Helmut Guth

Quantitation of potent odorants of virgin olive oil by stable-isotope dilution assays

The potent odorants of four olive oil samples differing in flavor were quantitated, and their odor activity values (OAVs) were calculated by dividing the concentrations of the odorants in the oil samples by the flavor threshold values in the oil. The odorants with higher OAVs were contrasted with the different notes of the flavor profiles of the olive oils. It was concluded that the following compounds contributed mainly to the flavor notes given in parentheses: (Z)-3-hexenal (green), ethyl 2-methylbutyrate, ethyl isobutyrate, ethyl cyclohexanoate (fruity), (Z)-2-nonenal (fatty) and 4-methoxy-2-methyl-2-butanethiol (black-currant-like). The results showed that the calculation of OAVs is an approach to objectify the flavor differences of olive oil samples.

Geruchsstoffe von extrudiertem Hafermehl, Veränderungen bei der Lagerung

Aroma extract dilution analysis of a fresh extrusion product (EP) of oat meal showed 25 odorants of which hexanal (I), octanal,trans-2,3-epoxyoctanal (II), (E,E)-2,4-nonadienal (III), (E,E)-2,4-decadienal (IV),trans-4,5-epoxy-(E)-2-decenal (V), 4-hydroxy-2-nonenoic acid lactone (VI) and vanillin (VII) appeared with high FD factors. Compounds I to VI and caproic acid (VIII), which increased during storage of EP, were quantified by an isotope dilution assay. Soaking the EP in water liberated especially VII from starch inclusion complexes; its concentration (mg/kg) which was determined after methylene chloride extraction increased from 0.09 to 6.7. During storage of EP in closed bags at 22° C the levels (mg/kg) of I and VIII increased, causing a rancid off-flavour: 0 d, 0.5 I, 1.9 VIII; 35 d, 1.2 I, 10.4 VIII; 1 year 9.61, 11.3 VIII.ZusammenfassungDie Aromaextraktverdünmmgsanalyse von einem frischen Haferextrudat (HE) ergab 25 Geruchsstoffe, von denen Hexanal (I), Octanal,trans-2,3-Epoxyoctanal (II), (E,E)-2,4-Nonadienal (III), (E,E)-2,4-Decadienal (IV),trans-4,5-Epoxy-(E)-2-decenal (V), 4-Hydroxy-2-nonensäurelacton (VI) und Vanillin (VII) hohe FD-Faktoren zeigten. Die Verbindungen I bis VI und Capronsäure (VIII), die bei der Lagerung von HE zunahmen, wurden durch Isotopenverdünnungsanalysen quantifiziert. Bei der Quellung von HE in Wasser wurde insbesondere VII freigesetzt, so daß seine durch Extraktion mit Methylenchlorid erfaßte Konzentration (mg/kg) von 0,09 auf 6,7 anstieg. Bei der Lagerung von HE in verschlossenen Beuteln bei 22 °C nahmen die Konzentrationen (mg/kg) von I und VIII zu: 0. Tag 0,5 I, 1,9 VIII; 35. Tag 1,2 I, 10,4 VIII; 1 Jahr 9,6 I, 11,3 VIII.

A comparative study of potent odorants in peanut, hazelnut, and pumpkin seed oils on the basis of aroma extract dilution analysis (AEDA) and gas chromatography‐olfactometry of headspace samples (GCOH)

