Alginate biopolymers are widely used as stabilizers, thickeners, and binders by diverse industries such as food, pharmaceuticals, textiles, etc. Furthermore, it has been used to manufacture encapsulates to preserve substances and microorganisms such as the yeast Saccharomyces cerevisiae. This approach can protect the microorganisms against other substances, and harmful environmental conditions that can generate stress and negatively impact the metabolism. Accordingly, encapsulation could be a route to improve fermentation performance and increase yeast’s vitality and viability, even the sensory profile of fermented foods such as beer could be modulated by manipulating the ratios of different strains without adding additives. This project is therefore dedicated to encapsulating four yeast strains in alginate with the main goal of evaluating the impact on fermentation efficiency and the sensory profile of the produced beer.<br/><br/>Alginate capsules of four yeast strains by direct assembly in cultures in YPD medium. The selected strains were the American strain SafAle US-05, the German SafAle K-97, the Belgian SafAle B-134 and the native Colombian CW-12 (previously isolated from local sugar cane manufacturing facilities). The alginate concentration was 3 and 1.5% w/v and the calcium chloride for crosslinking was 0.2M, 0.1M and 0.05M. The yeasts were mixed with the alginate at a rate of 20% w/v. Then, with a syringe (20 ml - 0.8 X 40 mm 21G X 1 ½”), the mixture was dripped into the calcium chloride solution, which led to the formation of capsules of approximately 3 mm diameter. The properties of the capsules were determined via TGA, NIR, and FTIR. Moreover, their morphologies were imaged by SEM and optical microscopy while their mechanical response was through a texturometer. Finally, cell viability was determined via confocal microscopy by staining live and dead cells. The 3% alginate capsules exhibited higher elasticity, firmness, and stability than the ones obtained at 1.5%. The pore size varies depending on the crosslinking gradient, which changes from the surface to the center of the sphere. We expect to make a robust correlation between the mechanical and morphological properties of the capsules and the overall performance of the alcoholic fermentation in terms of key organoleptic parameters such as taste, color, odor, appearance and turbidity.

Alginate-beer yeast encapsulates: Impact on fermentation yield and sensory profile

ACS Fall 2021

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