Purification and characterisation of relevant natural and recombinant apple allergens

Apple (Malus domestica) is the most widely cultivated fruit crop in Europe and frequently causes allergic reactions with a variable degree of severity. So far, four apple allergens Mal d 1, Mal d 2, Mal d 3 and Mal d 4 have been identified. Mal d 1, a Bet v 1 related allergen, and Mal d 4, apple profilin, are sensitive to proteolytic degradation, whereas Mal d 2, a thaumatin-like protein and Mal d 3, a nonspecific lipid transfer protein, are rather stable to proteolytic processes. Mal d 1 and Mal d 4 were purified after expression in Escherichia coli expression system, while Mal d 2 and Mal d 3 were purified from apple fruit tissue. All purified proteins were subjected to detailed physicochemical characterisation to confirm their structural integrity and maintained IgE binding capacity. Detailed investigations of carbohydrate moieties of Mal d 2 demonstrated their involvement in the overall IgE binding capacity of this allergen. It was concluded that the folded structure and IgE binding capacity of all four allergens were preserved during purification.     

Purification of natural Mal d 1 and Mal d 2 allergens and monitoring of their expression levels during ripening in Golden Delicious apple

Apple (Malus domestica) is the most widely cultivated fruit crop in Europe. Consumption of fresh apples can cause allergic reaction with a variable degree of severity in susceptible individuals. Previous studies have indicated that expression pattern of Mal d allergens is affected by growing and storage circumstances. At the same time only a few data are available on purification and expression levels of the heat labile Mal d 1 apple allergen localised in peel and pulp of the fruit because this protein can be extracted in an active form only if reactions with phenolic compounds present in apple are inhibited. Our aim was to concurrently purify and monitor the expression levels of the heat labile Mal d 1 (18 kDa), a Bet v 1 related allergen and the heat resistant Mal d 2 (32 kDa), a thaumatin-like allergenic protein from Golden Delicious apple cultivar with high potential to express Mal d 1 allergens. This assumption was proven by amplification of a polymorphic pattern of PCR products with 154–174 bp fragments by using Mal d 1.06A SSR primers. The apple proteins were extracted from frozen apple pulp under acidic circumstances at pH 3.0 to prevent reaction of the allergens with phenolic compounds of apple. Under such circumstances protein-binding brown pigments can be avoided and its deleterious effect on analysis of Mal d allergens can be eliminated. The separation of Mal d allergens was performed by cation-exchange chromatography and gel filtration. Mal d allergens were quantified during ripening in Golden Delicious apple extract. Mal d 1 and Mal d 2 specific ELISAs were developed to be used for quantification of the immune reactive Mal d allergens. It was found that during the ripening period, the contents of Mal d 1 and Mal d 2 allergens were continuously, but a bit differentially increased. According to the chromatographic results the content of Mal d 1 (0.1 –0.25 mg/100 g apple) increased intensively from 144th until 152th day, then it did not change (152th–164th days), while the content of Mal d 2 (0.18–0.75 mg/100 g apple) started to increase from 144th until 158th day. ELISA results showed the same tendency.     

High pressure,thermal and pulsed electric‐field‐induced structural changes in selected food allergens

Scope: The effects of high‐pressure/temperature treatment and pulsed electric field treatment on native peanut Ara h 2, 6 and apple Mal d 3 and Mal d 1b prepared by heterologous expression were examined. Methods and results: Changes in secondary structure and aggregation state of the treated proteins were characterized by circular dichroism spectroscopy and gel‐filtration chromatography. Pulsed electric field treatment did not induce any significant changes in the structure of any of the allergens. High‐pressure/temperature at 20°C did not change the structure of the Ara h 2, 6 or Mal d 3 and resulted in only minor changes in structure of Mal d 1b. Ara h 2, 6 was stable to HPP at 80°C, whereas changes in circular dichroism spectra were observed for both apple allergens. However, these changes were attributable to aggregation and adiabatic heating during HPP. An ELISA assay of temperature treated Mal d 3 showed the antibody reactivity correlated well with the loss of structure. Conclusion: In conclusion, novel‐processing techniques had little effect on purified allergen structure. Further studies will demonstrate if these stability properties are retained in foodmatrices.     

