A microbiological, physicochemical, and texture study during storage of yoghurt produced under isostatic pressure. (August 2019) - Vieira, Patrícia
Abstract: This work aimed to study refrigeration storage (4 °C for 23 days) of yoghurt produced at 43 °C under sub-lethal high pressure, at 10, 20, 30 and 40 MPa, in comparison with the fermentation process at atmospheric pressure (0.1 MPa). Lactic acid bacteria ( S. thermophilus and L. bulgaricus, LAB) and quality parameters like pH, titratable acidity, syneresis and colour were evaluated, along with textural analyses to infer how pressure would impact the obtained yoghurt along storage. Higher fermentation pressures resulted in slightly lower LAB loads (a maximum of 1.01 Log (CFU/mL)) and increased the fermentation time (a maximum of 3 h 25 min), syneresis (a maximum of 44%), all for 40 MPa and firmness (a maximum of 2.5-fold) for 30 MPa. Under refrigeration, LAB were more active during the first 15 days of storage in yoghurts fermented under pressure (increasing loads up to 0.54 Log (CFU/mL)). Colour, pH and titratable acidity were not affected by pressure or storage. Further research is of interest to ascertain the biotechnological potential of fermentation processes under sub-lethal high pressure in general and in particular for yoghurt production. Highlights: Lactic acid bacteria (LAB) are able to produce yoghurt under pressure (10 – 40 MPa) at 43 °C. Pressure slowed down fermentation, but LAB loads were only slight lower in yoghurt. Fermentation time increased linearly with pressure. Pressure increased yoghurt firmness and syneresis but decreased adhesiveness. pH, titratable acidity and colour did not change during 23 days storage.