Proficiency testing programmes as a tool in food quality assurance: Overview of Italian experiences

Proficiency testing involves the performance of test procedures on routine samples by a number of laboratories. Interlaboratory proficiency testings provide multiple benefits to participants since they play a key-role in the total quality control of laboratory activities. They serve as a means of self-improving, as a mechanism of continuing education and as a source of information for accreditation agencies. This review highlights basic principles, benefits, criteria and capabilities of a proficiency testing programme for food analysis laboratories as well as their role in the implementation of rapidly developing food control legislation.     

Front face synchronous fluorescence as a tool for the quality assurance of Greek milk

This research focuses on implementing the low cost and rapid front face synchronous fluorescence (SyFS) in order to ensure the quality assurance of Greek milk. Specifically, samples originated from the Greek domestic production of goat, sheep, cow, as well as foreign cow milk samples and adulterated cow milk samples. SyFS spectra were acquired in the excitation area of 250–500 nm with (Δλ)= 100 nm. Greek and foreign cow milk samples were differentiated based on intensity variations at wavelengths 350–515 nm, 540–579 nm, and 580–600 nm. The emissions at these wavelength positions correspond to tryptophan, vitamin A, and riboflavin. The supervised model with 94 samples exhibited p-value = 7,98E-11, RMSEE= 0,29171, RMSEcv= 0,29284 and RMSEP= 0,98013, AUROC for Greek samples= 0,61 and AUROC for foreign= 0,85. We differentiated milk samples according to the animal type with PCA and OPLS-DA models of 107 samples exhibiting RMSEE= 0,225842, RMSEcv= 0,228054 and RMSEP= 0,518635, AUROC for sheep samples= 0,99, AUROC for goat samples= 0,98 and AUROC for cow samples= 0,96. In fact, the emission band 350–591 nm characterized sheep milk and corresponds to aminoacids and fatty acids, cow milk was related to the 350–600 nm emission band related to the b-carotene and to the goat milk the emission bands 350–505 nm and 520–600 nm were attributed to tryptophan, NADH and Rivoflabin. Finally, we investigated whether SyFS coupled with chemometrics may provide preliminary evidence on adulterated cow milk samples. All models were validated with permutation testing, p-values and ROC curves.     

Application of a potentiometric electronic tongue as a classification tool in food analysis

This paper reports on the application of a potentiometric sensor array to the food analysis field, in order to distinguish simple tastes and to classify food samples. This array is formed by a set of non-specific all-solid-state potentiometric sensors and has been used in combination with principal component analysis (PCA) for the classification of food samples in batch and in flow injection mode. First attempt was to classify synthetic samples prepared with controlled variability. Once this ability is proven, satisfactory classification results are presented for commercial waters, orange-based drinks and tea samples. An interesting correlation is achieved between the natural juice content and its first calculated component, which allows for a very simple tool for screening purposes.     

Electrochemical immunoassay using magnetic beads for the determination of zearalenone in baby food: An anticipated analytical tool for food safety

In this work, electrochemical immunoassay involving magnetic beads to determine zearalenone in selected food samples has been developed. The immunoassay scheme has been based on a direct competitive immunoassay method in which antibody-coated magnetic beads were employed as the immobilisation support and horseradish peroxidase (HRP) was used as enzymatic label. Amperometric detection has been achieved through the addition of hydrogen peroxide substrate and hydroquinone as mediator.Analytical performance of the electrochemical immunoassay has been evaluated by analysis of maize certified reference material (CRM) and selected baby food samples. A detection limit (LOD) of 0.011 μg L⁻¹ and EC₅₀ 0.079 μg L⁻¹ were obtained allowing the assessment of the detection of zearalenone mycotoxin. In addition, an excellent accuracy with a high recovery yield ranging between 95 and 108% has been obtained. The analytical features have shown the proposed electrochemical immunoassay to be a very powerful and timely screening tool for the food safety scene.     

