Effects Of Adding Wheat Or Wheat Malt On Wort And Wheat Beer

Beer is the most important low alcohol beverage in the world and its yield is the highest among all alcohol beverages. In China, it is the youngest and the fastest growing brewing industry. Wheat and wheat malt are good raw materials for beer. They are cheaper, and some properties of them are better than barley malt. They contain less purine than barley malt, and thereby can reduce purine content of beer. Application of wheat and wheat malt in beer brewing can promote rapid, healthy and stable development of China's beer industry. In this research, the influences of the addition amount of wheat or wheat malt, protein rest time, and protease dosage in the saccharification process on wort properties were studied based on the determination of reducing sugar, total sugar, total acid, pH value,α-AN, arabinoxylan,β-glucan, viscosity, chroma, turbidity, protein components and purine contents. The influence of adding amount of wheat and wheat malt on worts composition was also comparatively studied. Meanwhile, changes of wheat beer during the storage were tracked by analyzing reducing sugar, total sugar, total acid, pH value,α-AN, arabinoxylan,β-glucan, viscosity and purine contents. The main results were as follows:1 The influence of saccharification ingredients, protein rest time and protease dosage on wort was researched. (1)When wheat or wheat malt was used as grists in wort, contents ofβ-glucan, adenine, guanine and xanthine decreased, while total nitrogen contents increased. The proportions of high-molecular-weight nitrogen (HMWN) and intermediate-molecular-weight nitrogen (IMWN) increased, however that of low-molecular-weight nitrogen (LMWN) decreased. No matter whether to add wheat or wheat malt, adenine and guanine contents in wort were higher, and hypoxanthine contents were least. Adding wheat or wheat malt instead of barley malt decreased the purine contents in wort. (2)Along with the increase of protein rest time,α-AN contents increased obviously, and adenine, guanine and total purine contents showed ascendant trend,β-glucan contents declined, and araboxylan contents had no significant change. At the same time, the contents of HMWN and IMWN decreased, but LMWN contents increased. Correlation analysis showed that protein rest time had significant positive correlation withα-AN content (r=0.919) and adenine content (r=0.944, P<0.05), and had significant negative correlation withβ-glucan content (r=0.886, P<0.05). (3)Along with the increase of the dosage of the protease, araboxylan contents decreased obviously,β-glucan contents declined, the contents of HMWN and IMWN significantly reduced, LMWN contents increased significantly. Protease had significant positive correlation with reducing sugar contents (r=0.908), pH value (r=0.942) and LMWN content (r=0.908, P<0.05), and had significant negative correlation with acidity (r=-0.878), and the proportion of intermediate-molecular-weight nitrogen (r=-0.938, P<0.05; r=-0.964, P<0.05). And it had significant positive correlation with araboxylan content (r=-0.981,P<0.01). There were no significant correlations between protease dosages and contents of adenine, guanine, hypoxanthine and xanthine.2 The influence of addition amounts of wheat or wheat malt on worts composition was studied comparatively. Along with the increasing of wheat and wheat malt proportions, theβ-glucan contents decreased, and the total sugar, arabinoxylan, total nitrogen contents and viscosity increased. Among them, the increasing trend of araboxylan and total nitrogen contents in the wheat-added worts (WAW) was relatively apparent. The pH value of the WAW and wheat-malt-added worts (WMAW) had little change, and the trend was similar. Theα-AN, total acid contents, chroma and turbidity declined in WAW. However, in WMAW, change trend ofα-AN and total acid contents was not apparent, and chroma and turbidity increased.In the WAW, the HMWN contents significantly increased, the IMWN contents had little change, and the LMWN contents decreased. However, in the WMAW, all the HMWN, IMWN and LMWN contents increased. Both in the worts adding wheat or wheat malt, the proportions of HMWN increased, the proportions of LMWN reduced, and the proportions of IMWN did not change significantly. In the worts adding wheat and wheat wort, total purine contents both gradually declined, and the decline trend in the worts adding wheat was more obvious.The adding amount of wheat had extremely significantly positive correlation with viscosity (r=0.984), the contents and proportions of HMWN in worts (r=0.932, P<0.01; r=0.948, P<0.01), and had significant positive correlation with the arabinoxylan in worts (r=0.806, P<0.05). It also had extremely significant negative correlation withα-AN (r=-0.975), the proportion of low-molecular-weight nitrogen (r=-0.952), adenine (r=-0.982), guanine (r=-0.974), hypoxanthine (r=-0.938), xanthine (r=-0.874) and total purine (r=-0.991) in worts (P<0.01), and had significant negative correlation with total acid andβ-glucan content in worts (r=-0.870, P<0.05).At the same time, the adding amount of wheat malt had extremely significant positive correlation with viscosity (r=0.973), chroma (r=0.943), arabinoxylan contents (r=0.918), total nitrogen contents (r=0.940), the contents and proportions of HMWN (r=0.994; r=0.896) and IMWN contents (r=0.909) in worts (P<0.01), and had significant positive correlation with total sugar content (r=0.854) and turbidity (r=0.848) in worts (P<0.05). It also had extremely significant negative correlation with the proportions of LMWN (r=-0.911), adenine (r=-0.975), guanine (r=-0.985), and total purine content (r=-0.991) in worts (P<0.01), and had significant negative correlation with hypoxanthine contents (r=-0.847) in worts (P<0.05).3 Wheat turbid beer of the same batch was storaged at 0oC, 10oC and 25oC respectively. Along with the increase of storage time at each storage temperature, total sugar, reducing sugar, total acid,β-glucan contents, viscosity declined, while pH value, arabinoxylan, adenine and guanine, hypoxanthine, total purine contents increased, andα-AN and xanthine contents had no obvious change. At 0oC, storage time had extremely significant negative correlation with total sugar (r=-0.804), reducing sugar (r=-0.732) and total acid content (r=-0.644, P<0.01). And storage time had significant positive correlation with adenine(r=0.683) and guanine content (r=0.672, P<0.05). At 10 oC, storage time had extremely significant negative correlation with total acid content (r=-0.826, P<0.01). Storage time had significant negative correlation with viscosity (r=-0.704, P<0.05), and had significant positive correlation with arabinoxylan (r=0.663) and hypoxanthine content (r=0.641, P<0.05). At 25 oC, the storage time had extremely significant negative correlation with total sugar (r=-0.755)and total acid content (r=-0.930, P<0.01). Storage time had extremely significant negative correlation with hypoxanthine content (r=0.887, P<0.01), and had significant positive correlation with adenine content (r=0.673, P<0.05).