Studies On Beer Foam Collapsing Process And Assessment Methods

Foam property is a distinctive character of beer, which discriminate beer from otheralcohol drinks. Foam quality is assessed by foam formation, appearance, retention, lacing androbustness. Perhaps the most important is foam stability, for it can fairly argued that lacingand other characteristics of foam will not be observed without foam having been formed inthe first place and with an inherent persistence to the head. Foam stability is always describedby its collapse. Currently, our knowledge on foam collapse process is limited and scientistsdisagree with each other on foam collapse mathematic model. This may be the reason whythere exists none standard and unified foam evaluation criterions in the worldwide untill now.Thusly, this paper designed foam observing equipment and researched the details of beerfoam’s collapse process in assistance of corresponding software. Based on static analyses ofdata from this foam-collapse observing, six foam collapse models proposed by other scientistsare tested and compared by significance and prediction accuracy. The best collapse modelwith highest significance and prediction accuracy was determined and used in the followingresearch. The influence of the choice of foaming method on collapse model was alsoresearched. To increase foam-collapse model’s stability and adaptivity, the strategy ofimprovement was executed, that is to substitute the original signal-line model with poly-linemodel. Sigma method, Constant method, Chinese standard method, Gales Foam Analyzer(GFA) method, NIBEM method, Steinfurth method and Flashing method are seven commonmethods for measuring foam stability. This paper determined these methods’ correspondingfoam collapse models, and also analyzed the degree of correlation between the seven methodsby foam assessment of21brands of beer. At the same time, the relationship betweencomposition and foam stability of these21beer samples was also studies. In the end of thispaper, based on the established foam collapse theory, a novel foam assessment method wasproposed and its applicability was confirmed by correlation analysis with current commonfoam assessment methods. The following are some discoveries and conclusions involved inthis research: (1) Model lnV=a+bt was confirmed as the best fitting model of all the six foam collapsemodels by all kinds of statistic test methods (t-test, F-test, correlation coefficient test andX2-test).(2) Foam collapse model’s prediction accuracy and adaptivity was improved by substitutingthe original single line model with poly-line model. Separate part of the poly-line model stillfollowed the equation of lnV=a+bt.(3) In the improved poly-line model, the number of segments of foam collapsing curve wasdetermined by the choice of foaming method. Foam generated from pouring and gassingpreferred collapse model with two segments, while foam generated by orifice apparatus fitsingal-line collapse model.(4) Degree of correlation between current existing common foam assessment methods is aslow as57.14%. Analysis of the eight methods, including the newly established method,revealed that reliability of appreciation results of one foam assessment method might begreatly influenced by its observing period, foaming method and pre-assumed foam-collapsemodel.(5) results from relationships between composition and foam stability of beer samples furtherconfirmed that proteins (MW>5,000) were decisive foam promoters in beer...