Investigating the Combined Effects of Physicochemical Conditions on Functional Properties of Two strains of Lactic Acid Bacteria

Abstract

Lactic acid bacteria (LAB) are widely used in the food industry due to their interesting technological activities and beneficial effects on human health. In technological processes, physicochemical conditions often appear in combination. To ensure the viability of LAB and improve their metabolic and functional properties, adjustment of optimal physicochemical conditions should be considered. In this study, the combined effects of temperature, hydrogen potential (pH), and sodium chloride concentration, on two functional properties, proteolysis and acidification, of two strains of LAB, Lactococcus lactis (LCL) and Enterococcus faecium (CHT4), were investigated. Both activities were assayed at the end of growth of the two strains at different values of the three factors using a central composite design (CCD). Graphical analysis of results transcribed as isoresponse contour plots showed that temperature positively affected the LCL strain’s proteolysis at 40°C. In contrast, the CHT4 strain’s proteolysis was affected by pH of about 7 and temperature of around 40°C in decreasing order. The LCL strain’s acidification was positively affected by reducing the salt concentration in the medium to about 2 to 3% combined with a temperature above 37°C; in contrast, the CHT4 strain’s acidification was affected by temperature (37 to 40°C), and pH (6.2 to 7). Statistical analysis of the results was used to generate mathematical models describing both activities according to the most significant factors. Applying these models when using the strains on an industrial scale will optimize food production conditions and improve their organoleptic quality, with health benefits that meet consumer expectations.