New insights into the formation of aroma-active strecker aldehydes from 3-oxazolines as transient intermediates

Michael Granvogl, Ersan Beksan, Peter Schieberle

Research output: Contribution to journalArticlepeer-review

54 Scopus citations

Abstract

2-Substituted-5-methyl-3-oxazolines, a novel class of aroma precursors that are able to release the respective Strecker aldehydes by hydrolysis, were identified. Hydrolysis can take place after the addition of water or with human saliva during mastication, respectively. 2-Isobutyl-, 2-sec-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 impact mode and in the chemical ionization mode as well as by one- and two-dimensional NMR experiments. With these compounds at hand, a variety of stability experiments were performed using headspace-GC-MS or proton transfer reaction-MS techniques on the basis of stable isotope dilution assays, proving the ability to release the respective Strecker aldehydes was dependent on the pH value as well as on the hydrolysis time. After the addition of water at 37 °C, for example, >70 mol % of 3-methylbutanal or >40 mol % of phenylacetaldehyde was liberated from a solution of 2-isobutyl-5-methyl-3- oxazoline or 2-benzyl-5-methyl-3-oxazoline, respectively, after 5 min. Furthermore, the presence of 2-isobutyl-5-methyl-3-oxazoline in dark chocolate containing 70% cocoa was proven by GC-MS.

Original languageEnglish
Pages (from-to)6312-6322
Number of pages11
JournalJournal of agricultural and food chemistry
Volume60
Issue number25
DOIs
StatePublished - 27 Jun 2012

Keywords

  • 5-methyl-3-oxazolines
  • PTR-MS
  • Strecker aldehydes
  • aroma precursors
  • aroma release

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