title: Study on Streptococcus thermophilus isolated from Qula and associated characteristic of acetaldehyde and diacetyl in their fermented milk.
abstract: In this study, the lactic acid bacterial population of Qula cheese from the Gansu and Sichuan provinces of China were isolated and identified. Eight strains of Streptococcus thermophilus were isolated, of which five strains were selected for further characterization based on their fermentation properties. The changes in a number of parameters, including titration acidity, pH, viable counts, PrtS protease activity and the production of acetaldehyde, diacetyl and organic acid, were monitored during fermentation and the storage of fermented milks produced by the respective strain. All of the strains displaying acidifying capacity and all five fermented milks maintained high viable counts of S. thermophilus from fermentation to storage. Our study found that the changes in the monitored parameters were strain-specific and varied considerably among the five tested strains. Fermented milks produced by strain IMAU80809 had the highest concentration of acetaldehyde and were most favorable in the sensory evaluation. This study confirms that Qula cheese is a good source for isolating novel lactic acid bacterial strains with different fermentation properties, which will be very useful for further development and industrialization of traditionally fermented dairy products.
authors.affiliation: Key Laboratory of Dairy Biotechnology and Engineering, Ministry Education of China.
authors.forename: Musu
authors.initials: M
authors.lastname: Zha
authors.forename: Jie
authors.initials: J
authors.lastname: Yu
authors.forename: Yong
authors.initials: Y
authors.lastname: Zhang
authors.forename: Hongmei
authors.initials: H
authors.lastname: Wang
authors.forename: Na
authors.initials: N
authors.lastname: Bai
authors.forename: Yanting
authors.initials: Y
authors.lastname: Qin
authors.forename: De
authors.initials: D
authors.lastname: Liangliang
authors.forename: Wenjun
authors.initials: W
authors.lastname: Liu
authors.forename: Heping
authors.initials: H
authors.lastname: Zhang
authors.forename: Menghe
authors.initials: M
authors.lastname: Bilige
mesh_terms: D000079:Acetaldehyde / Q000737:chemistry*; D000818:Animals; D002417:Cattle; D002611:Cheese / Q000382:microbiology*; D002681:China; D015169:Colony Count, Microbial; D003931:Diacetyl / Q000737:chemistry*; D005285:Fermentation; D005516:Food Microbiology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007778:Lactobacillus / Q000145:classification / Q000302:isolation & purification; D050296:Microbial Viability; D008892:Milk / Q000737:chemistry*; D009812:Odorants / Q000032:analysis; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D048249:Streptococcus thermophilus / Q000145:classification / Q000302:isolation & purification*; D013649:Taste
chemical_list: D012336:RNA, Ribosomal, 16S; D000079:Acetaldehyde; D003931:Diacetyl