The impact of isomerised hop extract on the heat resistance of yeast ascospores and Lactobacillus brevis in premium and alcohol‐free lager.

The effect of isomerised hop extract on the heat resistance of Saccharomyces cerevisiae BRYC 501 ascospores and Lactobacillus brevis BSO 566 was investigated. Heat resistance of yeast ascospores and L. brevis was determined in premium lager (4.5% ABV) and alcohol‐free lager (0% ABV) at their initial bitterness and after adjustment with isomerised hop extract to 25 and 50 IBU. Results showed that D60 of yeast ascospores in alcohol‐free lager was reduced by >30% at 25 IBU and >50% at 50 IBU compared to lager with no added hop extract. In premium lager, D60 was reduced by >10% at 25 IBU and >30% at 50 IBU. The addition of isomerised hop extract also had a significant impact on the z‐values, which increased with higher concentrations of isomerised hop acids in both premium and alcohol‐free lager. Slightly higher z‐values were observed in premium lager (z = 4.0, 4.5 and 5.0°C for IBU = 6.3, 25 and 50 respectively) than in alcohol‐free lager (z = 3.6, 4.0 and 4.2°C for IBU = 8.6, 25 and 50). The addition of isomerised hop extract also reduced the heat resistance of Lactobacillus brevis BSO 566. The findings in this study suggest that less bitter (low IBU) lagers should be pasteurised with higher pasteurisation units (PUs) than more bitter lagers (high IBU) which can be pasteurised at lower PUs. © 2022 The Institute of Brewing & Distilling [ABSTRACT FROM AUTHOR]