Detection of Acid Ester Content in Baijiu (Chinese Liquor) Based on Near Infrared Spectroscopy

To construct the near infrared spectrum model of acid ester content in Baijiu (Chinese Liquor) and detect rapidly the acid ester content in Baijiu. The chemical value of acid ester content in Baijiu was determined by reflux and acid-base titration, which was combined with the near-infrared spectra of 1 mm and 8 mm optical path colorimetric cell of Baijiu, and the near-infrared spectrum model of acid ester content in Baijiu was established by internal cross test and external independent verification test. The results showed that acid ester content in Baijiu had special absorption to near infrared spectroscopy (NIR). The processing method and the best band of 1 mm optical path colorimetric cell were first derivative and 9400~5448 cm⁻¹, and the processing method and the best band of 8 mm optical path cell were first derivative and 9400~7500 cm⁻¹ and 6100~5448 cm⁻¹. The coefficient of determination (R²) between the NIR predicted values and the chemical true values of acid ester content in 1 mm and 8 mm optical path colorimetric cells were 99.18% and 96.62%, and the correction standard deviation (RMSECV) were 0.989 mmol/L and 1.980 mmol/L. The coefficient of determination (R²) of external independent verification model between the predicted values and the chemical true values was 99.45%, and the prediction standard deviation (RMSEP) was 0.819 mmol/L. The results showed that the NIR model built by 1 mm optical path colorimeter cell had good prediction ability and could meet the requirements of rapid detection of acid ester content in Baijiu.