Stereoisomere Aromastoffe

Zusammenfassung Es werden Methoden zur racemisie-rungsfreien Stereodifferenzierung der 2-Methylbuttersäure (direkt bzw. nach Esterhydrolyse) aus Äpfeln und apfelhaltigen Lebensmitteln beschrieben. Die Enantiomerenverteilung der 2-Methylbuttersäure kann direkt an permethylierter-Cyclodextrinphase gaschromatogra-phisch bestimmt werden. Es wird stets hoher Enantiomerenüberschuß zugunsten des (S)-Isomeren der Säure nachgewiesen. Proben von naturidentischem und natürlichem (biotechnologisch hergestelltem) 2-Methyl-buttersäureethylester sowie Äpfel, Apfelsaft, Apfellikör, Calvados, Apfelwein, Apfelmarmelade und Joghurts mit Apfelzusatz werden untersucht. Ein Zusatz von naturidentischen, racemischen 2-Methylbuttersäureestern ist einfach nachweisbar.

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Stereoisomeric flavour compounds. XLII. Enantiomer distribution of 2-methylbutanoic acid in apples and apple-containing food

Summary The direct Stereodifferentiation of 2-methyl-butanoic acid and its esters (after hydrolysis) from apples and apple-containing food is described, using permethyl-ated-cyclodextrin as the chiral CGC phase. In all cases, high enantiomeric excess in favour of the (S)-enantiomer was ascertained. The method is applicable to apples, apple juice, apple liquor, calvados, apple wine, apple jam and apple-containing yoghurts. The addition of race-mic (nature-identical) esters may be easily detected.

     

Zur Problematik der selektiven Erfassung von PSP-Toxinen aus Muscheln

Zusammenfassung Die Messung der PSP-Belastung (paralytic shellfish poisoning) von Schalentieren erfolgt vor allem mit Hilfe des Maus-Biotestes. Um PSP-Toxine sowohl qualitativ als auch quantitativ besser bestimmen zu können, wurden chromatographische Verfahren mit Fluorescenzdetektion entwickelt. Diese HPLC-Methoden sowie die Kopplung HPLC/MS gelangten zum Einsatz, um in spanischen Muschelkonserven ein neben Saxitoxin vermutetes zweites PSP-Toxin nachzuweisen. Es zeigte sich, daß in den 1986 in der Bundesrepublik Deutschland wegen zu hoher PSP-Konzentrationen beanstandeten Muschelkonserven vor allem Decarbamoyl-Saxitoxin enthalten war.

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The problem of the selective determination of PSP-toxins in mussels

Summary Levels of paralytic shellfish poisoning (PSP) toxins in shellfish are routinely determined by mouse bioassay: In order to improve the qualitative and quantitative determination of PSP toxins, Chromatographic techniques with fluorescence detection have been developed. These HPLC methods and the HPLC/MS coupling were used to determine a second PSP toxin which was found, in addition to saxitoxin, in canned Spanish mussels. These canned mussels were rejected in 1986 by the German food control because PSP concentrations were too high. It has been shown that these samples contained mainly dc-saxitoxin.

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Herrn Professor Dr. A. Montag zum 60. Geburtstag gewidmet     

IV. Referate

Ohne Zusammenfassung     

Slotted ALOHA multiple access and error control coding for land mobile satellite networks

This paper considers a satellite network with data messages being transmitted by land mobile users according to slotted Aloha multiple access. The mobile communication links suffering from multipath fading and signal shadowing are modelled as Gilbert-Elliott channels. FEC block coding is used to correct transmission errors. The maximum achievable information throughput and the mean packet delay are derived from a combined analysis of the multiple access and FEC/ARQ protocol. The results show that the additional overhead necessary for FEC is outweighed by the benefit in throughput and delay. Finally, the capture effect and its consequences are discussed.     

Spiral-CT-based assessment of tracheal stenoses using 3-D-skeletonization

PURPOSE: Demonstration of a technique for three-dimensional (3-D) assessment of tracheal-stenoses, regarding site, length and degree, based on spiral computed tomography (S-CT). PATIENTS AND METHODS: S-CT scanning and automated segmentation of the laryngo-tracheal tract (LTT) was followed by the extraction of the LTT medial axis using a skeletonization algorithm. Orthogonal to the medial axis the LTT 3-D cross-sectional profile was computed and presented as line charts, where degree and length was obtained. Values for both parameters were compared between 36 patients and 18 normal controls separately. Accuracy and precision was derived from 17 phantom studies. RESULTS: Average degree and length of tracheal stenoses was found to be 60.5% and 4.32 cm in patients compared with minor caliber changes of 8.8% and 2.31 cm in normal controls (p < 0.0001). For the phantoms an excellent correlation between the true and computed 3-D cross-sectional profile was found (p < 0.005) and an accuracy for length and degree measurements of 2.14 mm and 2.53% respectively could be determined. The corresponding figures for the precision were found to be 0.92 mm and 2.56%. CONCLUSION: LTT 3-D cross-sectional profiles permit objective, accurate and precise assessment of LTT caliber changes. Minor LTT caliber changes can be observed even in normals and, in case of an otherwise normal S-CT study, can be regarded as artifacts.     

Erhitzen von Weizen

Zusammenfassung Teige aus erhitzten Weizenkörnern (45–75 °C/6 min bei 20% Wassergehalt) wurden mit der Capillarviscosimetrie und mit einem Mikrobackversuch untersucht. Beide Methoden zeigten eine erhitzungsbedingte Verfestigung des Klebers an. Eine Untersuchung der Mehlproteine ergab bei der Osbornefraktionierung eine Verschiebung von Albuminen/Globulinen in den Rückstand. Zugversuche sowie calorimetrische Messungen mit hitzebehandeltem Kleber lassen auf Konformationsänderungen der Proteine als Ursache für die Kleberverfestigung schließen.

