Surface tension and foam stability of commercial calcium and sodium caseinates

The static and dynamic surface tension of sodium and calcium caseinates was compared with their foam behavior. The surface tension behavior of sodium and calcium caseinates was similar but the foaming properties differed. Caseinates presented moderate surface activity lowering the surface tension of water to 40 mN/m. The surface pressure vs. composition data were analyzed using a new surface equation of state and obtained 0.1% (w/v) critical concentration and the molecular surface area; in the case of calcium caseinate was larger compared to sodium caseinate. Caseinates were evaluated at the critical concentration by means of dynamic surface tension to compare their behavior; calcium caseinate took longer time to reach equilibrium conditions. Their foam behavior was transient type with maximum foamability around the critical concentration; sodium caseinate presented better foaming properties than calcium caseinate.     

A food matrix reduces digestion and absorption of food allergens in vivo

Scope: Food allergy is caused by primary (class 1) food allergens, e.g. Bos d 5 (cow's milk) and Cor a 8 (hazelnut) or secondary (class 2) food allergens, e.g. Mal d 1 (apple). The latter cannot sensitize susceptible individuals but can cause allergy due to immunological cross‐reactivity with homologous respiratory allergens. Here, we studied the effects of food matrix on gastrointestinal proteolysis, epithelial transport and in vivo absorption of class 1 and class 2 food allergens. Methods and results: Mal d 1 lost its IgE‐reactivity immediately after simulated gastric digestion whereas Bos d 5 and Cor a 8 did not. Only Cor a 8 maintained IgE‐binding capacity after simulated intestinal proteolysis. The presence of hazelnut and peanut extracts, which served as protein‐rich model food matrices, delayed gastrointestinal degradation and reduced epithelial transport rates of all allergens through CaCo‐2 monolayers. Finally, IgE‐reactive allergens were assessed at different time points in sera from rats fed with all three allergens with or without hazelnut extract. The levels of all allergens peaked 2 h after animals were fed without matrix and increased over 8 h after feeding. Conclusions: A protein‐rich food matrix delays gastrointestinal digestion and epithelial transport of food allergens and thereby may affect their sensitizing capacity and clinical symptoms.     

Polymerase chain reaction (PCR) for detection of potentially allergenic hazelnut residues in complex food matrixes

Corylus avellana ) residues in complex food matrixes has been developed applying the polymerase chain reaction (PCR) with “hot start” and “time-release” features. By amplifying a 182 bp- fragment of the coding deoxyribonucleic acid (cDNA) of Cor a 1, the major hazelnut allergen, detection of even 0.001 % of hazelnut in commercial food products could be demonstrated. Results were confirmed by our previously described sandwich-type enzyme-linked immunosorbent assay (ELISA) that quantifies potentially allergenic hazelnut protein at trace levels. Received: 9 November 1999 / Revised version: 9 December 1999     

Isolation and characterization of natural Ara h 6: evidence for a further peanut allergen with putative clinical relevance based on resistance to pepsin digestion and heat

Peanut allergy is a significant health problem because of its prevalence and the potential severity of the allergic reaction. The characterization of peanut allergens is crucial to the understanding of the mechanism of peanut allergy. Recently, we described cloning of the peanut allergen Ara h 6. The aim of this study was isolation and further characterization of nAra h 6. We purified nAra h 6 from crude peanut extract using gel filtration and anion exchange chromatography. The preparation was further characterized by two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) with subsequent immunoblotting. Stability of nAra h 6 was studied by an in vitro digestibility assay as well as by resistance against thermal processing. Sequencing of nAra h 6 identified the N-terminal amino acid sequence as MRRERGRQGDSSS. Further results clearly demonstrated stability of nAra h 6 against pepsin digestion and heating. Immunoglobulin G (IgE) binding analysis and its biological activity shown by RBL 25/30-test of natural Ara h 6 supported the importance of this peanut allergen. Investigation of nAra h 6 revealed evidence for a further peanut allergen with putative clinical relevance based on resistance to pepsin digestion and heat.     

Comparative resistance of food proteins to adult and infant in vitro digestion models

IgE‐mediated allergy to milk and egg is widespread in industrialised countries and mainly affects infants and young children. It may be connected to an incomplete digestion of dietary proteins causing an inappropriate immune response in the gut. In order to study this, a biochemical model of infant gastroduodenal digestion has been developed, which has reduced levels of protease (eightfold for pepsin and tenfold for trypsin and chymotrypsin), phosphatidylcholine and bile salts, compared with the adult model. This model has been used to study the behaviour of three characterised food‐relevant proteins (bovine β‐lactoglobulin (β‐Lg), β‐casein (β‐CN) and hen's egg ovalbumin), all of which are relevant cows' milk and hens' egg allergens. Digestion products were characterised using electrophoresis, immunochemical techniques and MS. These showed that ovalbumin and β‐CN were digested more slowly using the infant model compared with the adult conditions. Resistant fragments of β‐CN were found in the infant model, which correspond to previously identified IgE epitopes. Surprisingly, β‐Lg was more extensively degraded in the infant model compared with the adult one. This difference was attributed to the tenfold reduction in phosphatidylcholine concentration in the infant model limiting the protective effect of this phospholipid on β‐Lg digestion.     

