中国农业科学 ›› 2018, Vol. 51 ›› Issue (23): 4535-4547.doi: 10.3864/j.issn.0578-1752.2018.23.012

• 食品科学与工程 • 上一篇    下一篇

基于BP神经网络和遗传算法的库尔勒香梨挥发性物质萃取条件的优化

张芳2(),未志胜2,王鹏2,李凯旋2,詹萍1(),田洪磊1()   

  1. 1陕西师范大学食品工程与营养科学学院,西安 710119
    2石河子大学食品学院,新疆石河子 832000
  • 收稿日期:2018-05-25 接受日期:2018-09-17 出版日期:2018-12-01 发布日期:2018-12-12
  • 基金资助:
    国家自然科学基金(31571846);石河子大学杰出青年项目(2015ZRKXJQ04)

Using Neural Network Coupled Genetic Algorithm to Optimize the SPME Conditions of Volatile Compounds in Korla Pear

ZHANG Fang2(),WEI ZhiSheng2,WANG Peng2,LI KaiXuan2,ZHAN Ping1(),TIAN HongLei1()   

  1. 1College of Food Engineering and Nutritional Science, Shaanxi Normal University, Xi’an 710119;
    2Food College of Shihezi University, Shihezi 832000, Xinjiang
  • Received:2018-05-25 Accepted:2018-09-17 Online:2018-12-01 Published:2018-12-12

摘要:

【目的】通过BP神经网络结合遗传算法对固相微萃取条件(萃取头种类、样品量、萃取温度、萃取时间和盐离子添加量)的优化,建立高效的库尔勒香梨汁香气物质的萃取分析方法,为库尔勒香梨相关产品天然风味的拟合及调控奠定基础。【方法】通过单因素试验确定最佳萃取纤维头种类和样品量、萃取温度、萃取时间和盐离子添加量的最佳萃取参数。在单因素试验设计的基础上,以库尔勒香梨汁中关键香气物质(己醛、丁酸乙酯、壬醛、乙酸乙酯、(E)-2-己烯醛、己醇、(Z)-2己烯醛、丙酸乙酯和己酸乙酯)的含量为评价指标进行中央复合设计试验进一步考察样品量、萃取温度、萃取时间和盐离子添加量对库尔勒香梨汁固相微萃取效果的影响。最后以中央复合设计的试验结果为初始种群,以样品量、萃取温度、萃取时间和盐离子添加量为输入值,以库尔勒香梨汁中关键香气物质含量为其函数的输出值,通过BP神经网络模型来调试函数适应度。使用中央复合设计数据以外的数据集对BP神经网络外推能力进行验证。利用遗传算法(算法参数:最大进化代数100、初始种群数20、变异概率0.2、交叉概率0.4)在试验水平范围内预测全局最优的萃取条件。【结果】统计分析结果表明,65 μm PDMS/DVB萃取头对库尔勒香梨汁中关键香气物质的萃取效果最好,样品量、萃取温度、萃取时间和盐离子添加量对固相微萃取效果具有显著影响(P<0.05)。BP神经网络的拓扑结构为‘4-15-1’。验证数据和训练数据的MSE均大于0.017;训练、测试和验证数据的相关系数分别为0.990、0.951和0.973,表明BP神经网络预测模型有很好的准确性,可以用于库尔勒香梨汁香气物质固相微萃取结果的预测。BP神经网络外推能力验证试验的结果与BP神经网络模型预测值的拟合度(R 2)为0.992,表明试验建立的BP神经网络模型有很好的外推能力,能够准确地预测不在训练集内的数据集的输出值。遗传算法迭代100代后确定的最优个体为3.41 μg·g -1,最佳固相微萃取条件是样品量5.33 g、萃取温度44.70℃、萃取时间25.22 min和盐离子添加量0.63 g。在尽可能接近此条件下进行验证试验(试验条件:样品量5.33 g、萃取温度45℃、萃取时间25 min和盐离子添加量0.63 g),测得库尔勒香梨汁中9种关键香气物质的含量为(3.37±0.23)μg·g -1,与最优个体预测值相比,误差仅为-1.19%。【结论】上述结果表明BP神经网络模型结合遗传算法是一种准确度较好的优化固相微萃取参数的新方法,同时也为解决非线性模型工艺优化的问题提供了新思路。库尔勒香梨汁香气物质固相微萃取的最佳萃取条件为:样品量5.33 g,萃取温度45℃,萃取时间 25 min,盐离子添加量0.63 g。

