β-casein Variants and Anti-oxidant Profiles of Milk of Siquijor Native Cattle (Bos taurus indicus L.) as Compared to those of Holstein Friesian x Sahiwal Cattle

Abstract

The study aims to isolate, characterize, and evaluate the antioxidant activity of A1 and A2 β-casein (β-CN) variants from milk of Siquijor native cattle (SN) and compare it to that of Holstein Friesian x Sahiwal (HF). Four milk samples from SN and three milk samples from HF, collected at 60-90 days during the first and second parities, were used in this study. Caseins were isolated from the milk samples by isoelectric precipitation at pH 4.5, urea denaturation, and SDS-PAGE. The fractions were quantified by Bradford assay. Antioxidant activity of the fractions was determined by DPPH scavenging assay. All the samples were analyzed using one-way ANOVA to determine the statistical difference. The concentrations of β-CN variants isolated from the milk of Siquijor native cattle and the milk of Holstein Friesian x Sahiwal were not significantly different (p>0.05). All of the casein samples exhibited DPPH scavenging activity with A2 β-CN exhibiting significantly higher scavenging activity (p<0.05). SN1 A2 β-CN exhibited the highest DPPH scavenging activity at 5.298% ± 0.17 among all of the samples. These results indicate that A2 β-CN may play a vital role in maintaining antioxidant homeostasis in the human body when the milk is consumed. These results also indicate the significance of A2 β-CN in extending the shelf-life of milk and other dairy products. In conclusion, this study successfully fractionated and characterized both A1 and A2 β-CN variants in the milk of Siquijor native cattle and Holstein Friesian x Sahiwal, with A2 β-CN having higher antioxidant activity compared to A1 β-CN.