Kinetic parameters of mass transfer in deep-fat frying of cassava slices (Manihot esculenta Crantz)

Abstract

Moisture and oil absorption changes occurred in the deep-fat frying of cassava slices (Manihot esculenta Crantz), ICA-costeña variety, were evaluated to determine the kinetic parameters of oil absorption and moisture loss. Slices with 3.5 cm diameter and 1.3 mm thick were pretreated with (i) blanching at 80°C for 4 min, (ii) osmotic dehydration in saline solution (3% w / w) at 30°C for 4 hours and a ratio of 1:20 by weight. The slices were processed in Caribbean® palm oil at 140°C, 160°C and 180°C and a ratio of 0.005 kg sample / L oil. The experiment was conducted under a randomized completely block design with factorial arrangement 32 (factors: temperature and pretreatment) with three replications. The moisture and oil contents were determined by AOAC 984.25/2002 and Soxhlet methods, respectively. Moisture ́s  effective  diffusivity  ranged  between  10.44  x  10-9 and  148  x  10-9  m2/s.  The  convective  moisture  transfer  coefficient ranged between 1.37 x 10-5 y 7.37 x 10-5 m/s having a linear behavior with respect to the oil temperature. In the equilibrium, the oil absorption content ranged between 0.1391 and 0.3607 g oil / g solids and the specific rates between 8.14 x 10-3 y 77.08 x 10-3 s-1. Blanching and osmotic dehydration significantly affected the effective diffusivity of mass transfer and the oil content at equilibrium (p < 0.05).