title: Inhibitory effect of aroma on the bitterness of branched-chain amino acid solutions.
abstract: Nutritional products for patients with liver failure available on the Japanese market contain many branched-chain amino acids (BCAAs) such as L-leucine, L-isoleucine, and L-valine, which not only have a bitter taste but also strong, unpleasant odours, leading to low palatability. The palatability of these nutritional products can be significantly improved by the addition of flavoured powders containing various kinds of tastants (sucrose, citric acid, etc.) and odourants (fruit, coffee aromas, etc.). The specific effects of the aroma of flavoured powders have not yet been clearly evaluated. In the present article, the inhibitory effect of aroma on the bitterness of BCAA solutions was examined. The bitterness intensity of a BCAA solution at the same concentration as Aminoleban EN was defined as 3.5 (measured by a previously described gustatory sensation method). The bitterness threshold of a BCAA standard solution without added aroma was estimated to be 1.87, while those of BCAA solutions containing green-tea, coffee, apple, vanilla, or strawberry aromas were 2.02, 1.98, 2.35, 2.40 and 2.87, respectively, when evaluated by the probit method. This shows that the addition of an aroma can elevate the bitterness threshold in human volunteers. The green-tea and coffee aromas predominantly evoked bitterness, while the vanilla aroma predominantly evoked sweetness. Apple and strawberry aromas evoked both sweetness and sourness, with the apple aroma having stronger sourness and the strawberry aroma stronger sweetness. Thus, a 'sweet' aroma suppresses the bitterness of BCAA, with coexisting sourness also participating in the bitterness inhibition.
authors.affiliation: School of Pharmaceutical Sciences, Mukogawa Women's University, Nishinomiya, Japan.
authors.forename: Junji
authors.initials: J
authors.lastname: Mukai
authors.forename: Emi
authors.initials: E
authors.lastname: Tokuyama
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Ishizaka
authors.forename: Sachie
authors.initials: S
authors.lastname: Okada
authors.forename: Takahiro
authors.initials: T
authors.lastname: Uchida
mesh_terms: D000328:Adult; D000597:Amino Acids, Branched-Chain / Q000737:chemistry*; D005260:Female; D005421:Flavoring Agents / Q000737:chemistry / Q000494:pharmacology*; D005526:Food, Formulated / Q000009:adverse effects*; D006801:Humans; D007532:Isoleucine / Q000737:chemistry / Q000494:pharmacology; D007930:Leucine / Q000737:chemistry / Q000494:pharmacology; D008297:Male; D019999:Pharmaceutical Solutions / Q000737:chemistry; D013549:Sweetening Agents / Q000737:chemistry / Q000494:pharmacology*; D013649:Taste / Q000187:drug effects* / Q000502:physiology; D013652:Taste Threshold / Q000187:drug effects* / Q000502:physiology; D014633:Valine / Q000737:chemistry / Q000494:pharmacology
chemical_list: D000597:Amino Acids, Branched-Chain; D005421:Flavoring Agents; D019999:Pharmaceutical Solutions; D013549:Sweetening Agents; D007532:Isoleucine; D007930:Leucine; D014633:Valine