Effect of the addition of pulse ingredients to milk on acid production by probiotic and yoghurt starter cultures

Pulses contain carbohydrates, proteins, minerals and vitamins which are essential requirements in the human diet and which could also serve as growth nutrients for probiotic and yogurt starter cultures. In this study, milk supplementation with pulse ingredients is examined as a means to increase the nutritional properties of yogurt and probiotic type beverages. The acid production rate of two yogurt starters (A and B) and two probiotic cultures (Lactobacillus rhamnosus and Lactobacillus acidophilus) was followed in milk supplemented with the following soy and pulse ingredients: pea protein, chickpea flour, lentil flour, pea fibre, soy protein concentrate and soy flour. The pulse ingredients had no negative effect on the acidification trends of the fermented milks. On the contrary, with yogurt culture B, pea fibre, pea protein and lentil flour significantly enhanced the acidification rate. All ingredients used for supplementation improved the acidification rate of probiotic cultures, and the highest effects were obtained with lentil and soy flour. Lentil flour had the lowest pH after 12 h which was significantly lower than the product enriched with the same quantity of skim milk powder. The effect of ingredient supplementation on the microbial composition (ratio of cocci to bacilli) of the yoghurt products was also examined. The ratio of cocci to bacilli was between 1.8 and 2.5 for all supplemented yogurt samples obtained with culture A, and these variations were not judged to be statistically significant (p < 0.05). With yogurt products obtained from culture B, however, there was a higher proportional level of lactobacilli in all supplemented samples, as compared to the milk control; the enhanced growth of the lactobacilli was particularly noted when lentil flour was added to milk.

► Fermented milks with probiotics. ► Addition of pulse ingredients. ► Stimulation of fermentation rates.