Effect of culturing lactic acid bacteria with varying skim milk concentration on bacteria survival during heat treatment

Four lactic acid bacteria (LAB) strains were cultured in reconstituted skim milk with different solids contents to compare the thermotolerance of resulting cultures. As concentration was increased from 5 30 wt%, population non-lactose-fermenting by around 1 log at stationary growth phase. High maintained relative stable pH (?pH<0.5) when fermented a lactose-fermenting strain, compared drastic drop 1.35 low milk. All four 20 or wt% demonstrated significant improvements cell survival (remaining viability > 108 CFU/mL) and capability after heat treatment 65 °C for 10 min, indicating general thermoprotective effect irrespective metabolic pathways. Besides cellular response high osmolality during bacterial growth, we proposed that protective dairy components viscosity thermal resistance culture medium also contributed excellent thermotolerance.