Conformational changes of Mal d 2, a thaumatin-like apple allergen,induced by food processing

Mal d 2, a thaumatin-like protein from apple was previously described to react to almost 75% of the apple allergic patient sera. Based on the molecular structure of this protein, the present study focused on the conformational stability of Mal d 2 in relation to in vitro IgE-binding under different physico-chemical conditions and proteolysis. The structural integrity of Mal d 2 was monitored using SDS–PAGE, Western blotting using polyclonal antibodies and human sera, fluorescence spectrometry and circular dichroism. Results confirmed the stability of Mal d 2. However, Mal d 2 was reactive to human serum IgEs mainly after reduction of disulphide bridges fixing the α-helical domain II. Contrary to previous assumptions, the current findings suggest that the allergenic epitopes of Mal d 2 are hidden inside the protein structure and none of the rigorous conditions applied in industrial juice processing or digestive proteolysis enhance or reduce the binding to IgE molecules.     

Allergenicity of different apple cultivars assessed by means of skin prick test and sensitisation to recombinant allergens Mal d 1 and Mal d 3 in a group of Italian apple‐allergic patients

To evaluate differences in skin prick test response to apple cultivars in patients with apple allergy, 19 patients (10 adults and 9 children) underwent prick‐to‐prick skin prick test with eleven commercial and noncommercial apple cultivars, and evaluation of specific IgE to apple and recombinant apple allergens Mal d 1 and Mal d 3. The results show that different reactions might be evoked in a single patient by different apple cultivars and also separately for the peel and the pulp of a single cultivar. The cultivars were ranked according to their allergenicity level, being Jonathan, Jonagold, Golden Delicious and Fiesta the most allergenic when considering the pulp and Gala, Fiesta and Golden Delicious for the peel. Further investigations are needed to clarify if a single patient can be allergic only to well‐defined apple cultivars and which allergometric tests are necessary to ascertain this.     

Cover Picture: Mol. Nutr. Food Res. 7'2011

Regular issues provide a wide range of research, review and food & function articles covering all aspects of Molecular Nutrition & Food Research. Selected topics of issue 07 are: Effect of supplementation with vitamin D3 on glucose production pathways in human subjects Bacterial Biofilms Associated with Food Particles in the Human Large Bowel Curcumin reduces pulmonary tumorigenesis in vascular endothelial growth factor (VEGF)‐overexpressing transgenic mice High pressure treatment reduces the immunoreactivity of the major allergens in apple and celeriac Distinctive effects of plant protein sources on renal disease progression and associated cardiac hypertrophy in experimental kidney disease     

Combination of Sodium Chlorite and Calcium Propionate Reduces Enzymatic Browning and Microbial Population of Fresh-Cut “Granny Smith” Apples

ABSTRACT: Tissue browning and microbial growth are the main concerns associated with fresh-cut apples. In this study, effects of sodium chlorite (SC) and calcium propionate (CP), individually and combined, on quality and microbial population of apple slices were investigated. “Granny Smith” apple slices, dipped for 5 min in CP solutions at 0%, 0.5%, 1%, and 2% (w/v) either alone or in combination with 0.05% (w/v) SC, were stored at 3 and 10 °C for up to 14 d. Color, firmness, and microflora population were measured at 1, 7, and 14 d of storage. Results showed that CP alone had no significant effect on the browning of cut apples. Even though SC significantly inhibited tissue browning initially, the apple slices turned brown during storage at 10 °C. The combination of CP and SC was able to inhibit apple browning during storage. Samples treated with the combination of SC with CP did not show any detectable yeast and mold growth during the entire storage period at 3 °C. At 10 °C, yeast and mold count increased on apple slices during storage while CP reduced the increase. However, high concentrations of CP reduced the efficacy of SC in inactivating E. coli inoculated on apples. Overall, our results suggested that combination of SC with 0.5% and 1% CP could be used to inhibit tissue browning and maintain firmness while reducing microbial population. Practical Application: Apple slices, which contain antioxidants and other nutrient components, have emerged as popular snacks in food service establishments, school lunch programs, and for family consumption. However, the further growth of the industry is limited by product quality deterioration caused by tissue browning, short shelf-life due to microbial growth, and possible contamination with human pathogens during processing. Therefore, this study was conducted to develop treatments to reduce microbial population and tissue browning of “Granny Smith” apple slices. Results showed that an antimicrobial compound, sodium chlorite, is effective in not only eliminating microbes but also inhibiting tissue browning of apple slices. However, the compound caused tissue softening and its antibrowning effect was short-lived, lasting only for a few days. Combination of the compound with a calcium-containing food additive was able to improve firmness and freshness of apple slices while reducing population of Escherichia coli artificially inoculated on samples and inhibiting the growth of yeast and mold during storage.     

