Abstract:

Fourier transform near infrared spectrometer was used in this experiment to collect the spectra of tilapia dorsal and belly muscle before and after being minced. By fitting the total volatile basic nitrogen (TVB-N) content to the spectra, quantitative prediction models were established. For modeling, Smoothing Average 3 Points (sa3), Smoothing Average 9 Points (sa9), Smoothing Savitzky-Golay 9 Points (sg9), 1st Derivative (Db1), Normalization by Closure (Ncl), Normalization
to Unit Length (Nle), Standard Normal Variate (SNV), and Multiplicative Scatter Correction (MSC) were applied to pretreat the spectra. According to the results, sg9 and Db1 compared with other pretreatment methods could remove the noise, improve the prediction ability of models and the models showed better prediction accuracy and modeling efficiency by using other methods combined with Db1. The best wavenumber region was chosen to get rid of the irrelevant information and the models were further optimized. The determination coefficient of calibration set and validation set for dorsal muscle before being minced was increased from 0.870 and 0.821 to 0.973 and 0.925, respectively. While the standard errors were reduced to 1.032 and 1.581 mg/100 g from 2.152 and 2.991 mg/100 g, respectively. By comparison of model performance, the process of mincing was beneficial to modeling. And the model of minced belly muscle showed the best performance,which showed a determination coefficient of 0.984 with a standard error of 0.879 mg/100 g for validation set. But when the actual requirements for rapid and non-destructive freshness evaluation are under consideration, the model established for flesh before being minced still has obvious advantages. At last, the belly muscle before being minced was used to establish the model. The calibration set gave a determination coefficient of 0.982 with a standard error of 0.962 mg/100 g and the validation set presented a determination coefficient of 0.976 with a standard error of 1.006 mg/100 g. This method showed enormous potential for TVB-N content prediction and non-destructive freshness evaluation of tilapia fillets.

Key words: near infrared spectroscopy, tilapia fillets, freshness, total volatile basic nitrogen, spectral pretreatment