PHOTOOXIDATIVE STABILITY OF VITAMIN-A FORTIFIED 2-PERCENT LOW-FAT MILK AND SKIM MILK

Lowfat milk and skim milk were fortified with either oil- or aqueous-based carrier blends of vitamins A and D, in l-gal polyethylene containers, and illuminated up to 72 h with 1080 1x (100 ft-c) at 5-degrees-C in a commercial display case. Vitamin A measurments and sensory analyses showed that vitamin A was more stable in 2% lowfat milk than in skim milk regardless of the carrier. The aqueous-based carrier provided more stability in lowfat milk while the oil-based carrier gave more stability in skim milk. Skim milk fortified with the aqueous-based vitamin A had 69% loss, while the unexposed control exhibited only 15% loss of the vitamin. Off-flavors were evident after 6 h in light-exposed 2% lowfat milk with the oil-based vitamin A, but the same milk with aqueous-based vitamin A did not exhibit off-flavors until after 12 h. Both 2% lowfat and skim milk samples exposed to light received similar lowered preference scores compared to nonexposed control samples. When both fortified and nonfortified 2% lowfat and skim milk samples were tasted after exposure to light, the flavor was not significantly different, but were in the unacceptable range.