Reconstitution followed by non-targeted mid-infrared analysis as a workable and cost-effective solution to overcome the blending duality in milk powder adulteration detection.

Mid-infrared analysis of reconstituted milk is proposed as a feasible solution for the detection of milk powder adulteration regardless of the blending practice. To challenge the concept, skim milk powders were spiked with three of the most reactive/unstable of potential milk adulterants: semicarbazide hydrochloride, ammonium sulfate and cornstarch. To create the wet-blended set, a fraction of each sample was reconstituted and re-spray dried at laboratory scale with a benchtop spray dryer. Dry and wet-blended adulterated samples were reconstituted prior to mid-infrared measurement and projected onto a one-class classifier SIMCA model for reconstituted skim milk. Quantitative sensitivities, determined from the normalized orthogonal distances, were compared. Although the non-industrial spray drying introduced a spectroscopic bias, as revealed by the control samples, the non-targeted mid-infrared model showed comparable sensitivities for both blending practices once the main bias-rich spectral regions were removed, validating thereby the proposed concept.