Performance of Bovine and Ovine Liquid Whey Protein Concentrate on Functional Properties of Set Yoghurts

Abstract

The effects of liquid whey protein concentrates (LWPC) on biochemical, physical and sensorial properties of set yoghurt were studied. Bovine and ovine LWPC were used to partially replace skimmed milk powder (SMP) in bovine yoghurt formulations. The properties of modified yoghurts were evaluated during their shelf-life and compared with conventional bovine and ovine yoghurts. The protein content of ovine yoghurt differs significantly (p<0.05) from the bovine ones (with or without LWPC supplementation). Higher values of hardness, adhesiveness and gumminess were observed for conventional yoghurts, although cohesiveness, resilience and springiness did not vary between formulations. During the products shelf-life a decrease in luminosity was observed, but no significant differences in colour occurred among formulations. Low syneresis indexes, ranging from 0.5 to 5.0%, which are typical in the range of yoghurts with high levels of solids, were achieved for the produced yoghurts. The decrease in viscosity led to an increase in syneresis, indicating that the gel structure was more open retaining water not so efficiently. Ovine yoghurts showed lower syneresis and higher viscosity values, while the yoghurts enriched with LWPC showed the opposite pattern. At the sensory level no differences (p<0.001) were found between conventional bovine yoghurt and yoghurts with LWPC. However, in the case of ovine yoghurt (LO) significative differences were identified, and this product was strongly penalized in the preference test. The results revealed that LWPC (independently of the source) can be used in set yoghurt formulations, increasing protein and total solids content, for total or partial replacement of the conventional adjuvant (SMP). The utilization of these products is very attractive due to the low complexity processing conditions needed, lower production costs and more effective whey disposal.