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 —CR 2 (OR 3 )—CO—X   (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, each optionally substituted with 1-8 substituents selected from hydroxyl, C 1 -C 3 alkyl, C 2 -C 3 alkenyl and C 1 -C 3 carboxyl; 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, each optionally substituted with 1-8 substituents selected from hydroxyl, C 1 -C 3 alkyl , C 2 -C 3 alkenyl and C 1 -C 3 carboxyl; R 3 represents hydrogen; or C 1 -C 3 acyl or C 1 -C 3 alkyl, each optionally substituted with 1-3 hydroxyl groups; and wherein X represents either (i) a six membered heterocyclic ring, comprising at least two nitrogen atoms, which heterocyclic ring is optionally further substituted with one or more substituents selected from the group of amino; hydroxyl; 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; hydroxyl; oxo; alkyl; and monosaccharide unit, said monosaccharide unit optionally being esterified with one or more mono-, di- and/or triphosphate groups.