Furan in coffee: pilot studies on formation during roasting and losses during production steps and consumer handling.

The occurrence of furan in some food products has already been known for a few decades, and it has been reconfirmed in more recent investigations that furan is present in a variety of foodstuffs. This list of products includes roasted coffee, which has been shown to generate furan as a result of the heat treatment at roasting which is applied to achieve the desired aroma and flavour profile of a roasted coffee. The objective of this study is to provide data to allow a better understanding of the available data of furan in coffee, the kinetics of furan generated during roasting, and to estimate the reduction of furan levels afterwards due to subsequent processing steps and consumer handling. Finally, the study is meant as a contribution to establish exposure data on the basis of scientific data at the stage of coffee consumption. This paper shows that the formation of furan during roasting is dependent on roasting conditions and is, therefore, directly linked to achieving targeted flavour profiles. Furthermore, it is demonstrated that modifications in process conditions potentially to reduce furan levels may have the opposite effect on other undesired reaction products of the roasting chemistry such as, for example, acrylamide. Due to the high volatility of furan, any subsequent processing step or consumer handling has an impact on the level of furan. As a guidance from this study and in consideration of the identified losses of each process and handling step on the basis of the trial conditions, it is estimated that only approximately 10% of the initially generated furan during roasting gets into the cup of coffee for consumption.

Formation of semicarbazide (SEM) in food by hypochlorite treatment: is SEM a specific marker for nitrofurazone abuse?

Semicarbazide (SEM) is considered to be a characteristic protein-bound side-chain metabolite of the banned veterinary drug nitrofurazone. It is therefore used as a marker for nitrofurazone abuse. Recently, there has been concern about other sources of SEM in tissue samples, which are not linked to the illegal use of nitrofurazone. The present studies have shown that SEM can occur naturally, e.g. in algae, shrimps and eggs, and is formed from natural substances, e.g. arginine and creatine. A significant formation of SEM was observed in samples treated with hypochlorite commonly used in food processing for disinfection or bleaching. SEM was formed in different kinds of nitrogen compound-containing samples (0.3-20 microg kg(-1)) after treatment with 1% active chlorine. It was detected in the mg kg(-1) range after hypochlorite treatment (0.015% active chlorine) of creatine. Lower levels were also formed from creatinine, arginine and urea. SEM present in hypochlorite-treated carrageenan proved mostly to occur in the tissue-bound form. Therefore, differentiation between SEM from nitrofurazone abuse and SEM originating from natural constituents (due to hypochlorite treatment) seems not to be unambiguously possible.

Evaluation of the results from an inter-laboratory comparison study of the determination of acrylamide in crispbread and butter cookies.

Analytical methods currently employed for determination of acrylamide (AA) in two carbohydrate-rich food samples, crispbread and butter cookies, obtained commercially, and native and spiked bread extract samples have been evaluated in a collaborative study. The objective of the study was to obtain information about the performance of the participating laboratories when analysing samples with an AA content close to the limit of quantification ( LOQ) and at a higher AA level, and to investigate the influence of sample-preparation procedures on the results of the analysis. For this purpose an aqueous native extract of white bread crumb, a fortified extract, and AA standard solutions, the analyte content of which were not disclosed to the participants, were included in the study. A total of 62 laboratories, applying seven different measurement techniques and a broad spectrum of analyte extraction and sample-preparation procedures reported their analytical results. Because the measurement data were not normally distributed, they were evaluated by application of robust statistics. The relative performance of the laboratories was highlighted by calculation of z-scores. For the crispbread sample, especially, a large percentage of the calculated z-scores were outside the satisfactory range. From their distribution it became obvious that one of the analytical techniques might be biased, if not applied correctly. Consequently, the impact of the applied methods was examined in more detail. Information about the analytical technique, extraction solvent, quantity weighed, calibration method, clean-up, and the experience of the participating laboratories were extracted from the analytical protocols and transcribed into a data matrix which was evaluated by multifactor analysis of variance. The applied measurement technique seems to have a statistically significant influence on the analytical results.

