The Effect Of Beer Adjunct On Beer Foam

Beer foam is an important characteristic of beer quality,Evaluation of beer foam is generally from the foam appearance,lacing index,foam ability,foam stability,in which beer foam stability is the most common and the most important index to evaluate beer foam,while other indicators are difficult to quantify with data.Beer foam stability(also known as beer foam retention)is generally expressed by the beer foam stability value.In the beer industry,in addition to the use of malt,often add a certain proportion of beer adjunct including rice,wheat,corn starch,syrup and so on.The difference of protein content in beer adjunct leads to the difference of total protein content in beer.Protein,as an important component of beer,constitutes the skeleton structure of beer foam,which is of great significance to maintain the stability of beer foam.In addition to the change of protein content,the beer adjunct addition can also affect the physicochemical properties(surface hydrophobicity,surface tension,Zeta potential,etc.)of beer protein.In this paper,the content of various components(protein,total saccharide,polyphenol,alcohol)in beer with different adjuvants was detected,and the effects of different components on beer foam stability were explored by correlation analysis,and the effects of different adjunct addition on the physical and chemical properties of beer protein and its protein foaming properties were also explored.The main conclusions are as follows:(1)At present,the common methods to measure beer foam stability are mainly aimed at finished beer,and there is a lack of methods to measure foam stability of beer fermentation broth in laboratory.A simple and rapid method(ultrasonic vibration method)for the determination of beer foam stability was established in our laboratory,then this method was improved,and the average relative standard deviation(RSD)value of the measured samples decreased from 6.65% to 2.33%,less than national standard(5%).The accuracy of the improved method was better.Improved ultrasonic vibration method can be used to measure foam stability of beer fermentation broth.(2)Do fermentation experiments by adding different beer adjunct,then the content of protein,total saccharide,total polyphenol,alcohol and beer foam stability were detected.The correlation of beer foam stability and components in beer were analyzed.The results showed that the protein content was the most important factor affecting the beer foam stability.It was found that corn starch content increased from 10% to 30%,beer foam stability gradually reduced,and with the wheat materials content increased from 10% to 30%,beer foam stability increases.However,with the increase of the proportion of rice auxiliary materials,beer foam stability decreased firstly and then increased.When the rice addition was increased to about 30%,the rice beer foam stability increased to the same level as whole malt beer.(3)It was found that protein foaming stability and beer foam stability has a high positive correlation(r=0.636,p<0.05),protein foaming ability and beer foam stability has a low positive correlation.(4)Beer adjunct addition will affect the physicochemical properties of beer protein(surface hydrophobicity,surface tension,zeta potential,etc.),protein surface hydrophobicity and protein foam stability showed a negative and the highest correlation(r=-0.737,p<0.05).As the addition of rice and wheat increased to 30%,the surface hydrophobicity of beer protein decreased by 12.4% and 33.9% respectively.It is proved by reverse addition experiments that protein with lower surface hydrophobicity from rice and wheat is beneficial to the beer foam stability.