Determination of protein and fat in meat by transmission Fourier transform infrared spectrometry

Abstract

Stabilized dry calibration powders and sample preparation protocols were developed for the rapid determination of protein and fat in raw meat by Fourier transform infrared (FTIR) spectrometry. Ground meat samples were suspended in 0.1 mol l^–1 NaOH at 67 °C, emulsified at 1360 atm (138 MPa) in a custom-designed high-pressure valve homogenizer and injected into a 37 µm FTIR transmission cell. Otherwise insoluble elastin particles were also reduced to colloidal proportions by shear forces during their forced passage through the valve gap of the homogenizer. Characteristic IR absorption bands of protein (1548.6 cm^–1) and fat 1744.6 (CO) cm^–1 were used for calibration. Under optimum sampling and emulsification conditions, the multiple correlation coefficients for calibration (seven standards) were in the range 0.9999–1.0000 and the reproducibility was superior to results obtained by conventional chemical methods. The simple correlation coefficients of FTIR predictions versus protein and fat concentrations obtained by primary chemical methods ranged between 0.9941 and 0.9996 depending on the sampling and sample preparation strategy. The accuracy of the spectrometric results was limited by two extrinsic factors: the analytical performance of the reference chemical methods used to standardize the calibration powders and the degree of homogeneity of the raw samples.