ABSTRACT

Seven yams and five cocoyam cultivars commonly planted ir National Root Crops Research Institute, Umudike and consumed in the Eastern Nigeria were screened for cyanogenesis using f3-glucosidase enzyme from three different sources. The -glucosidases from cassava peels and rubber seeds (Hevea brasihensis) used in this work were prepared in the University Laboratory, while the third source of f3-glucosidase is from kit B2 for cyanide analysis from Australian National University. Cyanide released from the yam and cocoyam cultivars using the commercial f-glucosidase from kit B2ranged from 5.14-23.68ppm (mg/kg fresh wt) and 6.33- 22.6Oppm (mg/kg fresh vt) for yams and cocoyams respectively. Assaying for cyanogenesis using cassava peels f3-glucosidase resulted in 0.39- 7.52pprn (mg/kg fresh vt) cyanide released from yams and 4.75-8.32ppm (mg/kg fresh wt) cyanide from cocoyarns. Also 2.38-7.92ppm (mg/kg fresh wt) CN were obtained for yam cultivars and 5.94-I 0.30ppm(mg/kg fresh vt) CN for cocoyams, using f3-glucosidase from brasihensis seeds. The enzyme activities of the f3-glucosidase from cassava peels and 1-levea brasihensis seeds were found to be 6.2ôunit/ml and I 2.2unit/ml respectively. The cassava f3-glucosidase was found to have a Kmof 1 .0 and. V1of 2.2 x 10'.