Food processing and storage effect on water soluble vitamins

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.

Certain water soluble vitamin are susceptible to oxidation (thiamin and cobalamin), the processes are different from those for the fat soluble vitamins.

Tofu

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.
Food processing and storage effect on water soluble vitamins

Deterioration of vitamin A in milk

Vitamin A is heat stable, therefore there is no loss of vitamin A when milk is pasteurized, evaporated or dried.

It is however, quite susceptible to oxidation especially in the presence of unsaturated fats under oxidizing conditions.

Light catalyzes oxidative deterioration of vitamin A in milk, which results in an off-flavor that has been describes as ‘haylike’, ‘strawlike’ and ‘raspberry’.

The reaction occurs frequently in lowfat milks and skim milk fortified with vitamin A.

Milk stores in green PET bottles experienced less lipid oxidation and vitamin A loss that milk stored in clear PET bottles or LDPE pouches and HDPE bottles. During the first week of storage, vitamin loss was lower in milk stored in green PET bottles than in milk stored in clear PET bottles and LDPE pouches.

It was reported that the off-flavor development was faster in skim and 2% milks fortified with an oil-based vitamin A than in an aqueous-based one, when each milk was exposed to the same intensity of fluorescent light.

Vitamin A also has been shown to be more stable in directly heated than is indirectly heated UHT milk, which is consistent with oxidation being partly responsible for loss of the vitamin.
Deterioration of vitamin A in milk