Postharvest changes in physicochemical characteristics and free amino acids content of immature vegetable soya bean (Glycine max L.) grains

The aim of this study was to investigate the changes in physicochemical characteristics and free amino acid profile occurring in immature vegetable soya bbean during postharvest storage under three temperatures [5, 10 and 20 (control), ±1 °C] for 7 days. The results showed that a lower temperature provided an effective control in reducing weight loss, maintained firmness, delayed changes in the pod colour and soluble sugars concentration. Twenty‐two free amino acids in immature soya beans also identified by the ¹H NMR spectroscopy were strongly affected by postharvest temperature, and there were time‐specific differences in the concentration. Those significant differences in free amino acids concentration among storage conditions were closely associated with aspartate and glutamate degradation. Additionally, after 7‐day storage at 5 and 10 °C, the soya bean grains accumulated the highest amount of some essential and flavour amino acids, which revealed storage conditions selected should be dictated by the goal.