Effect of Freezing Storage and High Hydrostatic Pressure on Microbial Viability in Liquid Whole Egg-Sucrose Mixture

抄録

Effects of freezing storage and high hydrostatic pressure on microbial (Escherichia coli) viability in liquid whole egg (LWE)-sucrose mixture were investigated. Liquid whole egg with different sucrose concentration (0, 20 or 50 wt%) was pressurized at 400 MPa and then frozen at -20°C for a week. The viable cell count was estimated by monitoring the changes in absorbance values during cultivation at 660 nm with 30-min interval. Survival curves obeyed the first-order inactivation kinetics. The viable cell counts in frozen-thawed LWE-sucrose mixture was lesser than those of unfrozen samples. Effect of sucrose content on high-pressure-mediated inactivation varied at 20 wt%. Thermal analysis of LWE-sucrose mixture showed that the thermal denaturation enthalpy of LWE-sucrose content of 20 wt% was highest in all tested conditions, which also showed protective effect against thermal denaturation. LWE-sucrose (20 wt%) mixture has protective effects on pressure inactivation of E. coli, while LWE-sucrose (50 wt%) showed inactivation effect based on the strong dehydration ability on E.coli and LWE mixture by osmotic pressure.