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基于太赫兹光谱的奶粉中葡萄糖及蔗糖定性定量检测方法
引用本文:吴建,刘燕德,李斌,胡军.基于太赫兹光谱的奶粉中葡萄糖及蔗糖定性定量检测方法[J].光谱学与光谱分析,2019,39(8):2568-2573.
作者姓名:吴建  刘燕德  李斌  胡军
作者单位:华东交通大学机电与车辆工程学院,光机电技术及应用研究所,江西南昌330013;华东交通大学机电与车辆工程学院,光机电技术及应用研究所,江西南昌330013;华东交通大学机电与车辆工程学院,光机电技术及应用研究所,江西南昌330013;华东交通大学机电与车辆工程学院,光机电技术及应用研究所,江西南昌330013
基金项目:国家自然科学基金项目(31760344),江西省2011协同创新专项资金项目(赣财教指[2014]156号)资助
摘    要:奶粉富含人体所需的五大营养物质,是婴幼儿主要的营养来源之一,奶粉中的营养成分对婴幼儿的生长发育具有重要影响,除乳糖外的糖类含量超标可能对婴幼儿健康产生不良影响。由于奶粉成分复杂,目前的色谱法和近红外光谱法检测技术都难以满足奶粉糖分快速无损检测的要求,因此亟须探索一种奶粉中葡萄糖、蔗糖含量快速无损检测方法。太赫兹波对不同大分子物质的吸收峰具有“指纹”特性,可利用该特性对不同的大分子物质进行识别。应用太赫兹时域光谱技术(THz-TDS)并结合化学计量学方法对奶粉中葡萄糖、蔗糖两种糖分的定性定量检测方法进行了研究。实验装置采用TAS7500TS太赫兹光谱系统,实验样品为不含糖的婴幼儿奶粉和纯度大于99%的葡萄糖、蔗糖晶体及不同梯度浓度的奶粉-葡萄糖、奶粉-蔗糖混合物,实验分别采集了3种纯品样品及15种不同梯度浓度的奶粉-葡萄糖、奶粉-蔗糖混合物样品的太赫兹时域信号,每个样品采集三次并取平均值作为其时域光谱信号,经快速傅里叶变换(FFT)得到各样品的太赫兹频域信号,再根据Dorney提出的光学参数提取公式计算得到各样品的吸收系数谱和折射率谱。最后分别基于两组混合物样品的吸收系数谱和折射率谱数据,采用偏最小二乘法(PLS)建立相应的定量分析模型,校正集和预测集样品比例为2∶1。实验结果表明,奶粉在太赫兹波段无明显特征吸收峰,葡萄糖和蔗糖分别在1.45,1.8,1.98,2.7 THz和1.5,1.9,2.6 THz频率处有较强的特征吸收峰,可根据两种物质的太赫兹指纹特征峰进行定性分析。不同梯度浓度的两组混合物的整体吸收峰位置与葡萄糖、蔗糖纯品太赫兹吸收峰位置基本一致,具有稳定的吸收特性。基于吸收系数谱和折射率谱数据建立偏最小二乘法模型,均可实现奶粉中葡萄糖和蔗糖的定量分析,且由折射率谱建立的葡萄糖、蔗糖定量回归模型效果均优于由吸收系数谱建立的模型效果,其中,奶粉-葡萄糖混合物中葡萄糖含量PLS模型的校正集相关系数(Rc)及均方根误差(RMSEC)分别为0.99和0.18%,预测集RP及RMSEP分别为0.96和0.66%,奶粉-蔗糖混合物中蔗糖含量PLS模型的校正集Rc及RMSEC分别为0.96和0.55%,预测集RP及RMSEP分别为0.99和0.25%,葡萄糖和蔗糖定量模型的预测效果均较为理想。研究结果表明THz-TDS技术可有效用于奶粉中葡萄糖和蔗糖定性定量分析,为运用THz-TDS技术开展奶粉掺假及品质快速检测方法研究提供参考。

关 键 词:太赫兹时域光谱  奶粉  糖分检测  折射率谱  偏最小二乘法
收稿时间:2018-07-06

Qualitative and Quantitative Detection of Glucose and Sucrose in Milk Powder Based on Terahertz Spectroscopy
WU Jian,LIU Yan-de,LI Bin,HU Jun.Qualitative and Quantitative Detection of Glucose and Sucrose in Milk Powder Based on Terahertz Spectroscopy[J].Spectroscopy and Spectral Analysis,2019,39(8):2568-2573.
