Studies Of Factors Affecting Organic Acids In Beer

Organic acids in beer are one of important flavour substances, which have their characteristic sourness, and key factors which influence on beer pH, beer buffering capacity and total acidity. Beer buffering capacity means that beer has intrinsic ability to control variation of itself pH during range of beer pH. It has correlation with beer quality stability at some extent. Optimal amount of organic acids can bring beer harmonious mouth-feel, but if the content of some organic acid is higher, it could cause choase or obvious sourness taste. So it is necessary to decide the major components of organic acids which significantly influence on beer mouth-feel and set up an evaluation system according to the organic acids in beer.In this paper, the metabolism on organic acids in beer was studied at first. Then the effect of factors on beer buffering capacity and beer pH was researched, and using international widely applied Statistical Analysis System, the major components of organic acids which influenced on beer buffering capacity and beer pH were determinded. The influence factors of organic acids in brewing was also studied. The main conclusions were as follows:1.With the organic acids'fermentation process, its content is the linear increase. Part of organic acids has the genetic pathway and physiological mechanisms. As an important part of organic acids, controlling acetic acid metabolism to a large extent determine the content of the organic acids; Different types of organic acid content of the reasons for the difference is very complicated, not only with brewer's yeast in a different physiological stage of the accumulation of organic acids, but also with the metabolic pathways related enzymes, metabolic networks, With the fermentation of organic acids transmembrane transport and advanced stage of decomposition of the organic acids.2.In accordance with the role of organic acids in yeast metabolism, the effect of organic acids on beer buffering capacity and beer pH and the major components of organic acids in beer were determinded, and they were composed of lactic acid, citric acid, fumaric acid, acetic acid and succinic acid.3.There were three organic acids including lactic acid, citric acid and acetic acid, which influenced on not only beer buffering capacity but also beer pH. Because of the double effect of these organic acids, the conclusion that beer buffering capacity play animportant role in determining beer pH and controling variation of beer pH was confirmed.The important and indicative position oforganic acids in brewing process was established.4.Although the composition of organic acids in beer depended on compose of wort at great extent, the concentration and proportion of organic acids in beer were determinded in fermentation processing. Oringinal wort extract, wort pH, fermentation temperature, yeast strain and pitching rate all had some influence on the formation and control of organic acids in beer.