Non-destructive evaluation of total volatile basic nitrogen (TVB-N) and K-values in fish using colorimetric sensor array

For rapid evaluation of fish freshness, a colorimetric sensor array has been developed for the sensitive detection to measure simultaneously TVB-N and K value of fish during its storage period. Silver carps were taken as fish samples which were stored at constant temperature of 4 degrees C during experiment period. 10 kinds of porphyrin compounds and 6 pH indicators were selected as chromogenic materials in this experiment according to the previous study and the theoretical research. For comparison, total volatile basic nitrogen (TVB-N) values of fishes were tested by conventional chemical method, and the K-values were measured using High Performance Liquid Chromatography (HPLC). As sensing materials used in the sensor array were chromogenic, the color of the sensor array changed when reacting with odor emitted by fish sample. The color change profiles of the sensor array before and after exposure to the odor of each sample were got using image processing method. And color features were extracted to be analyzed using principal component analysis (PCA), linear discriminant analysis (LDA). The relationship between these analysis results and the TVB-N values and K-values obtained by conventional methods were established using support vector regression (SVR). And therefore models were set up for rapid prediction of TVB-N values and K-values, respectively. For the SVR model of TVB-N content and K-values, calibration correlation coefficient (R-tr) was 0.8564 and 0.8712, and the root mean square error of calibration (RMSEC) was 4.2177 and 0.06127, respectively. It is feasible to predict TVB-N values and K-values according to experiment results of colorimetric sensor array. The results indicated that the novel method based on colorimetric sensor array developed provide a feasible way for rapid and nondestructive evaluation of fish freshness.