MALDI-based identification of stable hazelnut protein derived tryptic marker peptides.

Food allergy is an important health problem especially in industrialised countries. Tree nuts, among which are hazelnuts (Corylus avellana), are typically causing serious and life-threatening symptoms in sensitive subjects. Hazelnut is used as a food ingredient in pastry, confectionary products, ice cream and meat products, therefore undeclared hazelnut can be often present as a cross-contaminant representing a threat for allergic consumers. Mass spectrometric techniques are used for the detection of food allergens in processed foods, but limited information regarding stable tryptic peptide markers for hazelnut is available. The aim of this study was to detect stable peptide markers from modified hazelnut protein through the Maillard reaction and oxidation in a buffered solution. Peptides ³95Gly-Arg4°³ from Cor a 11 and ²°9Gln-Arg²¹7, ³5¹Ile-Arg³6³, 464Ala-Arg478 and 4°¹Val-Arg4¹7 from Cor a 9 hazelnut allergens proved to be the most stable and could be detected and confirmed with high scores in most of the modified samples. The identified peptides can be further used as analytical targets for the development of more robust quantitative methods for hazelnut detection in processed foods.

Age-dependent sensitization to the 7S-vicilin-like protein Cor a 11 from hazelnut (Corylus avellana) in a birch-endemic region.

BACKGROUND: Hazelnut (Corylus avellana) allergy exhibits age and geographically distinct sensitization patterns that have not yet been fully resolved. OBJECTIVE: To study sensitization to Cor a 11 in different age groups of hazelnut-allergic patients and infants with atopic dermatitis (AD) sensitized to hazelnut in a birch-endemic region. METHODS: Sera from 80 hazelnut-allergic patients, 33 infants under 1 year of age with AD (24 sensitized and 9 not sensitized to hazelnut), 32 healthy control individuals, and 29 birch pollen-allergic but hazelnut-tolerant individuals were tested for immunoglobulin (Ig) E reactivity to Cor a 11 by ImmunoCAP. IgE reactivity to Cor a 1.01, Cor a 1.04, Cor a 8, and Cor a 9 was studied by ISAC microarray. RESULTS: Forty patients (22 preschool children, 10 schoolchildren, and 8 adults) with systemic reactions on consumption of hazelnut were sensitized to Cor a 11 (respective rates of 36%, 40%, and 12.5%). Forty patients (6 preschool children, 10 schoolchildren, and 24 adults) reported oral allergy syndrome but only 2 of them (of preschool age) were sensitized to Cor a 11. Two (8%) of the AD infants sensitized to hazelnut showed IgE reactivity to Cor a 11. This reactivity was not observed in any of the AD infants without sensitization to hazelnut, in any of the birch-pollen allergic patients without hazelnut allergy, or in any of the healthy control individuals. CONCLUSION: Sensitization to Cor a 11 in a birch-endemic region is predominantly found in children with severe hazelnut allergy, a finding that is consistent with observations concerning sensitization to Cor a 9.

Effect of protein glycation in the presence or absence of wheat proteins on detection of soybean proteins by commercial ELISA.

Soybean (Glycine max) is the world's primary provider of protein and oil and is widely used in foodstuffs. However, the use of soybean in foodstuffs might pose a serious threat to allergic consumers since some proteins can cause allergic reactions. To date mostly ELISA methods are used for testing contamination of foodstuffs with soybean. In view of the complexity regarding allergen detection in foodstuffs and appropriate food product labelling, the aim of this study was to investigate the impact of the Maillard reaction on the detectability of soybean proteins using commercial ELISA kits. Accumulation of protein-bound carbonyls, modification of reactive lysine residues and severe aggregation as a result of incubation with glucose, in the presence or absence of soluble wheat proteins, were recorded. Moreover, detection of soybean proteins by means of three commercial ELISA kits was strongly altered and was highly dependent on the type of kit used.

ELISA detection of hazelnut proteins: effect of protein glycation in the presence or absence of wheat proteins.

Hazelnuts are widely used in the food industry, especially confectionary foods. Nevertheless, these nuts contain several allergenic proteins that may be unexpectedly present as contaminants in various foods and may pose a serious threat to allergic consumers. The enzyme-linked immunosorbent assay (ELISA) is the preferred method to assess the level of hazelnut protein contamination. It is commonly used by both the food industry and enforcement agencies. Several ELISA kits are commercially available. However, protein detectability by ELISA may be affected by severe changes that proteins undergo during processing. The aim of this study is therefore to investigate the impact of processing on the ability to detect hazelnut protein by four commercial ELISA kits. Hazelnut proteins in the presence or absence of soluble wheat proteins were modified with glucose via the Maillard reaction. Changes in hazelnut proteins, such as the formation of protein-bound carbonyls, losses of reactive lysine residues and free amino groups, and severe aggregation dramatically affected the hazelnut protein detection by the commercial kits. The observed impact was highly dependent on the type of ELISA kit used.

Effects of food composition on the inactivation of foodborne microorganisms by chlorine dioxide.

Chlorine dioxide (ClO2) is a strong oxidizing agent that can be applied in solution as well as in the gaseous state. It has bactericidal, fungicidal and viricidal properties. Several food-related microorganisms, including Gram-negative and Gram-positive bacteria, yeasts, mould spores and Bacillus cereus spores were tested for their susceptibility to 0.08 mg/L gaseous ClO2 during 1 min at a relative humidity of 90%. In this screening, the resistance of the different groups of microorganisms towards gaseous ClO2 generally increased in the order Gram-negative bacteria, Gram-positive bacteria, yeasts and mould spores and Bacillus cereus spores. With this treatment, reductions of microbial numbers between 0.1 and 3.5 log cfu/cm2 could be achieved. The effects of the food components starch, fat, protein and NaCl on the antimicrobial activity of gaseous ClO2 were also evaluated. Soluble starch, corn oil, butter, whey protein isolate and NaCl were added in incremental concentrations to portions of an agar medium. Then, plates of the supplemented agars were inoculated with Leuconostoc mesenteroïdes at numbers of 4 log cfu/cm2 and subsequently treated with ClO2. Both soluble starch and NaCl did not have an effect on the antimicrobial efficiency of ClO2. However, butter, corn oil or whey protein in the agar almost eliminated the antimicrobial effect of ClO2. In corn oil-water emulsions treated with gaseous ClO2 the peroxide value increased significantly, indicating the formation of primary oxidation products. Similarly, a treatment with ClO2 increased the protein carbonyl content and induced the transformation of SH-groups to -S-S-groups in whey protein. The findings suggest that gaseous ClO2 will be a highly effective decontaminating agent for carbohydrate-rich foods, but that it would be less effective for the decontamination of high-protein and fatty foods.