Showing papers by "Central Tuber Crops Research Institute published in 1995"

Cyanide detoxification in cassava for food and feed uses

Abstract: Cassava (Manihot esculenta Crantz) is an important tropical root crop providing energy to about 500 million people. The presence of the two cyanogenic glycosides, linamarin and lotaustralin, in cassava is a major factor limiting its use as food or feed. Traditional processing techniques practiced in cassava production are known to reduce cyanide in tubers and leaves. Drying is the most ubiquitous processing operation in many tropical countries. Sun drying eliminates more cyanide than oven drying because of the prolonged contact time between linamarase and the glucosides in sun drying. Soaking followed by boiling is better than soaking or boiling alone in removing cyanide. Traditional African food products such as gari and fufu are made by a series of operations such as grating, dewatering, fermenting, and roasting. During the various stages of gari manufacture, 80 to 95% cyanide loss occurs. The best processing method for the use of cassava leaves as human food is pounding the leaves and cooking the mash in water. Fermentation, boiling, and ensiling are efficient techniques for removing cyanide from cassava peels.

Enzyme inhibitors in tuber crops and their thermal stability.

Abstract: Tubers of Cassava (Manihot esculenta), yams (Dioscorea esculenta),aroids (Amorphophallus campanulatus, Colocasia esculenta, Xanthosoma sagittifolium) and Coleus (Solenostemon rotundifolius) were screened for inhibitory activities against amylase, trypsin and chymotrypsin. Coleus tuber possessed the highest anti-amylase activity, whereas Colocasia tuber was the most potent source of anti-tryptic and anti-chymotryptic activity. Xanthosoma tubers exhibited amylase inhibitory activity and Amorphophallus tubers antiprotease activity. Dioscorea esculenta had low levels of amylase and chymotrypsin inhibitors, while Cassava tubers were totally free of inhibitors. When tubers were processed by pressure cooking, there was significant reduction/complete elimination in inhibitory activity. Partial retention of inhibition was observed in the case of amylase inhibitor in Dioscorea, chymotrypsin inhibitor in Colocasia and trypsin inhibitor in Colocasia, Coleus and Amorphophallus. In vitro experiments on heat stability of the different inhibitors revealed almost similar pattern of inactivation.

Biochemical changes in cassava tuber during fermentation and its effect on extracted starch and residue

Abstract: The biochemical changes brought about in cassava tubers during fermentation (72 h) with a mixed culture inoculum are delineated. The initial starch content of the four cultivars studied ranged from 216 to 331.3 g kg -1 and only slight decrease in starch occurred after 72 h fermentation, the final values being 200-302.2 g kg -1 . There was a considerable decrease in the sugar content with fermentation in all the cultivars, indicating a predominant utilisation of the easily assimilable sugars by the microorganisms. A sharp decrease in pH (4.3-4.7) was observed after 24 h fermentation itself, resulting from the production of organic acids. There was increased recovery of the starchy flour from the fermented cassava tubers with concomitant decrease in the residue yield. The starchy flour had higher fiber content than that obtained from the non-fermented tubers. Optical and scanning electron microscopy revealed clustering of starch granules in the starchy flour from fermented tubers.