• Korean Journal of Food Science and Technology
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• v.40 no.2
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• pp.238-242
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• 2008

In this study, hydrogen sulfide ($H_2S$) production was examined during beer fermentation using two ale and two lager yeast strains. In the lager yeast fermentation, a large amount of $H_2S$ was produced in the early fermentation stages when the yeast were actively fermenting wort, indicating a positive relationship between the level of H2S production and the yeast growth rate during fermentation. The ale yeasts produced much lower levels of H2S than the lager yeasts. In the lager fermentation, a higher fermentation temperature shortened the fermentation period, but much higher levels of $H_2S$ were produced at higher temperatures. American pilsner lager yeast fermenting at $15^{\circ}C$ produced a relatively high level of $H_2S$ at the end of fermentation, which would require a longer aging time to remove this malodorous volatile sulfur compound. Not including the English ale strain, which produced a higher level of H2S at lower temperatures, the ale yeast produced lower levels of $H_2S$ at lower temperatures, suggesting that each strain has an optimum fermentation temperature for H2S production.

• Journal of the Korean Home Economics Association
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• v.46 no.3
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• pp.49-55
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• 2008

The purpose of this study was to investigate the effects of green tea extracts (GTE) on the fermentation properties of polyphenol-enriched beers. As such, the formation patterns of tannoid in beer with GTE were investigated at 3 different infusion times, while the ale and the lager beers fortified with GTE were analyze to ascertain effects on gravity, pH, yeast viability, total polyphenol, and tannoid during fermentation period. The results were as follows: 1) The formation of tannoid in beer with GTE in the tannometer; In reaction of GTE with polyvinylpyrrolidon (PVP), control lager beer peaked in the formation of tannoid at $70\;{\sim}\;80\;mg$ of PVP, the 1st extract exceeded the detection limit, the 2nd extract at $170\;{\sim}\;180\;mg$, while the third extract at $150\;{\sim}\;160\;mg$ of PVP. The GTE were slow in reacting with PVP, and their formation patterns were different from those of polyphenols from barley and hop. 2) Ale fermentation; The final alcohol content was 9.25% (ABV). The addition of GTE increased the yeast viability after 2 days and finally reached 52.3% from 30.9%. Total polyphenol in GTE beer increased by 1.5 times (p < .05). However, its tannoid contents increased by 6.4 times. 3) Lager fermentation; The final alcohol content was 5.93% (ABV). The effect of GTE on lager beer was minimal for all variables. However, total polyphenol of GTE beer increased by 1.4 times (p < .05). Its tannoid increased by 3.3 times (p < .05).

• Korean Journal of Food Science and Technology
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• v.49 no.2
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• pp.132-140
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• 2017

Nuruk, a traditional Korean alcoholic beverage starter, was evaluated as an additional saccharifying agent comprising up to 1.5% (w/w) of malt weight in ale-type beer processing. Sample characteristics were monitored during fermentation, ripening, and storage. Beer containing nuruk showed higher numbers of total viable bacteria and yeast cell counts. Additionally, ethanol (6.19-6.35%), color (Standard Reference Method), foam stability ($228.49-368.24{Sigma}$), saccharogenic power (307-417), and reducing sugar (3.83-5.25%) increased as the amount of nuruk was increased, while viscosity (3.13-2.07 cP) and bitterness unit (19.68-13.13) were lower than in samples without nuruk. Overall acceptance and aftertaste of the beer were significantly higher in a preference test. These results demonstrate that nuruk can be used to produce a new type of ale.

• The Korean Journal of Food And Nutrition
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• v.30 no.3
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• pp.491-500
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• 2017

Sweet potato-malt worts were prepared by using sweet potato paste of Shinyulmi and Shinjami as the main adjunct, enzymes, malt, hop, and water. We brewed low-malt beers of the lager- or ale-type by using these worts and inoculating bottom and top fermenting yeast, respectively. Moreover, the componential and functional characteristics of the resulting beers were evaluated. During saccharification of sweet potato, the addition of an enzyme agent containing ${\alpha}-amylase$ caused an improvement in filterability and an increase of total sugar. The sugar content of sweet potato-malt wort which was prepared by the addition of 0.1% enzyme agent containing ${\alpha}-amylase$ and a three-step infusion procedure was $13.5^{\circ}Brix$ adequate for beer brewing. The polyphenol and anthocyanin contents of Shinjami beer were increased with increasing content of the paste, and also increased DPPH and ABTS radical scavenging activities. But in Shinyulmi beer it were decreased. A strong correlation was obserbed between antioxidave activities and polyphenol and anthocyanin contents of sweet potato beers. In all lager- and ale-type low-malt beers using 41.6% of Shinjami pastes, sensory attributes very similar to those of 100% malt beer were obtained and they were very good as they had unique red color.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.9
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• pp.206-214
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• 2018

This study was conducted from August 2017 to May 2018. Beer was prepared by different ratio of rice and malt and different types of beer, and quality analysis were conducted. The ratio of rice and malt was divided into 0:100 (S0), 20:80 (S1), 40:60 (S2), 60:40 (S3) and 80:20 respectively. We compared the characteristics of the mashing methods(infusion and decoction method) and investigated the characteristics of different types of beer (lager, ale, wheat beer) using yeast (bottom and top yeast). Even with different ratios of rice and malt, normal infusion time was observed and the iodine test was confirmed to be normal. Also, the mashing proceeded normally and the sugar content of the primary wort was between $21.0{\sim}21^{\circ}brix$. In mashing method, the mash concentration, color and flavor of wort were the highest in the three mash method(decoction method). During the fermentation period of beer, the sugar content, pH and yeast number did not differ significantly depending on the ratio of rice and malt, and the type of yeast. Higher alcohol and esters also had no correlation with the ratio of rice to malt, and wheat beer was somewhat higher. The higher the ratio of rice, the more the color intensity(EBC) decreased, the bitter unit(BU) and the preference decreased. When the rice ratio was higher than the malt rate, the degree of preference decreased significantly. Based on the results of this study, it is expected that the rice ratio will be less than the malt ratio and the flavor of the wort will be improved by using the deccoction method. If the malt is supplemented with the use of the special malt and the various hops according to the beer type, it may be helpful to manufacture rice beer.