Effects of fermentation time and pH on quality of black carrot juice fermented by kefir culture during storage

The effects of fermentation time (17-48 h) and pH (3.37-4.50) on qualities of fermented beverages (FBs) produced from black carrot juice (BCJ) were monitored during storage at 4 °C for 20 weeks.Fermentation and adjusting the pH level provided significant increases (up to 22%) in anthocyanin content and the absorbance value at λmax (Amax ). Moreover, the stability of anthocyanins, color density, and Amax in FBs was somewhat higher than those in BCJ. Lactic acid showed a co-pigmentation effect on cyanidin-3-galactoside-xyloside-glucoside-sinapic acid and cyanidin-3-galactoside-xyloside-glucoside-ferulic acid. Sucrose was degraded much faster at pH 4.50 (17 h) and 4.35 (48 h) than at lower pH levels. During storage, pH 4.35 caused a balanced distribution between counts of lactic acid bacteria (LAB) and yeasts, and antioxidant activity of all FBs increased. Fermented beverages at 4.35 and 3.90 were found to be more palatable by panelists.We recommend FB production at pH 4.35 after 48 h fermentation due to the balanced distribution of probiotics, high color enhancement, and consumer preference. © 2021 Society of Chemical Industry.