Influence of different drying techniques on the quality and physicochemical properties of Ghana‐sourced turmeric ( Curcuma longa L.) samples

Abstract Background This study evaluated the influence of four drying techniques—freeze drying (FZD), microwave drying (MCD), oven drying (OVD), and sun drying (SUD)—on the bioactive, nutritional, and physical properties of turmeric. Using standard analytical procedures, the samples were examined for antioxidant activity (DPPH and ABTS assays), total phenolic content (TPC), total flavonoid content (TFC), chromatic characteristics (Chroma and Hue values), moisture content, rehydration ratio, percentage weight loss, and curcuminoid content. The purpose was to determine how drying methods affect the retention of essential quality attributes in turmeric. Results The results showed significant differences ( p < 0.05) among the drying techniques. Freeze drying recorded the highest values for antioxidant activities (DPPH: 142.73%; ABTS: 100.56%), TPC (129.50%), TFC (103.30%), curcuminoid content, Chroma (35.01), and Hue (74.03°), indicating superior retention of bioactive compounds and color quality. FZD also had the lowest moisture content (8%), the highest rehydration ratio, and the greatest weight loss, demonstrating efficient water removal and good preservation of structural integrity. Microwave drying (MCD) performed next best, maintaining relatively high levels of bioactive compounds and desirable color attributes. Oven drying (OVD) produced moderate results across the measured parameters. Sun drying (SUD) was the least effective, yielding turmeric of poorer quality characterized by low antioxidant activity, duller color, higher residual moisture, and reduced bioactive compound content. Conclusion Overall, the study demonstrates that freeze drying is the most effective technique for preserving the nutritional, functional, and sensory qualities of turmeric powder, with microwave drying serving as a suitable alternative for small‐scale processors. The findings highlight the importance of adopting low‐temperature drying technologies to improve the quality and market value of turmeric products, particularly in regions where traditional drying methods are commonly used.