Study On The Relationship Of Surface Tension And Foam Stability Of Beer

This paper mainly studies on the surface tension and foam stability of beer, Themethod for measuring the foam stability of the processes of beer and its products,method for determination of beer surface tension, the relationship between surfacetension and foam stability, The factors of surface tension, and which is applied toprotein hydrolysis process of beer saccharification and monitoring fermentationbroth were systematic studied. Ultimately its aim can predict foam stability by thesurface tension.The conclusions showed:1. The determation of foam stability by the method of NIBEM, modified Rudin,stopwatch, the results of stopwatch method had so large error, and was affectedgreatly by human factors. the results of NIBEM was good repeatability,however, it isstrongly influenced by the CO₂, those methods were suitable for the determinationof brewery products in factories,and measurement instruments were very expensive,the results of modified Rudin not only did have good reproducibility,but alsoeliminated the gas interference,which was suitable for laboratory operations andcost-effective method.2. Conditions of a modified Rudin method to measure the foam stability wereoptimized. The optimal conditions were: CO₂flow340mL/min, temperature ofsample pretreatment20℃, gas outlet pressure of total valve0.3MPa.Under optimalconditions, and their relative error was0.49%.3. Through comparing four kinds of methods used to determine the surfacetension of beer, the result of contact angle system OCA had a high accuracy andreproducibility.Therefore this method was choosed for the determination of surfacetension.4. Surface tension and foam stability of7beers which were selected at randomwere measured.The result follows: the better foam stability, the lower surfacetension.we found the regularity of draft beers and canned beers on present market:weak foam stability and increasing decline with shelf life, meanwhile its surfacetension increased.5. The factors of surface tension were studued, the result follows: Zinc sulfate,bovine serum albumin worked as the positive effect on foam stability and negative effect on surface tension; linoleic acid had a negative effect on foam stability, andpositive effect on surface tension; the effect of Calcium chloride, glutathione,anhydrous ethanol on foam stability was not significant, and had no correlation withsurface tension.6. Protein contents in the wort, meanwhile in the fermentation broth, had astrong negative correlation with the surface tension.the lower surface tension of thewort and fermentation broth, the higher protein contents in them.