Large Scale Production of Soy Sauce by the Use of Soy Sauce Koji Autolyzate Prepared at High Temperature

Abstract

A pre-fermentation moromi mash, made from a soy sauce koji autolyzate and sodium chloride, was subjected to fermentation processes in 44kl tanks for soy sauce manufacturing by inoculating salt-tolerant lactic acid bacteria (Pediococcus halophilus) and yeasts (Zygosaccharomyces rouxii and Candida versatilis). Fermentation method used was a modified 1 tank-2 steps method in which the pre-fermentation moromi mash containing about 13% (w/v) of sodium chloride was inoculated by P. halophilus and C. versatilis simultaneously to start the first step fermentation (mainly lactic acid fermentation), and incubated at 30°C for 14 days. The moromi mash was, then, divided into two equal portions and each portion was mixed by an equal volume of freshly prepared pre-fermentation moromi mash. Sodium chloride was dissolved to a concentration of about 15-16% (w/v) in the mixed moromi mash, and the mash was inoculated by Z. rouxii to induce the second step fermentation (mainly alcohol fermentation) and was kept at 28°C for 45 days. After the second step fermentation, incubation was allowed to continue at 25°C for additional 30 days for maturation. In the moromi mashes, production of lactic acid proceeded smoothly and that of ethanol ceased before excess consumption of reducing sugars. Matured-flavor compounds such as 4-ethylguaiacol, 4-ethylphenol and 2-phenylethanol were detected in the filtrate of the mash obtained after the second step fermentation, and well-balanced kiage (non-heated soy sauce) was produced within three months. Composition of the kiage thus prepared was very close to that of the kiage made by the conventional method and the former was not distinguished from the latter by a sensory test.