"In the future, the new amides may be alternatives for the expensive flavanones to create flavour solutions to mask bitterness of pharmaceuticals or foodstuffs," wrote lead author Jakob Ley, director of flavor science and new molecules at Symrise, in the Journal of Agricultural and Food Chemistry (doi: 10.1021/jf0617061).
Dr. Ley told FoodNavigator.com: "In general the discussed flavonoids are more expensive because of stereochemistry and substructures; natural sources of the most valuable types are not very common.
"Amides are accessible via different synthetic procedures and these compounds areplaying in a different cost segment."
The researchers, from Symrise's Flavor & Nutrition Research & Innovation group, looked into potential bitter-masking compounds by focussing on compounds that are structurally similar (analogues) to homoeriodictyol, the main bitter-masking flavanone in the Californian evergreen shrub Eriodictyon californicum.
The newly published paper shows the completion of the main parts of Symrise's SymLife Mask platform, said Dr. Ley, important elements for modern masking concepts for functional food applications.
As a first step along the route to potentially bitter-masking alternatives, the researchers decided to look at hydroxylated benzoic acid amides, which "are much simpler to synthesise but contain the most important structural elements of the original flavanones," said Ley.
Thirteen different analogues were synthesised using a protecting-group-free method, which gave "moderately good yields" of about 40 per cent. All the compounds were purified to 95 per cent, and thoroughly characterised by a range of analytical techniques, including NMR, HPLC-MS and HRMS.
An expert panel of tasters was assembled and asked to screen all the compounds for their bitter-masking potential by mixing with caffeine, and comparing with a 500 mg per litre caffeine solution. Despite some disappointing results for some of the compounds, Ley and his co-workers report that the benzyl amides, close structural relatives to homoeriodictyol, were able to mask the caffeine bitterness by 20 to 30 per cent.
The most promising of the analogues, 2,4-dihydroxybenzoic acid N-(4-hydroxy-3-methoxybenxyl)amide, was selected for further study, and tested with other bitter compounds, like quinine, salicin and N-L-leucy-L-tryptophan, a peptide that often causes bitterness in processed foods.
Both quinine and salicin bitterness was reduced by about 20 per cent, report the scientists, but no effect was observed for the peptide, N-L-leucy-L-tryptophan.
"We conclude that the hitherto unknown mechanism of inhibition of flavanones and the new amides is probably the same, because the behaviour of both structural classes was nearly the same," said Ley.
Further research into this area could lead, concluded the researchers, to less expensive alternatives to the expensive flavanones as maskers bitterness foodstuffs, and "may be used as a tool to find the molecular mechanism responsible for the bitter masking effect."
Globally, the flavours and fragrances industry is estimated at about €14.8bn, of which the top five players account for 40 per cent of the market. Swiss firm Givaudan continues to lead the industry with an estimated 13.5 per cent slice of the market in 2003, followed by US International Flavours & Fragrances with an 11.7 per cent share.
Firmenich, equity-owned Symrise and ICI-owned flavours company Quest International are slated to have about 9.8, 9 and 6.1 per cent of the market respectively. Symrise reported sales of €1.14 million in 2004, and controls over 40 registered patents.
Symrise's acquisition of Kaden Biochemicals back in January consolidated the company as one of the world's four largest flavour firms, and followed a £1.5m investment at its Nördlingen production site to create perfect conditions for developing and manufacturing innovative beverage flavourings to the standards demanded by the industry.