In recent years, the increasing awareness of diseases has led to the demand for functional foods and beverages that provide additional health benefits beyond basic nutrition. Water kefir is a healthy fermented beverage with unique aroma and flavor profile, obtained by the symbiotic fermentation of lactic acid bacteria (LAB), acetic acid bacteria (AAB), and yeast. In this study, a new functional beverage based on substrates such as longan juice (KL) and longan juice supplemented with herbs: butterfly pea (KLB), rosella (KLR), or safflower (KLS), and fermented at 25°C for 48 h with water kefir grains as starter, was developed. The occurrence of microbial community of LAB, AAB and yeast during fermentation in all treatments were not significantly different (p<0.05) However, each supplement showed its distinct color according to specific characters of the herbs. The addition of the herbs significantly enhanced total phenolic compounds (TPCs) and antioxidant activities as investigated by DPPH and ABTS assay, with the results varying with supplement type. The addition of KLS showed the highest TPC of 212.17 μgGAE/mL, while KLB and KLR displayed lower levels of 198.36 and 201.93 μgGAE/mL, respectively. Levels of DPPH and ABTS in all supplements showed the best condition at 24 h fermentation, but decreased at 48 h, suggesting the sensitivity of some antioxidants. Sensory evaluation revealed that KLS had the highest acceptance, while KLR was the least accepted by consumers. This study pointed out that longan kefir supplemented with herbal ingredients has the potential to be a novel functional beverage.
