Process Optimization of Sugar-free Probiotic Preserved Kiwifruit and Analysis of Nutritional Flavor

The sugar-free probiotic preserved kiwifruit was processed by the microwave-ultrasonic synergistic sugar penetration method. Based on the results of single-factor experiments, the response surface test was used to optimize the processing technology of preserved kiwifruit, and a regression digital model was established. It showed that the optimal process conditions were determined as follows: 28% xylitol addition, 0.16% excipient compound addition, microwave 35 min-ultrasound 1.25 h, the comprehensive score of the total sugar content and sensory evaluation of the obtained product was 61.93. Nutritional quality analysis showed that microwave-ultrasonic synergistic sugar penetration could not only greatly improve the sugar infiltration effect, but also reduce the loss of Vc, which maintained 86% of fresh kiwifruit Vc, and increased the contents of free amino acids, total phenols and flavonoids by 52%, 38% and 56%, respectively.High performance liquid chromatography (HPLC) analysis showed that the contents of 7 kinds of organic acids in the preserved kiwifruit processed with microwave-ultrasonic synergistic sugar penetration increased, including citric acid, malic acid, tartaric acid, and quinic acid, etc. Gas chromatography-mass spectrometry (GC-MS) analysis results showed that the main volatile flavor compounds of kiwifruit were changed from 2-hexenal to ethyl caproate after kiwifruit was processed into sugar-free probiotic preserved kiwifruit. It showed that microwave-ultrasonic synergistic sugar penetration treatment preserved the original flavor of kiwifruit to the greatest extent, more flavor substances such as fruit aroma and lipid aroma were produced at the same time, which made the preserved kiwifruit more flavorful.