Date of Award

1985

Degree Type

Thesis

Degree Name

Master of Science in Food Science and Nutrition

Department

Food Science, Technology, Nutrition and Dietetics

First Advisor

Marjorie J. Caldwell

Abstract

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 milk and holding it at 55oc was quite destructive to vitamin A, but had a smaller effect on riboflavin. After 12 hours of holding previously boiled milk at 55oc, 29% and 53% of the vitamin A were lost in whole and fortified skim milk, respectively. Riboflavin losses did not exceed 10-14% in whole or skim milk. A double cycle of boiling and holding milk at 55oc resulted in the largest losses of both vitamin A and riboflavin. After the second 12-hour holding at 55oc, vitamin A losses for whole milk were 30. 4% to 33 .1% • In fortified skim milk, • the loss was 54.7%. Riboflavin losses for the double boiling and holding at 55oc were approximately 20% for whole or skim milk.

Packaging material such as paperboard and plastic containers did not greatly influence the losses of vitamin A or of riboflavin. however, vitamin A retention was better for whole than for skim milk.

As a result of these experiments, it is recommended that milk in Saudi Arabia continue to be packaged in paperboard containers. However, for maximum retention of vitamin A and riboflavin, milk handlers and consumers should be educated to stop heating milk and to store it in the dark under refrigeration.

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