The cyanogenic glycoside contents of raw and processed limabean varieties

Eighteen varieties of limabean (Phaseolus lunatus), were subjected to the processes of cooking, autoclaving, soaking in water and germination for 6 days. The effects of these processes on the free and bound HCN contents of the raw limabean varieties were investigated. Total HCN in the raw varieties ranged from 265 mg kg^?1 in TPL 071-33 and 553 mg kg^?1 in TPL 13. Considerable variability was encountered in the different varieties and processing effects tended to make these varietal differences even more pronounced. Autoclaving gave a mean total loss of 53·9% in total HCN content while cooking effected a 64·8%–81·9% loss in total HCN content. Drastic reductions in both free and bound HCN contents were obtained in all cooked varieties. Soaking for 2 days effected the highest HCN loss in TPL 2 (40·1%), closely followed by TPL 13 (39·7%) and then TPL 3 (35·4%). All varieties, by the sixth day of soaking, lost between 61·3 and 86·4% of their total HCN contents. The effect of germination on HCN contents increased progressively from a mean total loss of 24·5% in day 2 to 55·6% in day 4 and 76·1% in day 6. Cooking and germination for 6 days appeared to be equally effective in reducing free and bound contents. Autoclaving was the least effective of all the processes studied.