Analysis and characterisation of amino acid contents of thua nao, a traditionally fermented soybean food of Northern Thailand

Abstract

Thua nao, a Thai traditional soy-fermented condiment, is extensively consumed in the northern part of Thailand. In this study, an analysis of free amino acid (FAA) profiles was determined using reversed-phase high performance liquid chromatography. For this, thua nao samples conventionally produced were collected from six local markets (Mae Wang, Mae Hia, Mae Taeng, Jom Thong, San Patong and San Sai) in Chiang Mai, Thailand and used for the analysis. Results indicate a variation in amino acid compositions and contents among these thua nao products. The quantities of total FAA were found between 11.03 - 61.23 g/kg, as dry basis. Predominant amino acids were Trp, followed by Glu, Cys, Lys and Leu. All essential amino acids (EAA) were present in considerable amounts in which the proportions of EAA7 and EAA10 values were 2.67 - 13.99 and 7.24 - 36.54 g/kg dry basis, respectively. The most abundant taste FAA class was the bitter FAA representing more than 50% of total FAA. This is the first paper to report thua nao amino acid profiles with an expectation to further shed light on its nutritive qualities. © 2011.