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Cyanogenic Glycosides
Published in Dongyou Liu, Handbook of Foodborne Diseases, 2018
During plant growth, amino acids not required for protein synthesis are metabolized into α-hydroxynitriles and then cyanogenic glycosides, which are stored in the cell vacuoles. This effectively segregates canogenic glycosides spatially from endogenous hydrolyzing enzymes (e.g., β-1,6-glucosidases and hydroxynitrile lyases) in the cell cytosol (or the cell wall and laticifers as in the case of cassava linamarase), preventing canogenic glycoside-related autotoxicity. Additionally, cyanide from cyanogenic glycoside (e.g., cyanogen linamarin) may be converted by β-cyanoalanine synthase into cyanoalanine plus hydrogen sulfide in the presence of cysteine, and cyanoalanine is then converted by nitrilase to asparagine. This also helps limit the potential self-damage by cyanogenic glycosides.
Cassava toxicity, detoxification and its food applications: a review
Published in Toxin Reviews, 2021
Anil Panghal, Claudia Munezero, Paras Sharma, Navnidhi Chhikara
From the above discussion, it is quite clear that a single method is not self-sufficient to reduce the cassava toxicity up to safe limits, so different methods can be used in conjugation to have cumulative impact. Blanching combined with drying has been described by Nambisan (1994). Blanching for 5–10 min can reduce cyanide by 50% but sun-drying of the blanched roots has no significant effect as the linamarase enzyme is deactivated during blanching process. By further boiling in water to cook the chips, 50% of the remaining cyanogens is lost (Nambisan 1994). Oke (1994) also confirmed that soaking cassava roots prior to sun drying increases the efficiency of detoxification (97.8–98.7%). Dipping fresh cassava roots for 3 d then drying for 3 d give the result of 85.9% cyanide reduction. On the other side, crushing roots before sun-drying allow 96–99% of total cyanogens to be removed (Nambisan and Sundaresan 1985). This is explained by the fact that crushing damages the plant cells and thus linamarase enzyme comes in direct contact with linamarin. Therefore, sun-drying decreases cyanohydrin and free cyanide (Heuberger 2005).