EFFECT OF COOKING METHODS AND DURATION ON ASCORBIC ACID CONCENTRATION OF SELECTED VEGETABLES

Abstract

Cooking vegetables before they are consumed helps in making them more palatable in addition to improving taste and texture. On the other hand, cooking causes a substantial change in the composition of chemicals thus affecting concentration and availability of nutrients. There are some cooking methods that cause oxidization of the antioxidants therefore affecting the retention of nutrients of the vegetables. Therefore, it is vital to opt for a cooking method which will lead to optimal retention of nutrients. This study was designed to determine the reduction in Vitamin C concentration associated with different cooking methods of green leafy vegetables. Vitamin C content of green leafy vegetables namely, African nightshade (Solanum nigrum) and amaranth (Amaranthus viridis) were selected for the study. Vitamin C content of the above sample vegetables were estimated using spectrophotometric method at a wavelength of 245nm. Processing methods which were employed were boiling and microwave heating which were performed at a timely interval. The findings showed that microwaving had the highest vitamin C loss. The results also showed that long duration of cooking led to massive loss from the selected vegetables. It was concluded that the water used for cooking vegetables should not be discarded for maximum retention of vitamin C in vegetables. Based on the study, it is recommended that the best duration for cooking Solanum nigrum and Amaranthus viridis should be less than 10 minutes (dependent on consumer preference) so as to retain maximum ascorbic acid.