ANALYSIS OF VIS/NIR SPECTRAL VARIATIONS OF WHOLESOME, SEPTICEMIA, AND CADAVER CHICKEN SAMPLES

The Instrumentation and Sensing Laboratory, ARS, USDA, has developed a Vis/NIR spectroscopic system for on–line poultry carcass inspection. This system was proven to be effective in distinguishing between wholesome and unwholesome carcasses. To better understand how the carcasses can be differentiated, a further in–depth study of Vis/NIR spectra of poultry samples was conducted. Results showed that Vis/NIR spectroscopy can be used to differentiate poultry samples more finely than merely between a wholesome category and a broadly inclusive unwholesome category. Using principal component analysis (PCA) and discriminant analysis, wholesome, septicemia, and cadaver chicken samples were differentiated from each other with high accuracy. The best Vis/NIR classification model, using nine principal components (PCs) and a linear discriminant function, correctly classified 100%, 90.0%, and 92.5% of the whole (skin and meat) samples for wholesome, septicemia, and cadaver categories, respectively. For skin only samples, similar models using nine PCs resulted in lower accuracies. Examination of the PCA loadings for the whole samples suggested that the better discrimination of whole samples was dependent on spectral variation related to different forms of myoglobin present in the chicken meat, i.e. deoxymyoglobin, metmyoglobin, and oxymyoglobin. In particular, key wavelengths were identified at 540 and 585 nm, which have been identified as oxymyoglobin bands, for PCs 1 and 2; 485 nm, metmyoglobin, for PC 3; and 440 nm, deoxymyoglobin, for PC 8.