Study On The Influence Of Polyphenol On Beer Flavor Stability

The beer flavor staling mechnism and the influence of polyphenol compounds on beer flavor stability was the key point of this thesis. The polyphenol content variation during the whole brewing processing and its influence on the beer flavor stability was investigated, combined with the large-scale beer production. Many factors which can influence the polyphenol content in the wort and beer was researched in the paper, such as the polyphenol compounds content in the raw material (malt, adjunct and hop), the polyphenol content control and protection. The polyphenol content was different in different raw material. The malt variety and quality will influence the the beer polyphenol content. The polyphenol content was the most in hop, it was more than 10 times than in malt, while the its content was little in adjunct such as rice and corn syrup. It was found that there was some positive relationship between total polyphenol content of final beer and beer flavor stability after determining the many domestic beer. It was showed that it would be helpful for beer flavor stability if the polyphenol content would be about 100mg/L and P.I.≤2.5 of 11oP beer. The polyphenol compounds of malt was infused quickly during the protein rest in the mashing; the polyphenol content and TBA value of wort would be influenced by the adjunct proporation, hop addition and time, wort pH and wort boiling degree. Beer flavor was greatly affected by the oxygen content. It was very important that whether there was oxygen coming into the boiling wort or not. Another important factor was the dissolved oxygen content in the clear beer. The beer TBA value and polyphenol content was influenced by them directly.The polyphenol content of wort was decreased greatly after formaldehyde was added in the mashing, and the beer flavor stability was destroyed greatly. The polyphenol was protected away oxidation and the beer flavor stability was improved when the potassium metabisulfite was used. It was proved that the beer flavor stability could be increased when the additive was used in the wort boiling (such as HD-003, green tea polyphenol and tannie), in the beer filtering (such as PVPP) and in the clear beer (such as sodium iso-vitamin C and tri-anti-oxidation regeant). The anti-staling effect of tri-anti-oxidation regeant was better than of sodium iso-vitamin C. It was found that the total polyphenol content of wort and final beer was increased by 61% and 37.3%, respectively, the TBA value of wort and beer was decreased by 5.9% and 16.7%, respectively, the RSV value of beer was increased by 53.6%, after the process adjustment in the large scale beer production. The other physical and chemical index was not changed compared with original beer. The beer flavor stability was improved by a month. The beer non-biologyical stability was not changed while the polyphenol content was increased after cool and heat water bath.