Determination of percentage loss of vitamin C in some leafy vegetables at different blanching conditions

This study was aimed to determine the percentage (%) loss of vitamin C in green leafy vegetables due to the effects of different blanching times (2, 4, 6, 8, 10 and 15 minutes) and physical form (intact and cut). Four types of leafy vegetable, namely Chinese spinach (Amaranthus oleraceus L.), Chinese mustard (Brassica chinensis var. parachinensis), Chinese white cabbage (Brassica chinensis L.) and Indian mustard (Brassica juncea (L.) Czem and Cosson), were selected from the main markets in Taman Kingfisher, Kota Kinabalu and blanched in boiling water at different time and physical form. The vitamin C content of the fresh vegetables and the loss of vitamin (%) in blanched vegetables were subsequently determined by indophenol titration method. The results of the study revealed that all the studied vegetable species possess different vitamin C content and its loss depends on the type of vegetables and blanching conditions. Blanching cause a significant (pChinese white cabbage>Chinese spinach>lndian mustard. This is because Chinese mustard has broader leaves and higher surface to volume ratio. The effect of different blanching times on vitamin C loss was significant (p<0.05), in which there were always a significant (p<0.05) differences in vitamin C loss at different blanching times of 2, 4, 6, 8, 10 and 15, intact and cut, except for 6 and 8 minutes in both Chinese mustard and Chinese white cabbage. The % vitamin C loss of all the studied vegetables, due to blanching, is in the order of 15 minutes > 10 minutes > 8 minutes > 6 minutes > 4 minutes > 2 minutes. The effect of the vegetable's physical form on vitamin C loss was also significant (p