The Research And Preparation Of Isomeric Hop Extract And Reductive Hop Extract And The Analysis Of Their Qualities

Hops are known as"the soul of beers", which is the one of important and indispensable raw material in brewing, and it has been widely used in beer factories. At present, there is deficient of deep processing technology, and the type of hops product was less, the utilizing rate of raw hops was lower, and there is rich of hop resource in Gansu. The aim of this study was to develop the isomeric hop extract and reductive hop extract, which would improve the utilization of hops, extend the industrial chain and enhance the level of hops processing, promote industrial sustainable development, as well as develop new variety of beer.In this paper, the compressed hops product of Tsingdao flower as raw materials, the processing technology ofα-acid hop extract was optimized by organic solvent extraction. Boiling technique was used to study the effect of each factor and level onα-acid isomerization by single factor and orthogonal experiment design. The optimal parameter to produce isomeric hop extract withα-acid hop extract as raw materials was obtained. And then measured the key quality indexes of isomeric hop extract, including iso-α-acid content, thermal stability, light stability and sensory characteristics (organizational status, color, odor). The method of single factor, Plackett-Burman and orthogonal experimental design were used to optimize parameters of preparing tetrahydroiso-α-acid extract from isomerized hop extract by hydrogenation with pressure. At last, the quality indexes of products were analyzed. The main results as follows:1. Established technology process of isomeric hop extract and reductive hop extract product: Hop powder→extract about 24 hours with organic solvent at 30℃→40℃decompression distillation→α-acid hops extract→isomerization at alkaline and boiling condition with catalyst→precipitate in acidic condition with HCl→isomeric hop extract→dissolve in alkaline condition ethanol→in the autoclave→hydrogenation with catalyst in the high pressure→decompression distillation→reductive hop extract.2. The single factor test results of the organic solvent extractα-acid showed that the order of the extractive rate ofα-acid was: methylene chloride>toluene>benzene >ethanol>methanol>hexane>Sherwood oil.The highest extraction ratio of methylene chloride toα-acid was 82.71%3. Boiling processing technology was used to study the order of impacting isomerization ofα-acid , the result was: pH> the concentration ofα-acid> the amount of catalyst> heating time, the optimum technology parameters was: pH 10,the concentration ofα-acid was 1.72mg/ml,the amount of catalyst was 4% and heating time was 135min. In this condition, the content of iso-α-acid in extract was up to 63.98% and the isomerization efficiency ofα-acid was 87.14%.4. Using Plackett-Burman and the orthogonal design methods, the optimized parameters of preparing tetrahydroiso-α-acid extract from isomerized hop extract was attained. It showed that the concentration of iso-α-acid was 55mg/ml, hydrogen pressure was 0.2MPa, pH 10, the amount of catalyst was 3%, hydrogen time was 4h. The primary and secondary factors in order were: the concentration of iso-α-acid> hydrogen pressure> pH> the amount of catalyst> hydrogen time.5. Evaluated the characterstics of three kinds of hop products, it showed that the amount of tetrahydroiso-α-acid in the extract was decreased 0.4%, the amount of iso-α-acid in the second extract was decreased 1.8% and that ofα-acid extract was decreased 33% after the three extract samples were respectively heated in 85-90℃for 20h.That was to say, the thermal stability of tetrahydroiso-α-acid extract was the best,and theα-acid extract was the worst. After the three extract products were incubated in the light incubator 28d, the amount of tetrahydroiso-α-acid in the extract was decreased 2.6%, the amount ofα-acid in the second extract was decreased 17.8% and that of iso-α-acid in the other extract was decreased 25.2%. The light stability of tetrahydroiso-α-acid extract was the best, and the iso-α-acid extract was the worst.The sensory characteristics of three extract were all paste shape, but the colour was respectively grey green, brown green and brown red, the hops special odor was gradually weaken, the dissolubility was obviously increased with processing.