Safeguarding Food Quality

It is a great pleasure for me to bring you words of welcome from the ISACB who have organized this workshop which is focused upon food safety and quality. It is altogether fitting and proper that this topic which primarily focuses upon foods of animal origin be discussed under one aegis by scientists with analytical interests in animal tissues. Hence, the leadership of the ISACB in bringing pre-eminent scientists together at this Conference. The scope of this field is large as witness the number of symposia at this conference which are closely related to the topic of food safety and quality. Symposium 2, the “Analytical Challenge of Water” is of broad importance in any field, be it the analysis itself or its quality. Symposium 6, “Immunoassay”, encompasses another broad analytical technique for the detection of antigens or antibodies in virtually all media. Symposium 7, “Mass Spectrometry”, together with “Immunoassay” are mainstays of drug testing in human or animal athletes, therapeutic drug monitoring or drugs of abuse. These techniques are directly translatable into the detection of residues in foods. Symposium 8 “Environmental Toxicity” is intimately related as environmental toxins enter our food chain. Similarly, symposium 13 “High Resolution Microbial Analysis” assumes great importance as it has been said that “only 10% of all the organisms in our environment are known”. Techniques from modern molecular biology must be brought to bear if we are to combat the many new and emerging problems which face us.

Since the beginning of nutritional research, food quality (nature, class) has been a central theme; a great deal of effort is concentrated on the goal of improving the quality of foods. To which extent this can be achieved, depends among other things on the definition of the term food quality.

Food quality represents the sum of all properties and assessable attributes of a food item. Usually this is done by the three accepted categories of quality: sensoric value, suitability value and health value. All three deal with assessments, that is, judgements with a subjective component.

In addition to the value-related interpretation of quality there is the value-neutral term in the sense of condition, that is the sum of properties of a product. From this can be concluded that quality is not easily definable scientifically and that it comprises many different aspects. Obligatory and uniform definitions are also made difficult, since those aspects are subject to constant change.

Contradictions in the discussion about food quality arise mainly because of self-serving interests of producers, processors and traders of food as well as consumers, since concerning the assessment of simple quality features of products these interest groups often hold quite different views. The existing contradictions can be overcome, if all justified interests are considered, that is, with a holistic view of all the separate aspects.

A holistic assessment of quality of food comprises, in addition to the three recognised partial qualities, additional categories of quality which are currently gaining in significance. On the one hand there is a psychological or notional value of food, based on usually difficult-to-explain conceptions, opinions (prejudices) and expectations of consumers concerning a product. Foods are imputed to have certain properties which determine, whether these will be selected and eaten. Without a clear delimitation to this area foods have a cultural or social value. The prestige value of food is determined by food habits of certain population groups as well as by supply and price. Foods that are taboo or that are used as reward get their social value in this manner. The political value of foods comprises aspects like the import of foods and feeds, especially from developing countries as well as production and handling of food surplus and employment of food aid. A further category of quality is the ecological value of foods which assesses the consequences on the environment due to food production and food processing, as well as their manifold interactions and feedbacks.

These additional criteria or properties of food are often more difficult to define and to include, since they cannot be identified and measured on the product itself. From this, however, it should not be concluded that these criteria in the spectrum of food quality are not important. Even though single interest groups in the food sector will still get their way in regard to expectations and demands concerning quality, social demands and necessities are gaining increasing importance. Future and social requirements relating to the quality of food are expected to avoid misjudgements by using a holistic assessment.

Today food companies have to consider many legal preconditions which comprise beside the individual production and the resulting products as well several other aspects. Besides, each company should define its own individual quality policy in which additional important quality factors are integrated. This external and internal points can only be realized through a comprehensive quality management creating the basis for a wide but detailed network or system of measures and control points and covering the whole range between product idea and consumer. And this is exactly what quality assurance means. If quality assurance is dealt with thoroughly, it is not a bureaucratic exercise but the key for the success in the future in a large but as well difficult market.

