Kombucha fermentation in yerba mate: Cellulose production, films formulation and its characterisation

The production of Kombucha fermented beverage generates a side-stream composed of bacterial cellulose, a source of biopolymer to develop food contact materials. This work aims to study Kombucha fermentation in yerba mate infusion to maximise cellulose production and its processing for film formulation. Yerba mate infusion with sucrose resulted in an extraordinary substrate for Kombucha fermentation with an optimised cellulose production of 19.4 g/l and 0.29 g/g of yield. Filmogenic dispersions were analysed in terms of rheology and particle size distribution. Microscopic characterisation of films exhibited homogeneous surfaces. The addi-tion of glycerol, as well as the solids from the fermented broth, resulted in a significant increase in hydration and a reduction in elastic modulus, ultimate tensile strength and glass transition temperature of the films. The results revealed that the formulation containing the Kombucha fermented media showed similar properties to the glycerol plasticised material. This could be considered a novel result as it may replace the use of traditional plasticisers. Bioactive compounds from yerba mate provided an antioxidant activity greater than 95% of ABTS radical inhibition to cellulosic material, demonstrating that natural bioactive cellulose-based films are materials that potentially protect food products against oxidation.