CHANGES IN HEATING RATE OF EGG-ALBUMIN SO LUTION DURING OHMIC HEATING

An egg albumin solution (10 w/v%) was subjected to Ohmic heating at 50 Hz-10 kHz under constant 10 V/cm. The heating rate of solution was al most constant and slightly increased as the frequency increased. The g el formation was observed at about 75 degrees C and the heating rate w as considerably/appreciably increased above this temperature irrespect ive of frequency used. The solution and the gel showed almost the same impedance in the examined temperature range (20-90 degrees C). When t he concentration of egg albumin was reduced to 2 w/v%, this solution g ave no gel formation and showed the constant heating rate at temperatu res below and above 75 degrees C. Little difference in breaking streng th was detected between the gels prepared by boiling water and by Ohmi c heating. These results suggest that the liquid components are not co mpartmentalized in the gel and that the steep rise of heating rate abo ve 75 degrees C will be caused by the reduction of heat transfer of th e gel attributable to phase transformation. Ohmic heating was also exa mined for fresh egg white at the same conditions as those for the egg albumin solution. The fresh egg white did not show any sudden increase of heating rate up to 90 degrees C. However, the homogenized fresh eg g white and thin egg white separated beforehand showed the slightly re duced heating rate and its abrupt increase at about 60 degrees C. Thes e results suggest that the gelatinous component, thick egg white, repr esses the transfer of generated heat during Ohmic heating.