Low-temperature brewing using yeast immobilized on dried figs.
Dried figs, following exhaustive extraction of their residual sugars with water, were used for immobilization of Saccharomyces cerevisiae AXAZ-1. The immobilized biocatalyst was used in repeated batch fermentations of glucose at 30 degrees C, where significant reduction of the fermentation time was observed, falling from 65 h in the first batch to 7 h after the sixth batch. Repeated fermentations of wort at room and low temperatures resulted in fermentation times that fell from 26 to 20 h and from 27 to 24 days at 18 and 3 degrees C, respectively. Ethanol and beer productivities were high, showing suitability of the biocatalyst for low-temperature brewing. Diacetyl concentrations were low (0.3-0.5 mg/L), and polyphenols were lower than in commercial products and decreased as the fermentation temperature was decreased (126-50 mg/L). Ethyl acetate concentrations increased from 53 to 88 mg/L as the temperature was decreased, while the concentration of amyl alcohols at 3 degrees C (58 mg/L) was lower than half of that at 18 degrees C (125 mg/L). The beers produced at the end of the main fermentation had a fine clarity and a special fruity figlike aroma and taste, distinct from commercial products and more intense than beers produced by cells immobilized on other food-grade supports (gluten pellets or delignified cellulosic materials). GC-MS analysis did not show significant differences in the qualitative composition of the aroma compounds of the beers produced by immobilized and free cells.
Bekatorou
A
A
Food Biotechnology Group, Department of Chemistry, University of Patras, GR-26500 Patras, Greece. abecatorou@in.gr
Sarellas
A
A
Ternan
N G
NG
Mallouchos
A
A
Komaitis
M
M
Koutinas
A A
AA
Kanellaki
M
M
D000433:1-Propanol / Q000032:analysis; D001515:Beer / Q000032:analysis; D000440:Butanols / Q000032:analysis; D018914:Cells, Immobilized; D000431:Ethanol / Q000032:analysis; D005285:Fermentation; D030681:Ficus; D005638:Fruit; D008401:Gas Chromatography-Mass Spectrometry; D005947:Glucose / Q000378:metabolism; D008854:Microscopy, Electron; D009812:Odorants / Q000032:analysis; D000439:Pentanols / Q000032:analysis; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D013696:Temperature; D014835:Volatilization
D000440:Butanols; D000439:Pentanols; D000431:Ethanol; C040507:isobutyl alcohol; D000433:1-Propanol; D005947:Glucose