雪莲果浆的真空泡沫干燥特性及数学模型

Drying Characteristics and Mathematical Modeling of Yacon Pulp by Vacuum Foam Mat Drying

为了研究乳清分离蛋白对雪莲果浆起泡特性的影响，确定雪莲果浆真空泡沫干燥特性和数学模型，以雪莲果浆固形物含量、起泡剂种类及质量分数和搅拌时间为因素，以泡沫膨胀率、泡沫稳定性和泡沫密度为指标，研究了雪莲果浆的起泡工艺，得到了雪莲果浆适宜的起泡工艺参数：果浆固形物含量5％0％，起泡剂15％乳清分离蛋白，稳定剂1％羧甲基纤维素钠，搅拌时间20min。研究了不同温度（55、65、75℃）和真空度（0．075、0．095MPa）下雪莲果浆的千燥特性。雪莲果浆干燥速率随着温度、真空度的升高而增加。与未经起泡处理的雪莲果浆相比，起泡处理显著增加了干燥过程中的有效水分扩散系数、降低了活化能，进而提高了果浆的干燥速率、缩短了干燥时间。用于描述雪莲果浆真空泡沫干燥的适宜模型为Midilli et al模型。

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.