The threshold tasts for sour taste were given to ten members of our office. Three test samples, hydrochloric and succinic acids were used to compare the suitability for the test. The test procedures were the same as described in the former report. SPEARMAN'S rank correlation cofficients and mean threshold values were calculated.
I. Through intensive research, we have determined that it is best to sterilize the kake-koji with 50% alcohol solution, to stop completely, the growth of Pulularia pullulans, appearing on the surface of the sake cake, after pressing the mash. By this method, we have also determined that the percentage of rice utilized have been higher. II. Before the fermented mashes were ready for pressing, various tests were held for the prevention of Pullularia pullulans in sake cake. In one separate test, we found that the addition of 10%-20% Yama-hai moto, which was added after the third step (Tome shikomi), Pullularia pullulans was controlled. The addition of potassium pyrosulfite in another test also proved successful, although this additive tends to make the smell unpleasant In still another test, the extracted enzyme solution was put in the fermenting mash, and this method, too, has been proven highly successful in preventing Pullularia pullulans in sake cake. III. Before indulging in further research of Pullularia pullulans, we believe that the substrate, for the enzymes, is found in koji.
1) We prepared a special sake mash, diminishing the percentage of koji used to 1/3 by volume. The mash fermentation was normal. 2) The contents of reducing sugars and amino acids were lower than in the ordinary mash. 3) The color of saké, made from this mash, was lighter and its taste was soft, in comparoon with the ordinary saké.