highly significantp < 0.01
Among the interaction terms, the largest F -value was found for X 3 X 4 interaction, followed by X 1 X 2 interaction, indicating that the interaction between ultrasonic time and ultrasonic power was highly significant ( p < 0.01), the interaction between pulse duration and electric field intensity was significant ( p < 0.05) and the rest of the factor interactions were not significant.