NMR AND ISOTOPIC RATIO ANALYSIS AS A FORENSIC TOOLS: A CASE STUDY ON BUTTER ADULTERATION

Butter is one of the most popular and commercially valuable dairy products due to its high nutritional value and functional properties. Due to its high commercial value, this is highly susceptible to adulteration, which aims to reduce production costs by using lower-quality fats and oils from other sources, such as vegetable oils and margarine. In this context, developing methodologies capable of identifying butter fraud is extremely important. In this work, the Nuclear Magnetic Resonance (NMR) and Stable Carbon Isotopic Ratio Analysis (SCIRA) were studied to observe evidence of misuse of vegetable oils, such as soybean and palm oils in butter. These techniques are useful tools for analyzing complex mixtures such as fats and oils, allowing simultaneous identification and discrimination. A total of 25 samples were employed, from seized (11); raw materials found on sites used for butter manufacturing and its adulteration (10); and commercial reference samples (04). Considering the ¹H-NMR spectra profile from reference samples, the short fatty acid chains hydrogens, naturally present in the milk fat, and the hydrogens from poly-unsaturated fatty acid chains, naturally present in vegetable oils, were observed successfully.  The isotopic ratio results of the sized samples were consistent with pure C3 sources such as palm vegetable oils, for example, even though NMR analysis revealed a small amount of animal fat in the samples. Thus, based on the analyses of the ¹H NMR spectral profile and isotopic ratio of the seized samples, it was possible to verify the samples submitted to analysis do not match the information declared on their labels, which identify them as butter. It was concluded that the seized products were a mixture of butter (dairy fat of animal origin) with fat of vegetable origin (soybean and palm oil).

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