The effect of pasteurization by ultrasound and thermal method on the color and microbial properties of grape juice

One of the most widely used methods for sanitizing and reducing the microbial load of fruit juices is thermal pasteurization, which damages bioactive pigments such as anthocyanins. this study was conducted to evaluate the possibility of pasteurization of grape juice by ultrasound (at powers 10, 105, and 200 w, temperatures 0, 30, and 60 °c, and times 2, 6, and 10 min) and to compare the microbial load and color properties by thermal pasteurization (pasteurization at 90 °c for 30 sec). according to the results, the number of color components (a*, b*, and l*) and the total count of microorganisms in pasteurized grape juice decreased significantly (p≤0.05) as the power, temperature, and time increased. optimal conditions for simultaneous pasteurization by ultrasound to achieve the minimum microbial load and the maximum number of color components with 90.196% desirability were predicted at a power of 113 watts, a temperature of 60 °c, and a time of 8.850 min. the microbial load of pasteurized grape juice by ultrasound was 0 (cfu/ml), and the number of color components was l*= 18.8021, a*= 37.8406, and b*=27.2104. the results indicated that the pigments of grape juice could be preserved and the same safety in terms of microbial load reduction could be achieved through pasteurization by ultrasound.