Investigation on Escherichia Coli Inactivation and Some Quality Changes in Carrot Juice by Ultrasound Technique

In this study Response Surface Methodology was used to optimize process conditions and to evaluate the effect of ultrasound on quality attributes (antioxidant activity, pH, total soluble solid, turbidity) and the inactivation of Escherichia coli bacteria in carrot juice. Independent variables in this study were temperature (25-50°C), time (20-40 min) and frequency (0-130 kHz). In this study thermal process (85°C, 10 min) was chosen as control sample. The Browning index (BI) was used to evaluate the color changes of carrot juice. Results showed that linear effect of frequency (X3) and also interaction effect of frequency-time (X2-X3) were significant (p<0.05) in the inactivation of E. coli. Moreover about antioxidant activity, it was shown that, linear and quadratic effects of time were significant (p<0.05). The pH of samples was changed significantly (p<0.05) under the effect of linear (X2) and quadratic effects of time and linear (X3) and quadratic (X22 ) effects of frequency and also interaction effect of temperature-frequency (X1-X3). None of parameters had significant (X32) effect on turbidity and total soluble solid (p>0.05). Control sample showed higher value for browning index comparing other treatments.