Halotolerant yeast participates in the cavity formation of hand-pulled dry noodles

Abstract

SEM observation showed the presence of cavities in hand-pulled dry noodles such as Inaniwa-udon, Himi-udon and Shiroishi-umen. Wheat flour (100 g) dough containing 8% (w/v) salt solution (55 ml) was matured for 24 hours, and dried noodles were made from the matured dough by hand-stretching and drying. The cavities of the handpulled noodles were formed by such an operation, and increased in size as the maturation temperature rose to 23°C or 30°C. We isolated several yeast samples from the Inaniwa-udon dough, and obtained pure M1 and M2 strains. These produced gas from glucose, sucrose, trehalose, galactose and maltose, utilized soluble starch, and showed tolerance to 10% (w/v) salt solution. Cultures were identified as Hyphopichia burtonii by the base sequence of ITS region and sugar utilization. With the addition of H. burtonii M1 and M2 to wheat flour dough, and incubation at 30°C, the dough volumes noticeably increased after 10 hours. Without H. burtonii M1 and M2, there was no volume increase in the dough for 36 hours. Thus, halotolerant H. burtonii appears to participate in the cavity formation of hand-pulled noodles such as Inaniwa-udon.