Biochemical properties of some thermophilic lactic acid bacteria strains from traditional fermented milk relevant to their technological performance as starter culture

Abstract

The aim of this study was to characterize isolates of thermophilic lactic acid bacteria from traditional fermented milk and to study some of their important technological properties. Five isolates of thermophilic lactic acid bacteria from traditionally raw cow's fermented milk were identified using phenotypic criteria and Sodium Dodecyl Sulphate-Polyacrylamide gel electrophoresis of whole cell proteins. Four isolates named 2, 8, 13 and 20 FM were identified as Streptococcus thermophilics while isolate 285 N was identified as Lactobacillus delbrueckii ssp. bulgaricus. All these strains exhibited good acidification activity although two strains of Sc. thermophilus (2FM, 20FM) and Lb. bulgaricus (285N) presented the best acidification rates. In addition to their fast acid production, strains 20FM and 285N produced exopolysaccharides. Based on these characteristics, strains 2FM, 20FM and 285N were selected and used as pure or mixed cultures in the manufacture of fermented milk. In mixed cultures, the Sc. thermophilus/Lb. bulgaricus association was positive for all combination tested. The combination of strain 285N with strain 2FM or 20FM had a significant effect on acid production by Lb. delbrue ckii ssp. bulgaricus strain (285N). These bacterial associations also affected the rheological properties of fermented milk samples. Strains 2FM, 20FM and 285N presented interesting biotechnological profiles and may influence the quality of fermented milk if they are used in association as starters in yoghurt manufacture. © 2007 Asian Network for Scientific Information.