Variations in carotenoids and retinol in milk and cheese from Jersey cows at an organic dairy compared to a conventional dairy over a pasture season

摘要

Carotenoids, widely distributed in nature, are considered to be potentially beneficial in the prevention of a variety of diseases including cardiovascular disease, certain cancers and eye diseases. As humans are unable to synthesize carotenoids, the diet is the only source of these beneficial components. Carotenoid concentration in cow's milk varies greatly as a result of feeding practice and season, but no research thus far has investigated these variations in Jersey cows over an entire pasture season. The objectives of this experiment were to 1) determine the differences in concentrations of carotenoids and retinol in milk from cows consuming different diets, 2) examine the changes that occurred over a pasture season, and 3) assess the relationship of these components between a fresh, mozzarella cheese and the milk from which it was made. Individual milk samples were collected biweekly, beginning in May and ending in November, from 18 Jersey cows, 9 at an organic dairy fed on pasture and supplemented with total mixed ration (TMR) and 9 at a conventional dairy fed exclusively TMR. High performance liquid chromatography (HPLC) was used to analyze carotenoid concentrations from each individual milk sample. Total carotenes, total xanthophylls, lutein, beta-cryptoxanthin, alpha- and beta-carotene and 13cis beta-carotene were significantly higher in milk from the cows fed on pasture compared to milk from the cows fed TMR. In milk from cows fed on pasture, total carotenes, total xanthophylls, lutein, beta-cryptoxanthin, alpha- and beta-carotene, and 13 cis beta-carotene varied significantly over the pasture season. In milk from cows fed TMR, only total xanthophylls, retinol and lutein changed significantly over time. Bulk milk samples were also collected biweekly at each dairy and made into Mozzarella cheese. HPLC was used to analyze carotenoid concentrations in the raw and pasteurized milk, the whey, and the cheese. Total carotenes in raw milk, pasteurized milk and whey were positively related to total carotenes in cheese, and total xanthophylls in pasteurized milk were positively related to total xanthophylls in cheese. Results indicate that even for Jersey cows, a breed known to have 'yellow' milk, pasture feeding will increase the carotenoid concentration in milk and its products and the concentration changes over time.