Noninvasive NIR spectroscopy to verify endpoint temperature of kamaboko gel

Noninvasive near-infrared (NIR) spectroscopy was employed to assess the endpoint temperatures (EPT) of kamaboko gel (n=140) prepared at different temperatures. Partial Least-Squares (PLS) and Multiple Linear Regressions (MLR) were used to develop a calibration which was tested with a validation set. Spectral changes upon heat treatment were related to the heating temperature which might be the reason for changes in the secondary structure of the gels due to the denaturation of proteins, and to changes in the state of water. The changes are most clearly seen in the 1300-1600 nm region in bands mainly attributed to absorption by functional groups in protein. NIR-predicted EPT and actual heating temperatures revealed a linear relationship (R=0.98). Between 30 and 90 °C, NIR spectroscopy detected EPT of kamaboko gels with a prediction error of 2.16 °C. The MLR and PLS calibration had similar performance for determining EPT of kamaboko gel if the appropriate wavelengths or wavelength region were selected.