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Microbiology of unfiltered beers from craft breweries and the possibility of shelf life extending
Janíková, Jolana ; Rada, Vojtěch (advisor) ; Chládek, Ladislav (referee)
In the last ten years can be recorded a multiple number of minibreweries, called sometimes craft breweries I tis not caused only by demand of kinds of beer characterised by special types of beer styles, but as well by the fact, that they are not anyway regulated
and keep their natural taste and smell. The problém of unregulated (unfiltered
and unpasteurized) beers starts by the contamination during their production and it may cause their relatively fast spoiling. Shelf life of these beers is e few weeks only. The time of their minimal shelf life is influenced by a lot of factors content of alcohol, rest extract
and mentioned extent of contamination. The breweries called as industrial or commercional treat their beers by pasteurization or filtration which cause inactivation or killing of the microorganisms or their elimination. These beers are microbiologically stabile, they are not liable to quick spiling and i tis possible to insure their longer shelf life. Pasteurized a filterd beers show changes in their sensorial character.
The aim of this diploma thesis was to determinate the condition of flash pasteurization of unfiltered beers with the aim of microbiological stability and simultaneously no changes
of their sensorial quality. The experiment is finally in treatment unfiltered beer by differnt dosing of pasteurization units and following microbiological analysis, able to demonstrate
the stability effect. The analysis were used with unfiltered and unpasteurized beers
and with unfiltered beers where the pasteurization doses 20 PU, 30 PU, 40 PU, 60 PU, 80 PU and 100 PU were used. The idividual parameters were watched within the horizont
of 4 months. The part of these tests was even microbiological analysis of the rinse water.
Another task was to find out the dates from the microbiological controls of beer
in selected small breweries, which use in order to heighten of microbiological stability, different kinds of filtration, to verify their effectivity and to appreciate their acceptability
for minibreweries.
The test showed the effectiveness of pasteurization of unfiltered beer with the rations 40 PU minimally. Where higher ratins were used could be seen apparent sensorial changes. The pasteurization of unfiltered beers are for craft breweries useful only in case of higher production of bottled beer or beer for export, because the financial expenses bound
with provision flash pasteurizer are to big and for minibreweries mostly limiting.
The kieselguhr filtration as well the ultrafiltration are for minibreweries unusefull, as they could not be able to insure such conditions that provide their proper affectiveness.
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