Screening For Cyanogenesis In Yam And Cocoyam Cultivars

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'.