A preliminary study of milk powder hydration using TEDSpiL continuous wave NMR.

Moisture content of foodstuffs are typically assessed by Titration or Near Infrared Spectroscopy which are labour intensive as a manual measurement or costly when automated. Magnetic Resonance offers a method for moisture evaluation but is also normally costly. In this work we revisit Look and Locker's "Tone Burst" experiment with a marginal oscillator to evaluate moisture content of powdered skimmed milk subjected to increased humidity. We refer to this technique as the Transient Effect Determination of Spin-Lattice (TEDSpiL) relaxation times. Moisture content in the samples ranged from 0-12% as determined from the weight gained by the dry powder when re-suspended in water to reach a concentration of 40% w/v. The relaxation properties of re-hydrated samples were measured with a CW NMR sensor. Solutions made up from powders with a higher retained moisture content provided lower measured relaxation values providing a method of measuring the moisture content of the powder. This technique provides a moisture measurement in under 5 seconds compared to several minutes for the equivalent pulsed method using low field hardware.