Euro food chem VIII: Current status and future trends in analytical food chemistry

Euro Food Chem VIII: It is perhaps fitting that Vienna, a city steeped in tradition but with a reputation for progressive thought in the arts and sciences, personified by the likes of Strauss, Klimt and Freud, should host a symposium concerned both with current issues and the future of analytical food chemistry. This was, in fact, the second time that the series of Euro Food Chem meetings, organized by the Federation of European Chemical Societies Working Party on Food Chemistry, had addressed the topic of analytical food chemistry. The presence of over 300 delegates, from 18 European countries, to listen to the 37 lectures was testimony to the enduring interest and panEuropean appeal of the subject. Sampling and sample preparation It was, in fact, the Euro Food Chem I meeting that had previously considered analytical food chemistry. Although in the intervening years there have been many developments, some things never change, and so it was that the first conference session addressed the perennial problem of sampling and sample preparation. The opening plenary lecture, given by R. Stephany (National Institute of Public Health and Environmental Health, Bilthoven, The Netherlands), entitled ‘Yield or recovery: a world of difference’, was an insightful and witty account of the difficulty of assessing the accuracy of a given method. In particular, how can the analyst be certain that recovery (i.e. the percentage recovered of a spiked analyte) equates to yield (i.e. the amount of ‘native’ analyte originally present in the sample)? Several equations and methodological approaches were given to aid in addressing this problem, and examples were cited where yield and recovery should not be considered to be the same. For example, in the extraction of nonpolar steroids from urine, where a deconjugation step is required, it is necessary to know the efficiency of the deconjugation step. The final part of Stephany’s lecture was dedicated to a discussion of how much effort (i.e. cost) an analyst should put into ensuring that results are correct. This theme of analytical economics was reprised by two of the next three speakers. W. de Koe (Inspectorate for Health Protection, Rijswijk, The Netherlands) discussed how the different perception of acceptable risk by the consumer and producer leads to differences in sampling plans to achieve a fair balance between the cost to the producer of sampling and the risks to the consumer of making the wrong decision. He proceeded to illustrate graphically how different sampling plans and accepted values for defective samples in a consignment can lead to varying likelihoods of national authorities

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Current Status and Future Trends in Analytical Food Chemistry* Simon Branch accepting samples contaminated with, in his example, aflatoxins. H. de Brabander (University of Gent, Salisburylaan, Belgium) continued the theme with a paper describing ways to improve sample throughput in residue analysis. He illustrated the rationale for increasing sample throughput by describing how, for a particular chromatographic analysis, the cost of the consumables had risen in some cases by 300% over the past 19 years, whereas the price paid for the analysis had fallen by 20%. Against such a background some simple and elegant practical steps to improve sample throughput were described. None of the approaches required any significant capital costs; the communication and sharing of ideas such as those presented are among the reasons that attendance at scientific symposia is useful. At the end of this first session, and throughout the next two days, it became clear that one current, and almost certainly also future, issue was a recurring theme: routine analysis is becoming increasingly competitive against a backdrop of reduced funding. For a delegate grappling with the difficult trading conditions in the UK analytical market it can be, in equal measure, both reassuring and depressing to see our European cousins struggling with the same problems. During the series of sampling papers, two presentations on subjects of great potential in preparation and analysis were given. The first of these (H. Kallio, University of Turku, Turku, Finland) described the advantages - cost effectiveness, speed, limited use of solvents - of supercritical fluid extraction (SFE) in contaminant analysis. Unfortunately, uptake of the technique has been hampered by a lack of familiarity within the analytical community, lack of instrument standardization and only a few collaborative trials to confirm the efficacy of methodology. With legislation and international agreements such as the Montreal Accord demanding alternatives to many common extraction solvents, SFE applications can only increase. The second of the presentations (M. Barroso, Basque Country University, Vittoria-Gasteiz, Spain) concentrated on dynamic headspace trap and desorption as a means of sample introduction in GC and GC-MS (gas chromatography - mass spectrometry). The advantages of this approach include reduced solvent usage, as extraction or 01995, Elsevw Scmce Ltd

