Making Traditional Japanese Vinegar

Traditional Japanese Vinegar Making

In Japan vinegar is made from various grains, with rice being predominantly used to produce a mellow, fragrant, all-purpose vinegar. Rice, barley and wheat combinations seem to be quite common but certainly this is not the limit. These grains produce decidedly different vinegars depending upon the combination of grain used. In the Japanese process the grain is ground, steamed in mesh baskets, inoculated with Aspergillus oryzae, and during a 1-2 day solid-state fermentation various hydrolytic enzymes (amylolytic and proteolytic) are produced. This mass is subsequently placed in clay pots, mixed with water, and inoculated with a backset mixed culture of yeast and Acetobacter. The contents are periodically hand-stirred during the 3-6 month, outdoor fermentation. During this extended fermentation Aspergillus enzymes convert starch into fermentable sugars, which are fermented to ethanol by yeast. Proteases are also active in this process, releasing a complex mixture of flavor compounds. In the aerobic surface layers, Acetobacter gradually convert ethanol to acetic acid. Although there are variations in microbial strains and unit processes in various Asian countries, this mixed culture approach is a common feature. The wild-type strains used for centuries in this process have been selected for their ability to co-exist (i.e. yeast are typically highly sensitive to acetate). In Japan, research has shown that Saccharomyces sake and Acetobacter pasteurianus can act in concert with Aspergillus oryzae.