Effect of manganese sulfate and vitamin B12 on the properties of physicochemical, textural, sensory and bacterial growth of set yogurt

Abstract

In this study, the effect of MnSO4·H2O (Mn2+) and vitamin B12 (VitB) on the physicochemical, textural, sensory properties, and bacterial growth of set yogurt were evaluated. A commercial culture containing Lactobacillus bulgaricus delbrueckii and Streptococcus thermophilus and the probiotic bacteria Lactobacillus acidophilus LA5 were used for yogurt production. Moreover, individual and combination treatments of Mn2+ at concentration of 0.006, 0.03, and 0.3 w/w and VitB 0.05, 0.1, and 0.5 w/w were used in the product. Changes in bacterial count of yogurt culture, probiotic bacteria, pH, amount of lactic acid production, hardness, syneresis, color, and sensory properties were examined duration incubation until a pH level of 4.6 at 37 °C. Results showed that the addition of Mn2+ and VitB had a significant beneficial effect on the incubation period time. The most significant decreases in incubation period were obtained at 0.006 Mn2+ + 0.5 VitB, 0.03 Mn2+, and 0.5 VitB % which were reduced the incubation time from 300 min to 165, 210, and 225 min, respectively. Combined treatments of Mn2+ and VitB were able to increase the growth of Lactobacillus bulgaricus delbrueckii by 23.6% compared to the control. However, the fermentation process became significantly slower than the control sample when treatments of 0.006 Mn2+ %, 0.3 Mn2+ %, 0.05 VitB %, and 0.1 VitB % were applied. Best results for textural, sensory, and color properties were observed in samples produced by 0.006 Mn2+ + 0.5 VitB. The results showed that the addition of ions and vitamins in milk to reduce the incubation time was directly related to their concentration and their synergistic effects, and therefore their critical levels must be carefully taken into account.