Evaluating the solubility of powdered food ingredients using dynamic nuclear magnetic resonance (NMR) relaxometry

Dynamic nuclear magnetic resonance (NMR) relaxometry was used to monitor hydration and solubility of powdered food ingredients (glucose, cellulose, β-lactoglobulin, and zein) and the effects of stirring rate on the hydration of powdered soy protein. A low-field (15 MHz) NMR spectrometer was used to measure the transverse relaxation times (T2) of stirred dilute aqueous mixtures (0.105 g/3.5 ml) of the powdered food ingredients for up to 50 min. The soluble and insoluble fractions of aqueous mixtures subjected to the same mixing treatment were determined by physically separating the soluble and insoluble components using filtration followed by freeze-drying and gravimetric measurements. Although the absolute value of T2 may not be useful for comparing solubilities of different ingredients, sequential low-field NMR measurements of T2 values can be used for monitoring changes in ingredient solubility over various mixing times, these results showed no significant differences (α=0.05α=0.05) from the filtration and freeze-drying results, and data can be collected in situ. It is proposed that this approach be used by the food industry for optimizing mixing processes.