Improvement of soybean quality by ground source heat pump (GSHP) cooling system

• A ground source heat pump (GSHP) cooling system was applied to the large warehouse.
• The temperatures in GSHP bin were 4.9 °C–6.1 °C lower than control for most of summer.
• Free fatty acid, respiration rate, microorganism load and soluble protein content were analyzed.
• Large warehouse with GSHPs is a promising approach to improve the quality of soybean.

Post-harvest low-temperature management is essential to maintain the quality of raw soybeans. In this study, we applied a ground source heat pump (GSHP) cooling system to a large warehouse and compared the physiological and physical changes of soybeans stored in this warehouse with those stored in a traditional warehouse with mechanical ventilation (control warehouse). The temperature of the soybeans was measured once every three months. The results showed that the average temperature the soybeans in the GSHP warehouse and traditional warehouses was 13.9 and 18.7 °C, respectively. The temperatures in GSHP warehouse were 4.9–6.1 °C lower than that in the control warehouse for most of the summer period. Compared with the control warehouse, the soybeans stored in the GSHP warehouse for 12 months had a notably lower level of the free fatty acid content, microbial load and respiration rate, and a higher level of water solute protein content. Our study suggests that large warehouses using with the GSHP system is a promising approach to improve the quality of stored soybeans.