Studies On Organic Acids In Beer

Organic acids in beer are one of important flavor substances, which have their characteristic sourness, and key factors which influence on beer pH, beer buffering capacity and total acidity. Optimal amount of organic acids can bring beer harmonious mouth-feel, but if the content of some organic acid is higher, it could cause sharp 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 relationship between organic acids and beer mouth-feel was studied at first. Then main factors which play vital role on the concentrations of organic acids in fermentation process were studied. A backd-propogation artificial neural netwok (BP-ANN) model based on the concentrations of organic acids and buffering capacity of different type of beers was constructed to evaluate and predict the quality of mouth-feel of beer. The main conclusions were as following:1. The major components of organic acids in beer were determined through three points of view, that is the flavor intensity Fu value, addition of certain organic acids in model beer and in commercial beer. Results showed that organic acids play a vital role on the sour taste of beer and succinic, lactic, citric, malic, acetic, pyruvic, decanoic, octanoic and hexanoic acids are the major organic acids to the mouth-feel of beer.2. The effect of components of wort, pH value, buffering capacity, yeast, yeast viability and technique of fermentation process were studied. Results showed that the components of wort play a relatively important role on the final organic acids component in the final beer. The viability of yeast used also make an obvious influence on the final component of organic acids in beer. If the viability used in fermentation is poor, it will definitely affect the aroma and flavor to the beer. Especially the acetic and middle-chain fatty acid will bring beer an unpleasant taste. 3L and 2000L practical level experiment were done in the lab and beer factory separately.3. Back-propagation model which is one of the typical Artificial Neural Network was applied to establish the evaluation system of mouth-feel of beer on the basis of organic acids and buffering capacity. The results of evaluation were consistent with the sensory evaluation with accuracy above 80 %.