Effects of ultra-high-temperature (UHT) processing and of subsequent storage on the vitamin content of milk

Abstract

SummaryThe 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 B6or vitamin B12on 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.

Nutritional, sensory and physico-chemical characterization of protein-standardized UHT milk

“…The concentration of riboflavin was not influenced by the type of UHT treatment used, which was expected in view of its reported high heat stability (Ga men et al, 1989). The concentrations of thiamine in the UHT milk samples were about half that of the value reported (Fink and Kessler, 1985) for raw milk (35-45 mg/L), concurring with the reported heat sensitivity of this vitamin (Ford et al, 1969;Burton et al, 1970).…”

“…Because control and protein-standardized milk products had approximately the same fat content, the concentration of fatsoluble vitamins was expected to be unchanged, as indeed seemed to be the case; variations in vitamin concentration were probably caused by fluctuations in the concentration of fat. The type of UHT heating had no effect on the concentration of retinol or oe-tocopherol in the milk products, indicating the thermal stability of these vitamins, as documented earlier (Ford et al, 1969;Burton et al, 1970;Le Maguer and Jackson, 1983).…”

The effect of oxygen content on flavour and chemical changes during aseptic storage of whole milk after ultra-high-temperature processing

“…Assays for riboflavin, thiamin, vitamin B 12 and folic acid were carried out as described by Ford et al (1969).…”

“…Kon & Watson (1936) had previously demonstrated the latter effect. Ford et al (1969) have shown that in ultra-high-temperature (UHT) treated milk processed by direct heating and containing less than 0-1 ppm of O 2 both ascorbic acid and folic acid were retained during storage. High O 2 content resulted in complete destruction of both vitamins within a few days.…”

Ácido fólico em leite e bebida láctea enriquecidos: estudo da vida-de-prateleira

“…DONG & OACE [10] , mostraram que leites submetidos a esterilização e subsequente estocagem apresentaram variada taxa de retenção de folatos (0 -80%), dependendo da raça e tipo de alimentação do animal, das condições do processo, da presença de vitamina C e da concentração de oxigênio durante e após o processo. FORD et al [12], FAVIER et al [11] e RENNER [17] ascórbico protetor e o oxigênio um agente que atua na degradação dos folatos.…”