Comparative Characterization of Whey Protein Concentrates from Ovine, Caprine and Bovine Breeds

Whey protein concentrates (WPC) obtained from ovine, caprine and bovine wheys were studied in terms of chemical composition (concentration of lactose, protein, moisture, ash, calcium, sodium and potassium) and physical properties (onset denaturation temperature and viscoelastic behaviour). Ovine, caprine and bovine WPC exhibited decreasing protein content and increasing lactose content, in this order. The differences in ash content were relatively small, but ovine and caprine WPC were quite different from bovine WPC in terms of calcium and potassium. Important differences in protein content have also been observed; ovine WPC showed the highest concentration in the protein beta-lactoglobulin, bovine WPC the highest concentration in the protein alpha- lactalbumin and caprine the highest concentration in the protein immunoglobulin G. No significant differences existed in terms of denaturation onset temperature between the three types of WPC; however, differences were found within WPC types between those cases where NaCl was present or absent. The gel maturation at 85°C was characterized by storage moduli that were close to one another for ovine and caprine WPC, but these were far from those of bovine WPC. The decrease in temperature from 85 to 20°C had a strong effect on the viscoelastic moduli of WPC gels, but the initial structure could be recovered by reheating the gels from 20 to 85°C.