Beer Molecules and Its Sensory and Biological Properties: A Review

Abstract

The production and consumption of beer plays a significant role in the social, political, and economic activities of many societies. During brewing fermentation step, many volatile and phenolic compounds are produced. They bring several organoleptic characteristics to beer and also provide an identity for regional producers. In this review, the beer compounds synthesis, and their role in the chemical and sensory properties of craft beers, and potential health benefits are described. This review also describes the importance of fermentation for the brewing process, since alcohol and many volatile esters are produced and metabolized in this step, thus requiring strict control. Phenolic compounds are also present in beer and are important for human health since it was proved that many of them have antitumor and antioxidant activities, which provides valuable data for moderate dietary beer inclusion studies.

Keywords: alcoholic fermentation; beer; beer adjunct; phenolic compounds; volatile esters.

Figure 1

Ester synthesis pathway: During yeast metabolism, fermentable sugars and lipids are converted into acetyl-CoA and nitrogen metabolism induces the formation of fusel alcohols. These compounds are further used to produce ester molecules by the catalytic activity of the enzyme ester synthase. The picture was adapted from Verstrepen et al. (b) [39].

Figure 2

Higher alcohol formation pathways: In both pathways, from glucose and aminoacid, α-keto acids are formed, and further decarboxylated to produce aldehydes, and finally dehydrogenated to produce the corresponding primary alcohol. In the Ehrlich pathway or the aminoacids pathway, the aminoacids are converted to α-keto acids by a transaminase enzyme. The figure was adapted from Kobayashi et al. [9].

Figure 3

Diacetyl metabolism pathway: Yeast cells in the fermenting wort internalize the soluble sugars and activate the glycolytic pathway. Pyruvate is converted into α-acetolactate that is expelled from the cell and converted to diacetyl, which can remain in the final beer or be reabsorbed and converted into the non-flavour 2,3-butanediol. This figure was adapted from Kobayashi et al. (2005) [76].