Effect of sonication on colour, ascorbic acid and yeast inactivation in tomato juice

Power ultrasound is recognised as a potential non-thermal technique to inactivate micro-organisms pertinent to fruit juices. In this study tomato juice was sonicated at different amplitude levels (24.4-61.0 mu m) at a constant frequency of 20 kHz for treatment times (2-10 min) and pulse durations of 5 s on and 5 s off. Hunter colour values (L*, a* and b*), pH, (degrees)Brix, titratable acidity, ascorbic acid and yeast inactivation were measured. No significant differences (p < 0.05) in pH, (degrees)Brix or titratable acidity were observed. Regression modelling was used to investigate the main effects of amplitude level and treatment time. Prediction models were found to be significant (p 0.05) with low standard errors and high coefficients of determination (R-2). Model predictions for critical quality parameters of Hunter colour values (L*, a* and b*), ascorbic acid and yeast inactivation were closely correlated with the experimental results obtained. (C) 2010 Elsevier Ltd. All rights reserved.