Abstract
This study provides important information about the impacts of various levels of oat (OBG) and bacterial (curdlan) β-glucan and fat contents in milk on survivability and metabolism of yogurt starter cultures. The results show that addition of β-glucans in the concentration higher than 0.25% reduced starter bacterial counts during storage and prolonged the milk acidification process. A significant increase in lactose consumption by starter cultures was noted in the yogurt samples with OBG addition up to 0.75%. The highest (by 567% on average) increase in lactic acid content was noted in the control yogurts. Whereas the lowest (by 351%) increase in lactic acid content was noted in yogurts with OBG. After 28-day storage, the acetic aldehyde content was significantly influenced by fat content, type and addition level of polysaccharide. A higher increase in acetoin content was noted in samples with 0.25% than in samples with 1% of polysaccharides. In turn, significantly lower increases in diacetyl and 2,3-pentanedione contents were observed in the yogurt samples with OBG than in these with curdlan, with diacetyl production increase along with the higher concentration of the polysaccharide. The addition of OBG and curdlan to milk contributed to differences in the starter culture metabolism, consequently, in the milk acidification dynamics.