Development of fermented beverage with citrus fruit extract using probiotics: impact on antioxidant activity and in vitro digestibility

Redhyang (Citrus hybrid ‘Kanpei’,CHK) is a subtropical citrus species introduced in Korea due to climate change. To enhance the nutritional value and usability of CHK as a processed food product, CHK extract was fermented with four types of commercial starters (YoFlex Harmony 1.0 (YFH), ABY-3 (ABY), YC-X11 (YXC), and YC-180 (YC)), and their antioxidant activities and changes in chemical properties during fermentation were investigated. The consumer acceptance of probiotic beverages containing fermented CHK extracts and their viability and antioxidant activity through in vitro digestion were also elucidated. The enumeration of lactic acid bacteria (LAB) in all samples after fermentation was above 7.60 log colony-forming units (CFU)/mL, with YC exhibiting the highest number after 24 h. Fermented CHK extracts containing higher levels of organic acids, total polyphenols, and flavonoids tended to exhibit higher antioxidant activities. YFH, ABY, and YC showed maximum antioxidant activity at 24 h, whereas YXC showed differences in the types of LAB at 12 h. After in vitro digestion, YXC showed higher antioxidant activity and LAB viability than the control. This result indicates that CHK extract fermented with YXC can increase antioxidant activity, bioactive ingredients, and sensory preference and positively impact the production of probiotic beverages.