Changes in major components of tea fungus metabolites during prolonged fermentation

Changes in major components and microbes in tea fungus broth (or kombucha; teakwass) prepared from nine different sources during a prolonged fermentat ion of up to 60 days were investigated. Cell concentrations of both yeasts and acetic acid bacteria in broth were generally higher than those in the c ellulosic pellicles. The residual sucrose concentration decreased linearly with time, although the rate fell after the first month. Metabolic fates of glucose and fructose produced as a result of the hydrolysis of sucrose wer e different. Glucose was not produced in parallel with fructose (0.085 g 10 0 ml(-1) d(-1)) but was produced with a lower initial rate (0.041 g 100 ml( -1) d(-1)). Both titratable acidity and gluconic acid increased steadily wi th time for all samples, although gluconic acid was not generated for 6 day s until the fermentation had begun. Acetic acid increased slowly to a maxim um value of 1.1 g 100 ml(-1) after 30 days; thereafter, it decreased gradua lly. Gluconic acid contributed to the titratable acidity and thus, the tast e of tea fungus broth, during the final stage of fermentation. It is conclu ded that the desired quality or composition of kombucha can be obtained thr ough the proper control of fermentation time.