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J. C. ALLEN and Y. Liu. Dept. of Food Science, North Carolina State Univ., Schaub Hall, Box 7624, Raleigh, NC 27695-7624 Under-fortification of vitamins A and D in reduced-fat dairy products has raised a public health concern. Vitamin A was reported to be more stable in skim milk when water-soluble carriers (such as protein) were used. Beta-lactoglobulin (BLG) is capable of binding vitamins A and D. The complex might shelter the vitamins against oxidation and extend nutrient shelf life. Our objective was to study the potential of BLG as a stable carrier for vitamins A and D in skim milk through shelf life studies. BLG-vitamin complexes were prepared by spray drying and freeze-drying. Binding of the vitamins with the protein was confirmed by fluorescence spectroscopy. Stability of BLG-vitamin complexes in HTST or UHT-processed skim milk was compared with that of oil-based fortifiers and Roche dry vitamins. Vitamins in the milk were assayed by HPLC. Higher recovery and less vitamin isomerization were obtained from freeze-drying than spray drying the fortifying vitamin-protein complex. In HTST-processed skim milk, no appreciable change of vitamin D3 concentration was observed in various types of fortification. BLG-vitamin A was stable while Roche dry vitamin A was not stable after 2 weeks of shelf life. Oil-based vitamin A was stable after thorough homogenization. Packaging materials did not affect shelf life of either vitamin. In UHT-processed skim milk, BLG-vitamin A dropped to 1/3 of the targeted fortification level during the UHT processing. BLG-vitamin D exhibited good stability while oil-based vitamin D dropped to half the original level at the end of the shelf life. Though BLG-vitamin A appeared to be stable in HTST-processed skim milk, it was less stable as a fortifier for UHT-processed skim milk. BLG-vitamin D3 is a more stable fortifier than the oil-based fortifier in UHT-processed skim milk. BLG can be used as a carrier to protect vitamins from oxidation in skim milk.
Session 64, Dairy Foods: Milk proteins
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