Ultrarapid detection of bovine whey proteins in powdered soybean milk by perfusion reversed-phase high-performance liquid chromatography

Liquid chromatography and mass spectrometry in food allergen detection

Food allergy is an important issue in the field of food safety because of the hazards for affected persons and the hygiene requirements and legal regulations imposed on the food industry. Consumer protection and law enforcement require suitable analytical techniques for the detection of allergens in foods. Immunological methods are currently preferred; however, confirmatory alternatives are needed. The determination of allergenic proteins by liquid chromatography and mass spectrometry has greatly advanced in recent years, and gel-free allergenomics is becoming a routinely used approach for the identification and quantitation of food allergens. The present review provides a brief overview of the principles of proteomic procedures, various chromatographic set ups, and mass spectrometry instrumentation used in allergenomics. A compendium of published liquid chromatography methods, proteomic analyses, typical marker peptides, and quantitative assays for 14 main allergy-causing foods is also included.

High performance liquid chromatography and capillary electrophoresis in the analysis of soybean proteins and peptides in foodstuffs

The increasing interest in functional and healthy food products has promoted the use of soybean in the manufacture of foods for human consumption. Soybean basic products (soybeans, textured soybean, soybean flour, soybean protein concentrate and soybean protein isolate) as well as soybean derivatives (soybean dairy-like products, soybean drinks with fruits, meat analogues, etc.) are commercially available. In addition, due to the interesting nutritional and functional properties of soybean proteins, they are usually employed as ingredient in the elaboration of a large number of food products such as bakery or meat products among others. In spite of the good characteristics of soybean proteins, their addition to some products is forbidden or allowed up to a certain limit. Therefore, analytical methodologies to achieve the determination of soybean proteins in foods are necessary in order to make possible adequate quality control and to prove that legal regulations controlling their addition are accomplished. However, this is not an easy task due to the diversity and complexity of the food matrices and the technological treatments to which some of these foods are submitted during their elaboration. This article presents for the first time a comprehensive review on the analytical methodologies developed using HPLC and CE to characterize soybeans and to analyse soybean proteins in meals. Moreover, the use of HPLC and CE in the characterization of soybean protein fractions and their hydrolyzates, and a study of their relationships to nutritional, functional and biomedical properties are included. Finally, the application of proteomic methodologies in soybean food technology is also reviewed.

Rapid detection of the addition of soybean proteins to cheese and other dairy products by reversed-phase perfusion chromatography

The undeclared addition of soybean proteins to milk products is forbidden and a method is needed for food control and enforcement. This paper reports the development of a chromatographic method for routine analysis enabling the detection of the addition of soybean proteins to dairy products. A perfusion chromatography column and a linear binary gradient of acetonitrile-water-0.1% (v/v) trifluoroacetic acid at a temperature of 60 degrees C were used. A very simple sample treatment consisting of mixing the sample with a suitable solvent (Milli-Q water or bicarbonate buffer (pH=11)) and centrifuging was used. The method enabled the separation of soybean proteins from milk proteins in less than 4 min (at a flow-rate of 3 ml/min). The method has been successfully applied to the detection of soybean proteins in milk, cheese, yogurt, and enteral formula. The correct quantitation of these vegetable proteins has also been possible in milk adulterated at origin with known sources of soybean proteins. The application of the method to samples adulterated at origin also leads to interesting conclusions as to the effect of the processing conditions used for the preparation of each dairy product on the determination of soybean proteins.

Methods for allergen analysis in food: a review

Food allergies represent an important health problem in industrialized countries. Undeclared allergens as contaminants in food products pose a major risk for sensitized persons. A proposal to amend the European Food Labelling Directive requires that all ingredients intentionally added to food products will have to be included on the label. Reliable detection and quantification methods for food allergens are necessary to ensure compliance with food labelling and to improve consumer protection. Methods available so far are based on protein or DNA detection. This review presents an up-to-date picture of the characteristics of the major food allergens and collects published methods for the determination of food allergens or the presence of potentially allergenic constituents in food products. A summary of the current availability of commercial allergen detection kits is given. One part of the paper describes various methods that have been generally employed in the detection of allergens in food; their advantages and drawbacks are discussed in brief. The main part of this review, however, focuses on specific food allergens and appropriate methods for their detection in food products. Special emphasis is given to allergenic foods explicitly mentioned in the Amendment to the European Food Labelling Directive that pose a potential risk for allergic individuals, namely celery, cereals containing gluten (including wheat, rye and barley) crustaceans, eggs, fish, peanuts, soybeans, milk and dairy products, mustard, tree-nuts, sesame seeds, and sulphite at concentrations of at least 10 mg kg(-1). Sulphites, however, are not discussed.

Identification and quantification of major bovine milk proteins by liquid chromatography

In the field of food quality, bovine milk products are of particular interest due to the social and economic importance of the dairy products market. However, the risk of fraudulent manipulation is high in this area, for instance, replacing milk powder by whey is very interesting from an economic point of view. Therefore, there is a need to have suitable analytical methods available for the determination of all milk components, which is currently not the case, especially for the main proteins. The detection of potential manipulations requires then a clear analytical characterisation of each type of bovine milk, what constitutes the goal of this work. The separation of the major milk proteinic components has been carried out by ion-pair reversed-phase HPLC with photodiode array detection, using a C4 column. The overall optimisation has been achieved using a statistical experimental design procedure. The identification of each protein was ascertained using retention times, peak area ratios and second derivative UV spectra. Quantification was based on calibration curves drawn using purified proteins. Major sources of uncertainty were identified and the full uncertainty budget was established. The procedure was initially developed using the skimmed milk powder certified reference material CRM 063R and then applied to various types of commercial milks as well as to raw milk. The method is able to separate and quantify the seven major proteins (K-casein, alphas2-casein, alphas1-casein, beta-casein, alpha-lactalbumin, beta-lactoglobulin B and beta-lactoglobulin A) in one run and also to provide precise determinations of the total protein concentration. These are important results towards the further development of a reference method for major proteins in milk. In addition, the use of a certified material reference is suggested in order to make comparisons of method performances possible.

