Rapid Determination of Main Physicochemical Indexes of Cantonese Soy Sauce in the Fermentation Process Based on Near-infrared Spectroscopy
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Abstract:
The production of soy sauce is crucial in the food industry. This study aimed to achieve the rapid detection of eight physicochemical indexes of Cantonese soy sauce, namely the content of amino acid nitrogen, total nitrogen, soluble salt-free solids, total acid, ammonium salt, total sugar, reducing sugar, and salt. To achieve this goal, first, quantitative prediction models were established for these physicochemical indexes using near-infrared spectroscopy (NIRS). Specifically, the NIRS spectra of Cantonese soy sauce were processed with five spectral preprocessing methods and two feature band screening methods, and the processed spectra were used to construct quantitative prediction models through partial leastsquares regression (PLSR) and support vector regression (SVR). Next, the performances of the models were compared to screen the optimal quantitative prediction models. The results showed that compared with the PLSR-based quantitative prediction models, the SVR-based quantitative prediction models had higher coefficients of determination (R2) and lower root-mean-square errors, indicating that the SVR-based quantitative prediction models were superior after abnormal sample removal, preprocessing, and feature band screening. The R2 values of the training and test sets for each physicochemical index were between 0.991 1~0.962 1 and 0.977 9~0.857 9, respectively. Furthermore, the optimal quantitative prediction models screened for each physicochemical index was externally validated. The absolute error between the predicted and chemical values of each index of the Cantonese soy sauce was ≤ 1.31, and the t-test results showed that there was no significant difference between the two groups of data, indicating that the quantitative prediction models can quickly and accurately detect each physicochemical index of the Cantonese soy sauce. The proposed models can quickly and nondestructively determine eight important physicochemical indexes of Cantonese soy sauce in the fermentation process, laying a foundation for quality control in the actual industrial production process of soy sauce.