关键词: 库尔勒香梨, 挥发性物质, 固相微萃取(SPME), BP神经网络, 遗传算法(GA)

Abstract:

【Objective】 In order to lay the foundation for fitting and regulation of natural flavors of Korla fragrant pear-related products, the extraction and analytical method for Korla pear aroma compounds was established by the optimization of solid phase microextraction (SPME) conditions (extraction fiber type, sample amount, extraction temperature, extraction time, and salt addition amount) with the back propagation neural network coupled genetic algorithm (BPNN-GA). 【Method】The type of extraction fiber and the best extraction parameters of sample amount, extraction temperature, extraction time, and salt addition amount were determined by single factor test. On the basis of the single factor test, the central composite design was applied to further investigate the effects of sample amount, extraction temperature, extraction time, and salt addition amount on the SPME of Korla pear juice by using the content of the key aroma substances in Korla pear juice (1-Hexanal, butanoic acid ethyl ester, 1-nonanal, hexanoic acid ethyl ester, acetic acid ethyl ester, (E)-2-hexenal, 1-hexanol, (Z)-2-hexenal, and propanoic acid ethyl ester) as evaluation indicators. The model of BPNN was used to debug fitness of the function based on the results of central composite design, and then the sample amount, extraction temperature, extraction time, salt addition amount and the content of the key aroma substances in Korla pear juice were used as initial population, input values, and output value, respectively. The generalization ability of BPNN was validated using the data set outside the central composite design. The global optimal extraction conditions within the experimental level were predicted using the genetic algorithm (algorithm parameter setting: maximum evolution algebra 100, population size 20, mutation probability 0.2, and crossover probability 0.4).【Result】The result of statistical analysis showed that the extraction fibers had a significant (P<0.05) effect on the extraction efficiency of SPME, and the 65 μm PDMS/DVB fiber was the best extraction fiber of SPME for volatile compounds of Korla pear juice. The sample amount, extraction temperature, extraction time, and salt addition had significant (P<0.05) effect on the SPME efficiency. The topology of the BPNN was ‘4-15-1’. The Root Mean Square Error (MSE) of the verification data and the training data were both greater than 0.017, and the correlation coefficients of training, test and verification data were 0.990, 0.951 and 0.973, respectively, indicating that the BPNN prediction model had good accuracy and could be used for the prediction of the result of SPME of the aroma substances in Korla pear juice. The fitting degree of the prediction value of BPNN and the verification experiment result validating the generalization ability of the BPNN was 0.992, which indicated the established BPNN model had good generalization ability and could accurately predict the output value of datasets outside the training datasets. Using genetic algorithm after evaluation of data for 100 generations determined the best individual (3.41 μg?g -1) and optimum condition: sample amount 5.33 g, extraction temperature 44.7℃, extraction time 25.22 min and salt addition 0.63 g. The verification test were conducted under these conditions as closely as possible (sample amount 5.33 g, extraction temperature 45℃, extraction time 25 min and salt addition 0.63 g), and the content of 9 key volatile substances in Korla pear juice was (3.37±0.23) μg?g -1, which compared with the predicted value, and the error was -1.19%.【Conclusion】 The above results indicated that BPNN-GA was a new method with better accuracy to optimize the solid-phase microextraction parameters, and the method of BPNN-GA provided a new way to solve the nonlinear problem. And the optimum extraction conditions for SPME of Koral pear juice were as follows: sample amount 5.33 g, extraction temperature 45℃, extraction time 25 min and salt addition 0.63 g.

Key words: Korla pear, volatile compounds, solid phase microextraction (SPME), back propagation neural network, genetic algorithm (GA)