The volatile flavor components of yellow passion fruits have been isolated using four different isolation techniques. The most representative and typical extract was obtained by vacuum headspace sampling and subsequent liquid−liquid extraction of the aqueous phase. This vacuum headspace concentrate was prefractionated by medium-pressure adsorption chromatography on silica gel. Approximately 180 components were identified in the LC fractions of yellow passion fruit flavor for the first time. Of these compounds, 14 components have not previously been reported as naturally occurring flavor ingredients. Moreover, 47 sulfur-containing volatiles were identified in yellow passion fruits after enrichment by preparative multidimensional capillary gas chromatography; 35 of these components are reported to be present in the tropical fruit flavor for the first time, and 23 of these sulfur-bearing compounds have not been previously reported as constituents of food flavors and are therefore new natural components. In addition, the enantiomeric distributions of several chiral flavor substances were determined by enantioselective multidimensional gas chromatography. Keywords: Yellow passion fruit flavor; comparison of sampling techniques; vacuum headspace method; sulfur volatiles; enantio-MDGC

A new class of water-soluble, amphiphilic star block copolymers with a large number of arms was prepared by sequential atom transfer radical polymerization (ATRP) of n-butyl methacrylate (BMA) and poly(ethylene glycol) methyl ether methacrylate (PEGMA). As the macroinitiator for the ATRP, a 2-bromoisobutyric acid functionalized fourth-generation hyperbranched polyester (Boltorn H40) was used, which allowed the preparation of star polymers that contained on average 20 diblock copolymer arms. The synthetic concept was validated by AFM experiments, which allowed direct visualization of single molecules of the multiarm star block copolymers. DSC and SAXS experiments on bulk samples suggested a microphase-separated structure, in agreement with the core−shell architecture of the polymers. SAXS experiments on aqueous solutions indicated that the star block copolymers can be regarded as unimolecular micelles composed of a PBMA core and a diffuse PPEGMA corona. The ability of the polymers to encapsulate and release hydrophobic guests was evaluated using 1H NMR spectroscopy. In dilute aqueous solution, these polymers act as unimolecular containers that can be loaded with up to 27 wt % hydrophobic guest molecules.

The localization and dynamics of fragrance compounds in surfactant micelles are studied systematically in dependence on the hydrophobicity and chemical structure of the molecules. A broad range of fragrance molecules varying in octanol/water partition coefficients P ow is employed as probe molecules in an aqueous micellar solution, containing anionic and nonionic surfactants. Diffusion coefficients of surfactants and fragrances obtained by Pulsed Field Gradient (PFG)-NMR yield the micelle/water distribution equilibrium. Three distinct regions along the log(P ow ) axis are identified: hydrophilic fragrances (log(P ow ) \ 2) distribute almost equally between micellar and aqueous phases whereas hydrophobic fragrances (log(P ow ) [ 3.5) are fully solubilized in the micelles. A steep increase of the incorporated fraction occurs in the intermediate log(P ow ) region. Here, distinct micelle swelling is found, while the incorporation of very hydrophobic fragrances does not lead to swelling. The chemical structure of the probe molecules, in addition to hydrophobicity, influences fragrance partitioning and micelle swelling. Structural criteria causing a decrease of the aggregate curvature (flattening) are identified. 2 H-NMR spin relaxation experiments of selectively deuterated fragrances are performed monitoring local mobility of fragrance and leading to conclusions about their incorporation into either micellar interface or micelle core. The tendencies of different fragrance molecules (i) to cause interfacial incorporation, (ii) to lead to a flattening of the micellar curvature and (iii) to incorporate into micelles are shown to be correlated.

No abstract

Cover: Schematic representation of an amphiphilic multi‐arm star‐block copolymer based on a hyperbranched polymer core. The copolymer was shown to be able to encapsulate and disperse significant loadings of volatile hydrophobic fragrances in aqueous media. Further details can be found in the Full Paper by C. Ternat, G. Kreutzer, C. J. G. Plummer, T. Q. Nguyen, A. Herrmann, L. Ouali, H. Sommer, W. Fieber, M. I. Velazco, H.‐A. Klok, and J.‐A. E. Månson* on page 131.