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정철,Karl Wackerbauer,Martin Beckmann,장기효,강순아 한국생물공학회 2008 Biotechnology and Bioprocess Engineering Vol.13 No.6
The effects of variations in cultivation conditions on trehalose concentration and the viability of brewing yeasts following preservation by filter paper or lyophilization methods were evaluated. In case of filter paper preservation, the cultivation period had no affect on yeast viability, while agitation and aeration during cultivation had a positive effect regarding viability of the bottom-fermenting strains, Rh and Frank. For effective preservation, it was necessary to harvest yeast cells from the stationary phase during cultivation. For lyophilization preservation, the yeast strains tested showed a negative effect on viability, independent of strain or cultivation method. No significant correlation was found between trehalose concentration and yeast viability following either filter paper or lyophilization preservation. However, the filter paper preservation method was suitable for both bottom and top brewing yeast strains with regard to feasibility, viability, and maintenance of the yeast’s specific character.
Influence of preserved brewing yeast strains on fermentation behavior and flocculation capacity
Chul Cheong,Karl Wackerbauer,Martin Beckmann,Soon Ah Kang 한국영양학회 2007 Nutrition Research and Practice Vol.1 No.4
Preservation methods on the physiological and brewing technical characters in bottom and top brewing yeast strains were investigated. The preserved yeasts were reactivated after 24 months storage and grown up to stationary phase. The samples of filter paper storage indicated a higher cell growth and viability during propagation than those of nitrogen and lyophilization storage independent on propagation temperature. In addition, the filter paper storage demonstrated a faster absorption of free amino nitrogen and a highest level of higher aliphatic alcohols production during propagation than other preservation methods, which can be attributed to intensive cell growth during propagation. Moreover, the filter paper storage showed a faster accumulation for glycogen and trehalose during propagation, whereas, in particular, lyophilization storage noted a longer adaptation time regarding synthesis of glycogen and trehalose with delayed cell growth. In beer analysis, the filter paper storage formed an increased higher aliphatic alcohols than control. In conclusion, the preservation of filter paper affected positively on yeast growth, viability and beer quality independent on propagation temperature. In addition, in this study, it was obtained that the HICF and Helm-test can be involved as rapid methods for determination of flocculation capacity.
Strategy for Prevention of Weakly Flocculating Characters in Bottom Brewing Yeast Strains
Chul Cheong,Karl Wackerbauer,Soon Ah Kang 한국식품과학회 2008 Food Science and Biotechnology Vol.17 No.3
To prevent weakly flocculating characters of bottom brewing yeast during first fermentation, various technical investigations were carried out using strain of Saccharomyces cerevisiae. It appeared that the propagation at 10℃ promoted the molecular structure and biochemical composition of cell wall in favor of flocculation. The yeast grown at 20℃ by addition of zinc ion also had a stimulating effect on flocculation behavior during first fermentation cycle. The zinc ion did not influence directly on the changes of cell wall in favor of stronger flocculence. The increased fermentation activity of yeast due to addition zinc ion was rather responsible for the intensified flocculation capacity. It was concluded that the weakly flocculating characters of bottom brewing yeast during first fermentation can be solved by using yeast propagated at 10℃ or by means of yeast by addition of zinc ion during propagation.
Optimal Conditions for Propagation in Bottom and Top Brewing Yeast Strains
Chul Cheong,Karl Wackerbauer,Si Kyung Lee,Soon Ah Kang 한국식품과학회 2008 Food Science and Biotechnology Vol.17 No.4
The method of yeast propagation has an influence on yeast physiology, fermentation ability, flocculation rate, and taste stability of beer. In order to find optimal conditions for propagation, several parameters were investigated in combinations. The bottom brewing yeast grown at 10℃ indicated that a higher flocculation capacity during the 1<sup>st</sup> fermentation. However, the taste stability and the aroma profile were not affected by parameters of propagation investigated. The beer quality was rather affected by storage duration. In addition, a correlation between tasting and chemiluminescence was found at the beer, which was produced using bottom brewing yeast. The propagation at 10-25℃ with addition of zinc ion indicated the best condition to improve fermentation ability, flocculation rate, and filterability for bottom brewing yeast, whereas the propagation at 30℃ with addition of zinc ion showed the best condition to increase fermentation ability for top brewing yeasts.