Retention of sulfur flavours by food matrix and determination of sensorial data independent of the medium composition

Interactions between food matrix and sulfur compounds (thioesters, sulfides, disulfides, pentanethiol and 2-ethoxythiazole) were studied in a real food system composed of fresh cheese, triolein or inulin, and water. Results obtained with the lipidic medium confirm that 10% of triolein is enough to significantly affect flavour perception. The lipophilicity index, log k(W), appears as an interesting physicochemical property allowing assessment of the aroma retention intensity. Results obtained with inulin indicate how different the retention will be when a polysaccharide is used as a fat-mimic. Formulation of dietetic products has to take that discrepancy into account. GC-odour port evaluation of diluted solutions appears as an interesting method for easy acquisition of best estimated GC-lower amounts detected by sniffing (BE-GC-LOADS), threshold values independent of the medium composition. (C) 2000 Elsevier Science Ltd. All rights reserved

Combinatorial approach to flavor analysis. 1. Preparation and characterization of a S-methyl thioester library

A new method for the "one-pot" synthesis of S-methyl thioesters has been developed by reacting methyl chlorothiolformate with carboxylic acids. The resulting "flavor library" contained all the intended thioesters and a single major impurity, identified by GC-MS as S,S-dimethyldithiocarbonate. Quantification of individual compounds present in the library was performed by GC analysis using two independent methods of detection, SCD and FID. It was shown that apart from S-methyl thioacetate (0.8 mol %), molar concentrations of other thioesters varied in a relatively narrow range from 4.2 mol % for S-methyl thiopropionate to 14.1 mol % for S-methyl thiohexanoate. In general, medium chain S-methyl thioesters were present in slightly higher molar concentration's than those prepared from short or long chain carboxylic acids. This variation was attributed to partial loss of the most volatile components during extraction and the lower reactivity of higher homologues. The library was used for the characterization of some physicochemical parameters of thioesters. In particular, lipophilicity coefficients (log k(w)) and thioester retention in 10, 20, and 33% triolein (used as a model lipid phase) were determined directly by reverse-phase RPLC and extrapolated from the respective data. This analysis illustrates that substantial information can be generated using a library containing a relatively large number of compounds in effectively the same way as is necessary for the analysis of a single sample

Combinatorial approach to flavor analysis. 2. Olfactory investigation of a library of S-methyl thioesters and sensory evaluation of selected components

The odor characteristics of individual components present in a library comprised of S-methyl thioesters were determined independently by two laboratories using similar but not identical techniques. The odor potency was assessed by values of best estimate-GC-lower amount detected by sniffing (BE-GC-LOADS). For small and medium chain S-methyl thioesters, these values were found to increase from 6 ng for S-methyl thiobutanoate to 90 ng for S-methyl thiostearate. All assessors detected a "green", "floral", or "pineapple" odor for S-methyl thiohexanoate and described thioesters containing a 2-6 carbon chain length as "cheesy". The results of this preliminary analysis were confirmed by a more extensive study of selected compounds, namely S-methyl thioacetate, S-methyl thiopropionate, S-methyl thiobutanoate, and S-methyl thiohexanoate, using a trained panel of 18 subjects. The subjects confirmed the presence of the "green" and "fruity" notes in the odor of S-methyl thiohexanoate. The analysis also revealed a significant difference in the odor of S-methyl thiopropionate relative to that of S-methyl thioacetate and S-methyl thiobutanoate. When "cheesy" characteristics were mentioned, the majority of panelists clearly associated the flavor of S-methyl thiopropionate with Camembert with almost 20% of all the descriptors given referring specifically to this cheese variety as compared to about 2 and 5% in the case of S-methyl thioacetate and thiobutanoate, respectively. Prompted by this observation, two samples of Camembert prepared from unpasteurized and pasteurized milk were analyzed and relatively large amounts of S-methyl thiopropionate were found in the former but not in the latter cheese. The results obtained in the course of this work suggest that the sensory analysis of combinatorial libraries is a useful new approach in the search for new commercial flavors and/or identification of characteristic flavors in foods

Revision of EN 1993-1-11 – fatigue design rules for tension components

As part of the ongoing revision of EN 1993‐1‐11 ”Design of structures with tension components“, the current fatigue design rules have been subjected to a critical review. This has resulted in modifications and amendments, including the adjustment of several parameters. This paper provides an introduction to as well as background information on those changes

International tightening tests with high strength bolts M20 x 100 of the systems HR and HV Tests performed in the Technical University of Hamburg-Harburg, Hamburg/Germany, Research Centre of the Belgian Metalworking Industry CRIF, Liege/Belgium, Test Laboratories of the Company ARS INDUSTRIES, Ars-sur-Moselle/France. Comparison of the test results of the three laboratories. Reports 4-7

SIGLEAvailable from TIB Hannover: RO 8022(4) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman