The vitamin content of ultra-high-temperature (UHT) processed milk was compared with that of the original raw milk. Three processes were used. In the first, which caused no change in oxygen content, the milk was heated and cooled in a plate-type heat exchanger. In the second, the milk was again heated indirectly and then evaporatively cooled, leaving in the milk about one-third of the initial oxygen content. In the third process the milk was heated by direct steam injection and cooled by evaporation and contained little or no residual oxygen.
On processing and during subsequent storage for 90 days there was no loss of vitamin A, carotene, vitamin E, thiamine, riboflavine, pantothenic acid, biotin or nicotinic acid. There was little or no loss of vitamin B6 or vitamin B12 on processing, but up to 50% of each of these vitamins was lost during 90 days' storage. All the dehydroascorbic acid (DHA) and about 20% of the ascorbic acid (AA) was lost on processing. There was no further loss of AA during 90 days’ storage when no residual oxygen was present, but in milks containing more than about 1 ppm oxygen all the AA was lost within 14 days. About 20% of the folic acid was lost on processing; thereafter, as with ascorbic acid, the extent of the loss on storage depended on the residual oxygen content of the milk: in the absence of oxygen the folic acid was stable.
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