Pak Choi (Brassica rapa ssp Chinensis L) quality response to pre-harvest salinity and temperature

The effects of pre-harvest salinity levels (1.7, 9.5 and 12.3 mS cm(-1)) an d temperatures (18, 21 and 25 degrees C) on the ascorbic acid and total chl orophyll contents of Pak Choi (Brassica rapa ssp. Chinensis L) were investi gated. The relationships of these chemical contents with storage period (0, 7 and 14 days) and water loss were also monitored. Increased production te mperatures significantly (p < 0.001) reduced the ascorbic acid and total ch lorophyll (p < 0.01). Ascorbic acid content in leaves grown at various sali nities was significantly (p < 0.01) reduced beyond 9.5 mS cm(-1). Total chl orophyll was not affected by these different levels of salinity. Ascorbic a cid contents of harvested shoots fell rapidly during the first seven days o f storage, most markedly in shoots taken fi om plants grown at high salinit y. The pattern of chlorophyll degradation depended on the plants' productio n environment where higher temperatures resulted subsequently in rapid degr adation during storage. For shoots grown at high salinity, the chlorophyll content was sustained during early storage. Linear relationships were appar ent between water loss and ascorbic acid and total chlorophyll contents of shoots from the range of treatments, (C) 1999 Society of Chemical Industry.