Detection of allergenic parvalbumin of Atlantic and Pacific herrings in fish products by PCR

The conventional polymerase chain reaction (PCR) method to detect the major allergenic protein parvalbumin beta 2 of Atlantic herring (Clupea harengus) and Pacific herring (Clupea pallasii) was developed. The specific set of primers for the amplification of the partial genomic sequence of the pvalb 2 gene encoding the main fish allergen of both herrings was designed and applied to the investigation of 24 commercial fish products. The targeted amplicon size was 189 bp of pvalb 2 gene of Atlantic herring and Pacific herring. As the internal amplification control, the DNA of 18S rRNA gene for eukaryotes (141 bp) was successfully used. The specificity of designed primer pair using 26 various fish species was assessed. The intrinsic detection limit was 10 pg µl^?1 of the present specific DNA. Atlantic herring or Pacific herring allergenic parvalbumins were detected in 22 investigated fish products in conformity with the package declaration. Two fish products were negative in spite of the declaration. The proposed PCR method is specific enough and can be used for the detection of Atlantic and Pacific herrings’ major allergen parvalbumin beta 2 in fish food products.     

Changes in phenolic compounds and colour in pale Sherry wines subjected to fining treatments

 Changes in the concentrations of hydroxybenzoic acids, hydroxycinnamic acids and their esters, monomeric and dimeric derivatives of flavan-3-ol, and flavonols, as well as in the UV-visible absorbances of pale Sherry wines were studied. The wines were subjected to four different fining treatments: casein + bentonite, casein + bentonite + activated charcoal, casein + bentonite + polyvinylpyrrolidone (PVPP) and casein + bentonite + Riduxhigh. Based on the results, the treatments including activated charcoal and PVPP were the most effective at decreasing the overall concentration phenolic compounds, with no significant difference between them. Likewise, these treatments provided the best results in relation to wine colour in the visible spectral region, and particularly at 420 nm, at which wavelength browning compounds are usually measured. Received: 24 March 1997 / Revised version: 11 June 1997     

Milk allergens, their characteristics and their detection in food: A review

Cow's milk allergy (CMA) is one of the most common food allergies in childhood. This allergy is normally outgrown in the first year of life, however 15% of allergic children remain allergic. Many studies have been carried out to define and characterise the allergens involved in CMA and described two major allergens: casein (αs1-CN) and β-lactoglobulin. In addition to this, many other milk proteins are antigenic and capable of inducing immune responses. Milk from sheep or goats differs from cow's milk (CM) in terms of composition and allergenic properties. Food processing such as heating affects the stability, structure and intermolecular interactions of CM proteins, thereby changing the allergenic capacity. Chemical and proteolytic treatments of milk to obtain milk hydrolysates have been developed to reduce allergic reactions. Prevention of CMA largely relies on avoidance of all food products containing cow's milk. To achieve this, interest has focused on the development of various technologies for detecting and measuring the presence of milk allergens in food products by immunoassays or proteomic approaches. This review describes the technologies implemented for the analysis of milk allergens (allergenicity, biochemistry) as well as their potential detection in food matrices.     

Molecular fragmentation of wheat-germ agglutinin induced by food irradiation reduces its allergenicity in sensitised mice

WGA, an agglutinin from wheat germ which is largely responsible for many of wheat’s allergies, was used as a model to investigate the action of ionising radiation on WGA’s anti-nutritive effects in sensitised mice. Based on the molecular structure, the present study also examined the structural modification of WGA in relation to the range of dose. Structural integrity was monitored using HPLC, fluorescence spectrometry and circular dichroism. Results showed a loss of intrinsic activity and the formation of insoluble amorphous aggregates with a lack of native conformational structures after irradiation. Current findings suggest that the allergenic epitopes of WGA became less active and antigenic after high-dose radiation. The reduction of cytokines typical of allergic reactions, with decreased lymphocytic infiltrate, was observed in the gut of mice given irradiated versus native WGA. Food irradiation proved effective and safe in combating immunological and allergic effects of WGA.     

The influences of cultivar and thermal processing on the allergenic potency of lychees (Litchi chinensis SONN.)

