Chinese soy sauce has been manufactured by low salt-solid fermentation process since 1956 in order to meet increasing consumption due to population growth. This process is characterized by fermentation finished in a short period aging (four weeks) and the addition of 12% NaCl in Moromi (mash). This report deals with an evaluation of the quality of soy sauces made by this method compared to commercial Tian Jin soy sauce and Japanese “Koikuchi” soy sauce using some standard measures of quality. Four samples of soy sauce were used for evaluation: laboratory-made soy sauces obtained from Moromi with 12% NaCl and 22% NaCl, commercial Tian Jin sauce made in low salt-solid fermentation method, and Japanese “Koikuchi” soy sauce. The main standard measures used in this study were: total nitrogen, formol nitrogen, L-glutamic acid, and direct reducing sugars and ethanol contents.
The results of the general analysis were as follows. The total nitrogen concentrations of 4 samples were 1.30%, 1.24%, 0.94% and 1.58%, respectively, formol nitrogen concentrations 1.11%, 0.99%, 0.81% and 1.29%, L-glutamic acid contents 722, 638, 451 and 1, 143 mg/100 ml of soy sauce, direct reducing sugar concentrations 2.32%, 2.49%, 1.15% and 2.38%, and ethanol contents 13.95, 6.31, 10.53, and 1, 420 mg/100 ml of soy sauce, respectively.
The above results demonstrate that soy sauce made by the low salt-solid fermentation process corresponds with second-class in Chinese standard and is of poorer quality than Japanese soy sauces of the same class. It was pointed out that poor quality might be derived from activity of microorganisms such as Bacillus during Moromi fermentation in addition to the use of wheat bran (“Fusuma”) instead of wheat as raw material.
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