Natural content of animal and plant sterols, alpha-tocopherol and fatty acid profile in sheep milk and cheese from mountain farming

Abstract

• This work focuses on alpha-tocopherol and sterol profile in sheep milk and cheese. • The cheese manufacturing does not influence the content of sterols (g 100 g −1 of fat). • The cheese making process influences lanosterol and the alpha-tocopherol content. • Phytosterols, which are nutraceutical molecules, were found in the milk and cheese. Milk and dairy foods from grazing animals contain a series of bioactive compounds that are important for human health such as fatty acids, vitamins, and sterols of animal and vegetal origin. To the best of our knowledge, no published studies exist on the phytosterol profile in sheep milk and cheese. In addition, there is little information on the changes in the vitamin E content and sterol profile in sheep milk as a result of the cheese manufacturing and ripening. This study investigates the alpha-tocopherol content, the sterol and fatty acid profile in sheep milk and in two traditional cheeses (Pecorino and Casu Axedu). We also compared the effects of two different commercial manufacturing processes on the trasfer of lipid components in the two cheeses made with the same sheep milk. The study involved a flock of Sardinian sheep in the advanced phase of lactation and grazed on natural mountain pasture. Every 15 days, four bulk milk samples were taken and analyzed. The milk was used to make two traditional cheese: Casu Axedu and Pecorino; cheese samples made from the same batch of analyzed milk were taken. The results of the composition of milk and cheeses (Pecorino and Casu Axedu) were analyzed by ANOVA considering as fixed effect of the product type. The milk alpha-tocopherol content detected was 3.24 mg 100 g −1 of fat, a tendence to decrese in alpha-tocopherol content was highlighted in the cheese fat compared to the milk, probably due to losses of this vitamin during cheese making and seasoning. Cholesterol was the main animal sterol in the milk and cheeses. We found significantly lower cholesterol content (mg 100 g −1 of fat) in cheeses than in milk. In the milk and Casu Axedu, the main minor sterol of animal origin was lanosterol, while in Pecorino lanosterol was less represented. The amount of total plant sterols detected in the milk and dairy products ranged from 9.89 mg 100 g −1 of fat in milk to 16.67 mg 100 g −1 of fat in Pecorino cheese. No significant differences were found in plant sterols among the products (mg 100 g −1 of fat), however a tendence to a higher content of beta-sitosterol was registered in Pecorino cheese on wet basis. Finally, Pecorino was richer in SCFA and PUFA than Casu Axedu, and showed significantly higher contents of some fatty acids of nutritional interest such as C18: 2 cis 9, cis12, C18: 3 omega 3 and CLA cis 9, trans 11. This work contributes to the knowledge of the bioactive components in milk and in the products of small ruminants reared on mountain pasture highlighing, for what we believe is the first time, the presence of minor sterols of vegetable origin in sheep milk and cheese. The cheese making process influences the fatty acid profile and the alpha-tocopherol transfer from milk to cheese, whereas has only few effects on the minor sterols.