title: Thermal resistance of Saccharomyces yeast ascospores in beers.
abstract: The industrial production of beer ends with a process of thermal pasteurization. Saccharomyces cerevisiae and Saccharomyces pastorianus are yeasts used to produce top and bottom fermenting beers, respectively. In this research, first the sporulation rate of 12 Saccharomyces strains was studied. Then, the thermal resistance of ascospores of three S. cerevisiae strains (DSMZ 1848, DSMZ 70487, Ethanol Red(®)) and one strain of S. pastorianus (ATCC 9080) was determined in 4% (v/v) ethanol lager beer. D60 °C-values of 11.2, 7.5, 4.6, and 6.0 min and z-values of 11.7, 14.3, 12.4, and 12.7 °C were determined for DSMZ 1848, DSMZ 70487, ATCC 9080, and Ethanol Red(®), respectively. Lastly, experiments with 0 and 7% (v/v) beers were carried out to investigate the effect of ethanol content on the thermal resistance of S. cerevisiae (DSMZ 1848). D55 °C-values of 34.2 and 15.3 min were obtained for 0 and 7% beers, respectively, indicating lower thermal resistance in the more alcoholic beer. These results demonstrate similar spore thermal resistance for different Saccharomyces strains and will assist in the design of appropriate thermal pasteurization conditions for preserving beers with different alcohol contents.
authors.affiliation: Department of Chemical and Materials and Engineering, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand.
authors.forename: Elham A
authors.initials: EA
authors.lastname: Milani
authors.affiliation: School of Biological Sciences, University of Auckland, New Zealand.
authors.forename: Richard C
authors.initials: RC
authors.lastname: Gardner
authors.affiliation: Department of Chemical and Materials and Engineering, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand. Electronic address: filipa.silva@auckland.ac.nz.
authors.forename: Filipa V M
authors.initials: FV
authors.lastname: Silva
mesh_terms: D001515:Beer / Q000382:microbiology*; D005285:Fermentation; D005516:Food Microbiology; D012440:Saccharomyces / Q000502:physiology*; D013172:Spores, Fungal / Q000502:physiology*; D013696:Temperature
keywords: Ethanol; Heat resistance; Pasteurization; Sporulation method; Sporulation rate; Strain