Authors:WU Jian  LIU Yan-de  LI Bin  HU Jun
Institution:Institute of Optics-Mechanics-Electronics Technology and Application, East China Jiaotong University, Nanchang 330013, China
Abstract:Milk powder is rich in human body’s five major nutrients, and is one of the main sources of nutrition for infants and young children also. So the nutritional components in milk powder have an important impact on the growth and development of infants. However, excessive sugar content may have adverse effects on the health of infants, except lactose. The chromatography and near infrared spectroscopy detection techniques are difficult to meet the requirements of the rapid and nondestructive testing of milk powder, due to the complex composition of milk powder. Therefore, it is necessary to explore a fast and nondestructive testing method for the content of glucose and sucrose in milk powder. Terahertz wave has fingerprint characteristics for the absorption peaks of different macromolecular substances, which can be used to identify different macromolecular substances. In this paper, the terahertz time domain spectroscopy (THz-TDS) combined with chemometrics method is used to discuss the qualitative and quantitative methods for the determination of glucose and sucrose in milk powder. The experimental device adopts the TAS7500TS terahertz spectroscopy system, and the experimental samples are free-sugar infant milk powder and glucose and sucrose crystals whose purity is greater than 99%, and different concentration of milk powder-glucose, milk powder-sucrose mixture. The terahertz time domain signals of the pressed-slices of pure milk powder, glucose, sucrose and 15 different concentrations of milk powder-glucose, milk powder-sucrose mixture sample, each sample was collected three times and the mean value was taken as the time domain spectral signal. Then the terahertz frequency domain signals of each sample are obtained by Fast Fourier Transform (FFT). The absorption coefficient spectrum and refractive index spectrum of all samples are calculated according to the Dorney optical parameter extraction formula. The partial least squares (PLS) method is used to establish the corresponding quantitative analysis model, based on the absorption coefficient spectra and refractive index spectra of the two mixture samples, respectively, and the ratio of calibration set and prediction set is 2∶1. The experimental results show that there is no obvious absorption peak in the terahertz band, while glucose and sucrose have strong characteristic absorption peaks at the frequencies of 1.45, 1.8, 1.98, 2.7 THz and 1.5, 1.9 and 2.6 THz, respectively. So the glucose and sucrose can be identified according to the THz “fingerprint” characteristic peaks. Meanwhile, the absorption peak of the two mixtures with the concentration varied basically are same as the location of terahertz absorption peak of pure glucose and sucrose, and have stable absorption characteristics. Quantitative analysis of glucose and sucrose in milk powder can be achieved by partial least square (PLS) method based on absorption coefficient spectrum and refractive index spectrum data, and the mixture regression models of glucose and sucrose PLS based on the sample refractive index spectrum are better than the models established based on absorption coefficient spectrum. The former modeling result shows that, the correction set correlation coefficient Rc and root mean square error RMSEC of the PLS regression model of milk powder-glucose mixture are 0.99 and 0.18%, and the prediction set RP and RMSEP are 0.96 and 0.66%. The correlation coefficient Rc and root mean square error RMSEC of the PLS model of sucrose content in the milk powder-sucrose mixture are 0.96 and 0.55%, and the predictive set RP and RMSEP are 0.99 and 0.25%. So the prediction results of glucose and sucrose quantitative analysis models are ideal. The results show that terahertz time-domain spectroscopy can be used in the qualitative and quantitative analysis of glucose and sucrose in milk powder, which provides a reference for the study of adulteration and rapid quality detection of milk powder by using THz-TDS technology.
Keywords:Terahertz time-domain spectroscopy  Milk powder  Sugar detection  Refractive index spectrum  Partial least squares  
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