Effects of microwave pasteurization on the thermal resistance of Zygosaccharomyces rouxii and on the physicochemical properties of organic intermediate moisture raisin

In this study, organic intermediate moisture raisin was pasteurized with microwave and conventional pasteurization methods. The thermal resistance (D and z values) of the target yeast, Zygosaccharomyces rouxii, was determined for both methods at different temperatures 60 degrees C, 70 degrees C, and 80 degrees C and at different time intervals. The effect of pasteurization methods on the quality properties of raisin samples was investigated. The D values of Z. rouxii were found as 6.50 +/- 0.49, 2.96 +/- 0.02, 1.91 +/- 0.01 min for conventional treatment and 3.46 +/- 0.31, 2.02 +/- 0.14 and 1 +/- 0.01 min for microwave treatment at 60celcius, 70celcius, and 80celcius, respectively. F-85(37) values for 5-log reduction and come-up time significantly decreased after microwave pasteurization. Brix, acidity, and color values were preserved better by microwave treatment. Hydroxymethylfurfural content of the microwave pasteurized samples was found 42% less than the samples pasteurized conventionally. Microwave pasteurization can be alternatively used for the conventional method for raisin improving quality with less heating time. Practical applications Microwave heating needs less come-up time rather than conventional pasteurization. Decreasing process time provides advantageous via the costs and energy saving so organic intermediate moisture fruits that are perishable can be safely pasteurized by a microwave method for longer shelf life in the industry. Z. rouxii, which may be found in high sugar content foods, can be inactivated to the target log that provides the fruit safe by using this method. in addition, quality properties, such as color, which is effective on the consumer preference also, protected better by the effect of volumetric heating.