Biochemical Characteristics and Viability of Probiotic and Yogurt Bacteria in Yogurt during the Fermentation and Refrigerated Storage

• Published in: Applied Food Biotechnology
• Main Authors: F Sarvari, A.M. Mortazavian, M.R. Fazei
• Format: Article
• Language: English
• Published: Shahid Behehsti University of Medical Sciences 2014-09-01
• Subjects: Bifidobacteria, Lactobacillus acidophilus, Probiotic, Viability, Yogurt
• Online Access: http://journals.sbmu.ac.ir/afb/article/view/7125
• ISSN: 2345-5357; 2423-4214

This research aimed to investigate the viability of probiotic bacteria (<em>Lactobacillus acidophilus </em>LA-5 and <em>Bifidobacterium lactis </em>BB-12) and yogurt bacteria (<em>Streptococcus thermophilus</em> and <em>Lactobacillus delbrueckii </em>ssp. <em>bulgaricus</em>) in yogurt during the fermentation, immediately after fermentation and during refrigerated storage (21 d, 4˚C). Also the biochemical characteristics of milk as affected by the commercial 4-strain mixed starter culture were investigated. Storage time affected the viability of all bacterial species. The concentration of lactic acid during the fermentation increased in parallel with the titrable acidity, and the concentration of acetic acid was proportional to the viability of <em>Bifidobacterium lactis</em>. The acetaldehyde level was decreased in the yogurt from day 0 up to the end of the storage. <em>Streptococcus thermophilus</em> and <em>Lactobacillus delbrueckii </em>ssp. <em>bulgaricus</em> were multiplied considerably during the fermentation. <em>Streptococcus thermophilus</em> could maintain its viability to the highest level, but <em>Lactobacillus delbrueckii </em>ssp. <em>bulgaricus</em> lost its viability rapidly during the cold storage compared to <em>Streptococcus thermophilus</em>. The multiplication and viability of probiotic bacteria were also influenced by the associative strains and species of yogurt organisms. Bifidobacteria counts were satisfactory. The loss of viability for bifidobacteria was gradual and steady during the storage, and they showed good stability during the storage as compared to <em>Lactobacillus</em><strong> </strong><em>acidophilus</em>.