Total cell counts and viability of yeast cells were determined by methylene blue method. A 1 mL of yeast suspension was mixed with 9 mL of modified Ringer solutio: NaCl, 0.86; KCl, 0.03; CaCl2 $2H2O, 0.044; Na2S2O3 $5H2O, 0.05; sucrose, 1.0; methylene blue, 0.025.