Molecular Mobility and Seed Longevity in Chenopodium quinoa

摘要

This work analyzed the relationship between water mobility and quinoa seed lon-gevity. Transverse relaxation times (T_2s) by time-resolved nuclear magnetic resonance (NMR) of four genotypes of quinoa seeds (cultivars Chadmo, NL-6, Sajama, and 2-Want) equilibrated at relative humidities (RHs) in the range of 22%-83% were measured. Quinoa seed germination and viability were tested. The curves obtained from seeds equilibrated at low RHs were fitted best to monoexponential decay, with T, values in the range of 100-130ms. The amplitude of the signal was related to the relative amount of lipid and was unaffected by RH. At –50% RH, curves began to fit biexponential decay best. The second term of the biexponential curves showed T_2 values in the range of 1.13-2.54ms, increasing as RH increased. The analysis of isotherm shapes and glass transition temperatures of quinoa seeds revealed that the second term could be attributed to protons both of water in multi-layers and of plasticized solids above the glass transition temperature. Germination tests showed different storage behaviors between cultivars. Water mobility alone did not explain quinoa seed longevity after storage under these experimental conditions.