Abstract
Acetic acid fermentation of yacon juice was performed with Acetobacter pasteurianus IFO 14814 of acetic acid bacteria. Reduction of the juice's grassy odor and the possibility for development of yacon vinegar containing natural fructooligosaccharides (FOS) were investigated. (1) Yacon juice with and without alcohol fermentation treatment was used. Acetic acid fermentation was conducted under the following conditions: 30°C, initial pH 5.0, initial ethanol concentration 5.5% (w/v) and acetic acid bacteria preculture concentration 10% (v/v). As a result, in surface culture, more than 4.0% acetic acid was produced from YJ⋅OC-2 (1d) after 32 days and from YJ⋅OC-2 (10ds) after 20 days, respectively. In shaking culture, more than 4.0% acetic acid was produced from YJ, YJ⋅OC-2 (1d), YJ⋅OC-2 (10ds) and YJ⋅OC-2 (Glc⋅1d) after 5 days, respectively. (2) A sensory evaluation on above sample juice containing FOS was carried out. As a result, the grassy odor was almost reduced completely in all the sample juice. Moreover, the smell became better in YJ⋅OC-2 (1d) of surface culture. while 2.4% (w/v) total FOS content was still retained in the juice. So, it was suggested that better yacon vinegar containing natural FOS was possibly developed from YJ⋅OC-2 (1d) juice of surface culture.
YJ; yacon juice. OC-2; Kyokai Yeast No. 1. YJ⋅(Glc); YJ after 70g glucose was added to one liter juice. YJ⋅OC-2 (1d); YJ after alcohol fermentation with OC-2 for one day. YJ⋅OC-2 (Glc⋅ 1d); YJ⋅(Glc) after alcohol fermentation with OC-2 for one day. YJ⋅OC-2 (Glc⋅2ds); YJ⋅(Glc) after alcohol fermentation with OC-2 for 2 days. YJ⋅OC-2 (10ds); YJ after alcohol fermentation with OC-2 for 10 days.
