The Masking Effect of Organic acids and Amino acids on Trimethylamine Odor

Abstract

Effective compounds in the fermented seasoning (Sakashio) for odor-masking of trimethylamine (TMA) were discussed. The fermented seasoning was fractionated into volatiles and non-volatiles. The non-volatile fraction was then divided into methylene chloride soluble and water soluble fractions. Furthermore, the water soluble fraction was fractionated into acid, nitrogen containing and neutral fractions. The odor-masking effect of the fractions mentioned above on TMA was examined by a combination of sensory evaluation and headspace analysis with GC. (1) The water soluble fraction was effective for masking TMA ordor. The acid and the nitrogen containing fractions were effective for the TMA odor-masking. (2) A strong effect for masking of TMA odor in the water soluble fraction was depended on the formation of salts that comprised of organic acids and amino acids. An ionic bond in the salt formation was so strong that the salts were easily isolated from the model mixture without any change of the compound. (3) In a model system with on amino acids solution, not only acidic amino acids but neutral and basic amino acids could make the ordor-masking effectively. A certain correlation (r=0.87, α=0.01) between the odor-masking effect and the isoelectric point (pI) of amino acid has been found. (4) The masking effect of the fermented seasoning for TMA ordor depends on hydrophilic compounds such as organic acids and amino acids, owing to a buffer action of the acids. Amino acids act weakly as a buffer but are effective in wide ranges of pH.