New synthetic ways for the preparation of high-performance liquid chromatography supports

The latest developments and in particular important synthetic aspects for the preparation of modern HPLC supports are reviewed. In this context, the chemistry of inorganic supports based on silica, zirconia, titania or aluminum oxide as well as of organic supports based on poly(styrene-divinylbenzene), acrylates, methacrylates and other, more specialized polymers is covered. Special consideration is given to modern approaches such as sol-gel technology, molecular imprinting, perfusion chromatography, the preparation of monolithic separation media as well as to organic HPLC supports prepared by new polymer technologies such as ring-opening metathesis polymerization. Synthetic particularities relevant for the corresponding applications are outlined.

Characterization of commercial soybean products by conventional and perfusion reversed-phase high-performance liquid chromatography and multivariate analysis

Conventional and perfusion reversed-phase high-performance liquid chromatography are used to characterize commercial soybean products for human consumption. For this purpose, previously optimized methods of conventional and perfusion chromatography applied to the separation of soybean proteins are employed. Sixty different samples corresponding to 26 different trademarks of soybean products [soybean protein isolate, soybean flour, textured soybean, soybean milks (liquid and powdered), and soybean infant formulas] are analyzed. Characterization of soybean products is carried out on the basis of their protein profiles obtained by both chromatographic methods. Data obtained are processed using multivariate methods such as principal components and discriminant analysis. Perfusion chromatography enables a further and faster characterization of commercial soybean products than conventional chromatography, of great value in the quality control of this kind of product.

Perfusion chromatography: an emergent technique for the analysis of food proteins

Perfusion chromatography is a technique arised to overcome the problem associated with mass transfer in the separation of large molecules such as proteins by high-performance liquid chromatography (HPLC). Perfusion media are constituted by two set of pores: throughpores (6000-8000 A) and diffusive pores (800-1500 A) which enable better access of macromolecules to the inner of the particle by the combination of convective and diffusive flow. As a consequence, times required for a chromatographic separation are reduced. Perfusion media are available in different chromatographic modes: reversed-phase, ion-exchange, hydrophobic interaction, and affinity. From the theoretical models developed to explain the dynamic of retention of solutes in perfusive supports, it was derived that efficiency of a separation was independent of the flow-rate and only depended slightly on the particle diameter. Furthermore, loading capacity was also independent of the superficial velocity. All these advantages have promoted the use of this chromatographic technique for the separation of biomolecules both in analytical and preparative chromatography. Characteristics of perfusion chromatography make this technique very interesting for the analysis of food proteins. Perfusion chromatography enables the assessment of protein composition of a foodstuff at sufficient speed and low cost to be suitable in routine analysis.

Analysis of bovine whey proteins in soybean dairy-like products by capillary electrophoresis

The simultaneous separation of bovine whey proteins [alpha-lactalbumin and beta-lactoglobulin (A+B)] and soybean proteins was performed, for the first time, by capillary electrophoresis. Different experimental conditions were tested. The most suitable consisted of 0.050 M phosphate buffer (pH 8) with 1 M urea and 1.2 mg/ml methylhydroxyethylcellulose, UV detection at 280 nm, 15 kV applied voltage, and 30 degrees C temperature. Quantitation of bovine whey proteins in a commercial powdered soybean milk manufactured by adding bovine whey to its formulation was performed using the calibration method of the external standard. Direct injection of a solution of the powdered soybean milk only enabled quantitation of alpha-lactalbumin in the commercial sample. Detection of beta-lactoglobulin (A+B) required acid precipitation of the solution of the sample in order to concentrate bovine whey proteins in the supernatant prior to the analysis of this protein in the whey obtained. Since alpha-lactalbumin could also be quantitated from the injection of the whey, the simultaneous determination of alpha-lactalbumin and beta-lactoglobulin (A+B) was possible upon acid precipitation of the powdered soybean milk solution. Detection limits obtained were 14 microg/g sol. for alpha-lactalbumin and 52 microg/g sol. for beta-lactoglobulin (A+B) which represent protein concentrations about 60 microg/100 g sample for alpha-lactalbumin and 100 microg/100 g sample for beta-lactoglobulin (A+B).

Characterization and quantitation of soybean proteins in commercial soybean products by capillary electrophoresis

Capillary electrophoresis was applied for the first time to determine soybean proteins in commercial soybean products. The most suitable conditions for the analysis of these products in less than 7 min were 0.05 M phosphate buffer (pH 8) with 1 M urea; detection wavelength, 254 nm; applied voltage, 20 kV; and temperature, 30 degrees C. Quantitation of soybean proteins was achieved using referenced conditions by means of the method of standard additions, using as standard a soybean protein isolate. This method was validated and applied to the quantitation of soybean proteins in commercial products derived from soybean protein isolate and soybean seeds.