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

G. T. A. Cuevas (Department of Chemistry, College of Arts and Sciences, University of the Philippines Visayas)
A. A. Angeles (Dairy Training and Research Institute, College of Agriculture and Food Science, University of the Philippines Los Baños)
F. E. Merca (Institute of Chemistry, College of Arts and Sciences, University of the Philippines Los Baños)
A. J. Salces (Animal Breeding Division, Institute of Animal Science, College of Agriculture and Food Science, University of the Philippines Los Baños)

Tropical Animal Science Journal
Vol. 44 No. 1 (2021): Tropical Animal Science Journal

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.