EVALUATION OF THE ALKALINE METHYLENE-BLUE STAINING METHOD FOR YEAST ACTIVITY DETERMINATION

To ensure reliable manufacture of high quality beer, the brewing yeast must be maintained in a highly active state. The conventional methyle ne blue staining method, which is very simple but not highly sensitive , has been improved to allow sensitive measurement of yeast activity. Two kinds of yeasts with different activity levels were stained with m ethylene blue solution with pH levels between 4 and 12. The results sh owed that highly sensitive measurement of yeast activity was possible when the staining solution was alkaline. When cells were stained with methylene blue solution with a pH of 10.6 at 25 degrees C for 15 min ( the alkaline methylene blue staining method), the percentage of unstai ned cells was consistent with viability measurements made using the sl ide culture method. The alkaline methylene blue staining method makes possible sensitive, quick, and simple measurement of yeast activity, w hich is essential to the management of fermentation process.