Neurosci. 2000,3, 113-119. ) or the heteromer T1R1+3 receptor (G. Nelson et al., Nature 2002, 416 (6877), 199- 202), which was reported to be a broadly tuned receptor stimulated by many L-amino acids, in particular also by glutamate. Monosodium glutamate (MSG) is the best-known compound eliciting umami taste (K. Ikeda, J. Tokyo Chem.

Soc. 1909,30, 820-826). Other compounds with similar sensory characteristics belong to the group of purine-5'- nucleotides, such as inosine-5'-monophosphate (IMP) (A.

Kuninaka, In : Symposium on Foods : The Chemistry and Physiology of Flavors ; Schultz, H. W.; Day, E. A.; Libbey, L. M. , Eds. ; AVI Publishing Company: Westport, CTg 1967 pp 515-535). These compounds occur in many savoury foods such as meat, fish, seafood, and mushrooms (S. Yamaguchi, J. Food Sci. 1967, 32, 473-478). An interesting property of umami compounds is their mutual taste synergism. The synergistic effects between MSG and IMP have been investigated and reported in the literature (S. Yamaguchi et al., J. Food Sci. 1971,36, 1761-1765).

The present invention concerns Pyridinium-Betain compounds and their use as taste modifying compounds (taste modulators). The term'taste modifying'is defined as the ability to enhance or to reduce the sensory properties of taste compounds.

The invention discloses a series of homologous betaine pyridinium compounds and their use as agents with taste- modifying properties. By taste-modifying properties we understand the ability of the compounds to enhance or to reduce the sensory quality of taste-active compounds. These taste-modifying compounds can be used as such or generated in-situ by thermal or enzymatic reactions.

The aim of the present invention is to identify compounds having taste modifying properties, for example to enhance the overall umami sensory quality of samples containing taste-active compounds.

The discovery of the compounds was made through the use of molecular modelling and quantitative-structure activity relationship (QSAR) methods. The series was specifically designed to match closely in sapophoric space known enhancers of umami taste, such as inosine monophosphate (IMP) or guanosine monophosphate (GMP).

Here we mean by the term sapophore the minimum set of chemical features needed to be present on a molecule in order this to elicit certain taste, in our case umami taste.

The present invention concerns compounds called Pyridinium-Betain compounds of the general formula (A):

wherein: Ri is H R2 is a chemical group formed by a sugar pentose or hexose ring, substituted at C5 or C6, respectively, with an acid residue taken from the group-phosphoryl, sulfonyl, or carboxyl, and R2 is connected to the pyridine ring either at Cl or C2 positions, wherein Cl, C2, C5 and C6 belongs to the sugar moiety, R3 is OH, including the ionised form 0-, R4 is an aliphatic chain (CH2) nt where n is the chain length in the range from n=0 to n=4, R5 is taken from the group consisting of residue- hydroxy, methoxy, ethoxy, iso-propoxy, propoxy, allyloxy, methyl, ethyl, phenyl, methylthio, ethylthio, ethoxyethylthio, ethoxycarbonylethylthio, furfurylthio, tetrahydrofurfurylthio, isopentenylthio, (beta- methylallyl) thio, (gamma-methylallyl) thio, and derivatives and wherein the counter-ion is taken from the group consisting of sodium, potassium, ammonium, calcium, magnesium, chloride, nitrate, carbonate, sulphate, phosphate, and the like.

In a preferred embodiment of the compound of the invention, R2 is the rest of a sugar phosphate, R3 is OH including the ionised form 0-, R4 is CH2, and R5 is a hydroxyl group (OH), including the ionised form 0-.

The compounds of the general formula (A) have zwitterionic character in a broad pH range. As shown below, the zwitterionic structure (A2) dominates under slightly acidic and neutral conditions with the negative charge primarily located at the phosphate group attached to the sugar moiety (R2 in (A) ). Under basic conditions represented by the structure (A3), the negative charge may be located at the phosphate group attached to the sugar moiety (group R2 in (A)) and at the hydroxyl group directly attached to the pyridinium ring (group R3 in (A)). Under strongly acidic conditions, both the phosphate and hydroxyl groups are protonated, as shown in the structure (A1). Depending on the pH of an aqueous solution containing the compounds of the general formula (A), the structures (Al), (A2) and (A3) may exist in an equilibrium.

The above-mentioned compounds are reaction products from reducing sugars or their derivatives with amino compounds and their derivatives.

The amount of the compound (A) is comprised between 0.01 and 3000 mg/kg of the whole composition.

In addition, the present invention concerns a process for the preparation of the compounds (A), wherein said compound is obtained by synthesis using 5- (hydroxymethyl) -2-furanaldehyde (HMF) and the corresponding amino sugar or derivatives thereof. Another way of proceeding is to use HMF producing precursors, such mono-and polysaccharides, and the corresponding amino sugar or derivatives thereof.

The following examples illustrate the invention in more details.

Rationale The above-mentioned compounds were designed as umami taste enhances. This property was deduced by virtual screening of the compounds through a sapophoric model.

The model was produced in order to capture most of the information contained in structure-activity data of molecules possessing umami taste enhancing properties.

Such molecules were collected through the available literature, such as S. Yamaguchi and K. Ninomyia, Food Rev. Int. 14 (2&3), 123-138,1989, and references mentioned therein.

Example 1: Schematic synthesis procedure Compounds of the general formula (A) can be prepared using suitable'starting materials and well-known

protection and coupling methods described in organic chemistry (J. March, Advanced Organic Chemistry: Reactions, Mechanisms, and Structure, 4th edition, J.

Wiley & Sons: New York, 1992).

As an example, 5-hydroxymethylfurfural (HMF), a well- known sugar degradation product, coupled with an amino sugar derivative results in compound (A4) according to the general method described in the literature (Koch et al., Carbohydrate Chemistry, 1988,313, 117-123). \ Hi +OH holz coo SO OH OH EIN mino Example 2: Synthesis via reductive amination of HMF Alternatively, compounds of the general formula (A) can be prepared by reductive amination of 5- hydroxymethylfurfural (HMF) according to the general procedure described in the literature (Müller et al., Tetrahedron, 1998,54, 10703-10712).

/\ H2N Raney-Ni CHO rfo -H2 HO o- X ra/H20 O X O ORExample 3 : Enhancement of the umami taste modality In Figure 1, we show how the well-known umami taste enhancer IMP projects on the optimal sapophore space (a) r as well as the mapping in the same space of a proposed betaine-pyridinium compound (b). In light grey are depicted the locations of hydrogen-bond acceptor sites (HBA) while in dark grey are depicted the locations of negatively ionisable groups (NI). The spheres diameters account for tolerances in these positions. Detailed geometric properties of the optimal sapophore are given in Table I.

Table I Hydrogen Bond Hydrogen Bond Negatively Acceptor Site 1, Acceptor Site 2, Ionisable HBA 1 HBA 2 Site, NI acceptor donor acceptor donor 0 Tolerances, A 1. 60 2.20 1.60 2.20 1.60 Co-ordinates, X 4.44 6.23-1. 48-1.57 2.09 Y 2.40 2.25-2. 39-5.33-1. 63 Z-1. 30 1. 10 0.28 0. 90-2. 22 e Inter-feature distances, A HBA-1, acceptor 0. 0 - - - - donor 3.0 0. 0- HBA-2, acceptor 7. 8 9. 0 0. 0 - - donor 10.0 10.9 3.0 0. 0- NI 4. 8 6.0 4.4 6. 1 0. 0