Effects of harvest maturity, steaming time and heat pump drying on phenolic content and antioxidant activity of Black ginger (Distichochlamys orlowii) powder

Abstract

This study focused on the effects of harvest maturity, steaming time and heat pump drying temperature on the total phenolic content (TPC) and antioxidant activity (IC₅₀) of Black ginger powder (Distichochlamys orlowii). The results indicated that the physiological ripening stage plays a decisive role in raw material quality; specifically, the 11-month post-planting harvest time was optimal with high total soluble solids (TSS) and high reducing sugar content, while there was an increase in TPC combined with a decrease in IC₅₀ values compared with earlier stages. In the pre-treatment stage, saturated steaming for 2 minutes significantly enhanced TPC and improved antioxidant capacity (achieving the lowest IC₅₀). Regarding the dehydration process, a heat pump drying temperature of 55 °C was the best for preserving heat-sensitive bioactive compounds, resulting in a Black ginger powder product with a TPC of 3.44 mg GAE/g DW, the lowest IC₅₀ value (451.56 µg/mL), and a solubility of 25.75%. The research results are an important scientific basis for standardising the processing of a Black ginger powder, which is rich in bioactive compounds and has high antioxidant activity.