Effects of fermentation temperature on the composition of beer volatile compounds, organoleptic quality and spent yeast density

Abstract

Production of good quality beer is dependent largely on the fermentation temperature and yeast strains employed during the brewing process, among others. In this study, effects of fermentation temperatures and yeast strain type on beer quality and spent yeast density produced after wort fermentation by two commercial yeast strains were investigated. Beer samples were assessed for colour, clarity and foam head stability using standard methods, whilst the compositions and concentration of Beer Volatile Compounds (BVCs) produced were assessed using GC-MS. The spent yeast density, measured as dry cell weight, ranged between 1.84 -3.157 mg/ml for both yeast strains with the highest yield obtained at room temperature fermentation. A peak viable population of 2.56 x 10 7 cfu/ml was obtained for strain A, also during fermentation at room temperature. The foam head of the beers produced at 22.5ºC was most stable, with foam head ratings of 2.66 and 2.50 for yeast strain A and B, respectively. However, there was no significant (p = 0.242) difference in colour intensity between the beers produced at the different fermentation temperatures. Eight different BVCs were detected in all beer samples and were found to affect the organoleptic properties of the beer produced. Further optimizations are required to determine the effects of other parameters on beer quality.

Monitoring Volatile Substances in Beer in Relation to Beer Production Technology

“…The ethyl acetate content exceeds the sensory sensation threshold to only a moderate extent. Since any higher concentration of ethyl acetate is undesirable in beer, the results are in agreement with quality requirements for the beverage [22]- [24].…”

“…The decrease in the content of volatiles in the beer as part of fermentation is not caused by reduced formation. Rather, displacing by carbon dioxide is the reason for the reducing level [20], [22]. With the beer becoming saturated after three weeks, the extent of the loss is not so considerable and the level of volatiles gradually increases (see Fig.…”

The effect of temperature on fermentation and beer volatiles at an industrial scale

“…Olaniran et al . also examined the effect of the different fermentation temperatures on the viability of the yeast population. In their study, the least viable population was observed at a fermentation temperature of 30°C compared with the much lower temperature of 18°C.…”

Application of Plackett-Burman experimental design for investigating the effect of wort amino acids on flavour-active compounds production during lager yeast fermentation

“…Numerous fermentation parameters affect the synthesis of higher alcohols and esters during lager yeast brewing, such as wort gravity, wort composition, temperature, pressure, oxygen and pitching rate (16)(17)(18)(19)(20)(21)(22)(23). A factor of significant importance for flavour production of beer is wort composition.…”