The Effect Of Different Storage Conditions On The Quality Of Hops

Hop is known as"the soul of beer", which is the one of important and indispensable raw material in brewing. The quality of hops determines the merits of beers.The loss of active ingredients are large in the period of storage and processing, but now there are not some effective technologies to prevent loss. In this experiment, Marco Polo and Tsingdao flower, which were the mainly cultivated varieties in the western region of China were used as the research materials. We have reserched the storage technologies and characteristics of fresh hops cones and processed hop (compressed hops and hop pellets). Selecting the best storage conditions of different hops states by determining the optimum harvest period and mensurating the effect of different degree of fragmentation,different storage cnditions on the raw hops and dried hop products, which would reduce the loss of active ingredients, raise the utilization rate and improve quality of hops, and could provide reference and theoretical support for processing enterprises on hop picking, buying, choice, storage and process. The main results as follows:1. Determined the optimum harvest period of Tsingdao flower in Yumen area of Gansu province was in late August to early September by mensurated the content ofα-acid during picking in mature period. In the period, the content ofα-acid was more than 7.0%. From then on,the content ofα-acid began decreasing, so it must be harvested within ten days that would ensure it having good quality,which is the foundation for storage and processing.2. Studied bitter substances in different fragmentized hop cones, the results showed that the content ofα-acid in the full hop cones was 6.22%, and that was 2.14% higher than in broken hops. The content ofβ-acid in the full hop (4.64%) was almost 2 times higher than that in broken hops (2.76%), but the HSI was close to each other. The HSI in full hops was 0.355 and in broken hops was 0.332. It showed that the loss caused by broken and pollen shedding was great in the process of picking, transportation and drying.3. The quality of Tsingdao flower and Marco Polo hop cones which storaged in piles, dark conditions and room temperature 12 days, mensuratedα-acid,β-acid, HSI, browning, PPO, POD. The results showed that the loss ofα-acid andβ-acid in Marco Polo was more than in Tsingdao flower. In the first two days the loss was greater than in other days,the PPO activity of Marco Polo and Tsingdao flower was decreasing with the continue of storage time, the downward trend was more obvious than in other days. The trend of POD activity of Marco Polo was rised initially and then decreased, that was same with the trend of Tsingdao flower. But the time of highest POD activity of Marco Polo appeared 4 days earlier than that of Tsingdao flower. The correlation between browning and PPO of Marco Polo and Tsingdao flower was respectively very significant positive correlation and significant positive correlation. So Marco Polo would be influenced easily by environment than Tsingdao flower.For the fresh hops, the first two days of storage time was the key to reduce the loss.4. The compressed leafy hops stored at the simulated factory conditions (kraft paper-gauze- plastic-bag four packages, room temperature, dark) 20 days and measured the quality indicators in this period. The results showed that the loss ofα-acid was lower 0.71% than the control of that without packing, the content ofβ-acids was more 0.61% than the control, and the loss of hop oil decreased 0.06ml/100g, HSI decreased 0.09 than the control. Under these conditions, the linear regression equation of HSI was: y = 0.0232x +0.297, R2 = 0.9816. So it concluded that dryied compression hops storage with four-layer packaging, under low temperature could reduce the loss of active ingredients.5. Measured the quality indexes of pellets hops that storaged at different temperatures and packaging within six months, the results showed that the temperature influenced the quality of hops was biggest, then was time, and finally was packaging. The higher the temperature was, the faster the content ofα-acids andβ-acid decreased, the higher browning degree was, and the bigger the PPO and POD activity were. The longer the storage was, the smaller the content ofα-acids andβ-acid were, the lower activity of PPO and POD were, the larger HSI and browning degree were. The quality of hops packaged in ziplock bag was worst, and packaged in aluminum-foil-vacuum was changed least.The HSI of pellets was under 0.5 after being storaged in aluminum-foil-vacuum and lower temperature, it showed the quality of hop was good yet.