Potent odorants in commercially processed peanut, hazelnut, and pumpkin seed oils were evaluated by the application of aroma extract dilution analysis (AEDA) and gas chromatography-olfactometry of headspace samples (GCOH). AEDA revealed 38, 28 and 27 odour-active compounds in peanut, hazelnut, and pumpkin seed oils, respectively. Fifteen odorants were present in all oils; two of them showed the highest flavour dilution factor (FD-factor): 2-ethyl-3,5-dimethylpyrazine and 2,3-diethyl-5-methylpyrazine. Application of GCOH led to the identification of 21, 24, and 24 odorants in peanut, hazelnut, and pumpkin seed oils, respectively. Nine of them were found in all oils: acetaldehyde, propanal, 2-methylpropanal, 2- and 3-methylbutanal, 2-ethyl-3,5-dimethylpyrazine, 2,3-diethyl-5-methylpyrazine, (E)-2-nonenal and vanillin. The following odorants appeared with relative high FD-factors in the headspace of a single oil: 1-penten-3-one in peanut, 5-methyl-(E)-2-hepten-4-one (Filbertone) in hazelnut, (Z)-4-heptenal and 3-ethyl-2,5-dimethylpyrazine in pumpkin seed oil. Vergleichende Untersuchung der potenten Geruchsstoffe von Erdnus-, Haselnus- und Kurbiskernolen auf der Basis von Aromaextrakt-Verdunnungsanalysen (AEVA) und Gaschromatographie-Olfaktometrie von Headspaceproben (GCOH) In kommerziell hergestellten Erdnus-, Haselnus- und Kurbiskernolen wurden potente Geruchsstoffe durch Anwendung von Aromaextrakt-Verdunnungsanalysen (AEVA) und Gaschromatographie-Olfaktometrie von Headspaceproben (GCOH) bestimmt. Die AEVA ergab 38, 28 und 27 geruchsaktive Verbindungen in Erdnus-, Haselnus- und Kurbiskernol. In allen Olen traten 15 Geruchsstoffe auf; davon zwei mit den hochsten Verdunnungsfaktoren: 2-Ethyl-3,5-dimethylpyrazin und 2,3-Diethyl-5-methylpyrazin. Die GCOH ergab 21, 24 und 24 Geruchsstoffe in Erdnus-, Haselnus- und Kurbiskernol; davon 9 in allen Olen: Acetaldehyd, Propanal, 2-Methylpropanal, 2- und 3-Methylbutanal, 2-Ethyl-3,5-dimethylpyrazin, (E)-2-Nonenal und Vanillin. Im Gasraum jeweils eines Oles wurden folgende Geruchsstoffe mit hohen Verdunnungsfaktoren gefunden: 1-Penten-3-on im Erdnusol, 5-Methyl-(E)-2-hepten-4-on (Filberton) im Haselnusol, (Z)-4-Heptenal und 3-Ethyl-2,5-dimethylpyrazin im Kurbiskernol.

Potent odorants formed by lipid peroxidation as indicators of the warmed-over flavour (WOF) of cooked meat

Hexanal (I), 1-octen-3-one (II), (E,E)-2,4-nonadienal (III), (E,E)-2,4-decadienal (IV) andtrans-4,5-epoxy-(E)-2-decenal (V) were quantified in cooked meat (beef, pork, chicken) in which the warmed-over flavour (WOF) was observed after storage for 2 days at 4°C. Odour activity values of the compounds on the basis of odour threshold values in water revealed that compounds I and V contributed most strongly to WOF. During the storage, free iron but not metmyoglobin catalysed the increase of compounds I, II, IV and V in models containing the lipids of beef meat.

Evaluation of Important Odorants in Foods by Dilution Techniques

Dilution techniques, like aroma extract dilution analysis (AEDA) and static head-space analysis and olfactometry (SHA-O), were applied to analyze food flavors. AEDA of soybean oil led to the identification of butane-2,3-dione and 3-methylnonane-2,4dione as the most important odorants, which mainly caused the “butter-like” “and beany” off-flavors which were formed during storage of the oil in the presence of light. AEDA and SHA-O were also applied to fresh tomatoes and tomato paste. Due to their high flavor dilution (FD)-factors, (E)-β-damascenone, acetic acid, methional, 4hydroxy-2,5-dimethyl-3(2H)-furanone, 3-hydroxy-4,5-dimethyl-2(5H)-furanone (sotolon) and eugenol were the most important odorants in both samples. Differences in the FD-factors were found for (Z)-3-hexenal, which was the most important compound in fresh tomatoes, but without significance for tomato paste. After quantification by isotope dilution assays 15 compounds in concentration levels equal to those in tomato paste were dissolved in water. As the aroma of this mixture was very close to that of the original, the conclusion was drawn, that all of the odorants contributing to the aroma of tomato paste had been detected by the application of AEDA and SHA-O.

