RESUMO
As components of starter cultures for Bulgarian yogurt, Streptococcus salivarius subsp. thermophilus and Lactobacillus delbrueckii subsp. bulgaricus revealed extensive exopolysaccharide (EPS) production activity when cultivated in whole cow's milk. The polymer-forming activity of thermophilic streptococci was lower (230-270 mg EPS/L) than that of the lactobacilli (400-540 mg EPS/L). Mixed cultures stimulated EPS production in yogurt manufacture, and a maximum concentration of 720-860 mg EPS/L was recorded after full coagulation of milk. The monomer structure of the exopolysaccharides formed by the yogurt starter cultures principally consists of galactose and glucose (1:1), with small amounts of xylose, arabinose, and/or mannose.
Assuntos
Lactobacillus/metabolismo , Leite/microbiologia , Polissacarídeos Bacterianos/biossíntese , Polissacarídeos Bacterianos/química , Streptococcus/metabolismo , Iogurte/microbiologia , Animais , Arabinose/análise , Meios de Cultura , Galactose/análise , Glucose/análise , Concentração de Íons de Hidrogênio , Lactobacillus/crescimento & desenvolvimento , Manose/análise , Streptococcus/crescimento & desenvolvimento , Temperatura , Xilose/análiseRESUMO
The dynamics of free amino acid production by the selected strains Streptococcus thermophilus 13a and Lactobacillus bulgaricus 2-11 were studied in pure and mixed cultivations during yogurt starter culture manufacture. L. bulgaricus 2-11 showed the highest activity for producing free amino acids with high individual concentrations over the first hour of growth (50% of the total amount). By the end of milk's full coagulation (4.5 h), 70% of the total amount of amino acids was released. S. thermophilus 13a showed poor proteolytic properties and consumed up to 70% of the free amino acids produced by L. bulgaricus 2-11 in the process of coagulation of milk with the mixed culture.
