Analysis of traditional Korean soybean pastes ‘Doenjang’ prepared by processing methods obtained from ancient documents

Abstract

The purpose of this study was to evaluate the amino acid score and quality characteristics of commercial (CCT, 'C' Co., Ltd.; CDT, 'D' Co., Ltd.; and CKT, 'K' Co., Ltd.) and traditional (CJS, Chunsie; NJ, Nanjang; CJ, Chungjang; NCJ, Nan-chungjang; and GCJ, Gihwa-chungjang) 'Doenjang' samples, and to compare the correlation between the manufacturing methods and quality characteristics. Variations in pH, titratable acidity, salinity, and reducing sugar (RS) content were observed among the samples. The total essential amino acid (TEAA) contents were 254.93-1,777.79 mg/100 g, while glutamic acid was most abundant in the CKT sample as 2,423.41 mg/100 g. The protein-digestibilitycorrected amino acid score was 0.49 for CSJ. Some commercial and traditional 'Doenjang' samples showed high total polyphenol content (GCJ, 2.59%), 2,2-dipenyl-1-picrylhydrazyl radical scavenging capacity (CDT, 19.84 mg AA eq/g; GCJ, 19.63 mg AA eq/g), and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) radical scavenging capacity (NCJ, 64.55 mg AA eq/g). The manufacturing method of 'Doenjang', pH, acidity, and salinity were positively correlated (p<0.05; p<0.01), whereas the manufacturing method of 'Doenjang', RS, and TEAA were negatively correlated (p<0.01). These results provide information regarding the quality characteristics for the selection of suitable traditional methods to produce high-quality 'Doenjang'.