COMPARISON OF SOLUBLE SUGAR DEGRADATION IN SOYBEAN SEED UNDER SIMULATED TROPICAL STORAGE-CONDITIONS

Storage of soybean [Glycine max (L.) Merr.] seed under tropical condit ions can lead to deterioration that affects product taste and color. A study was designed to assess the effect of extreme storage conditions on the degradation of soluble sugars and to relate these changes to s eed deterioration. Seed of six cultivars of soybean were stored for 9 mo. under control (4 degrees C, 45% RH) and simulated tropical (30 deg rees C, 82% RH) conditions. Soluble sugar metabolism was monitored by high performance anion exchange chromatography coupled to pulsed amper ometric detection (HPAE-PAD). Soluble sugar content was constant or on ly slightly affected under control conditions. However, substantial hy drolysis of stachyose, raffinose, and verbascose occurred under simula ted tropical conditions. The resulting release of glucose and galactos e, combined with the degree of hydrolysis of oligosaccharides, appears to be strongly linked to soybean seed quality as indicated by seed ge rmination. Storage behavior was cultivar dependent, pointing to the im portance of selecting cultivars for storability in tropical countries. Determination of glucose seems to be a sensitive analytical and pract ical tool for monitoring soybean seed quality and deterioration under extreme climatic conditions.