Determination of volume fraction of acetic acid in Chinese aged liquor by 3-D fluorescence spectrometry

SONG Xinshu; CHEN Guoqing; ZHU Zhuowei; MA Chaoqun; ZHU Chun; ZHANG Xiaohe; LIU Huaibo; ZHU Conghai

doi:10.7510/jgjs.issn.1001-3806.2018.04.018

Volume 42 Issue 4

May 2018

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Determination of volume fraction of acetic acid in Chinese aged liquor by 3-D fluorescence spectrometry

1.
School of Science, Jiangnan University, Wuxi 214122, China
2.
Jiangsu Provincial Research Center of Light Industrial Optoelectronic Engineering and Technology, Wuxi 214122, China
3.
School of Internet of Things Engineering, Jiangnan University, Wuxi 214122, China

Corresponding author: CHEN Guoqing, cgq2098@163.com ;
Received Date: 2017-06-26
Accepted Date: 2017-10-17

Abstract

In order to quickly determine the volume fraction of acetic acid in Chinese aged liquor, 3-D fluorescence spectroscopy and alternate fitting residual algorithm were used. Firstly, 3-D fluorescence spectra of different volume fraction of acetic acid of ethanol aqueous solution was used as the calibration set. 3-D fluorescence spectrum of liquor was used as the predicted set. Alternate fitting residual algorithm was used to analyze. Standard addition method was used to verify the accuracy of the results. Through theoretical analysis and experimental verification, the results show that, correlation coefficient between the predicted volume fraction and the experimental volume fraction is 0.9926. Average recovery percentage is 101.97%. 3-D fluorescence spectrometry combined with alternate fitting residual algorithm can quickly and effectively determine the volume fraction of acetic acid in Chinese aged liquor. This result is helpful for the detection of monomer volume fraction in Chinese aged liquor.
- spectroscopy,
- 3-D fluorescence spectra,
- alternate fitting residue algorithm,
- Chinese aged liquor,
- acetic acid

References

[1]	ZHU S, LU X, JI K, et al.Characterization of flavor compounds in Chinese liquor Moutai by comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry[J]. Analytica Chimica Acta, 2007, 597(2):340-348. doi: 10.1016/j.aca.2007.07.007
[2]	ZHU W H, CHEN G Q, ZHU Zh W, et al. Year prediction of a mild aroma Chinese liquors based on fluorescence spectra and simulated annealing algorithm[J]. Measurement, 2017, 97(11):156-164.
[3]	YANG J L, ZHU T, XU Y, et al. Study on ultraviolet fluorescence spectra of monomers of distilled spirits[J]. Spectroscopy and Spectral Analysis, 2009, 29(12):3339-3343(in Chinese).
[4]	TANG R. The relations of capproate bacteria, pit mud and Luzhou-flavour liquor[J]. Liquor Making, 2005, 32(4):24-27(in Chinese).
[5]	ZHU Zh W, QUE L Zh, CHEN G Q, et al.Year discrimination of mild aroma Chinese liquors using three-dimensional fluorescence spectroscopy combinedwith parallel factor and neural network[J]. Spectroscopy and Spectral Analysis, 2015, 35(9):2573-2577(in Chinese).
[6]	ZHU M, FAN W, XU Y, et al.1, 1-Diethoxymethane and methanethiol as age markers in Chinese roasted-sesame-like aroma and flavour type liquor[J]. European Food Research and Technology, 2016, 242(11):1985-1992. doi: 10.1007/s00217-016-2697-x
[7]	HAN S, ZHANG W, LI X, et al. Determination of three alcohols in Chinese Dukang base liquor by FT-NIR spectroscopy[J]. Food Analytical Methods, 2016, 9(8):2194-2199. doi: 10.1007/s12161-016-0403-z
[8]	MA L, SHEN X M, LI A J, et al. Determination of the content of lactic acid & acetic acid by HPLC[J]. Sichuan Food and Fermentation, 2016, 52(1):84-86(in Chinese).
[9]	WU J F, XU Y.Comparison of pyrazine compounds in seven Chinese liquors using headspace solid-phase micro-extraction and GC-nitrogen phosphourusdetection[J]. Food Science and Biotechnology, 2013, 22(5):1-6.
[10]	ZHU W, REN C, NIE Y, et al.Quantification of ochratoxin a in Chinese liquors by a new solid-phase extraction clean-up combined with HPLC-FLD method[J]. Food Control, 2016, 64(6):37-44.
[11]	CHEN G Q, WU Y M, WANG J, et al. Fluorescence spectroscopy study of synthetic food colors[J]. Spectroscopy and Spectral Analysis, 2009, 29(9):2518-2522(in Chinese).
[12]	ZHUNAG Y, MA Ch Q, WANG X H, et al. Simultaneous determination of three antibiotics based on synchronous fluorescence combined with neural network[J]. Laser Technology, 2017, 41(4):489-493(in Chinese).
[13]	DU J M, CHEN G Q, MA Ch Q, et al. Determination of carmine concentration with 3-D synchronous fluorescence spectrometry[J]. Laser Technology, 2017, 41(4):489-493(in Chinese).
[14]	URÍČKOVÁ V, SÁDECKÁ J, MÁJEK P.Classification of Slovak juniper-flavoured spirit drinks[J]. Journal of Food & Nutrition Research, 2015, 54(4):425-429.
[15]	ELCOROARISTIZABAL S, CALLEJÍN R M, AMIGO J M, et al.Fluorescence excitation-emission matrix spectroscopy as a tool for determining quality of sparkling wines[J]. Food Chemistry, 2016, 206(9):284-290.
[16]	ZHONG X D, FU D S, WU P P, et al.Rapid fluorescence spectroscopic screening method for the sensitive detection of thiabendazole in red wine[J]. Analytical Methods, 2014, 6(18):7260-7267. doi: 10.1039/C4AY00991F
[17]	WU H L, NIE J F, YU Y J, et al. Multi-way chemometric methodologies and applications:a central summary of our research work[J]. Analytica Chimica Acta, 2009, 650(1):131-142. doi: 10.1016/j.aca.2009.05.041
[18]	XIA A L, WU H L, FANG D M, et al. A novel trilinear decomposition algorithm for second-order linear calibration[J]. Chemometric and Intelligent Laboratory Systems, 2000, 52(1):75-86. doi: 10.1016/S0169-7439(00)00081-2