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distillation are not required, limited sample preparation, shorter retention times, and greater column lifetimes. Uniquely, in my experience, the analytes were desorbed by direct coupling of microwave power into the adsorbent cell. The method was applied to the analysis of flavour volatiles in cheese. Chromatography and coupled techniques The second component of the conference dealt with one of the food analyst’s most established tools: chromatography. In total, ten speakers addressed the topic. While it is not possible to detail here all of the presentations, it is possible to give the flavour of one or two. Both P. Schreier (University of Wtirzburg, Wtirzburg, Germany) and A. Mosandl (J.W. Goethe University, Frankfurt, Germany) spoke on the subject of chiral analysis. Schreier concentrated on a review of chromatographic methods [thin-layer chromatography (TLC), highpressure thin-layer chromatography (HPTLC), supercritical Auid chromatography (SFC) and high-pressure liquid chromatography (HPLC)], stationary phases and derivatizing agents available for separating chiral organic molecules; Mosandl focused on applications of chiral chromatography. In particular, Mosandl introduced the concept of using enantioselectivity during biosynthesis as an endogenous parameter that can be of value in authenticating natural flavour and fragrance compounds. By using multi-dimensional GC it was possible to discriminate between naturally occurring flavour compounds and their artificial racemates in yellow passion fruit flavour. Going one step further, for a real ‘belt-andbraces’ approach, coupled enantio-GC - isotope ratio MS was used to quantify adulteration in peppetmint oil. The topic of coupled techniques, also known as ‘hyphenated’ or ‘multidimensional’ detection methods, was exhaustively explored by A. Mangia (University of Parma, Parma, Italy), who managed to touch on 17 such techniques in his 30 minutes. In particular, he majored on LC-MS methods, with emphasis on how the coupling is achieved: thermospray, electrospray, heated nebulization, inductively coupled plasma (ICP), etc. This last topic introduced the theme of trace element speciation, and if one were to inject one note of criticism it is perhaps that the conference organizers did not include a presentation on this topic, since its importance has burgeoned during the past 20 years or so. With legislation for methyl mercury proposed, developing methods for speciating elements such as aluminium, arsenic, lead, mercury and selenium is likely to be one of the future challenges for the food analyst. Several speakers speculated on the potential of capillary electrophoresis and presented applications such as separations of fat- and water-soluble vitamins and of alkali metals and alkaline earth metals in red wine. As manufacturers improve the reliability of columns, this technique is likely to attract increasing attention. Sensor techniques Otto Wolfbeis (Karl-Franzens University, Graz, Austria) opened this section of the conference and 412

moved the audience into the realm of using analytical tools to solve industry’s problems and control its processes. In particular, elegant and relatively simple optical sensors and biosensors for determining pH, oxygen, carbon dioxide and ammonia were described. These sensors were applied, for instance, to measuring pH in bioreactors and CO, as an indicator of aerobic bacterial metabolism. The remarkable growth of enzymebased biosensors was also touched upon, as well as their value in determining substrates such as glucose, cholesterol, alcohol, sulphite and many others. During his presentation, Wolfbeis briefly touched on interest in ‘electronic noses’, which laid the ground for Th. Talou (Institut National Polytechnique, Toulouse, France), who spoke at length on ‘New trends in applications of multigas sensors’. The range of sensors - metal oxide, polypyrrole, polyindole, etc. - currently available, and the role of artificial intelligence were reviewed. The lecture finished in novel style: a video was shown comparing the performance of an electronic nose and a trained pig in finding buried truffles. At this early stage of development the nose was an ‘also-ran’, although it did have the advantage of not eating the truffle, unlike its four-legged competitor. The subject of electronic noses was reprised later by CD. Natale (University of Rome, Rome, Italy), who demonstrated how an electronic nose based on metal oxide semiconductors could be used in the quality control of wine. Wines were differentiated on the basis of vintage and, for wines from the same region, vineyard of origin. M. Tomassetti (University of Rome, Rome, Italy) reported progress in using the tyrosinase biosensor to evaluate olive oil quality via correlation with phenol content. When the sensor was immersed in phenol, the following reaction occurred: phenol + 02s

1,2 benzoquinone + H,O

Phenol was determined by following oxygen consumption using a Clark oxygen electrode. Interestingly, all of the measurements were carried out in an organic medium, typically n-hexane, although there was some evidence that this decreased sensor lifetime. Spectroscopic methods The third day began with a presentation on ‘NIR applications and statistical evaluation’ by T. Naes (MATFORSK, As, Norway). Two aspects of his talk stood out. Firstly, a number of the statistical techniques described had already been alluded to by other speakers, underlining the increasing importance of multivariate data methods in analysis. Secondly, he had to treat his plenary lecture somewhat as a tutorial, underlining what a long way our understanding has yet to travel. Nearinfrared reflectance spectroscopy was shown to be of value in determining whether meat had been heat treated and whether it had been previously been frozen. The role of statistics in analytical chemistry was further developed by both of the next two speakers. A.C. Tas (TNO, The Netherlands) and his co-workers had Trends

