Fast monitoring the dynamic change of total acids during apple vinegar fermentation process using a colorimetric IDA sensor array

In this work, a colorimetric sensor array (CSA) for quantitative determination of total acids in apple vinegar during fermentation was constructed. The sensor array was properly designed based on indicators displacement assay (IDA) using three metal ions (Cu2+, Zn2+ and Ni2+) as receptors to organic acids. The time stability results showed that the prepared CSA had good operational stability. Three quantitative models, including one linear (partial least square, PLS) and two nonlinear (support vector regression, SVR and back propagation artificial neural network, BP-ANN) models were used to estimate the content of total acids in fermentation broth of apple vinegar through image analysis. The correlation coefficient (RP), root mean square error of prediction (RMSEP) and residual predictive deviation (RPD) of the better SVR model were 0.8708, 0.0545 and 10.91, respectively. The results implied that the CSA had an excellent potential for quantitative monitoring of total acids in apple vinegar during fermentation.