impact occurrence (respiration rate) and during storage (sugar content). These changes are also influenced by the strength of the stress level (height of dropping treatment) and the time period after the application of the stress treatment. Rapid and appropriate postharvest handling and storage management, therefore, will delay the onset of deterioration of cabbage quality and extend its shelf life.