# Effect of Ultrasonic Treatment on the Quality of Pumpkin Juice Fermented by Yeast
## 4 Conclusions  
Through a series of single-factor analysis and response surface methodology optimization experiments, this study successfully determined the optimal fermentation process parameters for pumpkin juice: the content of pumpkin juice is 20 mL, the fermentation temperature is 30 \({}^{\circ}\)C, the fermentation time is 1 day, and the inoculation amount is 3%. Based on these parameters, the predicted sensory score of the pumpkin juice is as high as 8.5288 points. Compared with the fermented pumpkin juice without ultrasonic treatment, ultrasonic treatment shows significant advantages in improving the color, total acid content, and aroma components of pumpkin juice. In particular, when the ultrasonic power is set at 400 W, its sterilization effect on the microorganisms in the medium is the best, significantly reducing the number of microbial colonies in the pumpkin juice and meeting the microbial safety standards required by the commercial sector, thus ensuring the high quality and stability of the pumpkin juice. Ultrasonic waves with relatively high power (300 W) can effectively inactivate the activities of polyphenol oxidase and peroxidase, thereby reducing the enzymatic browning phenomenon of pumpkin juice. At the same time, they can retain the antioxidant active ingredients and vitamins in the pumpkin juice well. In terms of the natural biological activity in pumpkin juice, ultrasonic treatment not only effectively retains these active ingredients, but also reduces the particle size by disrupting the cell structure, improving the uniformity and taste of the pumpkin juice. This observation is consistent with the phenomena that the cell structure is damaged under the microscopic structure and the fragments of the cell wall decrease as the ultrasonic power increases. Microscopic analysis further reveals the mechanism by which ultrasonic treatment increases the carotenoid content by disrupting the cell structure. These results indicate that ultrasonic treatment has a positive impact on the fermentation process of pumpkin juice, especially in optimizing the fermentation process parameters and maintaining the product quality. Therefore, using ultrasonic treatment to assist the fermentation of fruit and vegetable juices by yeast not only meets the microbial standards and taste requirements of edible products, but also maximally retains the nutritional value of fruit and vegetable juices. At the same time, we believe that ultrasonic-assisted fermentation can protect the environment by shortening the fermentation cycle, improving raw material utilization, reducing energy and resource consumption, decreasing chemical reagent usage, and minimizing pollutant emissions, providing new ideas for improving the efficiency of the food industry. W.P. : Writing--original draft and Data curation. W.L. : Writing--original draft and Data curation. C.Z. : Writing--review and editing and Funding acquisition. M.Z. : Supervision. W.S. : Methodology. L.Y. : Validation. R.T.: Supervision. All authors have read and agreed to the published version of the manuscript. **Funding:** This research was financially supported by the National Natural Science Foundation of China (No. 32160580), Key project of the National Science Foundation of Jiangxi Province, China (Grant No. 224 ACB205009), and Key project of the Natural Science Foundation of Jiangxi Provincial Education Department (No. GJJ2201303). **Institutional Review Board Statement:** Consumers were recruited from the students and staff of Jiangxi Science and Technology Normal University. Written informed consent was obtained from all participants before the experiment was conducted. Participant consent was ensured by all participants signing and returning their consent forms to the research team prior to participation in the study. The sensory analysis experiments in this study strictly followed the ethical and professional practices outlined in the IFST (Institute of Food Science and Technology, UK) Ethical and Professional Practice Guidelines for Sensory Analysis of Food.