Molecular characterization of Api g 2, a novel allergenic member of the lipid-transfer protein 1 family from celery stalks

Scope: Celery represents a relevant cross‐reactive food allergen source in the adult population. As the currently known allergens are not typical elicitors of severe symptoms, we aimed to identify and characterize a non‐specific lipid transfer protein (nsLTP). Methods and results: MS and cDNA cloning were applied to obtain the full‐length sequence of a novel allergenic nsLTP from celery stalks. The purified natural molecule consisted of a single isoallergen designated as Api g 2.0101, which was recombinantly produced in Escherichia coli Rosetta‐gami. The natural and recombinant molecules displayed equivalent physicochemical and immunological properties. Circular dichroism revealed a typical α‐helical fold and high thermal stability. Moreover, Api g 2 was highly resistant to simulated gastrointestinal digestion. As assessed by ELISA, thermal denaturation did not affect the IgE binding of Api g 2. Natural and recombinant Api g 2 showed similar allergenic activity in mediator release assays. Api g 2‐specific IgE antibodies cross‐reacted with peach and mugwort pollen nsLTPs. Conclusion: Based on our results, it can be anticipated that inclusion of recombinant Api g 2 in the current panel of allergens for molecule‐based diagnosis will facilitate the evaluation of the clinical relevance of nsLTP sensitization in celery allergy and help clinicians in the management of food allergic patients.     

Influence of food processing on the immunochemical stability of celery allergens

Celery roots were processed by microwave heating, cooking, drying, γ-irradiation, ultra high pressure treatment and high voltage impulse treatment. The immunochemical stabilities of the three known allergenic structures of celery were tested with sera from patients who were sensitised to celery. In addition, rabbit antisera were used to detect the allergens profilin and Api g 1 on celery immunoblots. The specificity and reactivity of IgE from the patients' sera were investigated by immunoblotting, by an enzyme allergosorbent test (EAST) and by dose-related IgE inhibition experiments. The results of all three methods agreed closely and indicated high antigenic and allergenic activity in native celery which was reduced by thermal processing. The heat-stability of the known celery allergens decreased in the following order: carbohydrate epitopes> profilin>Api g 1. In contrast, the allergenicity was only mildly reduced by non-thermal processing. The results obtained with human IgE were confirmed by an in vitro mediator-release assay that is based on rat basophil leukemia cells (RBL cells) which were passively sensitised with celery-specific murine IgE. With sera from mice that had been immunised with native celery, the native sample and non-thermal celery preparations elicited the strongest mediator release, whereas a weak response was obtained with samples from heat-processed celery. These results agreed closely with the data obtained in allergic patients whose IgE antibodies were directed against the major protein allergen Api g 1. Our results may be helpful in risk assessment and in selecting food preparations which can be consumed without symptoms by a subgroup of celery-allergic patients with a known sensitisation pattern. ©1997 SCI     

THE EFFECT OF PRETREATMENT OF SHREDDED CELERIAC USING SOLUTIONS OF ENZYMATIC BROWNING INHIBITORS ON THE QUALITY OF MINIMALLY PROCESSED PRODUCT

