| چکیده انگلیسی مقاله |
Background and Objectives: Probiotic dairy products with their valuable nutritional and therapeutic properties, whose positive effects on human health have been confirmed, present one of the most controversial issues globally in the current domains of industry, nutrition and medicine. In order to have an upward trend in the promotion of the production and consumption of such products, it is essential for them to have desirable sensory and textural characteristics and preserve the probiotic strain at the defined level during shelf life. Doogh, an Iranian milk drink, is a popular fermented drink in Iran, the probiotic content of which can promote community health. The objective of this study was to determine the effects of Lactobacillus acidophilus La-5, as the probiotic bacterium, on microbial characteristics, post-acidification rate, and overall sensory acceptability of Doogh. Materials and Methods: In this research, in addition to commercial yoghurt culture (YF-3331), Lactobacillus acidophilus La-5, a probiotic bacterium, was used to produce probiotic Doogh, and alteration of probiotic bacterium and yoghurt culture bacteria (Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus), acidification, phase separation, and its sensory acceptability were evaluated during its twenty one-day storage at 4 °C and compared with the blank produced without probiotic strain. Results: The bacterial counts of the three bacteria reduced during cold storage. However, the probiotic bacteria, having the reduction of 0.93 log cycle/ml, could stand above the optimum level during the given time. Comparison between the probiotic Doogh and the blank showed that this bacterium could enhance the bacterial population reduction rate, reduce post- acidification, and improve the overall acceptability during storage. The addition of L. acidophilus did not have any significant effect on the textural stability of the probiotic sample, as compared to the blank. The percentage phase-separation of the 2 samples was high on days 1 to 7 of storage and then slowed down. Conclusion: The results demonstrated that Lactobacillus acidophilus La-5, as a probiotic bacterial strain, can be used in the production of Doogh with a pH=4.30, a salt content of 0.8 % (w/v) and a total solid content=7.4 % and it could enhance the yoghurt bacterial population reduction during storage. Thus, the probiotic Doogh produced was assessed as desirable with regard to the L. acidophilus viability, post-acidification reduction, overall sensory acceptability, and textural stability. |