This study was aimed at the cultivar-specific allergenic potency of lychees (Litchi chinensis SONN.) and its modification by typical industrial processing, investigating the fresh aril of seven different lychee lots which represented five cultivars. Technological focus was on thermal treatments during fruit preservation by canning. Canned lychee halves in syrup were produced by canning at 90 and 121 °C for various times to analyse the final products immediately after processing and after eight-months storage. SDS–PAGE and non-specific silver staining were performed to characterise the protein pattern. The allergenic potency of the proteins was demonstrated by immunoblotting with sera of probands suffering from lychee allergy. Furthermore, the allergenic potency was determined by inhibitive enzyme allergosorbent tests (EAST-inhibition). Any significant dependence between cultivar and the allergenic potency of the fresh fruit could not be established. According to their heat sensitivity during canning, lychee allergens with different behaviour could be distinguished. After excessive canning, inducing severe loss of sensory quality, the allergenic potency of the fruit decreased, even though high residual allergenic activity was observed.     

Allergenicity of soybean: new developments in identification of allergenic proteins, cross-reactivities and hypoallergenization technologies

Soybean is considered one of the "big eight" foods that are believed to be responsible for 90% of all allergenic reactions. Soy allergy is of particular importance, because soybeans are widely used in processed foods and, therefore, represent a particularly insidious source of hidden allergens. Although significant advances have been made in the identification and characterization of soybean allergens, scientists are not completely certain about which proteins in soy cause allergic reactions. At least 16 allergens have been identified. Most of them, as with other plant food allergens, have a metabolic, storage, or protective function. These allergens belong to protein families which have conserved structural features in relation with their biological activity, which explains the wide immunochemical cross-recognition observed among members of the legume family. Detailed analysis of the structure-allergenicity relationships has been hampered by the complexity and heterogeneity of soybean proteins. A variety of technological approaches have been attempted to decrease soybean allergenicity. This paper provides a comprehensive review of the current body of knowledge on the identification and characterization of soybean allergens, as well as an update on current hypoallergenization techniques.     

Responsiveness of the major birch allergen Bet v 1 scaffold to the gastric environment: Impact on structure and allergenic activity

Scope: Four Bet v 1 homologous food allergens from celeriac (rApi g 1), apple (rMal d 1), peach (rPru p 1) and hazelnut (rCor a 1), were used to probe the structural responsiveness of the Bet v 1 scaffold to gastric digestion conditions and its impact on allergenicity. Methods and results: Low pH induced conformational changes of all homologues, which was reduced at physiological ionic strength for all except rPru p 1 as observed by circular dichroism (CD)‐spectroscopy. The homologues were rapidly digested by pepsin, losing their IgE binding activity, although the kinetics and patterns of digestion varied subtly between homologues, rApi g 1 being the most stable. We have demonstrated for the first time that gastric phosphatidyl‐choline (PC) induced conformational changes in all homologues but only rMal d 1 penetrated the PC vesicles as detected by fluorescence polarization, slowing its digestion and retaining more of its allergenic activity. PC enhanced basophil activation of all digested allergens except rApi g 1. Conclusion: The Bet v 1 scaffold is generally susceptible to low pH and pepsinolysis and interacts with PC vesicles, properties which can explain effects of the gastric environment on their allergenicity. These data show the importance of including surfactants in model digestion systems.     

Qualitative and quantitative analysis of bovine milk adulteration in caprine and ovine milks using native-PAGE

Native-PAGE (polyacrylamide gel electrophoresis) was used for the simultaneous qualitative and quantitative analysis of bovine milk adulteration in caprine and ovine milk using whole milk samples as well as their whey protein fraction. Quantification was based on measuring band intensity of bovine β-lactoglobulins in all milk mixtures and bovine α-lactalbumin in caprine/bovine milk blends. Linear relationships were established between the band intensity of bovine β-lactoglobulins and α-lactalbumin vs. volume percentage of added bovine milk in all milk analysed, with the correlation coefficient from 0.9950 to 0.9998. These correlations enabling the quantification of bovine milk percentage within the wide range from 3% or 5% to 90% in caprine/bovine and ovine/bovine milk blends, respectively. The differences between the actual percentages of bovine milk present in the adulterated milk samples and those calculated using the regression lines were less than or equal to 5% for all samples. This method offers a rapid determination combined with unequivocal identification of the bovine whey proteins in almost every caprine/bovine or ovine/bovine milk mixtures.     

Influence of wine-making protocol and fining agents on the evolution of the anthocyanin content,colour and general organoleptic quality of Vinhão wines

This paper reports the evolution, over two years, of the anthocyanin content, colour and organoleptic quality of red wines prepared from a single batch of Vinhão grapes by means of three different protocols (maceration/fermentation with conventional pumping-over or in rotary vats, and fermentation after initial carbonic maceration), with and without the use of four different fining agents (polyvinylpolypyrrolidine, gelatin, egg albumin, and casein). Carbonic maceration led to lower anthocyanin levels and less intense coloration than the other two methods immediately following vinification, but during storage the carbonic maceration wines underwent less colour degradation than the others, so that after two years the colour density differences among the three were negligible. Wines treated with fining agents tended to have somewhat lower anthocyanin levels and, especially in the case of PVPP, less intense colouration than untreated wines, and their colour was at best only marginally more stable during storage, but they nevertheless generally achieved higher panel ratings for organoleptic quality than untreated wines, especially as regards taste.     