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used i3C NMR and pyrolysis mass spectrometry in conjunction with multivariate techniques, such as discrirninant analysis, for direct analyses of complex samples. For instance, two dietary fibre reference materials were subjected to step-wise hydrolysis by both the Englyst and AOAC International methods. It was possible to determine which sample had been prepared by which method by monitoring the reaction products. It was, perhaps, surprising that in a meeting on analytical food chemistry this was the only mention of the Englyst versus AOAC method debate, one of the subject’s great controversies. Anybody still with cobwebs in their mind following the previous night’s banquet had them blown away by the next presentation. In the conference’s most energetic display, Lars Munck (The Royal Veterinary and Agricultural University, Copenhagen, Denmark) sought to fire the audience with his enthusiasm for fluorescence spectroscopy. Examples included the use of fluorescence coupled with image analysis to monitor on-line bran removal in wheat flour mills, and how, by coupling the sensitivity and specificity of fluorescence with the discriminatory power of multivariate statistics, it is possible to undertake process control applications. In the latter study it was possible to identify which sugar beet factory was producing a product different from the majority and which factory had poor control of its process. The next plenary lecture in the series was given by G-W. Bog1 (Federal Institute for Health Protection of Consumers, Berlin, Germany), who detailed the rationale behind the irradiation of food and progress in establishing protocols for detecting irradiated products. In particular, he concentrated on thermoluminescence, electron spin resonance (ESR) spectroscopy, and GC determination of fat degradation products such as cyclobutanones. The suitability of each technique for analysing different types of foods, practical limitations and progress in collaborative trials for each were detailed. Looking further ahead, new approaches such as optically stimulated or photostimulated luminescence were briefly mentioned. D.N. Rutlege (Institut National Agronomique ParisGrignon, Paris, France) introduced the audience to timedomain NMR. Following a brief introduction to the theory he showed how the technique could be used for the rapid assessment of hydration state and water dynamics and content in gelatin systems. In one of the meeting’s most progressive papers, Peter Belton (Institute of Food Research, Norwich, UK) speculated on the use of infrared emission spectroscopy, proposing that the technique could be beneficial for investigating packaging materials and structural changes as foods are heated. Unfortunately, for thick samples (i.e. typical foods), theory dictates that the spectra will contain little information. However, when thin films were heated via a transparent potassium bromide base-plate, it was possible to obtain spectra for a 5 p.m thick sample of starch and for a polythene film. Trends

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Bioaffinity methods The final session of the meeting was concerned with various biochemical techniques that are finding favour in solving many current and future issues - food chemical safety, detection of adulteration, characterization of genetically modified organisms (GMOs), rapid screening for microbiological contamination, etc. Events kicked off with an overview of immunoassay-based and competitor techniques and their potential for achieving real-time analysis (G. Van Peteghem, University of Gent, Gent, Belgium). To achieve real-time analysis the measurement must be conducted at the production site and thus simple equipment is required. Dipstick immunoassays, using a portable photometer to aid in differentiating between similar colours, were proposed for determining, among others: chloramphenicol in raw milk, P-antagonists in urine, triazines in drinking water, and trichothecene T, in wheat. There then followed what will have been the most memorable lecture for many of the audience. Demonstrating great scientific rigour and a deadpan wit (especially with hecklers), U. Candrian (University of Beme, Beme, Switzerland) described the remarkable progress his laboratory has made in using the polymerase chain reaction (PCR) to identify GMOs, to detect trace levels of gliadins or wheat in purportedly ‘gluten-free’ products, to identify soy flour and protein extracts as fillers in sausage and, most memorably, to detect pork in sausages. In this latter study, an ingenious sequence of restriction enzyme digestions and PCR assays allowed cooked sausage adulteration to be classified as inadvertent, presumably as a result of poor hygiene (O.l-1.0% pork), or deliberate (>5% pork). Only 25% of sausages, purchased from retail outlets, that did not have pork declared on their ingredients list were found to be unadulterated. Finally, K-W. Bog1 reappeared to describe to his audience the future challenges faced in determining GMOs. In 1992 in Europe alone there were 400 studies underway on modifying plants, and the annual growth rate of GMOs worldwide is -30%. In Germany, a working group has been established to develop detection methods and it has already undertaken ring trials. As a UK delegate, I found that one of the pleasures of this excellent conference was learning what progress European colleagues have made in tackling many of food analysis’ vexed questions. It was a pity the UK was not better represented, perhaps reflecting the fact that some of our scientists have the same problem in being part of Europe as some of our politicians. Awards and prizes Major conferences often have memorable social events. In a city of striking architecture the organizers could not have arranged evening events in more memorable and sumptuous locations than von Erlach’s Vienna Town Hall or the Hapsburgs’ former hunting lodge, Laxendale Castle. It was at this second venue that Professor Czedik-Eysenberg was presented with the Royal Society of Chemistry (RSC) Food Chemistry 413

