title: Low-temperature brewing by freeze-dried immobilized cells.
abstract: We propose a novel biocatalyst in brewing. A cryotolerant strain of Saccharomyces cerevisiae was immobilized on delignified cellulosic material followed by freeze-drying of the immobilized cells without the use of any cryoprotectant. The freeze-dried immobilized biocatalyst was used in repeated-batch fermentation of wort and showed reduced fermentation time and increased productivities as compared with free freeze-dried cells (FFDCs). It also demonstrated suitability for low-temperature brewing (5 and 0 degrees C). The fermentation time in repeated-batch fermentations at 15 degrees C was 1.5-2 d for a period of 13 mo, showing a high operational stability of the system. At 0 degrees C the freeze-dried immobilized biocatalyst showed a 2- to 3.5-fold decrease in fermentation time in comparison with FFDCs. Polyphenol contents, bitterness, and diacetyl concentration were lower in beers produced by freeze-dried immobilized cells as compared with FFDCs. At 0 degrees C polyphenols were 40% lower than at 15 degrees C. Higher alcohols were reduced and ethyl acetate increased in comparison with FFDCs. Amyl alcohols at 0 degrees C were lower than half of their content at 15 degrees C, while ethyl acetate was 31 mg/L at 0 degrees C and 18 mg/L at 15 degrees C. These data justify the improved aroma and taste of beers produced by freeze-dried immobilized biocatalyst mainly at low temperatures.
authors: Department of Chemistry, University of Patras, Greece.
authors: Argyro
authors: A
authors: Bekatorou
authors: Magda J
authors: MJ
authors: Soupioni
authors: Athanasios A
authors: AA
authors: Koutinas
authors: Maria E
authors: ME
authors: Kanellaki
mesh_terms: D001515:Beer; D001709:Biotechnology / Q000379:methods*; D002384:Catalysis; D002851:Chromatography, High Pressure Liquid; D005285:Fermentation; D005612:Freeze Drying; D007700:Kinetics; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D013696:Temperature; D013997:Time Factors