Diacetyl Production During Brewing and its Management Through Process Optimization and Molecular Evolution of Yeast

Diacetyl is butter-tasting off-flavor compound produced as by-product of yeast valine metabolism during brewery fermentation. Yeasts produce diacetyl during primary fermentation and then reabsorb it in secondary fermentation. This causes a non-productive lengthy maturation period, which is costly. Several strategies have been proposed to manage diacetyl and improve the productivity of brewery industries. This review aimed to assess diacetyl production and proposed strategies to manage diacetyl production during brewing. Diacetyl production and its amount in the green beer are influenced by brewing condition and type of strain used. Green beer conditioning and brewing process optimization are regarded as simple and feasible approaches. However, these have their own inherent drawbacks. On the other hand, a plethora of researches declared that genetic manipulation of yeasts is an effective strategy in reducing diacetyl amount and ultimately to shorten the maturation period and thereby maximize profitability of brewery industries. But the applicability genetic engineering limited, due to firm regulation of utilization of genetically modified organisms in food processing industries. Therefore, though extensive research was done on identifying and understanding factors which influence yeast diacetyl formation and reduction, diacetyl management is persisting as a challenge in brewing systems.