Optimization of kombucha production using organic green tea (Camellia sinensis) and specialty coffee (Coffea arabica): Production optimization, physicochemical composition, microbial viability, and sensory evaluation

This study evaluated the effects of ingredient combinations on kombucha fermentation using a Central Composite Rotatable Design (CCRD), with tea, coffee, and sugar concentrations as process variables and pH, volatile acidity, and fixed acidity as response variables. Of the 17 formulations, only six met the kombucha identity and quality standards. These six formulations were further analyzed for nutritional composition, color, volatile compounds, total phenolic content, acceptance, and sensory preference. The CCRD models were statistically adequate and showed no lack of fit. Results indicated that tea had the greatest influence on the fermentation system, exhibiting a significant positive linear effect on volatile and total acidity. The pH was influenced by coffee and sucrose, contributing to the beverage's acid-base balance. Multiple Factor Analysis (MFA) demonstrated that initial substrate variation affected the microbiological dynamics of acetic acid bacteria and yeasts, thereby altering the development of secondary metabolites. Formulations with higher residual sucrose content (K7, K8, and K14) exhibited the greatest market potential, with purchase intention exceeding 60%, likely due to higher scores for overall acceptance and flavor. High tea concentration, as observed in K12, increased total phenolic content and acidity, which may have resulted in lower sensory acceptance. Volatile compounds derived from coffee, present in K3 and K12, did not enhance acceptance, even with low volatile acidity. Formulations characterized by high residual sugar, intermediate acidity, and a shared aromatic profile achieved high acceptance scores. These findings suggest that a balanced interaction among the ingredients demonstrates the fermented beverage's technological viability.