Strecker aldehydes are well-known aroma-active volatiles in foods eliciting pleasant aroma notes, e.g., malty, honey-like, or cooked potato-like attributes. In certain foods, they even act as important key odorants. For a long time, these compounds were seen as typical heat-induced compounds, generated during the Maillard reaction between the corresponding free amino acids and carbohydrate degradation products, such as α-dicarbonyls. The present study reports on a novel class of aroma precursors, the so-called 2-substituted-5-methyl-3-oxazolines, that are able to release the respective Strecker aldehydes by hydrolysis, which can take place after the addition of water or with human saliva during mastication. 2-Isobutyl-, 2-<i>sec</i>-isobutyl-, 2-isopropyl-, and 2-benzyl-5-methyl-3-oxazolines were synthesized and structurally identified by means of gas chromatography-mass spectrometry (GC-MS) in the electron ionization (EI) and in the chemical ionization (CI) mode as well as by one- and two-dimensional NMR. A variety of stability experiments were performed using headspace GC-MS or proton transfer reaction-mass spectrometry (PTR-MS) based on stable isotope dilution assays. Experiments clearly proved that the release of the respective Strecker aldehydes depended both on the pH value and on the hydrolysis time. After the addition of water at physiological relevant temperatures (37 °C), &gt;70 mol% of 3-methylbutanal or &gt;40 mol% of phenylacetaldehyde was liberated from a solution of 2-isobutyl-5-methyl-3-oxazoline or 2-benzyl-5-methyl-3-oxazoline after 5 min. Furthermore, the presence of 2-isobutyl-5-methyl-3-oxazoline in dark chocolate containing 70% of cocoa was proven via GC-MS. Due to the fact that these compounds are very stable in the absence of water, their addition to dry foods, e.g., instant foods or beverage powders, allows an enhancing flavor perception after adding (hot) water or during chewing/mastication.<br/>

Substituted 3-oxazolines: A novel class of Strecker aldehyde precursors in foods

256th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.