To develop vinegar from yacon juices containing fructooligosaccharides, the effect of the following factors on acetic acid fermentation was evaluated: initial pH, initial ethanol concentration, starter volume, type of yacon juice, and culture method. When the surface culture method was used with A. pasteurianus IFO14814, acetic acid fermentation was generally favorable when the initial pH, initial ethanol concentration and starter volume were 5.0, 5.5% and 10%, respectively. Under such conditions the desired acetic acid content was produced after 20 days of cultivation in the OC-2(l0ds) YJ sample and after 32 days in the OC-2(1d) YJ sample. However, acetic acid production was small in the YJ and OC-2(Glu・2ds) YJ samples, and no acetic acid was produced in the OC-2(Glu・ld) YJ sample. Using the shaking culture method, desired acetic acid content was produced after five days in almost all cases. In addition to reducing the cultivation period and facilitating consistent fermentation, the shaking method resulted in only a slight decrease in fructooligosaccharide content. Sensory tests of the yacon vinegar produced by normal acetic acid fermentation found a reduced odor level and relatively good product quality.

YJ: Yacon juice; OC-2(1d) YJ: Juice after one day of ethanol fermentation by OC-2;OC-2(Glu・ld) YJ: Juice after one day of ethanol fermentation by OC-2 following the addition of glucose (70g to 1l of juice); OC-2(Glu2・ds)YJ: Juice after two days of ethanol fermentation bv OC-2 following the addition of glucose; OC-2(10ds) YJ: Juice after 10 days of ethanol fermentation bv OC-2