Rapid Near-Infrared Spectroscopic Method for the Determination of Free Fatty Acid in Fish and Its Application in Fish Quality Assessment

A rapid, simple, and environmentally friendly near-infrared (near-IR) spectroscopic method has been developed to directly determine free fatty acids (FFA) in fish oil and for the assessment of mackerel quality. The use of first derivative mathematical treatment for near-IR spectra of fish oil samples provides better results than N-point smoothing and second derivative. Both Multiple Linear Regression (MLR) and Partial Least Squares (PLS) regression are used for calibration. However, the calibration equation for FFA obtained from PLS gives higher correlation coefficients of calibration and prediction (r c and r p ), and lower standard errors of calibration and prediction (SEC and SEP). The relative errors of prediction for FFA in mackerel fat are less than 8% using the calibration equation obtained from PLS. In this research, FFA change in mackerel has the same trend as hypoxanthine (Hx) change as a fish freshness index. Therefore, near-IR spectroscopy could be a useful technique to determine FFA contents in fish oil and for the assessment of mackerel quality.