Doenjang, a major traditional Korean condiment, is often dried to reduce volume and thereby shipping cost while increasing shelf life. However, changes of nutritional and sensory properties of doenjang during processing have not been well understood. Therefore, this study aimed to evaluate how drying processes influence the nutritional and chemical properties of doenjang. When two drying methods, hot air drying and freeze drying were compared from the nutritional point of view, air-dried doenjang at 60°C or lower showed similar quality parameters including sensory scores, proximate composition, antioxidant capacity, amino acid composition, amino nitrogen, and acid value to freeze-dried doenjang. In contrast, the sample dried at 80°C and 100°C showed lower quality parameters than the freeze-dried one. Ferric reducing antioxidant potential (FRAP), total phenolics content, amino acid composition, and acid value were shown to reflect the sensory and physical properties of dried doenjang. In particular, the FRAP value of dried doenjang was sensitively responsive to drying temperatures and may be utilized as an early biomarker for quality deterioration of dried doenjang.
Keywords: antioxidant; drying; nutrients; quality; traditional doenjang.