Abstract
When fermenting beer, in addition to the formation of basic, secondary, and by-products, which largely determine the taste and aroma of the beverage, yeast is accumulated. Such yeasts can be reused in subsequent serial repitching, which allows cost savings compared to yeast cultivated for each fermentation. This paper investigates the influence of yeast generation on the progress of the wort fermentation process and the quality of beer obtained, specifically in high gravity brewing. It was established that the increase in the number of yeast generation in the range from the first to the fourth generation causes a slight acceleration of the fermentation process of high-gravity wort, while at higher values of the fermentation generation number it slows down. Yeasts secreted after six or four serial wort fermentations with a gravity of 15 °P/18 °P, respectively, have a good physiological state and can be reused. The yeast generation number does not significantly affect ethanol content and sensory beer quality indicators. However, the use of yeast of the seventh and eighth generation causes a slight increase in the pH and color of high gravity beer, the appearance in the aroma of noticeable extraneous shades ‒ yeast tone, tone of young beer. As wort gravity increases, the number of yeast re-use cycles decreases, which is a consequence of the influence of various stress factors, specifically high osmotic pressure, and increased ethanol levels. Therefore, for the fermentation of wort with a gravity of 15 °P, it is recommended to use yeast up to five generations, for 18 °P wort ‒ to four generations. To obtain beer with appropriate physicochemical parameters and high sensory evaluation in high gravity brewing technology, it is advisable to ferment wort with a gravity of 15 °P with yeast for up to five generations.
Highlights
Literature review and problem statementA key criterion that plays an increasing role in the brewing market is the quality of beer
This paper investigates the influence of yeast generation on the progress of the wort fermentation process and the quality of beer obtained, in high gravity brewing
This study identified the recommended number of yeast generations of the Saflaqer W-34/70 race for the fermentation of wort with a gravity of 11‒18 °P at a temperature of 12‒15 °C
Summary
A key criterion that plays an increasing role in the brewing market is the quality of beer. There may be a decrease in the fermentation rate and incomplete fermentation in wort with a gravity of more than 18 °P Such fermentations lead to high residual sugars, mainly maltotriose and maltose, a decrease in the amount of ethanol formed, and changes in the taste and aromatic profile of the beer. A noticeable (39 %) slowdown in fermentation was detected after repitching the yeast of the third generation of all studied groups in 12 °P wort This means that the increase in the duration of fermentation is more due to the serial use of yeast than to the gravity of the wort. This, among other things, is due to particular research under different conditions In this regard, studying the effect of the reuse of yeast in high gravity brewing (at elevated values of wort gravity and process temperature) is relevant and of practical importance
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