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