Ionic liquids as a tool for determination of metals and organic compounds in food analysis

Ionic liquids (ILs) are non-molecular solvents, which are mainly characterized as possessing low melting points, low-to-negligible vapor pressures, and high thermal stability. Their unique solvation properties, coupled to the fact that they can be structurally tailored for specific applications, have increased study of ILs in many areas of fundamental and applied chemistry. Thus, ILs have successfully been utilized as novel solvents in different extraction and microextraction schemes in recent years, but mainly with environmental samples.Food samples are quite complicated matrices from an analytical point of view. They contain a large range of chemical substances, and sometimes they also have a high fat content. Even with the most advanced analytical techniques, food sampling and food-sample preparation prior to the analytical determination are labor-intensive and time-consuming, and normally require relatively large amounts of organic solvents.In this review, we summarize the most recent analytical developments aimed at employing ILs as a tool in food analysis. We discuss practical applications to determine metals and organic compounds in food samples of quite different natures, with special emphasis to the extraction step at which the IL is introduced, and the advantages of the IL-based methods developed over conventional extraction methods.     

The development of heat flow calorimetry as a tool for process optimization and process safety

Classical thermo-analytical micro methods (DTA, DSC) are still very useful for process work, but medium scale instruments based on heat flow measurement are attaining an increasingly important role in this domain. As in many areas, development of reaction calorimetry for industrial applications was driven by needs and by available means (technical capabilities). The needs have been fairly constant over the past decades. There are data needs:

Reaction rates

Heat release rates

Heat of desired reactions and decompositions

Heat capacities and heat transfer capacities

It took the specialists of calorimetry a long time to recognize and to accept the operational needs, namely:

Working under controlled temperature conditions (constant temperature, temperature ramps)

Adding components during runs (continuously or in portions)

Simulation of industrial mixing conditions

The main driving force for the development of process oriented calorimetric instruments was the evolution of electronic hardware which made the control of heat flow on a (non micro) laboratory scale easy. The paper gives an overview on the principles of heat flow control and reviews the developments of the fifties and sixties, when the matching of heat flow with heat release by reactions was the goal. With the advent of fast and powerful laptop computers, the focus has shifted. Now, the deduction of true heat release rates from signals which may be badly distorted, is the goal. Some recent developments are reviewed and the hope is expressed that calorimetric equipment, inexpensive enough to be affordable for every laboratory engaged in process work, will be available soon.     

Analytical quality assurance in the german food contamination monitoring programme

Summary The general and analytical strategy for a monitoring project for various chemical elements, nitrate and some halogenated organic compounds in milk, beef, pork, potatoes, lettuce, cabbage, apples and strawberries within the activities of official food control in the Federal Republic of Germany is outlined.

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Analytische Qualitätssicherung im Rahmen eines deutschen Programms zur Überwachung von Lebensmittelverunreinigungen

     

Quality assurance for the analytical data of micro elements in food

The micro element content of food is an important quality index due to the action of these elements on human health. In this article, we discuss how to ensure the reliability of analytical data on micro elements in order to truly represent the condition of food. Sampling, treatment of the analytical sample, selection of the analytical method, standard solution, and certified reference material, blank test, calibration of the instrument and equipment, application of the quality control chart, assessment of the final analytical result, and quality assurance system are briefly described. Received: 5 July 2001 Accepted: 19 November 2001     

Use of two-dimensional gel electrophoresis and autoradiography as a tool in cell biology: the example of the thyroid and the liver

Different applications of two-dimensional gel electrophoresis and the research strategies that this methodology allows, with examples drawn from our own work on thyroid and liver cells, are described.     

Capillary electrophoresis as a tool for a cost‐effective assessment of the activity of plant membrane enzyme chlorophyllase

The potential of the CE‐based enzymatic assay has been demonstrated in case of a typical plant membrane enzyme – chlorophyllase. An efficient, automated and rapid semi‐quantitative method has been developed, which allowed us to assess the activity of the enzyme via two strategies. Firstly, a reaction conducted in a vial placed directly on the sample tray was combined with the concomitant separation and detection of reagents. The method was used to monitor the reaction progress. Secondly, an online approach was applied using an electrophoretically mediated mixing. The reaction was performed in?capillary, resulting in an extreme reduction of the reagent amounts required for a single run. Both methods were effective in the assessment of the activity of a membrane enzyme, a member of protein class known to pose experimental difficulties.     