ABSTRACT

The study investigated the effect of soaking celeriac flakes in solutions containing various concentrations of enzymatic browning inhibitors on the quality of stored minimally processed product. Ascorbic acid (0.2–0.5%), 4‐hexylresorcinol (0.003–0.01%), sodium chloride (0.1–0.5%) and sodium lactate (2–3%) were used as browning inhibitors. On the basis of the conducted tests, it was found that among the applied browning inhibitors, only ascorbic acid had an advantageous effect on the quality of stored celeriac flakes. Along with an increase in its concentration in the solution (0.2–0.5%) used for the pretreatment of the flakes, the value of color parameter a* decreased, while the value of parameter b* increased. At the concentration of ascorbic acid in the solution exceeding 0.25%, flake color in the sensory examination was evaluated as desirable. An increase of ascorbic acid concentration in the solution in the range from 0.2 to 0.4% resulted in a decrease in the total mesophilic and psychrophilic bacteria counts, respectively, by 3 and 1 log cfu/g of the stored product.

PRACTICAL APPLICATIONS

Minimal processing of celeriac provides convenience for consumers and many economic benefits for producers. Minimal processing of celeriac can induce disadvantageous changes in tissue, which may lead to darkening of the flakes and deterioration of product sensory attributes. Moreover, shredded raw material constitutes an excellent medium for the development of microorganisms. This article contains information about the effectiveness of enzymatic browning inhibitors for extending the shelf life of celeriac flakes. We show a range of concentrations of inhibitors, which improve the preservation of color, intrinsic taste and microbial quality of minimally processed celeriac.

     

Evaluation of the effects of thermal treatments on color, polyphenol stability, enzyme activities and antioxidant capacities of innovative pasty celeriac (Apium graveolens L. var. rapaceum (Mill.) DC.) products

Initial heating was applied as the first processing step in the production of innovative pasty celeriac products. For this purpose, celeriac was converted into a paste and subsequently heated at 90 and 100 °C for 5–10 min. Alternatively, the fresh plant material was blanched prior to mincing. For the first time, phenolic compounds in celeriac were characterized by high-performance liquid chromatography coupled with mass spectrometry (LC–MSⁿ). Among the 14 phenolics detected, several caffeic, ferulic and quinic acid derivatives as well as malonylated and acetylated flavonoid derivatives were newly identified. Upon thermal treatment, the antioxidant capacities (TEAC assay) and the total phenolic contents remained virtually unchanged. The antioxidant capacities of heated samples determined by the FRAP assay were even higher than those of the unheated control. The contents of the main phenolic compound apiin decreased upon heat treatment, whereas the levels of the minor compounds malonylapiin A and B increased. Only by extended steam- and water-blanching at 100 °C, respectively, complete inactivation of peroxidase and polyphenol oxidase was achieved. The obtained celeriac products were characterized by their bright white color. Consequently, blanching is recommended as the initial operation in the processing of celeriac into novel pasty products.     

Purification and structural stability of the peach allergens Pru p 1 and Pru p 3

Pru p 1 (a Bet v 1 homologue) and Pru p 3 (a nonspecific lipid transfer protein; nsLTP) are major allergenic proteins in peach fruit, but differ in their abundance and stability. Pru p 1 has low abundance and is highly labile and was purified after expression as a recombinant protein in Escherichia coli. Pru p 3 is highly abundant in peach peel and was purified by conventional methods. The identities of the proteins were confirmed by sequence analysis and their masses determined by MS analysis. The purified proteins reacted with antisera against related allergens from other species: Pru p 1 with antiserum to Bet v 1 and Pru p 3 with antiserum to Mal d 3 (from apple). The presence of secondary and tertiary structure was demonstrated by circular dichroism (CD) and high field NMR spectroscopy. CD spectroscopy also showed that the two proteins differed in their stability at pH 3 and in their ability to refold after heating to 95 degrees C. Thus, Pru p 1 was unfolded at pH 3 even at 25 degrees C but was able to refold after heating to 95 degrees C at pH 7.5. In contrast, Pru p 3 was unable to refold after heating under neutral conditions but readily refolded after heating at pH 3.     

