S2-10
Role of Hydroxynitrilelyase in Development of
Cyanogen Free Cassava Foods
Nambisan
B. and Sandhya C.
Division of Crop Utilization and Biotechnology, Central
Tuber Crops Research Institute, Sreekariyam, Trivandrum- 695017,
Kerala, India
prsbn@md4.vsnl.net.in
The
sequential action of the enzymes linamarin and hydroxynitrilelyase is
essential for the complete hydrolysis of linamarin to free cyanide in
cassava. The activities of
these two enzymes could influence the removal of cyanoglucosides during
processing. The relative
distribution of linamarase and hydroxynitrilelyase and the kinetics of
cyanogenesis in different tissues were studied in low and high cyanogen
cultivars. The distribution
of hydroxynitrilelyase was strikingly different from that of linamarase.
The hydroxynitrilelyase/linamarase ratio showed large variation
between different tissues, and this was reflected in the rate of
cyanogenesis in these tissues. Rapid
cyanogenesis was observed in leaf, where activity of both enzymes was
high. In rind,
acetonecyanohydrin accumulated due to high linamarase activity and
negligible hydroxynitrilelyase, while in tuber, the rate of cyanogenesis
was lowest due to low activity of linamarase and negligible
hydroxynitrilelyase. Addition
of purified hydroxynitrilelyase resulted in rapid lowering of the
cyanogen content in both rind and tuber, due to faster dissociation of
acetonecyanohydrin. The
deficiency of this enzyme in root tissues causes accumulation of
cyanogens during processing, so addition of hydroxynitrilelyase would
ensure higher safety for cassava based food products.
|
