Determination of antioxidant activity of yoghurt enriched with polymerized whey protein

Abstract

The purpose of this study was to evaluate the antioxidant activity of yoghurt obtained from milk enriched with whey proteins in polymerized form. The influence of adding polymerized whey protein (PWP) on the antioxidant potential of yoghurt was demonstrated by determining the free radical con¬tent using 1,1-diphenyl-2-picrylhydrazyl (DPPH) and the ferric reducing antioxidant power (FRAP). The kinetics of coagulation was examined during fermentation at 37, 41 and 45. The number of lactic acid bacteria was determined as well as their proteolytic and lipolytic activity. The results have shown that the addition of PWP accelerated the process of reaching the target pH 4.45, thus reducing the fermentation time by as much as 21 %. PWP increased the antioxidant potential of yoghurt more than WPC80. The yoghurt obtained at 37 °C had a higher antioxidant potential (DPPH 5.02 mmol·kg-1; FRAP 5.52 mmol·L-1) than those obtained at 41 °C and 43 °C. In the yoghurt with PWP, Lactobacillus were determined to have a concentration of 5.2 × 109 CFU·mL-1. After 21 days, the number of Streptococcus bacteria decreased. There was no effect of PWP on the number of Bifidobacterium bacteria.

Keywords

• yoghurt
• polymerized whey protein
• antioxidant activity
• lactic acid bacteria