Investigation and comparison of color and microbial properties of pasteurized sour cherry juice by ultrasonic method under optimal conditions with thermal pasteurization

Conventional thermal pasteurization may cause pigment degradation as well as loss of nutritional value of fruit juices. It is therefore essential to develop non-thermal pasteurization methods to maximize retention of bioactive compounds while minimizing color changes in sour cherry juices. Ultrasound is an emerging non-thermal technology that could ensure microbial safety and extended shelf-life of fruit juices without having negative effect on their phytonutrient content. The aim of present study was to investigate the non-thermal method of ultrasound and the effect of three variables of ultrasound power (10, 105 and 200 W), ultrasound temperature (0, 30 and 60 ° C) and ultrasound time (2, 6 and 10 minutes) on Microbial load and Color properties of whole sour cherry juice and its comparison with heat treatment (90 ° C, 30 s). Examination of color parameters showed that with increasing ultrasonic power from 10 to 200 watts, ultrasonic temperature from zero to 60 ° C and ultrasonic time from 2 to 10 minutes, the amount of a *, b *, L * and microbial contamination in pasteurized sour cherry juice significantly (p≤0.05) decreased. Also, in sour cherry juice samples pasteurized by ultrasonic method in optimal conditions (ultrasonic power 109 watts, temperature 60 ° C and time 9.5 minutes) no microorganisms grow and no significant difference was observed between the microbial load of the samples with the pasteurized sample. and also the color parameters (L *, b * and a *) of the sample pasteurized by ultrasound method was higher in optimal conditions. According to these results, it can be said that the use of ultrasound in optimal conditions in pasteurization of sour cherry juice, in addition to reducing microbial contamination of this food product, effectively preserves color compounds such as anthocyanins in sour cherry juice.