Application of Mid-Infrared Spectroscopy in the Analysis of Key Indexes of Strong Flavour Chinese Spirits Base Liquor
ZHOU Jun1, 2, YANG Yang2, YAO Yao2, LI Zi-wen3, WANG Jian3, HOU Chang-jun1*
1. Bioengineering College of Chongqing University, Chongqing 400044, China
2. Luzhoulaojiao Co., Ltd., Luzhou 646000, China
3. China National Research Institute of Food & Fermentation Industries Co., Ltd., Beijing 100015, China
Abstract：Quantitative analysis of total acid and ethyl caproate content of key indicators in strong flavour Chinese spirits base liquor（SACSL）based on mid-infrared spectroscopy technology, data preprocessing using standard normal transformation (SNV) method, combined with combined interval partial least squares band selection method (SiPLS) and genetic algorithm (GA) to screen the characteristic absorption wavelength of each index, and finally use partial least squares (PLS) to establish an analysis model, through the determination coefficient R2, prediction standard deviation (RMSEP), performance and standard deviation ratio (RPD) and the actual production of independent test samples to evaluate the effect of the built model, and explore the effect of mid-infrared spectroscopy analysis technology combined with band screening for quantitative analysis of key indicators of SACSL. The results show that the effect of the model built using the mid-infrared full spectrum 397~4 000 cm-1 band is not ideal. The RMSEP values of the total acid and ethyl caproate models reach 0.156 and 0.981, respectively, the R2 is only 0.666 and 0.453, and the RPD value is 1.731 and 1.213, the overall fitting effect of the representative model is not ideal, the prediction error is large, and it cannot be applied to actual production. After the further screening of characteristic variables based on the optimization of the SiPLS band using GA, the effect of the built model has been significantly improved. The GA-BiPLS model with two indicators of total acid and ethyl caproate showed higher prediction accuracy, R2 is increased to 0.993 and 0.997, RMSEP value is reduced to 0.023 and 0.077, RPD value is increased to 11.739 and 15.455, and the number of variables is also reduced from 935 to 55 and 40, respectively, while retaining key information variables to reflect the base wine. While the index characteristics of total acid and ethyl caproate are absorbed, it effectively reduces the complexity of the model, and at the same time improves the calculation speed and prediction effect of the model, which fully reflects the application of band screening to the application of mid-infrared spectrum analysis technology to the quantification of key indicators of SACSL. The importance of analysis also illustrates the great potential of mid-infrared spectroscopy technology combined with chemometric methods in the quality analysis of liquor. Considering the complex composition of liquor, most of the key quality indicators are relatively low, and the fundamental frequency absorption intensity of the mid-infrared absorption region is dozens of times stronger than the frequency doubled and combined frequency absorption. Mid-infrared spectroscopy may be more suitable than other spectroscopy techniques. The rapid analysis of liquor liquid samplesprovide technical reference for the quality control of the liquor brewing process, and provide new ideas for the rapid analysis of liquor quality.
周 军，杨 洋，姚 瑶，李子文，王 健，侯长军. 中红外光谱技术在浓香型白酒原酒关键指标分析中的应用[J]. 光谱学与光谱分析, 2022, 42(03): 764-768.
ZHOU Jun, YANG Yang, YAO Yao, LI Zi-wen, WANG Jian, HOU Chang-jun. Application of Mid-Infrared Spectroscopy in the Analysis of Key Indexes of Strong Flavour Chinese Spirits Base Liquor. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2022, 42(03): 764-768.
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