| 摘要 |
PURPOSE: To simply and accurately evaluate a difference in flocculating properties of a beer yeast without carrying out fermentation tests by preculturing a beer yeast which is an object of evaluation in a culture medium prepared by regulating the total nitrogen content to a low concentration and then examining the flocculating properties of the beer yeast in the coexistence of Ca ions. CONSTITUTION: A beer yeast which is an object for evaluation is precultured in a culture medium prepared by regulating the total nitrogen content to a low concentration of <=40mg/100ml at 20 deg.C for 4 days and the microbial cell is recovered, collected and washed with distilled water. The recovered microbial cell is then diluted with distilled water so as to provide 8×10<8> cells/ml and the resultant diluted microbial cell liquid is taken in a test tube. A 0.1M acetic acid-sodium acetate buffer solution (pH4.6) and 40mM EDTA (pH8.0) are subsequently added thereto and 200mM aqueous solution of calcium chloride is further added. The resultant mixture is vigorously shaken and the shaking is stopped after 60min. The absorbance (at 660nm) is measured after the passage of 30min to simply and accurately evaluate the flocculating properties of the beer yeast using a value of the formula (1-A/B) (A is the absorbance of the test sample; B is the absorbance of the control sample) as an index indicating the extent of the flocculating properties.
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