Effect of red lentil flour and red grape concentrate on viability of Bifidobacterium bifidum and qualitative properties in set yoghurt

Due to importance of legumes proteins on human health, in this study the effect of red lentil flour and red grape concentrate on Bifidobacterium bifidum viability, physicochemical and sensorial properties in set yoghurt was examined during storage, using response surface method (RSM). Amounts of red lentil flour, red grape concentrate and storage time were in the range of 0-5%, 0-20.2% and 1-25 days, respectively. The results of statistical analysis showed that with increasing of red lentil flour up to 2.5% level and red grape concentrate to 10.1% level, Bifidobacterium bifidum viability increased significantly (P<0.05). As well, with increasing of lentil flour and grape concentrate, the amount of moisture content of samples reduced significantly (P<0.05). Acidity increased by addition of lentil flour up to 2.5% level; whereas higher amounts of flour caused a reduction of acidity. The higher the concentrate, the lower was the acidity (P<0.05). Results of colorimetric assessment showed that, red grape concentrate decreased L* and b* values and increased a* value significantly (P<0.05). Furthermore, increasing in red lentil flour to 2.5% level resulted significantly enhancement of b* value, but in more amounts, caused b* value to decrease. With respect to the results of sensorial evaluation of samples, addition of lentil flour caused an improvement effect on consistency and grape concentrate caused also better flavor in yoghurt samples, significantly (P<0.05). In conclusion, using of 2.439% of lentil flour and 15.34% of grape concentrate with storage period of 13 days was determined as optimum conditions.