Group’s Gold Medal for outstanding contributions to European food chemistry. At the close of the meeting awards were given for the three best posters (from over 180), which were judged to be: l

‘Applicability of neutron activation analysis (NAA) in quantitative determination of some essential and toxic trace elements in food articles’, by M. Dermelj al. (‘J. Stephen’ Institute, Ljubljana, Slovenia); et

l

‘A biosensor for the determination of flatulencecausing oligosaccharides in pea’, by M. Voldrich al. (Institute of Chemical Technology, Prague, Czech Republic);

et

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l

‘Mobilization and analytical availability of drug residues in food’, by J. Pomp and H. Burring-Pfaue (Institute of Food Chemistry and Food Science, University of Bonn, Germany).

Copies of the conference Proceedings are available for sale from G. Sontag, Institute for Analytical Chemistry, Wahringerstr. 38, University of Vienna, A-1090 Vienna, Austria (fax: 43-l-3196312). Euro Food Chem IX will be held in Interlaken, Switzerland, 24-26 September 1997. The theme will be ‘Authenticity and falsification of food - the analytical approach’. -

Conference Report

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2nd International Food were also well represented. Delegates included analysts involved in food compositional work, scientists involved in designing and compiling databases for nutrients and non-nutrients, and nutritionists and other health professionals interested in using databases to investigate various diet-health relationships. Two satellite meetings of European Union (EU) projects were also organized: a series of workshops under the auspices of the COST 99 programme on Food Composition and Consumption, chaired by Clive West (Wageningen Agricultural University, The Netherlands); and a Standards, Measurement and Testing project on Improvements in Vitamin Analysis in Foods, chaired by Paul Finglas (Institute of Food Research, Norwich, UK) and Henk van den Berg (TN0 Nutrition and Food Research Institute, Zeist, The Netherlands). The conference itself was divided into seven main sessions.

Data Base Conference: Food Composition Research - The Broader Context* Paul M. Finglas The 2nd International Food Data Base Conference was organized to honour the scientific achievements of Prof. Pekka Koivistoinen, holder of the Chair of Food Chemistry at the University of Helsinki, Finland until his recent retirement. The aim of the conference was to highlight the latest advances, problems and challenges in food composition research, and to discuss selected aspects of the design and use of food databases for nutritional research. Although a large proportion of the 175 delegates were from Europe, other regions of the world

* Held in Lahti, Finland, 28-30

August 199.5

Paul M. Finglas is at the Nutrition, Food Research, Norwich

Laboratory,

Diet & Health Norwich

UK NR4 7UA (fax: +44-l 603-507723).

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Nutritional concepts and recent advances in macronutrient research The first session was chaired by Pekka Koivistoinen, who gave a short introduction on ‘The early history of food composition analysis - source of artifacts until now’. The latest developments in the chemistry, physiology, classification and measurement of dietary carbohydrates were then thoroughly discussed in two general overviews by Nils-Georg Asp (Lund University, Lund, Sweden) and Hans Englyst et al. (Dunn Clinical Nutrition Centre, Cambridge, UK). Special emphasis was laid on dietary fibre. With some exceptions, there was general agreement on basic concepts of dietary carbohydrate analysis based on direct measurements of the various fractions in foods. Protein determination in foods was introduced by a comprehensive study (Pirjo Salo-Vaananen and Pekka Trends

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