Already many years ago the Commission of the EC has developed a first strategy with the so-called global approach, which of course is a relatively abstract concept. The standard series EN 29000 (ISO 9000) as to quality assurance defines the important quality elements independent on individual branches, and the difficulty lies in the transformation of these general standards into the specific situation of a company. Meanwhile the Commission of the EC has several times underlined the importance of quality assurance as well for the food field, and each company will be forced throughout the next years to develop a certifiable quality assurance system. The thorough dealing with quality assurance creates a unique chance to achieve more product safety and higher product quality but as well better economical conditions.

Dry chemistry or solid state chemistry is a relatively new technology introduced by several manufacturers for the medical diagnosis of diseases and metabolic disorders. The systems are based on the quantitative determination of enzymes, proteins, metabolites, electrolytes or other substances by means of a reaction monitored by the reading of a signal which is translated to a quantitative unit. Unlike the conventional wet chemistry technologies working with a pre-made solution, dry chemistry works with dried reagents, buffers and enzymes layered on a solid matrix or impregnated into a filter. Following the addition of a fixed amount of a liquid, the reagents are dissolved allowing a reaction to take place. The signal is read by reflectance rather than absorbance.

The possibilities of adapting this system for uses in the food industry and agriculture, for the determination of composition and quality of various products is being evaluated. Out of about 40 various tests commercially available today in the market, many can be easily adapted for a wide range of uses in fields other than blood chemistry.

Among tests and areas evaluated are: 1) protein, lactose, fat, minerals, enzymes, and metabolites in the evaluation of composition, degree of pasteurization, and quality of milk, 2) amylase, in beer manufacturing, 3) sugars and alcohol in wine production, 4) sugars and minerals in fruit juice, 5) meat processing, 6) minerals in soil analysis.

Kodak Ektachem DT60, Vettest 8008 (using Kodak’s Ektachem slides) and Boehringer- Mannhein’ s Reflotron systems were evaluated and the results presented. Results obtained are very encouraging, and strongly suggest the tremendous potential in the use of dry chemistry for the determination of food quality in the fields of food hygiene industry and research, opening new large markets to dry chemistry analysis.

These days the enzymatic analytics and physical measuring methods are of increasing significance. Theoretically this combination should solve all interference problems and improve the selectivity of analysis. However, this fails sometimes, e.g. measurements in complex solutions still raise a lot of problems for the analyst.

We have developed a biosensor designed for use by the food producing industry that enables us to examine turbid, heterogeneous, coloured and similar liquids. This sensor solves some of the problems mentioned above. The sensor is unique since its measuring head works without a membrane. In addition an electron-transfer-mediator and immobilized enzymes in the paste of the measuring head are used.

It was not the intention of this paper to show the analytical difficulties in residue analysis in food, but to draw the attention to the standard for such procedures, the Maximum Residue Limits (MRLs) for residues and contaminants in food. Only when the substance under question yields a discrete No Observable (Adverse) Effect Level (NO(A)EL) in the assay with sensitive laboratory animals, can the MRL for a specific food be derived with a formal correlation of NOEL, safety factors, body weight and food consumption. The NOEL however, is only discrete for substances with a clear dose-response relationship. For tumor-initiating (and perhaps tumor- promoting) substances this equation is not valid. As some of these substances have an environmental impact on food and a MRL setting is required at all costs to shut down the source and to protect the consumer (the latter intention is carried out first, but would be useless if performed in isolation), the MRL is just a compromise between the analytical possibilities of trace analysis and the mean occurrence in food. Specific problems are involved in the residues of veterinary drugs in food of animal origin, especially antibiotics. It seems obvious, apart from the more pharmacologic- toxicologic difficulties, that the analytical state-of-the-art needs considerable improvement to assure the consumer’s protection by the means of MRLs. The setting of a MRL for polychlorinated dibenzodioxins is difficult due to the discrepancy of the present contamination situation, the desired figure under the premise of precautionary health care and the tolerable daily intake (TDI). In the case of PCBs and aflatoxin M₁ in milk, the established MRLs have led to an improvement of the situation for different reasons. The lower of the two MRLs for AFM₁ in milk has helped to exert considerable influence on the feedstuff industry to limit the precursor in feed for dairy cattle. In the case of PCBs, herd’s bulk milk was officially designated as an indicator substrate to trace the pollution back to the origin to eliminate the source.