Furan fatty acids in butter and butter oil

ZusammensetzungNeun Furanfettsäuren (F-Säuren), unter denen die 12, 15-Epoxy-13,14-dimethyleicosa-12, 14-diensäure und die 10,13-Epoxy-11,12-dimethyloctadeca-10,12-diensäure dominierten, wurden in Butter und Butterschmalz nachgewiesen. In vier Butterproben variierte der Gehalt der F-Säuren zwischen 116 und 476 mg/kg.SummaryNine furan fatty acids (F-acids), among which 12,15-epoxy-13,14-dimethyleicosa-12,14-dienoic acid and 10,13-epoxy-11,12-dimethyloctadeca-10,12-dienoic acid predominated, were detected in butter and butter oil. The total amount of the F-acids in four butter samples varied between 116 and 476 mg/kg.

Dependence of the 12-methyltridecanal concentration in beef on the age of the animal

Zusammenfassung12-Methyltridecanal (12-MT), das zum charakteristischen Aroma von geschmortem Rindfleisch wesentlich beiträgt, wurde durch Isotopenverdünnungsanalyse in Proben aus neun Rindern unterschiedlichen Alters bestimmt. Die Ergebnisse, die auf den Phospholipid (PL)-Gehalt bezogen wurden, zeigen, daß das 12-MT mit dem Alter des Rindes ansteigt, z.B. von 36 μg·g−1 PL bei einem 4 Monate alten Kalb auf 810 μg·g−1 PL in einer 8 Jahre alten Kuh. Der Anstieg des 12-MT in den PL pro Monat schwankte zwischen 8,4 und 10,9 μg·g−1 (Mittelwert 9,3 ±0,78 μg·g−1). Möglicherweise ist das 12-MT als Indikator für die Altersbestimmung von Rindfleisch geeignet.AbstractThe content of 12-methyltridecanal (12-MT), which contributes greatly to the characteristic aroma of stewed beef, was determined by a stable isotope dilution assay in meat samples from nine bovine animals of different ages. The results, which were related to the amount of phospholipids (PL), indicate that 12-MT content increases with the age of beef, e. g. from 36 μg·g−1 PL in a 4-monthold calf to 810 μg·g−1 PL in an 8-year-old cow. The increase of 12-MT content in PL per month varied between 8.4 and 10.9 μg·g−1 PL (mean: 9.3 ± 0.78 μg·g−1 PL). Possibly 12-MT content is suitable as an indicator for the estimation of the age of a beef sample.

Quantitative analysis of caffeic and ferulic acids in oatmeal. Comparison of a conventional method with a stable isotope dilution assay.

Zusammenfassung[13C]-Kaffee- und [13C]-Ferulasäure wurden synthetisiert und als interne Standardsubstanzen für die Bestimmung dieser Säuren (frei und verestert) in Hafermehl angewandt. Ein Vergleich ergab, daß von der Ferulasäure 84%, aber von der leichter oxidablen Kaffeesäure nur 32% mit einer konventionellen Methode erfaßt werden.Abstract[13C]Caffeic acid and [13C]ferulic acid were synthesized and then used as internal standards for the determination of these acids (free and esterified) in oatmeal. A comparative study indicated that 84% of the ferulic acid, but only 32% of the caffeic acid, which is more susceptible to oxidation than the former, could be found by a conventional analytical approach.

Furanoid fatty acids in oils from soybeans lacking lipoxygenase isoenzymes

The concentrations of 10, 13-epoxy-11, 12-dimethyloctadeca-10, 12-dienoic acid (F20) and 12,15-epoxy-13, 14-dimethyleicosa-12, 14-dienoic acid (F22) were determined by a stable isotope dilution assay in oils extracted from the soybean cultivar Century and from five soybean genotypes that lacked one or two of the three lipoxygenase isoenzymes. The concentrations of F20 and F22 ranged between 190–225 mg/kg oil and 91–132 mg/kg oil, respectively. The concentration differences were not correlated to the differences in lipoxygenase activities of the soybeans.