DETERMINATION OF PROTEIN AND FAT IN MEAT BY TRANSMISSION FOURIER-TRANSFORM INFRARED SPECTROMETRY

Stabilized dry calibration powders and sample preparation protocols we re developed for the rapid determination of protein and fat in raw mea t by Fourier transform infrared (FTIR) spectrometry. Ground meat sampl es were suspended in 0.1 mol l(-1) NaOH at 67 degrees C, emulsified at 1360 atm (138 MPa) in a custom-designed high-pressure valve homogeniz er and injected into a 37 mu m FTIR transmission cell. Otherwise insol uble elastin particles were also reduced to colloidal proportions by s hear forces during their forced passage through the valve gap of the h omogenizer. Characteristic IR absorption bands of protein (1548.6 cm(- 1)) and fat 1744.6 (CO) cm(-1) were used for calibration. Under optimu m sampling and emulsification conditions, the multiple correlation coe fficients for calibration (seven standards) were in the range 0.9999-1 .0000 and the reproducibility was superior to results obtained by conv entional chemical methods. The simple correlation coefficients of FTIR predictions versus protein and fat concentrations obtained by primary chemical methods ranged between 0.9941 and 0.9896 depending on the sa mpling and sample preparation strategy. The accuracy of the spectromet ric results was limited by two extrinsic factors: the analytical perfo rmance of the reference chemical methods used to standardize the calib ration powders and the degree of homogeneity of the raw samples.