In view of the increasing demands by the consumers on milk and milkproducts and for reasons of national and international competition, the dairy farmers have to improve the quality of their milk. To enable the farmer to do this he needs support. Healthy dairy cows are the basis for the production of high quality milk. The official health inspection is insufficient. Our computerizied herd-health control program “BIPS” (Bonner Information and Preventiv System) renders possible the early detection of risk factors and their elimination. With the collection of the health and performance data and with the early warning indicators, the dairy farmer receives fast and detailed information and suggestions for the best possible alternatives for herd management. The aim of all these efforts is the production of high quality milk. Within this system we have tested “rennet clotting time” as a new quality attribute for raw milk. Milk with a short clotting time (≤ 20 min) has a much better hygienic quality, a higher nutritional and technological value and, significantly belongs, more often to cattle which have a better udder health than others.

For different reasons special attention is paid to milk in public discussion on residues and contaminants. Its role in the food chain and — as a consequence — in the burden on man is strongly influenced by concentration and deconcentration effects which are mostly related to contamination pathways via feed.

Chemical compound groups of residues and contaminants of major importance are presented in a brief overview, with particular reference to their present significance for the contamination of milk as well as pathways and sources of contamination as far as they are related to feed.

Scientific results and practical experience, as well as the key role of research on sources of contamination, practical care of the farmer and environmental protection measures to control milk contamination are emphasized.

Analysis of feed and milk for residues and contaminants means a particular challenge with respect to

A few examples will show that substantial analytical progress has been achieved in the past but that — on the other side — many unreliable and even completely wrong results are still taken as a basis for evaluation.

By different measures at different levels, contamination of milk has been considerably, sometimes even drastically lowered for most contaminants during the last 20 years.

Milk contains several bioactive proteins and peptides as original minor constituents. Peptides that are inactive within the sequence of major milk proteins (caseins, whey proteins) are of particular interest. Such peptides are e.g. casomorphins, caseinophosphopeptides and casokinins. These peptides may be released from the appropriate protein precursor during intestinal proteolysis or the manufacture of milk products.

Regarding the significance of bioactive peptides from milk as exogenous regulatory substances, different analytical techniques have been developed for the determination of peptide fragments that are liberated as a result of technological treatment or during intestinal proteolysis. In order to detect bioactive sequences that are hidden within milk proteins an enzymatic in vitro-proteolysis (e.g. with trypsin) has to be performed. The analysis of minor peptide concentrations demands an enrichment of the analyte as well as the application of methods with a low detection limit. For example, the solid phase extraction using C18 cartridges is suitable for the concentration of hydrophobic casomorphins; anion exchange chromatography is useful to isolate phosphopeptides. Reversed phase high-performance liquid chromatography (HPLC) has proved itself to be a versatile procedure for the determination of peptides.

Immunochemical analyses using enzyme-immunoassay (ELISA) provide an advantage regarding specifity and sample throughput as compared with liquid chromatographic methods. Anti-peptide-(lgY)antibodies can be easily prepared from the egg yolks of immunized laying hens and used in ELISA for the determination of peptides. Suitable standard substances and immunogens, respectively, are obtained by solid phase peptide synthesis (Fmoc strategy).

Further studies are needed to examine which bioactive peptides are ingested in physiologically significant amounts from milk and milk products. Nevertheless, the relatively new area of investigation in bioactive peptides have introduced a new criterion for defining the protein and food quality.

The use of antibiotics and sulfonamides in veterinary medicine may cause residues of these drugs to be present in food of animal origin. The microbial inhibition assay, which is used in routine testing of milk, however, is sensitive for penicillin but not for other antimicrobials. Therefore immunoassays have been developed for the detection of chloramphenicol, tetracycline, streptomycin, sulfonamides and trimethoprim.

