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Reproducibility Trials in a Research Brewery and Effects on the Evaluation of Hop Substances in Beer - Part 2: Reproducibility in Moderately Aged Beers
A. Gahr, A. Forster and F. Van Opstaele

The good reproducibility of the 2 hl research brewery as proven in our previous study has been now reviewed after storing the beers at 0 ?C and deep frozen (at ? 24 ?C) for 240 days. Except for some Strecker aldehydes all other ageing aldehydes, fermentation by-products and particularly the analyzed hop aroma compounds show good stability at 0 ?C. The analytical standard deviations of the three-fold determinations are even a little lower than those of the fresh beers. Also the spread (standard deviations) of the results of the repeated brews did not increase. Opposite to that some hop aroma characteristics of the deep frozen dry hopped beers differed significantly from the ones of the fresh beers. On the basis of these findings this kind of sample preservation for considerably hopped beers cannot be recommended.

Descriptors: reproducibility of brewing trials, aroma stability, hop aroma substances, fermentation by-products, ageing aldehydes

BrewingScience, 71 (November/December 2018), pp. 110-115