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引言

白酒年份酒是指有着一定贮存时间的白酒，白酒年份酒因其相对于其它白酒更加醇厚的口感而得到广大消费者的青睐，但同时由于白酒年份酒行业标准的不完善，使得市场上年份酒质量参差不齐。因此，亟需运用新兴技术对白酒年份酒中的物质进行检测。

白酒是一种成分比较复杂的混合物^[1]，其中水和乙醇为主要物质，体积分数约为0.98，另有上千种微量物质的体积分数约为0.02，但正是这0.02的微量物质对白酒的品质有着较大的影响^[2-3]。乙酸对于浓香型白酒香型的形成的贡献很大，它在一定程度上影响浓香型白酒的质量与风格^[4]。它具有窖泥臭气，醇、甜，并带有底窖香味。随着白酒的贮存，白酒里也同时发生着水解、氧化、酯化等反应^[5]，有些白酒中单体物质的体积分数随着白酒年份有着一定的变化，所以检测白酒年份酒中单体体积分数可以有助于白酒的质量鉴定以及白酒年份的鉴别^[6-7]。

目前，常见的检测白酒年份酒中物质体积分数的技术有很多，主要包括气相色谱法^[8]、超高效液相色谱法^[9]、顶空固相微萃取法和气相色谱-质谱联用法^[10]、固相萃取-高效液相色谱^[11]等，上述几种方法在测量之前需对待测样本进行预处理，而且过程较为复杂繁琐。荧光分析法是一种新型的灵敏度较高的检测手段，其具有检测速度快、检测成本低廉、需要样品少、对样品损伤小等优势，使得3维荧光光谱在食品技术检测方面有着广泛的应用^[12-16]。作者已经应用3维荧光光谱研究白酒中的主要微量物质对白酒光谱的影响，但是尚未进一步在白酒荧光光谱上进一步细化研究，比如应用荧光分析法来检测白酒中单体物质的体积分数。

