Effect of drying temperature on color and desorption characteristics of oyster mushroom

Abstract Oyster mushroom (Pleurotus ostreatus) slices were dried in a hot air dryer at three temperatures (45, 55 and 65 °C). The sorption isotherm of dried samples in the water activity (aw) range of 0.556-0.970 was also determined at three temperature levels. Moisture desorption isotherms were obtained from changes in water activities of oyster mushroom slices during drying, and the fitness of GAB, BET, Oswin, Henderson and Halsey isotherm equations to sorption data was calculated. The effect of temperature on color change kinetics of oyster mushroom slices was also investigated during drying. GAB model was the best equation for the prediction of the desorption moisture content of samples. Mathematical modeling of color change kinetics indicated that both zero and first order kinetic models were adequate to describe the browning index (BI) value; however, total color change (ΔE) followed zero-order kinetics. The values of the reaction rate constant, found after the drying at 45, 55 and 65 °C, of the ΔE value were respectively 0.058, 0.065 and 0.089.

摘要：本研究采用热风干燥设备对平菇（Pleurotus ostreatus）切片进行干燥处理，设置45、55、65 ℃三个干燥温度梯度。在0.556~0.970的水分活度（water activity, a_w）范围内，测定了不同干燥温度下干制平菇样品的吸附等温线。通过监测干燥过程中平菇切片的水分活度变化，得到其水分解吸等温线，并计算了GAB、BET、Oswin、Henderson及Halsey等温线方程对吸附数据的拟合优度。同时考察了干燥过程中温度对平菇切片色泽变化动力学的影响。结果表明，GAB模型是预测样品解吸水分含量的最优模型。色泽变化动力学的数学建模结果显示，零级和一级动力学模型均可较好拟合褐变指数（browning index, BI）值，但总色泽变化量（ΔE）仅符合零级动力学规律。在45、55、65 ℃下干燥测得的ΔE值对应的反应速率常数分别为0.058、0.065和0.089。