The combined effect of low frequency ultrasound (20 kHz, with waves of amplitude 20 and 40) with temperature (45oC for periods of 5 and 10 min) on the survival of a baker’s yeast suspended in water was studied. Irradiation was conducted for periods of 2–10 min. Colony counting analyses in Sabouraud agar media were performed for comparison. Application of ultrasonic waves at a non-lethal temperature (45oC) did not display a deactivating action to initial 4min irradiation time and higher CFU/gr values at higher heating time was observed. These results proved that the ultrasonic waves do not destroy the yeast s cells especially in initial 4min ultrasonication, but the consequence also showed the resistance of cells decreased as ultrasonic amplitude and irradiation time increasing.

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