Changes in chemical composition during soybean seed development

This study examined the compositional change of five specialty soybean genotypes, which are low in oligosaccharides, high in oil, high in protein, large seeded or small seeded, along with two commercial cultivars, Jack and Ozark, during seed development and maturation. Seeds were sampled at 7-day intervals from initial seed formation to full maturity for approximately 8 weeks, and analysed for oil, protein, soluble saccharides, and starch. Although there were significant differences among the seven soybean genotypes in their chemical compositions, some compositional changes followed similar trends. Protein content decreased during the first 3–5 weeks after flowering and then gradually increased. Oil was accumulated rapidly during the early stages. The percentage of starch ranged from 6 to 15% in developing seeds, but declined sharply to 0.2–1% at maturity. Sucrose decreased during seed development and maturation, while non-digestible oligosaccharides (raffinose, stachyose, and verbascose) remained at low levels during early stage until 3 weeks before harvest and increased towards maturity. These findings provide valuable information for developing and selecting specialty soybean varieties for specific applications.