Saturday, December 19, 2015

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 

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