本文中通过将白酒年份酒的3维荧光光谱结合三线性交替拟合残差算法来直接检测白酒年份酒中乙酸的体积分数，实现快速准确定量白酒中单体物质的目的。

1. 算法原理

1.1. 三线性模型

在荧光分析时，扫描k个样品的3维荧光光谱可构成一个大小为I×J×K的3维荧光矩阵，三线性模型如下^[17]：

式中, N代表组分数，即有荧光贡献的成分数；⊗为张量积；a_k代表组分k的激发光谱矩阵；b_k代表组分k的发射光谱矩阵；c_k代表组分k的体积分数矩阵；E代表测量误差的大小为I×J×K的3维残差矩阵。

1.2. 交替拟合残差算法

交替拟合残差算法(alternating fitting residue algorithm, AFR)基于三线性模型的循环对称性来获得新的残差，并在此基础上得到3个目标函数^[18]：

式中, p, q, r为拟合因子，一般情况下选p=q=r=1;上标T表示转置，+表示共轭转置，F表示矩阵范数; A, B, C为因子载荷矩阵。再使用交替最小化上述目标函数来进行分解，即据(1)式通过初始值A, B求C；同理通过B, C求A；通过A, C求B，最终使得残差矩阵可以收敛。

2. 实验

2.1. 实验仪器与样品

实验仪器：英国Edinburgh FLS920P型稳态和时间分辨荧光光谱仪、移液器、酒精计。

实验样品：某酒厂提供的某浓香型年份白酒样品，分别为1999年、2004年、2009年、2011年、2012年生产。乙酸由国家标准物质研究中心提供的分析纯，乙醇为SIGEMA公司购买的分析纯，水为超纯水。

参量设置：激发波长的测量范围为460nm~500nm，步长2nm。发射波长的测量范围为514nm~550nm，步长为2nm，激发和发射狭缝宽度分别设置为5nm，积分时间设置为0.1s。

2.2. 实验方法

使用酒精计测得白酒年份酒样品酒精度为68°，使用乙酸和体积分数为0.68的乙醇水溶液配制成乙酸乙醇水溶液，乙酸的体积分数范围为0.0000~0.005，体积分数间隔为0.0005，共计11个样本作为校正集，编号为1~11，如表 1所示。扫描其3维荧光光谱，使用AFR算法结合留一交互验证法预测乙酸体积分数来检验算法的有效性与校正集的可靠性。

calibration sample volume fraction of acetic acid

1 0.0050

2 0.0045

3 0.0040

4 0.0035

5 0.0030

6 0.0025

7 0.0020

8 0.0015

9 0.0010

10 0.0005

11 0.0000

Table 1. The concentration of calibration

将5个年份的酒样作为预测集，不做任何预处理, 按照年份由高到低编号为1~5。使用FLS920P荧光光谱仪测定上述样本的3维荧光光谱并使用AFR算法预测其乙酸的体积分数。

最后使用标准添加法来验证预测结果的准确性。

4. 结论

提供了一个简单快速的方法来检测白酒年份酒中乙酸的体积分数，在有干扰物存在的情况下，不需要经过任何对样品预处理的过程。使用乙酸乙醇水溶液作为校正集，待测酒样为预测集，使用AFR算法进行解析并测定，待测酒样中乙酸的体积分数分别为0.00089, 0.00119, 0.00186, 0.00276, 0.00383，再通过使用标准添加法验证得到上述测定结果是比较准确的。由此可以说明本方法测量的结果准确可靠，可为检测白酒年份酒中单体的体积分数测量提供一个新的思路。

Reference (18)

