Umami peptides: assessment of their alleged taste properties

Abstract

In the literature there are reports that 31 di-and tripeptides elicit umami (i.e. monosodium L-glutamate-like or MSG-like) or savoury tastes. However, the occurrence of “umami peptides” is questioned with regard to the high specificity of those that give an umami taste. A total of 12 dipeptides and 4 tripeptides were selected for a re-examination of their taste properties. Criteria were that: (1) their taste has been described as umami, savoury or brothy; (2) they have a threshold value; and (3) they should fit into the theoretical framework of L-glutamyl peptides discussed. The peptides – in aqueous solutions, at room temperature, at pH 6.0 and 4.0, and at concentrations well above the reported threshold values – were tasted. Panel members were selected on the basis of their ability to perceive the umami taste of 2.67 mM MSG at pH 6.0. None of the peptides tested was found to elicit an umami taste. The taste of L-glutamic acid in the peptides was lost and furthermore the taste of bitter amino acids in the peptides was no longer perceivable. Within the range of Glu-X peptides, even Glu-Glu and Glu-Asp, which have previously been reported to elicit umami tastes, did not taste MSG-like either in pure solution or in the presence of sodium chloride. The tripeptide Ala-Glu-Ala, reported to have an “umami threshold” value as low as 0.8 mM, was found not to have an umami taste or any other specific taste up to 10 mM. The general occurrence of umami peptides appears to be highly unlikely.