The researchers, however, said oil-soluble fortified milks had less or no taste differences.
The study, by researchers at North Carolina State University and Cornell University, was published in the Journal of Dairy Science.
In use since the 1930s
The authors note vitamin fortification of fluid milk has been in use in the US since the 1930s, initially to prevent rickets in children.
Vitamin D deficiency causes rickets in children and osteomalacia in adults, and the authors note recent studies also suggest that vitamin D plays a role in the prevention of prostate, breast, and colorectal cancers.
Vitamin A is needed for normal growth, vision, reproduction, and differentiation of epithelial cells.
Vitamin A deficiency results in night blindness, xerophthalmia (progressive blindness caused by drying of the cornea of the eye) and keratinization (accumulation of keratin in digestive, respiratory and urinary-genital tract tissues).
Vitamin fortification is a standard procedure for pasteurized fluid milks in the US, and vitamin concentrates – in either oil-soluble or water-dispersible formats – are added to milk before pasteurization.
Helping the industry
How vitamin concentrates affect the flavor of fluid milk has not previously been investigated.
The researchers say understanding the flavor contributions of vitamin sources to fluid milk can help the dairy industry position vitamin fortification and enhance fluid milk quality.
Comparing oil and water
The study was designed to determine the influence of vitamin A and D fortification on the flavor of milk, with the aroma profiles of 14 commercial vitamin concentrates (vitamins A and D), in both oil-soluble and water-dispersible forms evaluated.
Water-dispersible vitamin concentrates had overall higher aroma intensities and more detected aroma-active compounds than oil-soluble vitamin concentrates.
Trained panelists and consumers were able to detect flavor differences between skim milks fortified with water-dispersible vitamin A or vitamin A and D, and unfortified skim milks.
Consumers were unable to detect flavor differences in oil-soluble fortified milks, but trained panelists documented a faint carrot flavor in oil-soluble fortified skim milks at higher vitamin A concentrations (3,000–6,000 IU).
No differences were detected in skim milks fortified with vitamin D, and no differences were detected in any 2% milk.
The researchers say the results demonstrate that vitamin concentrates may contribute to off flavor(s) in fluid milk, especially in skim milk fortified with water-dispersible vitamin concentrates.
They said it is possible to increase fortification levels in fluid milk products to improve dietary vitamin D intake in the US without affecting fluid milk flavors.
The dairy industry should reduce the use of water-dispersible vitamin premixes or conduct research to improve the flavor quality of water-dispersible premixes, especially for vitamin A, to improve fluid milk quality, the researchers concluded.
Funding was provided in part by the National Dairy Council.
Source: Journal of Dairy Science
The effect of vitamin concentrates on the flavor of pasteurized fluid milk
Authors: E.B. Yeh, A.N. Schiano, Y. Jo, D.M. Barbano, M.A. Drake