Research on Identification of Corn Storage Years Based on Raman
Spectroscopy
HUANG Ji-chong1, SONG Shao-zhong2*, LIU Chun-yu1, XU Li-Jun1, CHEN An-liang1, LU Ming1, GUO Wen-jing1, MIAO Zhuang1, LI Chang-ming1, TAN Yong1, LIU Zhe3
1. Jilin Province Key Laboratory of Spectral Detection Science and Technology, School of Physics, Changchun University of Science and Technology, Changchun 130022, China
2. School of Information Engineering, Jilin Normal University of Engineering and Technology, Changchun 130052, China
3. School of Biology and Agricultural Engineering, Jilin University, Changchun 130015, China
摘要： 以松原粮食集团提供不同年份的玉米储备粮为实验样品，采用三级显微拉曼光谱检测仪对不同状态下的玉米单籽粒进行光谱采集，并结合密度泛函理论（DFT）得到分子光谱，研究其内部成分随时间变化的规律。通过DFT理论优化分子结构和分析，将求得分子中每个键对应的振动频率与实际测得的玉米籽粒拉曼光谱进行对比，完成部分峰位指认；对不同储存年份的玉米籽粒外表面拉曼光谱进行了测量，对原始光谱进行预处理后分别在476、1 006、1 156、1 459、1 519、1 597和1 633 cm-1这几处发现了较强的拉曼峰，表征着玉米淀粉、叶黄素、木质素的存在；对不同年份玉米籽粒纵切面的拉曼光谱进行测量，将此部分光谱归一化处理后得到了对应峰位的相对峰强与相对峰面积。通过比较发现除在表面得到的拉曼峰外，在850~1 450 cm-1附近处还发现了新的拉曼峰。其中位于475、863、944、1 260、1 338和1 378 cm-1几处表征淀粉含量的拉曼峰峰强、峰面积、半高宽（FWHM）值随储存年份的增加产生了或增加或减少的现象，表明其物质组成、成分含量、分子结构均发生了不同改变，基本与玉米淀粉老化的机理一致。其中在1 080和1 130 cm-1拉曼峰在三个不同年份玉米纵切面拉曼光谱中的变化差距较大：1 080 cm-1的拉曼峰只存在于2018年、2019年储存的玉米光谱中，1 192 cm-1处的拉曼峰只存在于2020年份的玉米光谱中，且峰强、Full Width at the half of the maximum(FWHM)值有不同程度的变化，可能表示淀粉内某种糖类物质之间的相互转换，可作为鉴定不同年份玉米样品的特征峰。对叶黄素含量相关峰位的物理参数进行了比较，并将其中的峰强、峰面积值与年份做线型拟合分析，拟合程度较好，相关系数均达到了0.9以上，表明叶黄素含量随储存时间延长呈线性下降的趋势。通过与理论计算得到的叶黄素光谱对比分析，发现叶黄素的流失对化学键振动均有不同程度的影响，其中对C═C双键的伸缩振动影响最大。该研究使用密度泛函理论的计算与实验比对结果，探讨玉米的拉曼光谱随时间推移的变化规律，通过分析不同年份玉米的内部成分变化，为使用拉曼光谱鉴别玉米年份提供了一定的依据，拓展了光谱在农产品质量检测分析上的应用。
关键词：拉曼光谱；密度泛函理论；玉米储备粮；成分分析
Abstract：In this study, Songyuan Grain Group Storage's corn grain reserves from various years were used as samples, and a three-stage micro Raman spectrometer was used to gather the spectra of individual grains of corn from multiple conditions. The regularity of its internal components changes over time was investigated using the molecular spectra produced by Density Functional Theory (DFT). The DFT theory optimised the chemical structure, and the vibration frequency associated with each molecule's bond was analyzed. The partial peak location was then determined by comparing the vibration frequency to the Raman spectra of corn grains as measured in practice. Strong Raman peaks were discovered in the original spectra after pretreatment at 476, 1 006, 1 156, 1 459, 1 519, 1 597, and 1 633 cm-1. It indicated the presence of lignin, lutein, and corn starch. Measurements were made of the Raman spectra of longitudinal corn sections from various years. After spectral normalisation, the relative peak intensities and areas of all peak sites were determined. In addition to the surface-based Raman peaks, fresh Raman peaks in the 850～1 450 cm-1 range had also been discovered. With more storage years, distinct changes occur in the starch content's Raman intensity, peak area, and FWHM at 475, 863, 944, 1 260, 1 338, and 1 378 cm-1. It demonstrates how its molecular structure, substance, and makeup have distinctly altered. This modification essentially fits the corn starch aging process. The Raman peaks at 1 080 and 1 130 cm-1 revealed a significant variation in the vertical section Raman spectra of maize across three years. While the Raman peak at 1 192 cm-1 only occurs in the spectrum of maize stored in 2020, the peak strength and FWHM value varies to variable degrees, the Raman peak at 1 080 cm-1 is only present in the spectrum of corn stored in 2018 and 2019. It suggests that the reciprocal conversion of specific carbohydrate compounds in starch can be utilized as a distinctive peak to distinguish between corn samples from various years. The peak strength and peak area values were assessed by linear fitting with the year after the physical properties of the peak sites associated withlutein content were compared. The coefficients were above 0.9, and the fitting degree was good, showing that the lutein concentration declined linearly as storage duration increased. The loss of lutein has varied impacts on the vibration of chemical bonds, with the stretching vibration of the C═C double bond being the most affected. It is discovered by comparing and evaluating the spectrum of lutein acquired from theoretical calculation. This study investigates the changes in the Raman spectra of corn with time using density functional theory calculations and experimental comparisons. It gives a definite basis for identifying corn years using Raman spectroscopy. It increases the application of spectroscopy in agricultural product quality detection and analysis by analysing the internal composition variations of maize in different years.
Key words：Raman spectroscopy; Density functional theory; Corn grains; Componential analysis
黄纪翀，宋少忠，刘春宇，徐立君，陈安亮，鹿 鸣，郭雯静，苗 壮，李长明，谭 勇，刘 哲. 基于拉曼光谱技术的不同年份玉米成分分析[J]. 光谱学与光谱分析, 2024, 44(08): 2166-2173.
HUANG Ji-chong, SONG Shao-zhong, LIU Chun-yu, XU Li-Jun, CHEN An-liang, LU Ming, GUO Wen-jing, MIAO Zhuang, LI Chang-ming, TAN Yong, LIU Zhe. Research on Identification of Corn Storage Years Based on Raman
Spectroscopy. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2024, 44(08): 2166-2173.
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