Sasa Despotovic
University of Belgrade, Serbia

MIKROBIOLOGIA
Słowa kluczowe: yeast, production, volatile components, beer

It is well known that fermentation speed, flocculation behavior, the variety of secondary metabolites and aroma profile of beer are highly dependent on the specific strain of yeast used in production process. No less effect has the generation of used yeast. Re-pitching is a common practice in most breweries and depending on brewery it often goes from 4-10 times. In this study, the influence of yeast generation on fermentation process and sensory profile of beer have been investigated. An experiment was conducted in a local brewery. The fermentation process was conducted according to a traditional method for lager beer production. The pitching was performed at 8oC, the fermentation process was carried out at 10oC while maturation process was at 0oC for 25 days. The extensive chemical analyses and sensory evaluation were performed. Impact on fermentation speed was significant and in favor of seventh and ninth generation of yeast. With increasing of yeast generation, fermentation and yeast biomass have increased the quality of fermentation and sensory properties of products were not significantly changed. Amount of volatile components such as acetaldehyde, ethyl acetate, isoamyl acetate, isoamyl alcohol and DMS have been significantly different from 3th and 9th generation, while methyl acetate did not show a significant difference.Furthermore, there was no significant difference in the percentage of dead cells and cells viability. Yeast from ninth generation has significantly speeded up the fermentation process.

Acknowledgement: This work was performed within the framework of the research project 46001and 31020 supported by the Ministry of Education, Science and Technological Development, Republic of Serbia.