NMR assessment of water uptake in different Vigna spp. seeds

Water uptake in seeds of ten wild and cultivated Vigna spp. accessions was investigated by NMR Spectroscopy. Water absorbed by the intact seeds was measured at intervals by changes in unabsorbed water using analysis of transverse magnetization decay of water protons. Widely different hydration kinetics of first and higher orders were found amongst the samples. the time required to reach saturation hydration capacity ranged from 3 to 16 h; total amount of absorbed water varied from 1.06 to 1.39g H₂O g⁻¹ sample and kinetic constant from 8.2 to 20.4 10⁻³ min⁻¹.
Accessions with a rough seed coat showed a fast water uptake within the first hour while some accessions smooth seed coat need an activation period of 1–5h.
No significant relationships were found between kinetic constant, absorbed water and protein content or some morphological characteristics (100 seed mass, length/width, width/thickness).
Wild species did not absorb water for days, an attribute related to biological survival, but after dehulling they absorbed water at similar rates to the cultivated cowpeas.
NMR can be a suitable technique to investigate some technological characteristics of legumes related to domestic and industrial processing (cooking, canning). It has potential to give data on the various forms of free and bound water, although this was not fully derived in the present work.