Osmotic dehydration kinetics of biofortified yellow-flesh cassava in contrast to white-flesh cassava ( Manihot esculenta)

Abstract

In recent times, the cultivation, processing and consumption of biofortified yellow-flesh cassava is of significant interest to breeders and food processors due to its relatively high pro-vitamin-A content, compared to the conventional white-flesh cassava. In light of this, osmotic dehydration (OD) kinetics of a recently released biofortified yellow-flesh cassava was compared to that of a white-flesh cassava, using salt, sugar, and salt–sugar solutions at different temperatures (30, 45, 60 °C) and fixed cube/solution-ratio. Water loss (WL) and solids gain (SG) data were fitted by non-linear regression using four models (Page, Weibull, Azuara, and Peleg). Azuara model was most appropriate in describing OD kinetics for both cultivars. Azuara estimates for equilibrium WL and equilibrium SG, respectively, ranged between 0.101–0.120 and 0.049–0.094 g/g for salt solution, 0.158–0.212 g/g and 0.107–0.268 g/g for sugar solution and 0.234–0.306 g/g and 0.189–0.276 g/g for salt–sugar solution. The best conditions for OD of both cultivars by salt solution and sugar solution was at 60 °C and 45 °C, respectively, while that for salt–sugar solution varied with cultivar. Increasing temperature increased water loss and solids gain. Salt-OD conformed to Arrhenius temperature dependence of diffusivity, but sugar-OD and salt–sugar-OD did not. Micrographs reveal biofortified yellow-flesh cassava was more susceptible to cell wall collapse than white-flesh cassava. Extent of dehydration by OD agents ranked: salt–sugar > sugar > salt. Osmotic dehydration may be useful as a means of dehydration for cassava prior to drying, and is especially relevant for the carotenoids-rich biofortified yellow cassava.