Quantitative characterization of food products by two-dimensional D –T2T2 and T1T1–T2T2 distribution functions in a static gradient

We present new NMR techniques to characterize food products that are based on the measurement of two-dimensional diffusion–T2T2 relaxation and T1T1–T2T2 relaxation distribution functions. These measurements can be performed in magnets of modest strength and low homogeneity and do not require pulsed gradients. As an illustration, we present measurements on a range of dairy products that include milks, yogurt, cream, and cheeses. The two-dimensional distribution functions generally exhibit two distinct components that correspond to the aqueous phase and the liquid fat content. The aqueous phase exhibits a relatively sharp peak, characterized by a large T1/T2T1/T2 ratio of around 4. The diffusion coefficient and relaxation times are reduced from the values for bulk water by an amount that is sample specific. The fat signal has a similar signature in all samples. It is characterized by a wide T2T2 distribution and a diffusion coefficient of 10−11m2/s for a diffusion time of 40 ms, determined by bounded diffusion in the fat globules of 3 μm diameter.

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