Abstract
The level of vitamin C in both leaves and stalks of three Chinese vegetables before and after different cooking (Taasai, Tingensai and stalk of garlic) was determined. The color tone and the level of chlorophyll in leaves of Taasai and Tingensai before and after cooking were also examined. The residual rate of vitamin C in the stalks after cooking was entirely higher than that in the leaves. The losses of reduced vitamin C in leaves of Taasai which were pan-fried with salt and of total vitamin C for boiled leaves of Taasai were high, with residual rates of 35.1 and 40.4% of raw samples, respectively. Vitamin C content in stalk of garlic showed a small loss, with a residual rate of 82-100% of raw sample. The changes in L, a and b values for Tingensai were larger than those for Taasai. The chroma of all cooked samples decreased. The color difference of these samples during cooking showed minimum with microwave heating and maximum with boiling with salt. The residual rates of total chlorophyll for Taasai and Tingensai were 74-90 and 72-87% of raw samples, respectively. The degradation reaction of chlorophyll by microwave heating was the fastest among both samples on rate constants, and chlorophyll of Taasai was entirely more stable to heating than that of Tingensai.
