Certain vitamins are sensitive to processing and storage. Processing medium or the environment is a critical factor in influencing the stability or retention of water soluble vitamin. Generally, the water soluble vitamins especially thiamin, riboflavin, and vitamin C , are more susceptible to losses due to leaching during washing and blanching.
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Water soluble vitamins are generally more heat heat-sensitive than fat soluble vitamins. Vitamin C and thiamin are the most heat sensitive. Thiamin is extremely water soluble and destroyed by heat is much can be leached into the cooking or storing liquids during preparation of both meats and vegetables. Losses in the making of soy flour are minimal, but losses in the making of soy flour into tofu stored in water are 85% or greater.
Vitamins stable at acidic pHs include ascorbic acid, niacin, free folacin and thiamin. Biotin, thiamin, free folic acid, pantothenic acid and ascorbic acid are loss more readily at alkaline pHs.
Physical factors also contribute to the loss of vitamins during processing and storage. Electromagnetic radiation in the visible and near ultraviolet region is one such factor.
Folic acid is easily lost during storage of fresh vegetables at room temperature and through many heat processes. Oxidative destruction of 50-95% of the folate can occur with protracted cooking or canning. Riboflavin and niacin are both relatively stable on heat preservation, although riboflavin is very sensitive to light and will undergo degradation in the present of both heat and light together.
Impact of processing and storage to water soluble vitamins
