Rheological characteristics of yoghurt enriched with soy flour

Yoghurt was prepared using streptococcus thermophiles (ST) and Lactobacillus delbruckii ssp bulgaricus (LB). Yoghurt samples were prepared by replacing skim milk powder (SMP) with soya flour in three trials each at 0, 25, 50 and 100% with culture of 1, 1.5 and 2% levels. With increase in level of replacement of skim milk powder by soy flour; protein content increased from 5.5 to 10.23%, while carbohydrate content decreased from 8.7 to 2.4%. Curd strength increased with increased substitution of skim milk powder by soy flour. Comparable scores for sensory parameters whey separation, were obtained for yoghurt prepared with 1% culture and substituting added SMP with 25% soy flour. The viable count in soy flour treated yoghurt was found to be lower compared to control. The viability of yoghurt culture declined, while acidity and soluble nitrogen content increased in yoghurt prepared by substituting SMP with 25% soy flour compared to control, stored at refrigeration temperature and had good shelf life upto 15 days under refrigeration condition.