A method of using the transverse relaxation rate (R2) of solvent NMR signal to noninvasively assess if an alum-containing product, such as a vaccine, has been acceptably resuspended for use following transport and/or storage. This technique allows for the manufacturer and/or distributor and/or end user to monitor for unexpected stressors associated with transport and/or storage including, but not limited to, temperature fluctuations, pH changes, vigorous shaking during transportation, exposure to sunlight, and freezing.