Kombucha Fermentation in Coffee: Application of Constant Air Flow Reactor

SCOBY (symbiotic culture of bacteria and yeasts) is an artificially created mixed culture containing selected strains of acetic acid and lactic acid bacteria and yeast which are present in the cellulose membrane. The growing popularity of kombucha consumption and high popularity of coffee creates the possibility of developing coffee-based kombucha production on an industrial scale, which currently does not differ in method from production on a laboratory scale and at home. Therefore, the aim of this work was to determine the possibility of using an alternative method of coffee fermentation using SCOBY, in which the fermentation was carried out in a bioreactor with a constant air flow (rate 2L/min). This study determined the effect of the fermentation method on the processing time, SCOBY mass gain, and selected properties of the fermented coffee beverage. The alternative fermentation method did not negatively affect the properties of the fermented coffee beverage, i.e., caffeine content, colour, polyphenol content, and antioxidant properties, in comparison with the traditional fermentation method. Additionally, it accelerated the fermentation process, shortening it from 8 to 4 days, and in some cases caused an increase in the total polyphenol content and antioxidant activity, almost 10% and over 40%, respectively. The results of this study show a possibility to use alternative methods for coffee fermentation, which can be easily adapted for industrial scale. Variants of fermented and aerated beverages with 4% coffee, and 4 and 5% sugar concentrations stood out among the others as having the best properties and might be introduced to the industry.