Use of ultrasound for lipoxygenase inactivation in whole soy flour sus
pension was studied. Inactivation of the enzyme was influenced by the
time of exposure, pH, and the amplitude of ultrasound. Exposure to cav
itating 20 kHz ultrasound for 3 h at pH > 5.0 had no effect on the act
ivity of the enzyme. However, under similar conditions, the activity d
ecreasd by 70-85% when pH was lowered to 5.0 and 4.0, respectively. Li
poxygenase activity also decreased with increase in frequency of the u
ltrasound waves when pH was less than or equal to 5.0; above pH 5.0, i
ncrease in frequency did not affect the enzyme activity after an expos
ure of 1 h.