Impact of time and temperature on the physicochemical, microbiological, and nutraceutical properties of laver kombucha (Porphyra dentata) during fermentation

Temperature and time have an important role in every fermentation process. The present study aimed to explore the effect of both temperature and time on the dynamic changes induced during fermentation on the properties of laver kombucha. Laver extracts were obtained by ultrasound-assisted extraction, and fermentation with kombucha scoby was performed at 25 and 30 degrees C (K-25 and K-30) for 22 days. Higher temperature promoted a faster rate of fermentation as evidenced by the lower pH, higher titratable acidity, and biofilm yield, as well as greater counts of mesophilic, and acetic acid bacteria noted in the product with lower counts of total yeast and amino acids at the end of the fermentation. Samples at a lower temperature (K-25) exhibited higher amounts of bioactive components and greater alpha-amylase inhibitory activity (92% in the K-25 samples vs. 83% in the K-30 samples at 14 d). In turn, longer fermentation was found to further enhance acid accumulation, showing higher acidity and lower pH, while the amount of bioactive components was reduced. These findings provide a better understanding of the dynamic changes in the characteristics of the newly developed laver kombucha based on the regulation of its fermentation conditions.