Effect of Temperature and Packaging Material on Vitamin A and Riboflavin in Milk

The effect of different heating times and temperatures and packaging on vitamin A and riboflavin retention was studied in whole and skim milk. Refrigerated storage (40C) in the dark for 15 days resulted in losses of vitamin A ranging from 9-12% in pasteurized whole milk, and 14% in pasteurized skim milk fortified with vitamins A and D. Riboflavin losses did not exceed 8 % • Vitamin A was also more labile than riboflavin when stored at room temperature ( 230C) • ' Vitamin A was retained better in whole milk than in skim milk where there was no protection from milk fat. After 48 hours of storage at room temperature, pasteurized whole milk stored in a paperboard container lost 26. 3% while that in plastic container lost 30%. Losses of vitamin A in skim milk stored in paperboard were 52%. In contrast, the losses or riboflavin of whole and skim milk were about 18%. Boiling of milk at loooc for 10 seconds resulted in more destruction of vitamin A than of riboflavin. Whole milk lost 10. 2% of the vitamin A after a single boiling and 14. 4% after twice boiling. Skim milk lost 17. 4 and 28. 5%, respectively. The riboflavin content remained very stable in both whole and skim milk. Losses did not exceed 1% for a single and 4% for twice boiling. Boiling


ABSTRACT
while that in plastic container lost 30%. Losses of vitamin A in skim milk stored in paperboard were 52%. In contrast, the losses or riboflavin of whole and skim milk were about 18%.
Boiling of milk at loooc for 10

INTRODUCTION
As fluid milk is a universally accepted nutritious food for people of all ages, it is important that the milk be processed and packaged to maintain maximum high quality over a period of · time. Quality factors which require careful control should include not only such parameters as microbiological content and organoleptic indices but also nutrient retention.
Of the many vitamins present in pasteurized milk, it is well known that retention of ' Only about 2 to 6% is present as the alcohol. The breed of cow or stage of lactation has little or no effect on the relative proportions of ester and alcohol present in milk.
Carotenoids make up from 11 to 50% of the total vitamin A activity of milk, and can be converted to the vitamin in the animal body. The exact percentage depends upon the breed of the cow and the level of carotenoid intake (Reinart and Nesbitt, 1956). Since the intake of these substances is generally higher during the summer than during the winter, the fraction of total vitamin A activity due to the provitamin is greater in summer milk (Lord, 1945).
The yellow color of milk fat and of animal _fat is due to the presence of carotenoids. The fat in Guernsey ' milk has a much more golden color than has that of Holstein milk because it has a higher content of carotene.
{J-carotene makes up the greatest fraction of the carotenoids in the milk (Strain, 1939). aie-carotene, is generally absent from butterfat, but if cows are fed carrots, which contain about 25% of their total carotenoids in the form of 0<-carotene, this form of carotene will also appear in the milk (Hauge, 1942).
A part of the total carotenoids in milk may consist of compounds that are completely inactive as provitamin A.
Inactive substances can range from 5 to 25% of the total carotenoids (Thompson and Kon, 1950). in the diet, vitamin A secreted in milk was increased very rapidly within 1-2 weeks (Thompson, and Ascarell, 1962).
A relationship between carotene and vitamin A and off-flavors in milk was reported by several researchers.
The feeding of carotene but not of vitamin A was thought, in the beg inning, to prevent the occurrence of oxidized flavor in milk (Whitnah, et al, 1937 (Dimick, 19781 Siddall, 1957). Both the polyethylene and the polycarbonate containers have been shown to absorb contaminants, and to impart off odors into the product (Landsberg et al, 1977). Barnard (1974)

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The riboflavin content of milk is usually higher during the spring or summer. This difference has been associated with a change in ration from indoor feeding to fresh pasture feeding (Kramer et al, 1939  Heating milk in dark brown bottles at loooc for 15 minutes caused only 5% loss in riboflavin (Funai, 1957).
pasteurization caused only a negligible amount of destruction of the vitamin (Holmes, 1944) / or none at all (Ford, et al, 1959 since it is known that there will be a loss  Period. This is a loss of approximately 50%, and is greater than the losses found in the whole milk samples < 2 8-30%). The loss is graphically shown in Figure 3. It is apparent that whole milk packaged in either paperboard or plastic retained vitamin A better than skim milk stored in paperboard containers.
While measurement of quality was not an objective of this experiment, some observations relating to milk quality were made.    Riboflavin values found in milks which had been boiled and then held at 55oc in a laboratory room for one to 12 hours are given in Table 15 and are shown graphically in Fig. 10.
The data in Table 15 shows that boiling results in very little, if any, loss of riboflavin. After 6 hours at 55oc, riboflavin losses were 5 .1%, 5. 8% and 6. 4% for whole milk from paperboard, whole milk from plastic and skim milk from paperboard, respectively. After 12 hours, the losses for the above •ilk increased to 10.2%, 11.5% and 13.5%, respectively.
Correlation coefficients relating riboflavin content to time are shown in Table 19.
In this experimental phase, it is noteworthy that boiling to loooc for 10 seconds did not alter riboflavin content.
Stamberg and Theophilus (1945) found that boiling milk for 30 minutes in a pan with a lid caused only a 1% decrease in riboflavin. As reported by Sure and Ford (1943) indicated that no decrease in riboflavin occurred when pasteurized milk was heated at 37oc for 22 hours. Experiments with raw milk gave similar results.
In the present research, heating to ssoc for 12 hours resulted in riboflavin losses which ranged from 10. 2% to 13.5%. Undoubtedly, the losses obtained in the milk kept ' hot at ssoc in an uncovered pot were influenced by the intensity of the existing light.
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