Study On Evaluation Of Antioxidant Activity And Its Relation With Ageing Compounds In Beer

Flavor stability is one of the important quality indicators in beer, however, the originalfresh taste and flavor of beer are lost gradually and then the ageing flavors emerge with theincreasing of storage time, which will greatly affect the potability of beer. Therefore, it is anurgent challenge to delay the favor ageing and improve favor stability of beer in brewingindustry currently. The change rules of content of three kinds of antioxidants, antioxidantactivity and nine kinds of ageing compounds in different kinds of lager beers and the internalrelationship among them during storage were investigated systematically in this article. It wasexpected that some theoretical basis could be provided for enhancing beer antioxidant activity,inhibiting beer ageing and thereby improving flavor stability by optimizing brewing processparameters in beer industry. The main results were as follows:(1) The comprehensive evaluation index of antioxidant activity (CEI) was built by principalcomponent analysis, and then it was used to evaluate the antioxidant activity in differentbrands of beer, and this new evaluation method was more accurate and intuitive. Theextremely significant positive correlations (P<0.01) were found among CEI, DPPH radicalscavenging activity, ABTS radical cation scavenging activity, oxygen radical absorptioncapacity, reducing power, and metal chelating activity. The better correlations were foundbetween CEI and ABTS radical cation scavenging activity, reducing power. It was indicatedthat the ABTS radical cation scavenging activity and reducing power could accurately reflectthe antioxidant activity of beer.(2) The changes of antioxidants content and antioxidant activity during storage and theinternal relationship between them were clarified. After storage at25℃for6months, the totalphenolic content in beer reduced, the content of maillard reaction products and maillardreaction intermediate slightly increased, and the antioxidant activity decreased significantly.The bigger changes were shown in reducing power and DPPH radical scavenging activity forbeer during storage, so the two indexes could well indicate the changes of antioxidant activityin beer. The significant positive correlations were found among DPPH radical scavengingactivity, ABTS radical cation scavenging activity, oxygen radical absorption capacity,reducing power and metal chelating activity. Moreover, the highly significant positivecorrelations (P<0.01) were found among DPPH radical scavenging activity, ABTS radicalcation scavenging activity and reducing power. Phenolics were closely associated with beerantioxidant activity, followed by the maillard reaction intermediate.(3) The TBA value and content of3-methylbutanal,2-methybutanal, furfural, 2-acetyl-furan, benzaldehyde, phenylacetaldehyde, diethyl succinate, ethyl nicotinate andγ-nonalactone increased during beer storage. The content of diethyl succinate and ethylnicotinate increased rapidly among them,. The significant negative correlations (P<0.05) werefound among the total ageing compounds content increment and DPPH radical scavengingactivity increment, reducing power increment of beer after storage for six months. It wasinferred that the formation of ageing compounds could be effectively inhibited by increasingDPPH radical scavenging activity and reducing power of beer.