Yacon juices were fermented using a Beni-koji fungus (Monascus purpureus AHU9451), wine yeast (OC-2) and two strains of lactic acid bacteria (Lactococcus cremolis IFO03427 and Streptococcus thermophilus lFO0l3957) to evaluate the possibility of reducing the grassy odor natural to yacon juice while simultaneously studying the effects of fermentation on the yacon juice's principal components. Use of these microorganisms resulted in a fermented product exhibiting a moderated odor, lower pH value, and superior flavor. In addition, the removal of suspension by centrifugation was ameliorated.

Fructose and glucose were completely consumed during the cultivation of Mon. purpureus. Sucrose and fructooligosaccharides, however, were not consumed. Byproducts were ethanol and a small amount of succinic acid. Unlike fermentation with Mon. purpureus, yacon juice sucrose and fructooligosaccharides contents were eventually consumed during OC-2 fermentation. Ethanol and succinic acid concentrations of 4.2% and 0.2%, respectively, were formed during OC-2 fermentation. Grassy odors were not directly decreased by the fermentation of yacon juices with lactic acid bacteria. However, an odor reduction was achieved by adding a 5% concentration of skimmed milk, which resulted in a yogurt-like aroma.

These results indicate that it may be possible to develop attractive seasonings, low-alcoholic drinks and lactic-acid drinks through the microbial fermentation of yacon juice.