Evaluation of manganese sulfate and vitamin B12 influence on physicochemical, sensory and textural attributes of fermented milk with Lactobacillus bulgaricus subsp. Delbrueckii and Lactobacillus acidophilus La-5

Dairy products fortified with minerals and vitamins play an important role in the development of functional foods. Among lactic acid bacteria, yogurt starters have a special role in the industry, and their health-promoting function has been confirmed. The long duration of fermentation time by lactic acid bacteria in dairy products, takes time and energy and leads to increased production costs. Therefore, the identification of appropriate conditions and factors affecting the growth of different strains are the basic necessities of production. Hence, in this research, the effect of adding manganese sulfate (0, 0.006 and 0.03%) and vitamin B12 (0 and 0.5 ppm) alone as well as their combination on the physicochemical, textural, and sensory properties of fermented milk produced in the presence of Lactobacillus bulgaricus subsp. Delbrueckii and Lactobacillus acidophilus La-5 were investigated. The results showed a decrease in pH and an increase in acidity during the storage period. The L* and b* index decreased and the values ​​of a* increased during the storage period (P<0.05). Also, textural characteristics and syneresis rate in samples containing 0.006% manganese sulfate and 0.5 ppm of vitamin B12 alone and their combination treatment, containing 0.006% manganese sulfate+0.5 ppm vitamin B12 were significantly improved (P<0.05). As the storage time proceeded, the sour taste of samples enriched with vitamin B12 and manganese increased (P<0.05). While the off-odor and off-taste were not felt in these samples. Also, storage time had no significant effect on these sensory characteristics (P˃0.05).