# Effect of Ultrasonic Treatment on the Quality of Pumpkin Juice Fermented by Yeast
## 3 Results
### Influence of Ultrasonic Treatment on the Aroma of Pumpkin Juice  
The results of the influence of ultrasonic waves on the aroma components of pumpkin juice are shown in Figure 4A-C. After ultrasonic treatment, 127 volatile flavor components were identified in the pumpkin juice fermented by yeast through gas chromatography. Among them, 14 volatile substances are the common flavors of different treatment groups, all of which are characteristic aroma profiles of pumpkin juice. This indicates that ultra  
Figure 3: The influence of different ultrasonic power treatments on the total microbial count and microstructure of fermented pumpkin juice. (**A**): Effects of ultrasonic treatment on the number of microorganisms in pumpkin juice. (**B**): Microscopic structure of fermented pumpkin juice without ultrasonic treatment. (**C**): Microscopic structure of fermented pumpkin juice with ultrasonic treatment at a power of 100 W. (**D**): Microscopic structure of fermented pumpkin juice with ultrasonic treatment at a power of 200 W. (**E**): Microscopic structure of fermented pumpkin juice with ultrasonic treatment at a power of 300 W. (**F**): Microscopic structure of fermented pumpkin juice with ultrasonic treatment at a power of 400 W.  
sonic treatment (US) has little impact on the natural flavor of pumpkin juice. Ultrasonic treatment has newly generated a variety of substances such as acetic acid, eicosane, and isopropyl caprate in the aroma of the pumpkin juice fermented by yeast, indicating that ultrasonic treatment can cause the generation of new aroma components in the pumpkin juice fermented by yeast. This is consistent with the findings of [PERSON] [1] et al. that ultrasonic treatment can lead to the formation of new compounds or the disappearance of compounds found in untreated samples. [PERSON] et al. [42] compared the enzyme-treated orange juice with the fresh, untreated orange juice and found that the enzyme-treated one contained 15 new aroma compounds, while 3 aroma compounds disappeared. In this experiment, the main volatile substances in the pumpkin juice fermented by yeast are esters, alcohols, and ketones. Hydrocarbons have a relatively high threshold and no special odor. Aldehydes usually have a fresh, fruity, and fatty aroma, with a low threshold, so they play a crucial role in flavor development. Aldehydes are mainly produced via the oxidative degradation of unsaturated fatty acids. After ultrasonic treatment, the overall content of aldehydes in the aroma of the pumpkin juice fermented by yeast shows a downward trend. The decrease in the content of aldehydes indicates that autoxidation and enzymatic oxidation may be involved [43]. Alcohols are mainly generated via the thermal oxidation of lipids. Alcohol compounds have low odor activity and exist in the form of glycoside conjugates in fruits [44]. After fermentation by yeast, the number of  
Figure 4: The influence of ultrasonic treatment on the types of aroma components in pumpkin juice (**A**–**C**). Sensory evaluation of pumpkin juice treated with ultrasonic waves of different powers (**D**). (**A**): Heat map of the influence of ultrasonic treatment with different powers on the types of aroma components in pumpkin juice. (**B**): Bar chart of the influence of ultrasonic treatment with different powers on the types of aroma components in pumpkin juice. (**C**): Venn diagram of the influence of ultrasonic treatment with different powers on the types of aroma components in pumpkin juice. (**D**): Radar chart of the sensory evaluation results of pumpkin juice treated with ultrasonic waves of different powers. alcohol substances in the pumpkin juice increases, and the relative content increases by 344.64% compared with the untreated group. This indicates that ultrasonic treatment is conducive to the generation of new aroma components in the pumpkin juice fermented by yeast. After ultrasonic treatment, the content of esters in pumpkin juice increased significantly. This is consistent with the findings of [PERSON] et al.