Effect of fermentation temperature in kombucha production on the concentration of organic acids, residual sugars and ethanol

Kombucha is a traditional beverage prepared by fermenting tea using a symbiotic culture of bacteria and yeasts. In this experimental work the concentration of lactic and acetic acid (analysed by isotachophoresis), saccharose, glucose and fructose (analysed by high-performance liquid chromatography-refractive index detector) and ethanol (analysed by solid-phase microextraction followed by gas chromatography-mass spectrometry) were determined in kombucha samples fermented at 20 °C, 25 °C and 30 °C. Active acidity (pH) was measured during fermentation, and after 7 days, the pH values of all samples ranged between 2.99 and 3.01. Lactic acid bacteria (LAB) and yeast counts were determined on day 0 and day 7. LAB counts remained the same (106 CFU·ml-1) in all samples, whereas the yeast counts increased from 104 CFU·ml-1 (day 0) to 106 CFU·ml-1 (day 7) in all samples. The highest concentration of lactic acid (129.4 ± 6.5 mg·l-1) and ethanol (21.6 ± 2.7 ml·l-1), and the lowest concentration of sugars (11.9 ± 1.2 g·l-1) were detected in the samples fermented at 25 °C. On the contrary, the sharpest drop in pH, the lowest concentration of lactic acid (36.9 ± 1.8 mg·l-1) and ethanol (1.72 ± 0.01 mg·l-1), and the highest concentration of acetic acid (17.7 ± 0.9 g·l-1) were detected in the samples fermented at 30 °C.