Novel inactivation methods of Doenjang (fermented soybean paste) by high pressure and ohmic heating

The changes of the total cell number in doenjang (Korean traditional fermented soybean paste) by conventional conduction heating, high pressure non-thermal treatment, and ohmic heating were compared. A total of (10(1)-10(2)) CFU/g cells were decreased by heating at (100-105) degrees C for 10 min. The inactivation rate was improved when heated to a temperature higher than 110 degrees C, but the taste, color of doenjang were severely changed. Inactivation by high pressure at (200-800) MPa was not achieved, because the total cell did not reach a reduction of 10(1) CFU/g. The total bacterial counts of 10(3) CFU/g were decreased during ohmic heating at 15 V and 60 Hz for 10 min, and showed the most effective inactivation. Therefore, application of the ohmic heating in doenjang with high viscosity can kill target microorganisms related to quality deterioration, and rapid and uniform ohmic heating leads to reduction in sensory quality damage.