Influence of temperature and addition of sugar on the fermentation of soymilk by monocultures of probiotic bacteria

Sojino mlijeko fermentirano je s tri komercijalne monokulture probiotičkih bakterija (Bifidobacterium lactis Bb12, Lactobacillus acidophilus La5 i Lactobacillus casei Lc01). Fermentacija je provedena pri dvije različite temperature (37°C i 43°C), te sa ili bez dodatka šećera u koncentraciji od 5 % (saharoze za Bb12 i La5, te glukoze za Lc01). Praćena je promjena kiselosti i promjena broja živih bakterijskih stanica tijekom fermentacije i nakon 24 h čuvanja uzoraka pri temperaturi hladnjaka 4-7°C. Kod sve tri monokulture primjećen je bolji rast broja stanica pri temperaturi 37°C nego pri 43°C. Dodatkom šećera fermentacija je kod svih ispitivanih sojeva bila kraća, a broj živih bakterijskih stanica na kraju fermentacije veći nego pri fermentaciji bez dodatka šećera. Najveći utjecaj dodatka šećera je primijećen kod fermentacije kulturom L.casei Lc01. Izbor bakterijske monokulture nije značajno utjecao na izgled i konzistenciju fermentiranog sojinog mlijeka, osim u slučajevima kada nije postignuta odgovarajuća kiselost, pa nije došlo do koagulacije.Fermented soymilk beverages were made by fermentation with commercial monocultures of probiotic bacteria: Bifidobacterium lactis Bb12, Lactobacillus acidophilus La5 and Lactobacillus casei Lc01. Fermentation was carried out at two different temperatures (37°C and 43°C), with or without 5% sugar addition. pH-values and numbers of viable cells were measured during the fermentation and after storage of fermented soymilk at refrigerator temperature (4-7°C) for 24 hours. All tested probiotic bacteria survived better at 37°C than at 43°C. In all 3 tested cultures addition of sugar made the fermentation shorter and the number of viable cells bigger compared to non additional sugar fermentation. The influence of sugar on the acid production and viable cells count was the greatest in the soymilk fermented with the monoculture L. casei Lc01. The choice of monoculture didn't have a significant influence on the appearance and consistency of the fermented soymilk, except when the achieved acidity was to high and soymilk didn't coagulate