Studies On Hydrophobic Protein In Beer Foam And Strain With Low Proteinase A Activity

Beer foam-positive protein mainly deriving from malt, have the greaterhydrophobic character. These proteins interact principally with hops to stabilize beerfoam. Study found that several proteins have a very strong correlation with beerfoam. Decrease in beer foam stability due to proteinase A activity has been reportedby several research groups. Proteinase A from brewers’ yeast may digest wortproteins responsible for the beer foam stability, leaving peptides with reduced or nofoaming properties and, hence, leading to a final product with poor foam stability.Studys demonstrated that different proteins in beer possess differenthydrophobicity and surface-viscometric activity and that hydrophobic proteins playan important role in foam stability. This article gives a rather systematic research onhow to optimize the extracting procedures concerning hydrophobic proteins in beer,as well as to study the method of isolation and sepeperation of the hydrophobicprotein in beer foam by hydrophobic interaction chromatography(HIC). It is shownthat the greater is the surface hydrophobicicty, the stronger is the foam stability. Sothe most stable foams are given by polypeptides of greates hydrophobic characterwhereas hydrophobic polypeptides give much less stable foams. Besides thehydrophobic proteins from isolating and sepeperating have been identified as proteinZ4by Mass Spectrometry. And a significant relationship between the foam stabilityand the hydrophobic protein content in beer.A large number of results show that low-yielding strains of yeast proteinase Aconducive to the stability of beer foam. And as a basis, through selecting oflow-producting proteinase A strains, after a series of screening, the final selectionout of0002only to filter out the low-producting protease A mutant strain of yeast.Through the small scale tests found that the low-producting protease A strains canreduce the expected producting of protein A to improve beer foam stability. And thequality, flavor and taste of the finished wine is not affected. The results canfundamentally solve the effect on the beer foam stability of protease A. Theselecting of low-producting proteinase A strain to determine the hydrophobic protein in beer foam in order to build the relationship between low-producting protease Ayeast protein and the hydrophobic interaction.In addition, this paper also followed the key process control points of thebrewing process, to analyze the hydrophobic protein content in the process of beerbrewing. we found that the content of hydrophobic which the loss rate of8.5%fromoriginal wort to the boiled have significantly decreased by tracking the criticalprocess control point of beer brewing process. The process of boiled wort to pot fullhave smoothly changed. The process that the content of hydrophobic proteins whichthe loss rate of40.6%from the full tank to for wine storage period has significantdeclined. Therefore, we think the biggest loss of hydrophobic proteins in thefermentation process. So this conclusion has a good prospects for industrialapplications.