花生中主要过敏原Ara h1的纯化

为了得到花生中引起过敏反应的主要致敏成分Ara h1,以新鲜花生为材料,通过粉碎、脱脂、硫酸铵分步盐析等方法进行粗提;并用离子交换柱以及凝胶柱等方法来进一步纯化过敏原Ara h1。采用聚丙烯酰胺凝胶电泳（SDS-PAGE）分析了纯化后的过敏原Ara h1的纯度,并用高效液相色谱法测定其纯度达到90%以上。      

Direct determination of phenolic compounds in Sicilian wines by liquid chromatography with PDA and MS detection

Phenolic compounds in Sicilian wines were directly detected using an HPLC with a PDA detector coupled on-line with a MS system equipped with Electrospray Ionisation (ESI) source operated in the negative-ion mode and a quadrupole mass analyzer. In this work, MS spectra were recorded at different voltage, to obtain structural elucidations in addition to molecular mass informations. The different response of the compounds identified has been also evaluated. MS characteristics of cis- and trans-piceid were determined on the basis of the response obtained with the ESI interface.     

Isolation and full characterisation of a potentially allergenic lipid transfer protein (LTP) in almond

Non-specific lipid transfer proteins (nsLTP) were shown to be among the most significant allergens, in particular in several fruits belonging to the Rosaceae family. The molecular features of LTPs, such as the presence of eight cysteine residues forming four disulfide bridges, confer a compact structure, decreasing the probability of degradation due to cooking or digestion, thereby increasing the chance of systemic absorption and severe allergic reactions. Few studies on LTP-induced allergies regarding almond (Prunus dulcis L) are available in the literature. In the present work, we describe for the first time the extraction and purification of an almond LTP, achieving its full characterisation by using liquid chromatography and exact mass spectrometry; the full sequence was identified by means of LC-ESI-Orbitrap?-MS applying a bottom-up approach. The characterised protein consists of 92 amino acids and has a calculated exact MW of 9579.0. The presence of four disulfide bridges was confirmed after reduction, as shown by a mass increment of 8 Da. Finally, its potential allergenicity was confirmed via an in silico approach. The results presented here demonstrate the enormous potential of advanced MS techniques for obtaining high-quality structural and functional data of allergenic proteins in a short time.     

Analysis of metalaxyl residues in wines by SPE in combination with HRCGC and GC/MS

Solid phase extraction (SPE) with the porous carbon sorbent CARB GR was used for the preconcentration of metalaxyl residues from a variety of Slovak grape wines with subsequent capillary GC and GC/MS analysis. Recovery was tested at various concentrations of metalaxyl in standard solutions (recovery,R92%, relative standard deviation RSD4.3%) and in wines. The value of recovery in spiked wines was dependent on the concentration (studied in the range 0.02–1.96 mg/1) and on the variety of wine (R=80–99%; RSD=2–7%). Limits of quantitation (for a sample volume of 50 ml) were determined to be 0.75 g/1 with GC-FID and 0.50 g/1 with GC/MS-ITD. Concentration levels of metalaxyl residues were determined in treated wines (with 0.25% Ridomil plus 48 WP) and a strong dependence on the protective term before the harvest was shown.     

Sensitive and specific detection of almond (Prunus dulcis) in commercial food products by real-time PCR

Almond has been widely used in all sorts of food products, mostly due to its pleasant flavor and health benefits. However almonds can become an important health problem since they are responsible for triggering adverse immune responses in allergic individuals, and since they are present in many processed foods they are considered as a potential hidden allergen. Consequently, it's important for food processors and regulatory agencies to be able to ensure accurate labeling of foods to protect the safety of the public and to avoid expensive recalls. We propose a simple and highly sensitive approach to detect almond in a wide range of processed foods. The method consists of a real-time PCR assay targeting the gene encoding for the ITS1 in almond, using a nuclease (TaqMan) probe labeled with FAM and BBQ. Sensitivity of real time PCR was determined by analysis of raw and heat treated almond-wheat flour mixtures with a range of detection of 0.1–100,000 mg/kg. The assay was successfully trialed on a total of 214 commercial foodstuffs allowing the detection of trace amounts of almond down to the level of 0.1 mg/kg, and is therefore proposed as a ready-to-use analytical tool to trace almond allergens in foods.