The authors would like to state that they inadvertently omitted one of the authors
when preparing the manuscript. The authors of this work are as follows:
Miha Ocvirk1, Nataša Kočar Mlinarič2, Peter ...Raspor3 and Iztok Jože Košir1*
1Slovenian Institute of Hop Research and Brewing, C. Žalskega tabora 2, 3310 Žalec, Slovenia
2Pivovarna Laško Union d.o.o., Pivovarniška ulica 2, 1000 Ljubljana, Slovenia
3Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, 1000 Ljubljana, Slovenia
The production of lager beer includes successive repitchings of a single
starter culture. During the beer production process, the yeast is exposed to several stress factors which could affect the ...fermentation performance. An incomplete fermentation represents a waste of fermentable extract and leads to a beer with higher carbohydrate levels, which could result in a beer with an atypical flavour profile. The aim of the present study is to determine the impact of successive exploitation of a single
starter culture on the wort saccharide uptake dynamics.
The fermentation was monitored during the production of twelve batches of beer, where the starter yeast culture was reused twelve times without any further treatment. The following beer production steps were monitored: wort production, yeast starter culture propagation, primary fermentation, secondary fermentation and the final product. The work was conducted on an industrial scale employing standard process conditions.
Monitoring of the starter culture viability during successive fermentations indicated no reduction in the viability and vitality of the yeast culture. Monitoring of the fermentable wort saccharide concentrations (glucose, fructose, disaccharides and trisaccharides) revealed a correlation between an improvement in saccharide utilisation and starter culture age. Saccharide uptake efficacy proportionally matched the repitching frequency. Successive exploitation of
starter culture has a positive impact on the dynamics of saccharide utilisation from classical hopped wort and the young beer. Furthermore, the final lager beer contains no residues of fermentable saccharides that could affect the overall quality and flavour profile.
Results showed the impact of twelve successive wort fermentations on the dynamics of saccharides uptake that gives brewers important information. The added value of the experiment is all the work done on the industrial scale, with control of all processes and usage of exactly the same raw materials. This study contains usable technological data on the behaviour of saccharides during brewing on the industrial scale, which is not yet found in the literature.
Although beer evaluation runs with sensory experts, we cannot neglect the influence of the human factor and subjectivity. This problem could be solved with chemical analysis of the volatile part of ...beer aroma from which we can build a data bank for construction a model to classify samples comparable to sensory assessment.
22 batches of the same beer brand were assessed for sensory and chemically described with the contents of alcohols and esters (9),hop essential oils compounds (15) by GC and other aroma volatiles (33), analysed by head space SPME-GC/MS. The best matchings of 91 % regarding samples classification on the base of chemical analyses to sensory scores were achieved with a data set of results from HS-SPME and higher alcohols and esters analyses by RDA.
Results shows that deviations in beer aroma are not a consequence of a permanent repeatable error in brewing process and are not influenced by raw materials but are the consequences of the alcoholic fermentation. The sensory analysis could be replaced with chemical/statistical analysis on an appropriate data set and for a distinct beer brand. Good results confirm our approach, however for different beer brands or types, this method should me optimised.
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