Potential of near infrared spectroscopy for the analysis of volatile components in cheeses

Near Infrared Spectroscopy (NIRS) was used for the determination of volatile compounds in cheeses allowed to ripen for different times using a remote fibre-optic reflectance probe. To do so, cheeses with known and varying percentages of cow's, ewe's, and goat's milk were elaborated and used as reference material. The volatile compounds determined were: acetaldehyde, ethanol, 1-propanol, 2-butanol, 2-pentanol, 3-methyl-1-butanol, 2-butanone, 2-pentanone, 2-heptanone and 2-nonanone. The regression method employed was the modified partial least squares (MPLS). The calibration results using 67-72 samples of cheese had a correlation coefficients (RSQ) between 0.600 for the 3-methyl-1-butanol and 0.903 for the 2-nonanone. The robustness of the method was confirmed by applying it to twenty new samples of different compositions and ripening times which did not belong to the calibration group. Likewise, the correlations between the factors of influence studied and the volatile compounds were carried out. The results of the NIRS method are comparable with those of the purge-and-trap-gas chromatography-mass spectrometry.