Deep-fat frying of cassava: influence of raw material properties on chip quality

Thirteen cultivars of cassava (Manihot esculenta Crantz) were used to obtai n chips by deep frying slices of fresh cassava flesh in palm oil. The culti vars were representative of three different levels of four major characteri stics (water, cyanide, starch and amylose content) in parenchyma. The effec ts of raw material composition and crop age (10 and 12 months) on mass tran sfer (dehydration and oil uptake), texture and colour were assessed for 1.5 mm thick chips with a final water content of 0.04kg kg(-1) wet basis, corre sponding to a water activity of about 0.3. Frying time varied from 70 to 90 s and oil bath temperature from 140 to 160 degreesC. All cultivars gave a h igh frying yield (>0.5kg chips kg(-1) fresh cassava) and a chip fat content of between 0.23 and 0.37kg kg(-1) wet basis, with the highest frying yield s and lowest fat contents being obtained from roots with the lowest water c ontent and cyanide content. The intensity of darkening reactions increased in accordance with the level of reducing sugars, while the rigidity modulus of the chips was negatively correlated with the fibre content. The other c haracteristics (starch, amylose and total sugar content) were either not or poorly correlated with any of the chip quality parameters studied. Cyanogl ucosides were only partially eliminated during frying (over 40% retention), so cultivars with a high cyanide content gave bitter chips. For a similar composition, drying rates and cooking rates were much lower when crop age i ncreased. This could be attributed to a structural effect characterising cr op age. (C) 2000 Society of Chemical Industry.