| Hops have significant effects on beer flavor. Hop varieties, freshness, recipes andhopping methods affect the flavor of beer. The domestic hop varieties are little. To institutethe domestic hops, different hop varieties from Germany, America, Czech, China and othercountries were studied. The screening for hopping recipes and the brewing characteristics ofaroma-bitter hops, low-bitter hops and high α-acid hops were studied. The effects of the hopfreshness on the beer flavor were also studied.Firstly, the quality of more than40hop varieties from different countries were evaluated,including the analysis of bitter substances by HPLC, hop oil components by GC-FID, thecontent of hop total polyphenol and its antioxidant potential by Spectrophotometry andsensory evaluation of hop flavor. The results showed that the bitter taste of European andAustralian hops were finer than American hops considering the contents of β-acid. The bittertaste of Qingdao Flower was harsher than almost all the other hop varieties because of thehigh content of cohumulone, which is up to38.12%. With regard to the ratio ofhumulene/caryophyllene, the aroma of European hops especially German hops were betterthan American hops. The ratio of humulene/caryophyllene in Australian hops was unusual low,even lower than domestic hop varieties. The total polyphenol content of aroma hops usuallyhigher than the bitter hops, contributing more antioxidant capacity. The cluster analysis ofbitter substance showed that the varieties which were similar to Qingdao Flower were Cluster,Galena and Topaz. By cluster analysis of hop oil components, SA-1were similar to Saaz,Sterling and Lublin.Then, the screening of hop varieties for recipes and hopping methods were studied. Thebitter-aroma hops brewing used Cascade to provide bitterness and Saaz to provide aroma forbeer. Bitter taste wort was better than the control. The content of linalool and geraniol in thewort were11.33and15.67μg/L respectively, namely better aroma quality. The alcohol-esterratios of the beers were5.21and5.42, that is to say, the flavor were similar. The low-bitterhops Cluster and aroma hops Saaz for brewing could achieve the desired bitterness value,while the T/C value of iso-α-acid were0.46, which is higher than the control, namely thebitter stability was inferior to the control. The content of linalool and geraniol in the wortwere9.29and6.55μg/L respectively, namely worse aroma quality. The alcohol-ester ratio ofthe beer was little different. High α-acid hops brewing showed that the taste and bitternesswere better than the control Qingdao flower. However, when adding the same content ofα-acids, polyphenol provied by the high α-acid content hops was lower than the control. Thismight decrease its antioxidant capacity. Fortunately, this problem could be solved by addinghop polyphenol pellet.Finally, the variation of bitter substances of the domestic hops SA-1, Qingdao Flower andMarco Polo during storage was studied. The results showed that the level of α-acid and β-acidhad a certain degree of loss in each variety after six months storage and the Hop StorageIndex increased gradually. The loss ratio of α-acid of Qingdao Flower, SA-1and Marco Polowere25.43%,37.74%and11.64%, respectively. The order of the three hop varieties were Marco Polo, Qingdao Flower and SA-1in accordance with the storage stability. The rationalusage time of the hops was clarified. The one-year stored hops and fresh hops were used inthe brewing test. It was found that the antioxidant capacity of wort adding with aging hopswas inferior to fresh ones. The alcohol-ester ratio of the beer fermented by the hops withdifferent degree of fresh hops had little difference, but the Resistant Staling Value of beerbrewed by aging hops was less than that of fresh hops. |
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