1. Flavour composition comprising at least 0.1 wt. % of flavouring substances and at least 1 ppb and less than 10 ppm of one or more taste improving substances according to formula (I) and/or edible salts thereof: 
 R 1 â€”CR 2 (OR 3 )â€”COâ€”Xâ€ƒâ€ƒ(I), wherein R 1 represents hydrogen, C 1 -C 8 alkyl, C 2 -C 8 alkenyl, C 3 -C 8 cycloalkyl or C 3 -C 8 cycloalkenyl; R 2 represents hydrogen, C 1 -C 8 alkyl, C 2 -C 8 alkenyl, C 3 -C 8 cycloalkyl, or C 3 -C 8 cycloalkenyl; R 3 represents hydrogen, or C 1 -C 3 acyl or C 1 -C 3 alkyl; and X represents either (i) a six membered heterocyclic ring, comprising at least two nitrogen atoms, said heterocyclic ring optionally being further substituted with one or more substituents selected from the group of amino, hydroxy, oxo, alkyl, and monosaccharide unit, said monosaccharide unit optionally being esterified with one or more mono-, di- and/or triphosphate groups; or (ii) a bicyclic ring system comprising a five membered heterocyclic ring and a six membered heterocyclic ring, each ring comprising at least two nitrogen atoms, and each ring being optionally further substituted with one or more substituents selected from the group of amino, hydroxy, oxo, alkyl, and monosaccharide unit, said monosaccharide unit optionally being esterified with one or more mono-, di- and/or triphosphate groups.