EPR as an analytical tool in assessing the mineral nutrients and irradiated food products-vegetables

EPR spectral investigations of some commonly available vegetables in south India, which are of global importance like Daucus carota (carrot), Cyamopsis tetragonoloba (cluster beans), Coccinia indica (little gourd) and Beta vulgaris (beet root) have been carried out. In all the vegetable samples a free radical corresponding to cellulose radical is observed. Almost all the samples under investigation exhibit Mn ions in different oxidation states. The temperature variation EPR studies are done and are discussed in view of the paramagnetic oxidation states. The radiation-induced defects have also been assessed by using the EPR spectra of such irradiated food products.     

Using in situ Raman monitoring as a tool for rapid optimisation and scale-up of microwave-promoted organic synthesis: esterification as an example

Microwave-promoted esterification reactions have been monitored using in situ Raman spectroscopy. Having optimised a reaction on a 23 mmol scale, it was transferred to a larger reaction vessel and scaled up to 0.26 mol, again with Raman monitoring. With conditions in hand, an automated stop-flow apparatus was used to prepare 5.7 moles of product.     

Micro and nanoparticles in biosensing systems for food safety and environmental monitoring. An example of converging technologies

We report on the integration of micro and nanostructured materials in biosensing devices to obtain analytical nano-bio-systems with improved performance. The simplest case of electrochemical biosensing presented here is based on graphite microparticles to obtain a graphite-epoxy composite. The integration of the bioreceptor within the composite provides an analytical biosystem with improved performances for biosensing. The further addition of gold nanoparticles results in an analytical nano-bio-system which allows an improved strategy for the immobilization of the bioreceptor. And finally, the integration of magnetic beads to graphite-epoxy composite magneto electrodes provides further advantages in terms of separation of the analyte from complex matrix and enhanced biological reactions, resulting in analytical magneto-nano-bio-systems. The application of these systems mainly in food safety and environmental monitoring are reported. The benefits of the integration of these materials to obtain improved analytical systems are discussed and represent an example of converging technologies.     

Visual DNA as a diagnostic tool

We report on the incorporation of the Visual DNA concept in a genotyping assay as a simple and straightforward detection tool. The principle of trapping streptavidin‐coated superparamagnetic beads of micrometer size for visualization of genetic variances is used for PrASE‐based detection of a panel of mutations in the severe and common genetic disorder of cystic fibrosis. The method allows a final investigation of genotypes by the naked eye and the output is easily documented using a regular hand‐held device with an integrated digital camera. A number of samples were run through the assay, showing rapid and accurate detection using superparamagnetic beads and an off‐the‐shelf neodymium magnet. The assay emphasizes the power of Visual DNA and demonstrates the potential value of the method in future point‐of‐care tests.     

Two-step FRET as a structural tool

The power of FRET to study molecular complexes is expanded by the use of two or more donor/acceptor pairs. A general theoretical framework for distance measurements in three-chromophore systems is presented. Three energy transfer schemes applicable to many diverse situations are considered: (I) two-step FRET relay with FRET between the first and second chromophores and between the second and third, (II) FRET from a single donor to two different acceptors, and (III) two-step FRET relay with FRET also between the first and third chromophores. Equations for the efficiencies involving multiple energy transfer steps are derived for both donor quenching and sensitized emission measurements. The theory is supported by experimental data on model systems of known structure using steady-state donor quenching, lifetime quenching, and sensitized emission. The distances measured in the three-chromophore systems agree with those in two-chromophore systems and molecular models. Finally, labeling requirements for diagnosis of the energy transfer scheme and subsequent distance measurements are discussed.     

Capillary electrophoresis: a useful tool for the management of plant genetic resources

Capillary electrophoresis (CE) is a powerful analytical tool that is widely applied to the analysis of biological samples. Proteins, peptides, nonprotein amino acids, phenolic compounds, and ions can be analysed using this electrophoretic methodology. This review summarises some applications of CE to the evaluation and characterisation of plant genetic resources of both Triticum and legume species, as carried out at the Istituto di Genetica Vegetale, National Research Council (IGV-CNR) in Bari (Italy). Different protein fractions as well as nonprotein amino acids were investigated by capillary zone electrophoresis (CZE), the most user-friendly mode of CE application. The described case studies show that CZE can be applied to some institutional activities of gene banks such as the evaluation of genetic diversity within stored collections, the acquisition of new samples, the differentiation of species belonging to the same genus, the identification of misclassified accessions, and the measurement of compounds relevant to nutrition or health.     

