Evaluation of Fermentation Parameters During High-Gravity Beer Production

Abstract

A large number of advantages are obtained from the use of highly concentrated worts during the production of beer in a process referred to as "high-gravity". However, problems related to slow or stuck fermentations, which cause the lower productivity and possibility of contamination, are encountered. This study examines the influence of factors pH, percentage of corn syrup, initial wort concentration and fermentation temperature on the fermentation parameters, namely productivity, wort attenuation and the yield coefficient for sugar-to-ethanol conversion. The results show that productivity increased when the higher temperature, the higher wort concentration and the lower syrup percentage were used, while wort attenuation increased when lower wort concentration and no syrup were used. The yield coefficient for sugar-to-ethanol conversion was not influenced by any of the factors studied

Yeast responses to stresses associated with industrial brewery handling: Figure 1

“…Higher temperatures during high-gravity fermentations typically result in reduced viability, reduced cellular glycogen levels, reduced alcohol dehydrogenase activity and an increase in the incidence of petite mutation (Nagodawithana & Steinkraus, 1976;Casey et al, 1984;Stewart, 2001). from 10 to 15 1C (Dragone et al, 2003), at higher temperatures wort attenuation, fermentation rates and alcohol productivity are reduced (Casey et al, 1984;Almeida et al, 2001;Stewart, 2001). Rapid fermentations of 25 1C Brix honey solutions resulted in a logarithmic loss of yeast cell viability at 30 1C; the same fermentations at 15 1C caused no loss in viability (Nagodawithana & Steinkraus, 1976).…”

Amino Acids in Beer

“…A similar correlation was found between the wort amino acid content and the formation of higher alcohols, ester and carbonyl compounds in the resulting beer by Äyräpää (1971) . The compounds responsible are mainly butane-2,3-dione (diacetyl) and pentane-2,3dione, by-products of valine, leucine and isoleucine amino acids ( Almeida et al , 2004 ). The effect of the fermentation temperature on the yeast causes different use of single amino acids with different aromatic profi les in beer.…”

Dried Spent Yeast and Its Hydrolysate as Nitrogen Supplements for Single Batch and Repeated-Batch Ethanol Fermentation from Sweet Sorghum Juice

“…In addition, the risk of bacterial contamination can be reduced [12]. On the other hand, the drawbacks of this process include increases in osmotic pressure, ethanol stress and nutrient limitation, resulting in decreased yeast viability and slow or stuck fermentations [13].…”