Simultaneous Quantification of Fat and Water Content in Cheese by TD-NMR

The usefulness of a one-step time domain nuclear magnetic resonance (TD-NMR) method for the simultaneous quantification of fat and water content in cheese has been evaluated. The proposed method consists of a combined relaxation analysis, where the magnetization at a certain time is determined by both the longitudinal (T ₁) and the transverse (T ₂) NMR relaxation processes. Calibration models for fat and water quantification in cheese were constructed using partial least square regression in the whole spectral region, evaluated by cross-validation and subsequently tested with external samples. The results were compared with fat and water values determined by means of IDF standard norms 5A (IDF 1969) and 4A (IDF 1982). The proposed TD-NMR methodology allowed a satisfactory determination of fat and water content in cheese samples (root mean square errors ≤1 % and determination coefficients ≥0.98) of different origins (Mallorca and Menorca), cheese makers, milk treatments (raw and pasteurized), and ripening stages (fresh, half-ripened, ripened, and old-ripened).