Determination of free and conjugated indole-3-acetic acid, tryptophan, and tryptophan metabolites in grape must and wine.

Tryptophan (Trp) and its metabolites, especially indole-3-acetic acid (IAA), are considered to be potential precursors of 2-aminoacetophenone (AAP), an aroma compound that causes an "untypical aging off-flavor" (UTA) in Vitis vinifera wines. In this study, RP-HPLC with fluorescence detection was used for the qualitative and quantitative analysis of Trp and Trp metabolites in grape musts and wines to which different viticultural measures had been applied (time of harvest, soil treatment, leaf plucking, vine prune). An alkaline hydrolysis was developed to release bound IAA and Trp. A sensitive and selective determination of different Trp metabolites was achieved after solid phase extraction using a strong anion exchange material. In the examined grape musts, more than 95% of the total IAA was bound either as ester conjugate or as amide conjugate. Free IAA and other Trp metabolites were below the detection limit (<3 microg/L) or could be determined only in traces. Their amounts increased significantly during fermentation, whereas the amount of Trp decreased. It could be shown that the different viticultural measures applied (except the vine prune) as well as the climatic conditions of the vintage exhibited significant influences on the amounts of Trp and Trp metabolites in grape musts or wines.

Off-flavor compounds in wine and other food products formed by enzymatical, physical, and chemical degradation of tryptophan and its metabolites.

Tryptophan (TRP) and its metabolites are considered as potential precursors of 2-aminoacetophenone (AAP) in different food products causing different off-flavors. AAP is also responsible for the "untypical aging flavor (UTA)" in wine, developing a floor polish-like flavor in white wines within a few months of storage. In this study the formation of AAP was elucidated by GC-MS analysis of volatile components in model systems, grape musts and wines, spiked with TRP and different TRP metabolites like indole-3-acetic acid (IAA) and sulfite. In sulfurized wines and model solutions which were stored at different temperatures (20 degrees C, 45 degrees C) formylaminoacetophenone (FAP) and AAP were formed mainly from IAA with formation rates up to 20 mole%. Minor formation rates of AAP (< 1 mole%) were found in sulfurized solutions of TRP, indole-3-lactic acid, and indole-3-pyruvic acid. The results showed that the formation of AAP in wine can be referred to an oxidative degradation of IAA by superoxide- and hydroxyl-radicals, which can be formed in wine after the sulfuration by cooxidation of sulfite to sulfate. After decarboxylation, pyrrole oxidation, and ring cleavage, FAP was the main volatile compound of the nonenzymatic degradation of IAA by sulfite which was quantitatively hydrolyzed to AAP. The formation of AAP and FAP was significantly lower in white wines than in ethanolic solutions spiked with IAA. However AAP formation rates of up to 5 mole% were still enough for an UTA. Due to the fact that the AAP- and UTA-formation by cooxidation of sulfite and IAA was completely blocked in red wines, it could be deduced that polyphenolic compounds, typical for red wines, have a scavenger effect on the radical oxidation of sulfite. Possibilities for an inhibition of the IAA degradation during winemaking to avoid the UTA in white wines by addition of radical scavengers like grape marc or ascorbic acid are discussed.

Determination of tryptophan and tryptophan metabolites in grape must and wine.

Tryptophan (Trp) and its metabolites, especially indole-3-acetic acid (IAA), are considered as potential precursors of 2-aminoacetophenone (AAP), an aroma compound which causes the "untypical aging off-flavor" (UTA) in Vitis vinifera white wines. In this study RP-HPLC with fluorescence detection was used for the qualitative and quantitative analysis of Trp and Trp-metabolites in 39 grapes, 22 grape musts and 16 wines, to which different viticultural conditions (ripeness, pruning, strip of leaves, soil condition) have been applied. A sensitive and selective determination was achieved after solid phase extraction using an anion exchange material. Only traces of Trp-metabolites could be determined in the examined grapes and grape musts, but their amounts increased significantly during fermentation, whereas the amount of Trp decreased. Different viticultural measures, besides the time of grape harvest, showed no significant influences on the amount of Trp and Trp-metabolites.