Impact of HPP on probiotics: Kinetic and metabolic profiling study of yogurt produced under different pressure conditions

Abstract Novel food biotechnological applications using high-pressure (HP) technology are now emerging, such as fermentation under sublethal pressures. In order to explore this phenomenon, a study of the effect of HP (0.1–100 MPa) on yogurt fermentation kinetics and lactic acid bacteria (LAB) metabolic profiles was carried out. Physicochemical (titratable acidity, pH, and the reducing sugar concentration) and microbiological parameters (Streptococcus thermophilus and Lactobacillus bulgaricus counts) were evaluated in order to monitor fermentation, which was found to slow down under pressure with total inhibition occurring at 100 MPa. However, yogurt could be produced by prolonging fermentation at 5 MPa to 600 min. In addition to these physicochemical parameters, metabolic profiling by nuclear magnetic resonance (1H NMR) spectroscopy was carried out to obtain the first insights into HP effects on the LAB exometabolome during yogurt fermentation. Metabolic differences between yogurt produced under pressure (5 MPa) and at atmospheric pressure were identified, namely a higher acetate content in yogurts produced under pressure. This difference suggests a possible relative higher importance of heterofermentative metabolism by LAB compared to homofermentative, when yogurt production occurs under sublethal levels of pressure.