Viable counts of S. thermophilus in lentil flour and skim milk powder supplemented yogurt, varied from log 8.3 to 8.6 after
production and important reductions occurred in some samples after 28 days of storage (Table 2). CFU values of L. delbrueckii subsp. bulgaricus after fermentation were lower than those of S. thermophilus and viability losses during storage also occurred (Table 2). In the 4 treatments based on milk, there was a positive correlation (R2 between 0.76 and 0.78) between the CFU data after fermentation and the buffering capacity of the milk. Thus, in this range of milk solids, the higher the milk solids level, the higher were the populations in the fermented milk. This is in agreement with the literature (Badran & Reichart, 1994). However, when the data of lentil-supplemented yoghurts were combined with those of milk, in the regression
analyses the R2 values dropped to 0.60 (streptococci) and 0.13
(lactobacilli). Therefore, in a given medium, the buffering capacity is a
strong regulator of growth, but not when different media are
compared. These data show that the nutrients brought by the lentil
flour affect growth of the yoghurt cultures differently than did skim
milk powder. Interestingly, the addition of lentil flour accelerated the
rate of acidification, but did not increase the CFU values in the
fermented products (Table 2) as compared to skin milk powder
supplementation. The nature of the stimulatory factors in lentil flour
remains unknown. It is hypothesized that complex carbohydrates
(e.g., resistant starch, sucrose, raffinose, stachyose, verbascose and
oligosaccharides) made this ingredient a very good source of potential
prebiotic components (Wang & Daun, 2004). Amino acids, vitamins
and minerals have also been shown to stimulate the growth of starter
cultures in milk