Low-temperature brewing by freeze-dried immobilized cells on gluten pellets.
A biocatalyst, prepared by the immobilization of a cryotolerant strain of Saccharomyces cerevisiae on gluten pellets, was freeze-dried without any protecting medium and used for repeated batch fermentations of wort for each of the temperatures 15, 10, 5, and 0 degrees C. The fermentation time for freeze-dried immobilized cells was about 2-fold that of the corresponding time for wet immobilized cells on gluten pellets, and lower than the corresponding time for freeze-dried free cells, especially at 5 and 0 degrees C. Beers produced by freeze-dried immobilized cells contained alcohol levels in the range of 5.0-5.5% v/v, diacetyl concentrations lower than 0.5 mg/L, polyphenol concentrations lower than 145.5 mg/L, and free cell concentrations lower than 3 g/L. As a result, they had a very good clarity after the end of primary fermentation. The amounts of amyl alcohols were lower than 129.1 mg/L and reduced as the temperature was decreased. Ethyl acetate concentrations were found in the range of 22.1-29.2 mg/L, giving a very good aroma and taste in the produced beers.
Bekatorou
A
A
Food Biotechnology Group, Department of Chemistry, University of Patras, GR-26500 Patras Greece.
Koutinas
A A
AA
Psarianos
K
K
Kanellaki
M
M
D000438:Alcohols / Q000032:analysis; D001515:Beer / Q000032:analysis; D002384:Catalysis; D005285:Fermentation; D005524:Food Technology; D005612:Freeze Drying; D005983:Glutens; D011786:Quality Control; D012441:Saccharomyces cerevisiae; D013649:Taste; D013696:Temperature; D014835:Volatilization
D000438:Alcohols; D005983:Glutens