The Glycation Happened To Beer Foam Proteins And Its Influence On Foaming Properties

Beer foam is one of the most important characteristics of beer and foam stability is the most important indicator of beer foam.Elegant and stable foam can give consumers a good drinking experience.Beer foam protein is the skeleton composition of beer foam,which plays an important factor in maintaining the stability of beer foam.Recent studies found that the Maillard Reaction in beer brewing can bring effect on the structure of beer foam proteins,which is an important reason for the impact of beer foam.However,there is few research on the conjugation of proteins and carbohydrates in beer,so,it is important to explore the effect of the Maillard Reaction on the structure and functional properties of the proteins.It can be able to study beer foams from a new perspective.In this paper,the effects of various components on the stability of beer foam were investigated by correlation analysis and partial correlation analysis.The effects of different components on the stability of beer foam were studied.Then,malt thermostable protein isolate(MPI)and maltose were used as reactants to study the structure and functional properties changes caused by the conjugation with maltose.The main conclusions are as following:(1)The beer foam and residue liquid were separated and collected.Then the protein,total saccharide,total polyphenol contents and beer foam retention were detected.Proteins were enriched in beer foam and the protein concentration in beer foam was 27 ~ 74 ?g?mL-1 higher than that in the beer residue.It was proved that the protein was the skeleton component of the beer foam.The correlation and partial correlation of beer foam stability and components were analyzed.It was found that protein content had a strong positive correlation with beer foam stability(R = 0.875,P <0.01).Total saccharides also had a strong positive correlation with beer foam stability(R=0.594,P<0.05).But the partial correlation analysis showed that the total saccharides content was almost directly related to the foam retention,which indicated that the saccharides can help to improve foam stability with proteins.(2)The Maillard Reaction of malt water soluble thermostable protein(MPI)with glucose,fructose,maltose,maltotriose and xylan during mashing process was studied.It was found that the higher the molecular weight of the saccharide was,the harder the saccharide can conjugate with MPI.Maltose was chosen to mimic the mashing process with MPI and the physicochemical properties of MPI-maltose conjugation(MMC)was detected.At the end of the reaction,the surface hydrophobicity was reduced by 7.6%,surface tension was 3.33 mN?m-1 decreased and the solubility increased by 8%.These changes had positive effects on proteins foaming properties.However,the zeta-potential was decreased by 9.3 mV,which had a negative influence on proteins foaming properties.(3)The molecular weight(MW)and structure changes of MMC was analyzed.The results showed that there is a slight increase on the MW of MMC,but the secondary structure of MMC was almost the same as MPI.The scanning electron micrographs(SEM)showed that the protein aggregates were smaller and more homogeneous and dispersed.This change was conducive to the dissolution and water holding capacity of proteins,which is helpful for the improvement of foam stability.(4)The foaming properties of MPI and MMC were verified.The results showed that the foaming capability and stability of MMC increased by 11.7% and 7.5%,respectively.The fermentation mimic experiments verified that the foaming stability of broth with MMC was 29% higher than that with MPI.