Quantitative data on powder swelling kinetics is essential to understand phenomena occurring during rehydration, e.g. lump formation. In this study, swelling kinetics of food powders (gelatin powder, soy protein isolate, pea protein concentrate) were quantified by Nuclear Magnetic Resonance (NMR) relaxometry. Using gelatin plates as a model system, it was successfully demonstrated that NMR relaxometry is an efficient, non-destructive method to study swelling kinetics of non-dissolving systems with moderate swelling speeds. For plant-based proteins, high swelling speeds were observed. The obtained maximum water uptake due to swelling was 5.10 ± 0.80 g/g for soy protein isolate and 3.93 ± 0.16 g/g for pea protein isolate, which is in the expected range. Measurement speed was too low to resolve early swelling kinetics (below 84 s), evaluation was more elaborate and results less unambiguous.