Effect of lupine powder on rheological, chemical and microbiological properties of yoghurt

The effect of different concentrations (2, 4, 6 and 8%) of lupine powder on sensory, rheological, chemical and microbiological properties of yoghurt samples were investigated during refrigerated storage at 4°C for 15 days. The results indicated that the overall pH of lupine yoghurt lowered with increasing of % lupine powder as well as acidity increased gradually by adding lupine powder. The development of acidity in yoghurt (control) or which supplemented with lupine was increased gradually during storage with increase the lupine powder in yoghurt. The synersis of fresh lupine yoghurt was the lowest value compared with the results after 7and 15 days. The texture properties of lupine powder yogurt during storage were noted that control increased in firmness and gumminess, while cohesiveness, chewiness, springiness and resilience were decreased. On the other hand all concentrations recorded high values in firmness, cohesiveness, gumminess, chewiness, springiness and resilience during cold storage. There are significant (P ≤0.05) differences in the overall acceptability between control and those prepared by adding 2 4 %. Panel test showed that fresh yoghurt lupine prepared from control, 2 4% are more acceptable compared to that of 6 8%. Also the results revealed that the concentrate 8% of lupine powder represented the optimum concentration in decreasing total bacterial count and Staphylococcus aureus counts from 9×10^5 and 9×10^3 to 9×10^2 and 5×10 cfu/g respectively and increasing Lactobacillus bulgaricus and Streptococcus thermophilus from 10×10^4 and 8×10^4 to 8×10^6 and 5×10^6 cfu/g respectively. While the total coliform and faecial coliform bacteria were completely disappeared as well as yeast Moulds were eliminated after 15 days during storage time at 4°C.