紫菜热风/微波联合干燥工艺优化及品质分析

Optimization of Two Step Drying Process of Porphyra by Hot Air and Microwave and Quality Evaluation

本研究采用热风/微波联合干燥紫菜,以紫菜干燥总时间、干紫菜中蛋白和总糖含量作为评价指标,采用中心组合试验设计、二次多项式(或神经网络)拟合、遗传算法对干燥工艺进行优化,得到紫菜干燥的最佳工艺。结果表明:与微波(先)+热风(后)干燥相比,采用热风(先)+微波(后)的干燥方式能够更加有效地缩短干燥周期,紫菜前期在65℃热风干燥1 h后,采用400 W微波干燥到含水量降至0.1 g/g DM所需的干燥总时间最短,为62.5±1.4 min。对比两种干燥方式最优工艺条件下所得到的干紫菜中蛋白和总糖含量,热风(先)+微波(后)干燥所得到的干紫菜品质要优于微波(先)+热风(后)干燥。前期采用48℃热风干燥3 h,后期在240 W微波功率下干燥所得干紫菜中蛋白质含量最高,为68.82±1.46 mg/g DM;前期采用65℃热风干燥2 h,后期在240 W微波功率下干燥所得干紫菜中总糖含量最高,为124.72±7.17 mg/g DM。总体上,热风(先)+微波(后)的联合干燥方式更适合于紫菜的干制。

In this paper, a two-step hot air and microwave drying method was used to dry Porphyra, and the drying process was optimized. Taking the total drying time of Porphyra, the contents of protein and total sugar in dried Porphyra as indexes, the optimal drying process was obtained by using central composite design, model fitting by either quadratic polynomial or neural network, and genetic algorithm optimization. The results showed that the total drying time for sequential hot air drying(first) and microwave drying(later) was shorter than that for sequential microwave drying and hot air drying. In the case of sequential hot air drying(first) and microwave drying(later), the total drying time required to reduce the moisture content to 0.1 g/g DM was the shortest(62.5±1.4 min), if the hot air drying temperature and time were65 ℃ and 1 h, and the subsequent microwave power was 400 W. Comparing the contents of protein and total sugar in dried Porphyra obtained under the optimal process conditions of the two drying methods, the quality of dried Porphyra obtained by sequential hot air drying(first) and microwave drying(later) was better than sequential microwave drying(first) and hot air drying(later). A highest protein content of 68.82±1.46 mg/g DM was obtained, when the hot air drying temperature and time were 48 ℃ and 3 h, and the subsequent microwave power was 240 W. Moreover, if the samples were first air dried at65 ℃ for 2 h and then microwave processed at 240 W to the end, the total sugar content was the highest(124.72±7.17 mg/g DM). Generally, the sequential hot air drying(first) and microwave drying(later) would be suitable for the dehydration of Porphyra in terms of drying time and product quality.