Foam Mat Drying of Yellow Cassava Using Egg Albumin and Properties of the Associated Products
Oluwatoyin Ayetigbo1, Sajid Latif1, Christina Boura2, Joachim Müller1
1University of Hohenheim, Inst. of Agricultural Engineering, Tropics and Subtropics Group, Germany
The main challenges of the use of fresh cassava as food are the rapid post-harvest deterioration and the toxicity due to the presence of cyanogenic glucosides. Foam-mat drying (FMD) was considered to solve these problems. Response surface method was used to optimise the foaming variables. Five independent variables were considered including pulp concentration (20, 25, 30 %), holding time (1, 3, 5 days), concentration of foaming agent (egg albumin) (2, 16, 30 %), concentration of stabiliser (NaCMC) (0.1, 0.8, 1.5 %), and whipping time (1, 3, 5 min). Two responses were measured: foam overrun (FO) and air volume fraction (AVF). The optimum foaming variables were achieved when pulp concentration was 20 %, holding time was 1 day, concentration of egg albumin was 30 %, concentration of NaCMC was 0.1 %, and whipping time was 5 min. The predicted and validated FO were 33.9 % and 30.2 %, respectively, and the predicted and validated AVF were 0.25 and 0.23, respectively. Drying kinetics at 70 °C showed that Page model was the best model to describe moisture removal ratio, and cassava foam dried faster than the non-foamed cassava pulp. The total carotenoids content (TCC) reduced significantly with FMD. The cyanogenic glucosides content (CGC) of the cassava foam powder was 10.6 μg g-1. The foam air bubbles size and the pulp starch granules size had slight positive skew probability distribution. Luminosity (L*) increased with FMD. The water absorption capacity (WAC) of the foam powder was 0.89 g/g and the oil absorption capacity (OAC) was 0.73 g/g. The swelling power (SP) and solubility of the foam powder was 966.9 % and 38.2 % respectively. The foam powder required a least gelation concentration of 6 % w/v and the pulp powder required 20 % w/v. Freeze thawing led to syneresis of 38.7 % water from the foam powder and 17.2 % from the pulp powder. The viscosity of the foam powder and the pulp powder at different temperatures (25, 55, 85 °C) and shear rates (100, 300, 500, 700, 900 s-1) showed that the powders had pseudoplastic, non-Newtonian rheology.
Keywords: Carotenoids, cassava foam, egg albumen, foam mat drying, viscosity
Contact Address: Oluwatoyin Ayetigbo, University of Hohenheim, Inst. of Agricultural Engineering, Tropics and Subtropics Group, Garbenstr. 9, 70599 Stuttgart, Germany, e-mail: ayetigbo_oluwatoyinuni-hohenheim.de