Abstract
Development of a novel directly marketable beer brewed at low temperature in a domestic refrigerator combined with yeast immobilization technology is presented in this study. Separately, freeze-dried wort and immobilized cells of the cryotolerant yeast strain Saccharomyces cerevisiae AXAZ-1 on tubular cellulose were used in low-temperature fermentation (2, 5 and 7 °C). The positive effect of tubular cellulose during low-temperature brewing was examined, revealing that freeze-dried immobilized yeast cells on tubular cellulose significantly reduced the fermentation rates in contrast to freeze-dried free cells, although they are recommended for home-made beer production. Immobilization also enhanced the yeast resistance at low-temperature fermentation, reducing the minimum brewing temperature value from 5 to 2 °C. In the case of high-quality beer production, the effect of temperature and initial sugar concentration on the fermentation kinetics were assessed. Sensory enrichment of the produced beer was confirmed by the analysis of the final products, revealing a low diacetyl concentration, together with improved polyphenol content, aroma profile and clarity. The proposed process for beer production in a domestic refrigerator can easily be commercialized and applied by dissolving the content of two separate packages in tap water; one package containing dried wort and the other dried immobilized cells on tubular cellulose suspended in tap water.
Highlights
A combination of immobilized biocatalysts and low-temperature fermentation has led to products with acceptable sensory characteristics [1,2]
The aim of the present study is to develop a dry ready-to-use mixture of immobilized yeast biocatalyst on tubular cellulose and wort, and evaluate its suitability for brewing in a domestic refrigerator
The proposed technology is based on the use of freeze-dried tubular cellulose-supported biocatalyst in a dry mixture with freeze-dried wort, which can be dissolved in tap water and placed in a refrigerator for fermentation
Summary
A combination of immobilized biocatalysts and low-temperature fermentation has led to products with acceptable sensory characteristics [1,2]. For fermentations at extremely low temperatures (below 5 °C), the use of psychrotolerant yeast strains is necessary. Immobilization of psychrophilic yeast strains has enabled the use of an extremely low brewing temperature (0–7 °C), leading to acceptable fermentation efficiency and product quality. Cell immobilization on tubular cellulose [5] resulted in high efficiency in fermentations at extremely low temperature, together with the high fermentation activity of freeze-dried cells [6]. This opened a way for wine and beer making in a domestic refrigerator [7]
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