COMPARISON OF 2 INFRARED SPECTROSCOPIC METHODS FOR CHEESE ANALYSIS

Two infrared spectroscopic methods, optothermal near infrared (NIR) sp ectroscopy and Fourier transform mid-infrared-attenuated total reflect ion (FTIR-ATR) spectroscopy, were applied to 24 cheese samples in orde r to obtain protein, fat and moisture contents. Reference values of th e protein, fat and moisture contents in weight percent were obtained u sing standard wet chemistry analysis. Prediction correlation coefficie nts between 0.93 and 0.96 and standard errors of prediction between 2% and 5% were obtained using optothermal spectroscopy while the corresp onding values for FTIR-ATR were 0.81-0.92 and 4-9%. Inhomogeneities in the cheeses, primarily due to the fat droplets, are probably the main reason for the differences in the error sizes. The superior results f or optothermal spectroscopy are the more attractive because the instru ment is easier to use than the FTIR-ATR instrument, it provides result s more quickly with simpler statistical analysis and it is more compac t and robust.