Since the yeast Saccharomyces cerevisiae carrying either SUC gene or MAL-constitutive gene ferments sucrose, these two genes could not be distinguished unless extracellular invertase activity was determined. The present work shows the strain carrying SUC fermented fructooligosaccharide, and the strain carrying MAL-constitutive did not. We applied these findings to genetic analysis of YOY10-13D, a haploid strain derived from a baker's yeast. The segregation of sucrose, maltose, and fructooligosaccharide fermentability in the tetrads of the cross between YOY10-13D and the tester strain showed that this strain carried one SUC and one MAL-constitutive.