Impact of Vacuum Cooking Process on the Texture Degradation of Selected Apple Cultivars

ABSTRACT:  Thermal treatments are known to affect the textural properties of fruits and vegetables. This study was conducted to evaluate the influence of vacuum cooking process on the mechanical properties of various apple cultivars. A total of 10 apple cultivars were industrially processed by vacuum pasteurization at 95 °C for 25 min. The raw material was characterized by penetrometry, uniaxial double compression, soluble solid content, and titrable acidity. Textural properties of processed apples were analyzed by uniaxial double compression. As expected, for all cultivars, fruit resistance was lower after processing than before. Results showed that texture degradation due to vacuum pasteurization was different from one cultivar to another. Indeed, some cultivars, initially considered as the most resistant ones, such as Braeburn, were less suitable for processing, and became softer than others after thermal treatment. Consequently, it is worth noting that the texture classification of the investigated apple cultivars was changed by the vacuum-cooking process.     

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.     

Identification of four IgE-reactive proteins in raspberry (Rubus ideaeus L.)

IgE-reactive proteins in raspberry (Rubus ideaus L.) were identified using PCR, RT-PCR, 2-DE and MS/MS peptide sequencing. Specific polyclonal antibodies and patient sera were used in Western blotting to identify crossreactive epitopes. Initially, two potential allergens Rub i 1 and Rub i 3 were detected using PCR, showing high sequence identity to proteins in Rosaceous species like Mal d 1 and Mal d 3 from apple, Pru av 1 and Pru av 3 from cherry and Pru p 1 and Pru p 3 from peach. Furthermore, de novo identified peptides of a protein band at about 30 kDa reacting with most of the patient sera tested (> 80%) revealed a high sequence homology with class III chitinases. Raspberry chitinase, when subjected to glycoproteomic analysis, showed typical complex plant-type N-glycans with a core alpha1,3 fucose and a beta1,2 xylose at least at one position, indicating the presence of crossreacting carbohydrate determinants (CCDs). Finally, MS/MS analysis revealed an IgE-reactive raspberry cyclophilin, homologous to Bet v 7. Results obtained suggest that the consumption of raspberries might be responsible for adverse reactions in sensitised individuals.     

Towards a better understanding of the pectin structure-function relationship in broccoli during processing: Part I—macroscopic and molecular analyses

To investigate the structure-function relationship of pectin during (pre)processing, broccoli samples (Brassica oleracea L. cultivar italica) were subjected to one of the following pretreatments: (i) low-temperature blanching (LTB), (ii) LTB in combination with Ca²⁺ infusion, (iii) high-pressure pretreatment (HP), (iv) HP in combination with Ca²⁺ infusion, or (v) no pretreatment (control sample), whether or not in combination with a thermal treatment of 15 min at 90 °C. The macroscopic attributes of broccoli were linked to the chemical structure of broccoli pectin. By enhancing the cross-linking of pectic polymers, both LTB and HP reduced the texture loss that occurred during thermal processing of broccoli. During these pretreatments, homogalacturonan was de-esterified by pectin methylesterase, which led to changes in pectin solubility. When LTB or HP was combined with Ca²⁺ infusion, changes in the structure of pectin occurred, however not always reflected at the macroscopic level. The degree of esterification of pectin in Ca²⁺-soaked broccoli samples was lower compared to non-Ca²⁺-soaked samples and, in addition, a higher amount of ionically cross-linked pectin was retrieved.     