Biosensors as a tool for the antioxidant status evaluation

Antioxidants are one of the main ingredients that protect food attributes by preventing oxidation that occurs during processing, distribution and end preparation of food. Physiological antioxidant protection involves a variety of chemical system of endogenous and exogenous origin in a multiplicity of pathways. Associate to this, researches have been directed in the development of methods as biosensors that can characterize antioxidants capable of removing harmful radicals in living organisms in an adequate way. Biosensors have represented a broad area of technology useful for environmental, food monitoring, clinical applications and can represent a good alternative method to evaluate the antioxidant status.The demonstration of the highlighted current application of biosensor as a potential tool to evaluate the antioxidant status is the main aim of this review.     

Thermal and exergoeconomic analysis of a dairy food processing plant

The dairy processing industry in India, on an average basis, involves an extensive amount of thermal and electrical energy consumption, i.e. 2.51 × 10⁵ kW MT⁻¹ and 1.44 × 10⁵ kW MT⁻¹, respectively, for an installed milk food processing capacity of 1.21 × 10⁵ TPD. However, energy consumption spectrum depends upon the level of automation along with better utilisation of utility resources. The global ultra-high-temperature (UHT) pasteurised milk trade was valued at € 52.29 billion in 2012 and is expected to reach € 114.38 billion by 2019–2020. In the present work energy, exergy and exergoeconomic evaluation of ultra-high-temperature milk pasteurisation plant have been considered. The overall energy efficiency and efficiency pertaining to executable potential of energy in UHT Milk Processing Unit were reported to be 86.36% and 53.02%. The specific exergy destruction and specific exergy improvement potential were estimated to be 219.23 kJ kg⁻¹ and 137.60 kJ kg⁻¹, respectively. The highest possible retrievable exergy potential of the plant was associated with heating coil, i.e. 158.98 kW, followed by homogeniser (54.62 kW), which pinpointed towards the possibility of huge technical improvement. The processing cost was enumerated to be highest for heating coil (r_k: 38.35%) followed by regeneration-1 (r_k: 23.40%). Further, the total operating cost rate associated with thermodynamic deficiencies of subunits was estimated to be highest for heating coil (4859.82 € H⁻¹) followed by regenerator-2 (1264.88 € H⁻¹) and homogeniser (1187.14 € H⁻¹). The broad survey of thermoeconomic indices of subunits indicated that the level of exergetic destruction was far more on higher side.

     

Development of a multiplex DNA-based traceability tool for crop plant materials

The authenticity of food is of increasing importance for producers, retailers and consumers. All groups benefit from the correct labelling of the contents of food products. Producers and retailers want to guarantee the origin of their products and check for adulteration with cheaper or inferior ingredients. Consumers are also more demanding about the origin of their food for various socioeconomic reasons. In contrast to this increasing demand, correct labelling has become much more complex because of global transportation networks of raw materials and processed food products. Within the European integrated research project ‘Tracing the origin of food’ (TRACE), a DNA-based multiplex detection tool was developed—the padlock probe ligation and microarray detection (PPLMD) tool. In this paper, this method is extended to a 15-plex traceability tool with a focus on products of commercial importance such as the emmer wheat Farro della Garfagnana (FdG) and Basmati rice. The specificity of 14 plant-related padlock probes was determined and initially validated in mixtures comprising seven or nine plant species/varieties. One nucleotide difference in target sequence was sufficient for the distinction between the presence or absence of a specific target. At least 5% FdG or Basmati rice was detected in mixtures with cheaper bread wheat or non-fragrant rice, respectively. The results suggested that even lower levels of (un-)intentional adulteration could be detected. PPLMD has been shown to be a useful tool for the detection of fraudulent/intentional admixtures in premium foods and is ready for the monitoring of correct labelling of premium foods worldwide.     

Calorimetric analysis of three hydroxy acids as markers for quality and safety in food

A new analytical methodology to quantify three hydroxy acids (orotic, ascorbic, L-malic acids), by isothermal solution microcalorimetry, was outlined and applied to different foods. Three specific enzymatic reactions were used to ensure the correctness of the results. The considered acids can be considered as markers in food quality for their biochemical peculiarities. The enzymatic microcalorimetric method is very reliable and linearity is satisfied in the concentration ranges useful for food analyses. The analytical results of the underlined method are very accurate, precise, sensitive and in good agreement with the values obtained with other common methods.