[关键词]
[摘要]
目的 探索茯苓丁真空干燥+倾斜式热风联合干燥过程中,真空温度、切换水分比、热风温度及其交互作用对干燥时间、单位能耗、多糖含量、破碎率的影响,以期得到干燥时间短、品质好、能耗低的茯苓丁干燥工艺参数。方法 以茯苓丁为原料,当真空干燥到某一含水率时再进行倾斜式热风干燥;选取真空干燥温度(x1,65~85 ℃)、切换水分比(x2,70%~90%)、热风干燥温度(x3,65~85 ℃)为因素,设计Box-Behnken响应面试验,分析影响各指标的主次因素及各因素间的交互作用,建立干燥时间、单位能耗、多糖含量、破碎率的二次回归模型。构建适应度函数,分别用综合评分法、遗传算法、NSGA-II法进行优化,通过比较3种优化方法的结果,得到最佳工艺参数并加以验证。结果 影响干燥时间、单位能耗、多糖含量、破碎率的主次排序为x2>x3>x1、x2>x1>x3、x3>x2>x1、x2>x3>x1。建立的干燥时间、单位能耗、多糖含量、破碎率回归模型具有统计学意义(P<0.001),可用于对茯苓丁联合干燥评价指标的分析和预测。综合评分法优化结果为真空温度65.12 ℃、切换水分比70.07%、热风温度74.19 ℃,该条件下干燥时间、单位能耗、多糖含量、破碎率分别为330.4 min、4.13 kJ·h/kg、3.52 mg/g、4.48%;遗传算法优化结果为:真空温度82.23 ℃、切换水分比81.10%、热风温度69.04 ℃,该条件下干燥时间、单位能耗、多糖含量、破碎率分别为245.27 min、2.01 kJ·h/kg、3.32 mg/g、23.05%;NSGA-II算法优化结果为真空温度65.04 ℃、切换水分比70%、热风温度70.96℃,该条件下干燥时间、单位能耗、多糖含量、破碎率分别为340.86 min、4.22 kJ·h/kg、3.87 mg/g、4.21%。以适应度为评价指标,可得出NSGA-II算法优化结果最好。结论 NSGA-II算法可用于茯苓丁真空干燥+倾斜式热风干燥工艺的多目标优化,从Pareto集合中选取的较佳工艺参数并进行修正;确定最佳条件为真空温度65 ℃、切换水分比70%、热风温度71℃,该工艺条件下的干燥时间、单位能耗、多糖含量、破碎率分别为(335±13)min、(4.28±0.32)kJ·h/kg、(3.82±0.31)mg/g、(4.33±0.35)%。优化后的联合干燥工艺总体上具有干燥时间短、单位能耗低、多糖含量高、破碎率低等优点,节能增效作用显著,可为茯苓丁的工业化加工提供理论依据和技术支持。
[Key word]
[Abstract]
Objective To investigate the vacuum temperature (x1) switching moisture ratio (x2), hot air temperature (x3) and their interaction on drying time, unit energy consumption, polysaccharide content and crushing rate in the process of "vacuum drying + inclined hot air" combined drying of Poria cocos. Therefore, the drying process parameters of P. cocos with short drying time, good quality and low energy consumption were achieved. Methods Taking P. cocos cube as raw material, when the vacuum drying reaches a certain moisture content, the inclined hot air drying is carried out; The factors of vacuum drying temperature (65—85 ℃), switching moisture ratio (70%—90%) and hot air drying temperature (65—85 ℃) are selected to design Box-Behnken response surface test was used to analyze the primary and secondary factors influencing the indexes and the interaction among them. The quadratic regression model of drying time, unit energy, polysaccharide content and crushing rate were established. The fitness function was constructed and optimized by comprehensive scoring method, genetic algorithm and NSGA-II method respectively. By comparing the results of the three optimization methods, the optimal process parameters were obtained and verified. Results The order of influencing drying time, unit energy consumption, polysaccharide content and crushing rate was x2 > x3 > x1, x2 > x1 > x3, x3 > x2 > x1, x2 > x3 > x1. The regression model of drying time, energy consumption per unit, polysaccharide content and crushing rate was statistically significant (P < 0.001), which could be used to analyze and predict the evaluation index of P. cocos cube combined drying. The optimal process parameters were optimized by comprehensive scoring method as follows: vacuum temperature 65.12 ℃, moisture ratio 70.07%, hot air temperature 74.19 ℃. Under this circumstance, the drying time, unit energy consumption, polysaccharide content and crushing rate was 330.4 min, 4.13 kJ·h/kg, 3.52 mg/g and 4.48%, respectively. The process parameters optimized by genetic algorithm was as follows: vacuum temperature 82.23 ℃, switching water ratio 81.10% and hot air temperature 69.04 ℃. And the drying time, unit energy consumption, polysaccharide content and crushing rate was 245.27 min, 2.01 kJ·h/kg, 3.32 mg/g and 23.05%, respectively. NSGA-II algorithm optimized the optimal process parameters as follows: vacuum temperature 65.04 ℃, switching moisture ratio 70%, hot air temperature 70.96 ℃, under which the drying time, unit energy consumption, polysaccharide content, crushing rate were 340.86 min, 4.22 kJ·h/kg, 3.87 mg/g and 4.21%, respectively. Taking fitness value as the evaluation index, the NSGA-II algorithm optimization can be considered as the best result. Conclusion NSGA-II algorithm can be used for the multi-objective optimization of “vacuum drying + inclined hot air” drying process of P. cocos cubes, and the better process parameters selected from Pareto set are modified. The optimal conditions are determined as follows: vacuum temperature 65 ℃, switching moisture ratio 70%, hot air temperature 71 ℃. The drying time, unit energy consumption, polysaccharide content and crushing rate were (335 ±13) min, (4.28 ±0.32) kJ·h/kg, (3.82 ±0.31) mg/g, (4.33 ±0.35)%, respectively. The optimized combined drying process has the advantages of short drying time, low energy consumption per unit, high polysaccharide content, low crushing rate, and significant energy saving and synergistic effect, which can provide theoretical basis and technical support for the industrial processing of P. cocos.
[中图分类号]
R283.6
[基金项目]
现代农业产业技术体系建设专项资金资助项目(CARS-21);河北省自然科学基金资助项目(C2020207004);河北省高等学校科学技术研究项目(QN2021054);北京市自然科学基金项目(6204035);北京市教委组织部优秀人才项目(2018000020124G034)