Outer Product Analysis Applied to near Infrared and Mid Infrared Spectra to Study a Spanish Protected Denomination of Origin Cheese

Abstract

Near infrared to mid infrared (NIR–MIR) spectroscopy correlation analysis was applied to test its feasibility in understanding the contribution of the absorption bands related to cheese components for the characterisation of protected denomination of origin (PDO) products. The influence of sample presentation on spectral response was also investigated. Idiazabal cheese, a Spanish PDO cheese, was used as a model. Acidity, expressed as pH, dry matter, fat and total nitrogen content were evaluated in duplicate. The NIR–MIR interactions were analysed by outer product analysis. This study allowed the identification of the main absorption bands associated with fat, protein and water, by using the correlations between constituents in the two studied domains. Confirming preliminary results, it was highlighted that quantitative determination is influenced by sample presentation mode.