Total antioxidant activity of milk from different dairy species

Food antioxidants have been associated with positive effects on human health, leading to the definition of nutraceuticals. Several studies demonstrated that milk contains a variety of antioxidant molecules such as thiols, tocopherols, carotenoids, ascorbic acid, phenols, lactoferrin as well as biopeptides derived from caseins and whey proteins showing antioxidant properties. Milk total antioxidant activity (TAA) is defined as the sum of each antioxidant contribution, related to the aforementioned molecules. The characterisation of this new phenotypic trait in different dairy species would represent an important step for the valorisation of milk. Therefore, the aim of the present study was to characterise TAA of cow, buffalo and sheep milk. Individual milk samples from 300 Holstein Friesian cows, 110 Italian Mediterranean buffalos and 85 Comisana sheep were collected, added with preservative and stored at 4 °C. Milk TAA was measured with a near infrared spectrophotometric ABTS based method and expressed as μmol/l. Trolox equivalents (TE), and milk quality traits were predicted through mid-infrared spectroscopy. The greatest TAA was measured in sheep milk (7.33 μmol/l TE), followed by buffalo (7.26 μmol/l TE) and cow milk (6.83 μmol/l TE). The coefficient of variation of TAA was greater in cow (17.91%) and sheep (14.95%), and lower in buffalo milk (9.38%). Moderate to low Pearson correlations of TAA with somatic cell score in sheep (0.35; P<0.01) and cow milk (0.19; P<0.05) were assessed. Regarding buffalo milk, a low positive correlation was observed between TAA and casein content (0.15; P<0.05), and a low negative correlation was estimated between TAA and fat content (-0.20; P<0.05). Further analyses are being carried out in order to assess the impact of sources of variation such as stage of lactation and parity on the variability of milk TAA.