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A Review on the Anti-Phage Mechanism of Lactic Acid Bacteria
XI Yu, WANG Zhengyu, ZHANG Heping, CHEN Xia
Journal of Dairy Science and Technology    2015, 38 (6): 22-26.   DOI: 10.15922/j.cnki.jdst.2015.06.006
Abstract188)   HTML0)    PDF (1202KB)(92)       Save
The contamination of phage is considered as one of the major risks for food fermentation. It may cause the fermentation to slow down or even fail, and then cause huge economic loss. So, understanding the classification, morphology, and infection mechanism of phages and discussing the anti-phage mechanisms of lactic acid bacteria (LAB) are very important to the application of LAB and the production of related products. The aim of this paper is to describe the anti-phage mechanism of LAB, which may provide a certain theoretical support to the selection of anti-phage strains and prevention of phage contamination.
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Acid-Producing Ability of Streptococcus thermophilus and Organic Acid Composition in Fermented Milk
CHEN Hongxia, DE Liangliang, REN Yan, ZHANG Donglei, YANG Yanrong, LIU Wenjun, ZHANG Heping
Journal of Dairy Science and Technology    2015, 38 (2): 1-5.   DOI: 10.15922/j.cnki.jdst.2015.02.001
Abstract203)   HTML0)    PDF (1688KB)(129)       Save
In the present study, 5 strains of Streptococcus thermophilus which were isolated from traditional fermented dairy products were selected to perform fermentation experiments. During the fermentation process and 504 h of storage at 4 ℃, some indexes such as fermentation time, titratable acidity (TA), pH value and viable cell counts were determined, and the composition of organic acids was tested by reverse phase high performance liquid chromatography(RP-HPLC). Fermentation and acid-producing properties of Streptococcus thermophilus were evaluated; meanwhile changes in organic acid composition and post-acidification characteristics during storage were determined. After 2 h of fermentation at 42 ℃, the pH of fermented milk by each of the five strains declined rapidly. The fermentation reached its end-point at 5–9 h, and the shortest fermentation time was required for strains IMAU10632 and IMAU20772. Over the 504 h storage period, the pH of milks fermented by Streptococcus thermophilus was reduced by about 0.5 and finally reached a stable level of about 4.2, and acids were produced at lower rates in all fermented milks until the acidity values reached levels below 90 oT , suggesting the weak post-acidification ability of the 5 strains. Furthermore, IMAU10632 was selected from these strains, which could shorten milk coagulation time, increase acid-producing rate, enhance post-acidification ability and reach a viable cell count exceeding 108 CFU/mL which remained unchanged over the entire storage period.
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