[1]	ZHU S, LU X, JI K. Characterization of flavor compounds in Chinese liquor Moutai by comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry[J]. Analytica Chimica Acta, 2007, 597(2): 340-348. doi: 10.1016/j.aca.2007.07.007
[2]	ZHU W H, CHEN G Q, ZHU Zh W. Year prediction of a mild aroma Chinese liquors based on fluorescence spectra and simulated annealing algorithm[J]. Measurement, 2017, 97(11): 156-164.
[3]	YANG J L, ZHU T, XU Y. Study on ultraviolet fluorescence spectra of monomers of distilled spirits[J]. Spectroscopy and Spectral Analysis, 2009, 29(12): 3339-3343.
[4]	TANG R. The relations of capproate bacteria, pit mud and Luzhou-flavour liquor[J]. Liquor Making, 2005, 32(4): 24-27.
[5]	ZHU Zh W, QUE L Zh, CHEN G Q. Year discrimination of mild aroma Chinese liquors using three-dimensional fluorescence spectroscopy combinedwith parallel factor and neural network[J]. Spectroscopy and Spectral Analysis, 2015, 35(9): 2573-2577.
[6]	ZHU M, FAN W, XU Y. 1, 1-Diethoxymethane and methanethiol as age markers in Chinese roasted-sesame-like aroma and flavour type liquor[J]. European Food Research and Technology, 2016, 242(11): 1985-1992. doi: 10.1007/s00217-016-2697-x
[7]	HAN S, ZHANG W, LI X. Determination of three alcohols in Chinese Dukang base liquor by FT-NIR spectroscopy[J]. Food Analytical Methods, 2016, 9(8): 2194-2199. doi: 10.1007/s12161-016-0403-z
[8]	MA L, SHEN X M, LI A J. Determination of the content of lactic acid & acetic acid by HPLC[J]. Sichuan Food and Fermentation, 2016, 52(1): 84-86.
[9]	WU J F, XU Y. Comparison of pyrazine compounds in seven Chinese liquors using headspace solid-phase micro-extraction and GC-nitrogen phosphourusdetection[J]. Food Science and Biotechnology, 2013, 22(5): 1-6.
[10]	ZHU W, REN C, NIE Y. Quantification of ochratoxin a in Chinese liquors by a new solid-phase extraction clean-up combined with HPLC-FLD method[J]. Food Control, 2016, 64(6): 37-44.
[11]	CHEN G Q, WU Y M, WANG J. Fluorescence spectroscopy study of synthetic food colors[J]. Spectroscopy and Spectral Analysis, 2009, 29(9): 2518-2522.
[12]	ZHUNAG Y, MA Ch Q, WANG X H. Simultaneous determination of three antibiotics based on synchronous fluorescence combined with neural network[J]. Laser Technology, 2017, 41(4): 489-493.
[13]	DU J M, CHEN G Q, MA Ch Q. Determination of carmine concentration with 3-D synchronous fluorescence spectrometry[J]. Laser Technology, 2017, 41(4): 489-493.
[14]	URÍČKOVÁ V, SÁDECKÁ J, MÁJEK P. Classification of Slovak juniper-flavoured spirit drinks[J]. Journal of Food & Nutrition Research, 2015, 54(4): 425-429.
[15]	ELCOROARISTIZABAL S, CALLEJÍN R M, AMIGO J M. Fluorescence excitation-emission matrix spectroscopy as a tool for determining quality of sparkling wines[J]. Food Chemistry, 2016, 206(9): 284-290.
[16]	ZHONG X D, FU D S, WU P P. Rapid fluorescence spectroscopic screening method for the sensitive detection of thiabendazole in red wine[J]. Analytical Methods, 2014, 6(18): 7260-7267. doi: 10.1039/C4AY00991F
[17]	WU H L, NIE J F, YU Y J. Multi-way chemometric methodologies and applications:a central summary of our research work[J]. Analytica Chimica Acta, 2009, 650(1): 131-142. doi: 10.1016/j.aca.2009.05.041
[18]	XIA A L, WU H L, FANG D M. A novel trilinear decomposition algorithm for second-order linear calibration[J]. Chemometric and Intelligent Laboratory Systems, 2000, 52(1): 75-86. doi: 10.1016/S0169-7439(00)00081-2

samplenumber	the realvolume fraction	the predicted volume fraction	recoverypercentage/%
1	0.00500	0.00496	99.20
2	0.00450	0.00467	103.78
3	0.00400	0.00405	101.25
4	0.00350	0.00334	95.43
5	0.00300	0.00278	92.67
6	0.00250	0.00254	101.60
7	0.00200	0.00212	106.00
8	0.00150	0.00155	103.33
9	0.00100	0.00099	99.00
10	0.00050	0.00059	118.00
11	0.00000	-0.00009	—
RMSEP		0.00162
average recovery percentage		102.03%
correlation coefficient		0.9974

sample number	the real volume fraction	the predictedvolume fraction	recovery percentage/%
Ⅰ	0.00165	0.00155	93.94
Ⅱ	0.00184	0.00182	98.91
Ⅲ	0.00205	0.00217	105.85
Ⅳ	0.00246	0.00252	102.44
Ⅴ	0.00264	0.00287	108.71
RMSEP		0.00045
average recovery percentage		101.97%
correlation coefficient		0.9926

Determination of volume fraction of acetic acid in Chinese aged liquor by 3-D fluorescence spectrometry