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Heating of wheat. 2. Rheological and baking behaviour, changes in Osborne fractions

Dough from heated wheat kernels (45–75° C/ 6 min, 20% water content) were examined by capillary viscosimetry and by a micro-baking test. Both methods showed an increase in gluten strength. Osborne fractionation of the proteins showed a shift of albumins/globulins to the residual protein. Load-extension tests and calorimetric measurements with heat-treated gluten led to the conclusion that changes in protein conformation are responsible for the increase in gluten strength.

     

Nichtst?rke-Polysaccharide des Kakaos

Zusammenfassung Die Nichtstärke-Polysaccharide (NSP) der Kakaobohne wurden nach ihrer Löslichkeit in Wasser und Natronlauge steigender Konzentration fraktioniert. Die Fraktionen wurden durch das Muster der Zuckerbausteine nach Hydrolyse bzw. Methanolyse charakterisiert und gelchromatographisch aufgetrennt. Im Verlauf der Kakaoverarbeitung waren nennenswerte Veränderungen nur beim Alkalisieren des Kakaopulvers zu beobachten. Die Meßwerte für die wasserlöslichen Kakao-NSP können bei der Analyse der Dickungsmittel in Kakaoerzeugnissen berücksichtigt werden.

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Non-starch polysaccharides of cocoa

The non-starch polysaccharides (NSP) of the cocoa bean were fractionated according to their solubility in water and in solutions of increasing alkalinity. In these fractions, the monosaccharide patterns after hydrolysis or methanolysis and the molecular mass distributions were determined. During cocoa processing, distinct changes in the NSP composition were observed only for the solubilisation of cocoa powder by alkaline treatment. The results obtained for the water-soluble cocoa NSP may be considered as blank values for the analysis of thickeners and gums in cocoa products.

     

Zum Aroma von Speisepilzen

Zusammenfassung Kopfraum-Proben, Wasserdampfdestillate und Dichlormethanextrakte der beliebtesten Speisepilze Champignon (Agaricus campestris undAgaricus bisporus), Parasol (Riesenschirmpilz,Lepiota procera), Hallimasch (Armillaria mellea), Steinpilz (Herrenpilz,Boletus edulis) und Pfifferling (Eierschwamm,Cantharellus cibarius) wurden mittels GC/FID, GC/FTIR/MS und GC-Sniffing-Technik untersucht. Ziel dieser Untersuchungen war es, die für den typischen Duft der einzelnen Pilzarten verantwortlichen Inhaltsstoffe zu identifizieren. Um Daten aus GC/FTIR/MS-Messungen mit olfactorischen Daten direkt vergleichen zu können, wurde die GC-Sniffing-Technik verwendet. Die Ergebnisse, besonders solche von Kopfraumproben, zeigten, daß 1-Octen-3-o1, ein bekannter Pilzduftstoff, von grundlegender Bedeutung für die Kopfnote der untersuchten Pilze ist. Mehr als 70 Einzelkomponenten tragen qualitativ und quantitativ zum Gesamtgeruchseindruck der einzelnen Arten bei, wobei besonders C₈-Derivate in signifikanter Weise den Duft der meisten Kopfraumproben beeinflussen. Carbonylverbindungen und Ester (C₄-C₁₄) dagegen spielen eine wesentliche Rolle (z. B. Anisaldehyd in Champignonproben) vor allem in den Wasserdampfdestillations- und Extraktproben.

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The aroma of edible mushrooms. Headspace analysis using GC/FID and GC/FTIR/MS

Headspace samples, steam distillates and dichloromethane extracts of the most well liked edible mushrooms (Agaricus campestris, Agaricus bisporus, Lepiota procera, Armillaria mellea, Boletus edulis and Cantharellus cibarius) were investigated by means of GC/FID, GC/FTIR/MS and a GC-sniffing technique. The aim of these analyses was the identification of constituents responsible for the typical mushroom odour of each species. To relate GC/Fouriertransform Infrarot-Detektor/MS (GC/FTIR/MS) data with olfactoric ones, the GC-sniffing technique was used. The results, especially of the headspace samples, showed that 1-octen-3-ol, a well-known mushroom aroma compound, is of basic importance for the top note of the investigated mushrooms. More than seventy constituents that additionally have an effect (qualitatively and quantitatively) on the odour impression of these species were identified. Among them especially C₈-derivatives contribute in a significant way to the headspace odour of most of the samples. Carbonyls and esters (C₄-C₁₄) on the other hand play an important role (e.g. anisaldehyde inAgaricus samples) more in the steam distillate and extract samples.

     

'Polymorph Method' Determination of Monoclinic Zirconia in Partially Stabilized Zirconia Ceramics

The polymorph method, which provides phase analysis from a small number of integrated intensities in a powder diffraction scan, is adapted for the determination of monoclinic zirconia in a mixture with cubic, tetragonal. and orthorhombic zirconias and the γ-phase (Mg₂Zr₅O₁₂). Such a mixture is representative of Mg-PSZ after subeutectoid aging. The quantitative determination of the monoclinic depends in principle on a knowledge of the relative amounts of the other phases present in the mixture. It is demonstrated, however, that without this knowledge, even in complex mixtures, the traditional polymorph method analysis gives an acceptable estimate of the monoclinic fraction in the sample.