Ultrasound-Assisted Lactic Acid Fermentation of Bakraei (Citrus reticulata cv. Bakraei) Juice: Physicochemical and Bioactive Properties

In this study, ultrasonication (US) (50 W, 30 kHz, 1-6 min) was used to increase the efficiency of Limosilactobacillus reuteri PTCC 1655 fermentation process (37 degrees C; 30 h) of Bakraei juice. Total sugars, pH, Brix, organic acids, vitamin C, polyphenols, antioxidant activity, alpha-amylase inhibition and anti-inflammatory properties were measured during the fermentation period. The results showed that by increasing the ultrasound time up to 5 min, pH, vitamin C, citric acid, and polyphenolic compounds decreased, while lactic acid, antioxidant capacity, alpha-amylase inhibition and anti-inflammatory properties were increased. When the ultrasound time was increased up to 6 min, compared to the non-ultrasound-treated sample, the efficiency of the fermentation process decreased and promoted a decrease in the microbial population, lactic acid levels, antioxidant activity, alpha-amylase inhibition, and anti-inflammatory properties of the juices. The initial anti-inflammatory activity (11.3%) of juice reached values of 33.4% and 19.5%, after US treatments of 5 and 6 min, respectively, compared to the non-sonicated juice (21.7%), after 30 h of fermentation. As a result, the use of ultrasound in the controlled fermentation process can increase the efficiency of fermentation process.

Automated summary

In this study, ultrasonication (US) was used to improve the efficiency of Limosilactobacillus reuteri PTCC 1655 fermentation process of Bakraei juice. The results showed that increasing the ultrasound time up to 5 min enhanced several beneficial properties such as antioxidant activity and anti-inflammatory properties, while further increasing the ultrasound time to 6 min decreased the efficiency of the fermentation process and negatively impacted the microbial population and various properties of the juices.