For that purpose specific antibodies had to be developed as well as enzyme labelled antigens. The sensitivity and the specificity of the assays were characterized using standard test protocols for competitive enzyme immunoassays.

The detection limits (0.5–20 ng/ml milk) of the enzyme immunoassays were found to be well below the regulatory limits. The results characterizing the specificity showed, that the enzyme immunoassays for sulfamethoxypyridazine and trimethoprim were highly specific, whereas the other assays showed cross reactivity with several substances of related structure (group specificity). The range of recovery, analyzing artificially contaminated milk samples, was between 68 and 104%.

Enzyme immunoassays for antimicrobial drugs have the advantage of sensitivity and speed together with the simplicity of manipulations involved in the procedure. Therefore these methods are easily automated and show good cost-effectiveness. Concerning the results of the specificity studies as well as the possibility of false positive results due to unspecific inhibition of the assay, confirmation of immunoassay results is still needed for all legal and statutory purposes. For routine testing of milk, however, enzyme immunoassays represent a versatile analytical tool.

Nowadays it is no longer sufficient to have only isolated dimensions of quality in view. In addition it is necessary to include all aspects of processing and product quality: environmental protection, animal health and welfare as well as quality features of the pork and monitoring of drug residues.

There is therefore, a demand for an integrated CAQ-system (Computer Aided Quality assurance) in the whole pork production chain. Current pig production is widely distributed geographically and highly specialized. As a result, the available information is fragmented and the different enterprises like farms and slaughter-houses have no overall view of the pig production. A technical and an organisational integration between breeding, piglet producing, fattening, slaughtering and processing is required. It is necessary for the various parties involved that the information exchange within the different steps is possible. Potentialities under this aspect are

Assignment of analysis in a CAQ-concept is to supply additional data and predictive and prescriptive information for the individual farmer as well as the adviser. CAQ is an instrument that helps in making professional analysis of data, detecting and solving problems and making plans for the future. Therefore the collection, storage and analysis of data from the following fields is stimulated:

In the last years several keystones of a CAQ-system have already been developed. Now, it is necessary to combine them efficiently to a total system.

The increasing demand from authorities and consumers for quality assurance and quality documentation for meat and meat products has led to the development and application of a range of on-line measuring methods. The main aim of these methods is to convert the wide biological variations in meat into a range of specified, well defined products. Other important objectives are to increase the consumers’ confidence in the products and to improve value for money as a result of product optimisation.

The conditions for application of on-line measurements and the technical requirements are discussed.

Some on-line methods — especially for carcass classification — are used extensively in the industry. It is likely that many other methods will be applied commercially in the near future.

Hygienic quality parameters are of increasing importance to consumers. This is an area where a significant research effort is required to satisfy the requirement for documentation of guaranteed purity and safety of meat.

The most important quality criteria for food are that it must be safe in terms of health and therefore free from harmful substances.

Some important classes of chemical compounds are presented, which may occur in meat as residues or contaminants. With two topical classes of substances — antimicrobial drugs and anabolics — some problems of impurities in meat are discussed.

The occurrence of residues in animal tissues is influenced by many factors, they were taken in consideration when withdrawal periods for veterinary drugs were laid down. The main sources of residues in meat and edible offal are — improper and illegal use of drugs, — withdrawal time not followed, — contaminated feed, — recycling of drugs from litter.

Many antimicrobial drugs cannot be detected with required sensitivity and different matrices may interfere the results. Suitable methods are relatively complicated and can only be applied to determine a single drug or a single class of drugs.

In the EC the use of anabolics to fatten animals is strictly forbidden. Besides the usual analytical methods, which are relatively complicated, for some anabolics now there exist some sensitive methods, which can be handled relatively simple (particularly enzyme-immunoassays).

Because immunoassay-tests now are available for a lot of substances there exist a real chance to test animals for residues and contaminants even during breeding and fattening. But many tests are still incomplete.