Drying Characteristics and Mathematical Modeling of Yacon Pulp by Vacuum Foam Mat Drying
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Abstract:
The purpose of the present study was to illuminate the effect of whey protein isolate on the foam properties of yacon pulp and determine the drying characteristics and mathematical model of vacuum foam mat drying. Effects of total solid content of yacon pulp, types and mass fractions of foaming agent, and whipping time on the foam expansion, foam stability and foam density were investigated. The optimum for stable foam formation was yacon pulp with total solid content of 5%~7%, with 15% whey protein isolate as foaming agent and 1% carboxymethylcellulose sodium as foam stabilizer, and whipping time of 20min. Drying characteristics of foamed yacon pulp at different temperatures (55, 65 and 75 ℃) and vacuum degrees (0.075 and 0.095 MPa) were investigated. Drying rate increased with increasing drying temperature and vacuum degree. Compared with non-foamed pulp, foam mat treatment significantly increased the effective moisture diffusivity coefficients and decreased the activation energy for the diffusion of the moisture associated with yacon pulp and therefore increased the drying rate and lowered the drying time of yacon pulp. Midilli et al. model achieved the best fit and can be used to describe the foam mat vacuum drying process of yacon pulp.
