Feasibility of the use of visible and near infrared spectroscopy to assess soluble solids content and pH of rice wines

Visible and near infrared (Vis/NIR) transmission spectroscopy and a hybrid chemometric method were applied to determine the soluble solids content (SSC) and pH of rice wines. Rice wine samples were scanned by a spectroradiometer within a wavelength region of 325–1075 nm. The calibration set was composed of 240 samples and 60 samples were used as the validation set. Two pre-processing methods were applied on the spectra prior to build PLS regression models. The correlation coefficient (r), standard error of prediction (SEP) and root mean square error of prediction (RMSEP) were 0.95, 0.16 and 0.17 for SSC, while 0.94, 0.02 and 0.02 for pH, respectively. Adequate wavelengths for the SSC and pH prediction were proposed according to the x-loading weights and regression coefficients. The results indicated that Vis/NIR spectroscopy is a promising approach for predicting the SSC and pH of the rice wine.