Production of vinegar from organic broken rice noodles

Abstract

Organic broken rice noodles (OBRN) are generally considered as waste material from noodle processing factories and are of low value. The purpose of this research study was to increase the value of OBRN by converting it to fermented vinegar. In the first step, the hydrolysis methods of OBRN were studied. The conversion of starch into reducing sugar using acid hydrolysis, mold inoculation, and rice cake starter (loog-pang) were compared. For acid hydrolysis, 0.6 M sulfuric or hydrochloric acid at 80, 100, and 121°C was used. For biological hydrolysis, steamed OBRN was soaked in water at a ratio of 1:2 for 1 h, then mixed with 0-0.4 % (w/w) koji or ricecake starter and left to ferment. The latter methods yielded the highest glucose of 167.66 and 178.94 g/L, respectively, when 0.2 % of starters were inoculated for 3 days. In a second step, OBRN wine was made from a mixture of hydrolyzed OBRN liquid and 20° Brix of pineapple juice at a 1:1 ratio and subsequently fermented for 7 days. The alcohol produced from OBRN showed the highest concentration of 10.05 % (v/v) at 7 days of incubation. Lastly, wine was prepared at various alcohol concentrations of 4-6 % (v/v) and at a pH of 5.5 for further vinegar fermentation using Acetobacter pasteurianus TISTR 102, by shaking at 150 rpm for 7 days. The result showed that the appropriate alcohol concentration for producing vinegar was 4 % (v/v) and the OBRN vinegar exhibited clear, light yellow color, and had total acidity content of 3.52 % (v/v) and a pH of 3.28 after 4 days of incubation.