Towards a better understanding of the pectin structure–function relationship in broccoli during processing: Part II — Analyses with anti-pectin antibodies

To investigate the structure–function relationship of pectin during (pre)processing, broccoli samples (Brassica oleracea L. cultivar italica) were subjected to one of the following pretreatments: (i) low-temperature blanching (LTB), (ii) LTB in combination with Ca²⁺ infusion, (iii) high-pressure pretreatment (HP), (iv) HP in combination with Ca²⁺ infusion, or (v) no pretreatment (control sample), whether or not in combination with a thermal treatment of 15 min at 90 °C. Anti-homogalacturonan antibodies were used to perform in situ (microscopy) and ex situ (immuno-dot assays) analyses on broccoli pectin which resulted in information concerning the localisation of defined pectic domains in broccoli cell walls and pectin's structure. Water-soluble pectin appears to contain unbranched, high-esterified pectin and some pectic polymers with abundant side chains that are less esterified. Ionically cross-linked pectin, on the other hand, contains low-esterified pectin with either highly branched or unbranched domains. The in situ visualisation of pectin in broccoli suggested that de-esterification of pectin by PME during LTB as well as during HP mainly takes place in the tricellular junctions of adjacent cells in broccoli tissue. Ca²⁺-cross-linked pectin could be found in cell walls lining intercellular spaces and was particularly abundant at the corners of intercellular spaces, indicating its important role in cell–cell adhesion. Both LTB and HP created pectin–Ca²⁺-cross-links in parts of the cell wall where these cross-links were originally absent. The influence of thermal processing and the effect of pressurisation on the pectic components in the cell wall could also be visualised using the antibodies.     

Enhanced bacterial inactivation in apple juice by synergistic interactions between phenolic acids and mild food processing technologies

This study demonstrated an innovative processing approach based on synergistic antimicrobial activity of two phenolic acids with mild thermal and non-thermal processing technologies. The two selected model phenolic acids were gallic acid (GA; 10 mM) and ferulic acid (FA; 1 mM). The processing technologies evaluated for processing of a model clarified apple juice were UV-A light, mild heat (55 °C) and moderate pressure (250 MPa), with processing times ranging from 1 to 30 min. The results demonstrated that combinations of selected phenolic acids and a mild physical processing were able to lower E. coli O157:H7 and Listeria innocua counts from 6-log CFU mL⁻¹ to below the detection limit of 1-log CFU mL⁻¹. Bacterial inactivation was significantly enhanced by the combination of UV-A light processing and FA, where 10 min of treatment enhanced bacterial inactivation by 5-log as compared to light processing alone, which presented no bacterial inactivation. In contrast, the combination of GA and mild-temperature thermal processing (55 °C) or mild-levels of high-pressure processing (250 MPa), enhanced bacterial inactivation by 4-log as compared to the physical treatments alone, which presented only 1-log of inactivation. The influence of these synergistic combinations on bacterial membrane damage was assessed by selective plating technique under osmotic pressure. Furthermore, the total intracellular thiol content was also measured to assess for thiol oxidation. Overall, the results demonstrated enhanced bacterial inactivation based on synergistic interactions of selected phenolic acids with both mild-thermal and non-thermal technologies in a model food system and illustrate potential to create diversity of novel antimicrobial strategies for food processing.Industrial relevanceThis study showed that the presence of naturally-based compounds can significantly reduce intensity levels of physical processing required to inactivate model gram-positive and gram-negative bacteria in apple juice. In this study two phenolic acids, ferulic acid and gallic acids were selected as these compounds are naturally present in many fruits and other food products including grains. Furthermore, the levels of these natural phenolic acids used in this study are comparable to the levels naturally present in some of the food materials.     

Pulsed electric field and mild thermal processing affect the cooking behaviour of carrot tissues (Daucus carota) and the degree of methylesterification of carrot pectin

For the first time, the effect of pulsed electric field (PEF) and mild thermal processing on the texture of cortex and vascular carrot tissue during subsequent thermal processing (i.e. cooking behaviour) was compared and the degree of methylesterification (DM) of pectin from the pretreated tissues was investigated. The PEF and mild thermal pretreatment slowed down the cooking behaviour of the carrot tissues, especially when the pretreatments were combined. The DM of pectin from vascular tissue was lowered after both types of pretreatments, the effect being most pronounced in the case of the combination of the PEF and mild thermal pretreatment. In contrast, the DM of cortex pectin only decreased after the mild thermal pretreatment and after the combination pretreatment. This study demonstrates that besides mild thermal pretreatments also PEF pretreatments can be considered in the context of texture preservation of thermally processed fruits and vegetables.     

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.