Effect of the food matrix and processing on the allergenic activity of foods Presented by Sirapassorn Tirabanchasak, MD.

1. Effect of the Food Matrix and Processing on the Allergenic Activity of Foods

2. Overview
•Introduction
•Development of Food Processing
•Processing-Induced Modification of Food Proteins
•Impact of Processing on Food Allergens

3. Introduction
•Challenging
•Allergic reaction: IgE–binding capacity
•Food allergies are largely caused by protein molecules
•Food processing affect the way which food proteins are presented to the immune system
Middleton 8th edition

4. Epitopes
The sites on a molecule recognized by IgE: epitopes
•Linear epitopes
–short regions of about 8-15 amino acid residues
–mobile
–stable in response to food processing procedures
•Conformational epitopes
–Formed from various segments of a polypeptide by protein folding
–Food processing procedures can either destroy conformational epitopes or reveal new epitopes previously hidden by protein folding
Middleton 8th edition

5. Introduction
•The effects of thermal processing on allergenicity of foods is difficult
–Many time-temperature combinations
–Impact of water activity
–Different methods
Middleton 8th edition

6. Development of Food Processing
•125,000 years ago, enabled the development of cooking
•Heated stones for boiling, burying food wrapped in leaves in the hot embers of fires, or baking fish in clay
•Processing procedures: remove inedible tissues and debris and the use of combined physical, chemical, and agrochemical treatments that prevent spoilage by insect pests or fungal and microbial growth
Middleton 8th edition

7. Processing-Induced Modification of Food Proteins

8. Processing-Induced Modification of Food Proteins
•Food processing
–Destroy linear and conformational IgE-binding epitopes
–Establish the exposure of formerly hidden antigenic sites
–Change the susceptibility to digestion
•The presence of other components (fats, sugars) determine the extent to which proteins are modified during cooking

9. Food Processing
•Thermal treatments reduce the size of the milk fat globule, prevent microbiologic spoilage and enhance shelf life
–Pasteurization: heating milk to 72 c for 15 sec
–Sterilization
–UHT: heating milk to 140-150 c for a few sec
–Retorting/canning

10. Middleton 8th edition

11. •Subjects: 6 mo-21 yr
•Muffin: 350 F x 30 min, Waffle 500 Fx 3 min total milk protein 1.3 g, 4 equal portions over 1 hr, repeat 2 hr later
•Heated milk–reactive subjects: larger SPT, higher specific IgE with sen 100%, NPV 100%
•At 3 months, subjects ingesting heated milk products had significantly smaller SPT, higher casein- IgG4
Nowak-Wegrzyn A, et al. J Allergy Clin Immunol 2008;122:342-7

12. Food Processing
•Dry processing procedures: roasting and frying
•Freeze-drying such as herbs and spices, for which preservation of flavor is important
•Proteolysis/hydrolysis in lentils and cow’s milk
–reducing the proteins to such small peptides that no longer able to trigger an allergic reaction
–either through chemical means (extreme pH) or food-grade enzymes (often from microbes)

14. Food Processing
•Bleaching and deodorizing processes involved in oil refining removes almost all the protein residues, rendering them almost protein-free
Crevel RWR et al. Food Chem Toxicol 2000;38:385-93
Middleton 8th edition

15. Food Processing
•Fermentation of the complex food
–Complex mixtures of microbes involves lactic acid bacteria and yeast
–Cheese, yogurt, preserved meat products; sausages and salamis, derived soybean product; miso and soy sauce

16. Food Processing
•Fermented beverages; beer and wine
–May originate from fish collagen or egg
–Removal of residual yeast particles
–Reported allergic reactions to residual fining agents
–Safe for most individuals with egg, milk, or fish allergies

18. Food Processing
•Maillard reaction: a form of nonenzymatic browning
–a hexose sugar such as glucose with a free amino group from a protein
–formation an unstable Schiff base that then cyclizes to form more stable Amadori products (early glycation products)
•Melanoidins: advanced Maillard reaction products that confer the brown color of baked, roasted, and fried foods and the associated toasted flavors

21. Impact of Processing on Food Allergens

22. Impact of Processing on Food Allergens
•Affect the way in which food proteins are presented to the immune system
•Labile epitopes: Native lgE epitopes lost during unfolding (especially globular proteins) or obscured in aggregates
•Neoepitopes: New lgE epitopes revealed during unfolding
•Stable epitopes: Disordered structures remain even after unfolding of native proteins

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24. Cupins
•A number of plant food allergens share the core β-barrel motif of the cupin superfamily, includes the vicilin-like 7S seed storage globulins and the legumin-like 11S seed storage globulins
Middleton 8th edition

25. Cupins
•Legumes; soybean, peanut, lupin
•Tree nuts; hazelnut, walnut, cashew, pecan, almond
•Other seeds; sesame, mustard
•Seed storage globulins: prone to aggregate formation, especially after heating or after treatment with solutions of extreme pH and low ionic strength

26. Cupins
•Boiling the 7S globulin from peanut (Ara h 1)
–aggregates formed
–reduces IgE-binding capacity formation
–Unaltered T cell reactivity
Blanc F, et al. Mol Nutr Food Res 2011;55:1887-94.

27. Roasted peanuts
•Hydrolysis of both Ara h 1 and Ara h 2/6
•Ara h 1
–Decreased the IgE-binding capacity
–Increased the capacity to elicit mediator release
•Ara h 2/6: decreased both the IgE-binding capacity and degranulation capacity
Vissers YM, et al. Clin Exp Allergy 2011;4: 1631-42 Vissers YM, et al. PLoS One 2011;6:e23998

28. Frying or boiling compared with roasted peanuts
•Less Ara h 1, reduction of IgE-binding intensity
•Lee IgE binding to Ara h 2 and Ara h 3
•Similar protein amounts
•Explain the difference in prevalence of peanut allergy observed in the 2 countries
Beyer K, et al. J Allergy Clin Immunol 2001;107:1077-81
USA
Roasting: 170c, 20 min
Frying in pure vegetable oil 5-10 min
Boiling: 100 c, 20 min

29. Middleton 8th edition

30. Cupins
•Not as well characterized in other legume allergens
•Boiling lentils
–Lost allergenic globulin and destroy most of the IgE-binding activity
–Some resistant fragments do remain

31. Prolamin superfamily
•Sensitization to seed storage prolamins is associated with conditions such as atopic dermatitis and exercise-induced anaphylaxis
•3 groups of proteins that share a conserved skeleton of cysteine residues in a three-dimensional structure

32. Prolamin superfamily
•Containing 5 α-helices arranged in a right- handed superhelix
1.2S albumins: low-molecular-weight seed proteins, some of which act as storage proteins
2.Lipid-transfer proteins (LTPs); disulfide bonds allows lipids to bind
3.Cereal α-amylase inhibitors

33. Prolamin superfamily
•Lipid-transfer proteins (LTPs)
–Expression in fresh fruits and vegetables changes during ripening and storage
–Located in the outer layer of fruits and seeds, and removal of these outer layers, such as by peeling, significantly reduces the potential for an allergic reaction

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35. Prolamin superfamily
•The level of LTP allergen from apple; Apple, Mal d 3
•Increased when mature, the rate was dependent on cultivar and tree position
•Decreased during postharvest storage
•Cox’s orange pippin, Jonagored, and Gala
Sancho AI, et al. J Agric Food Chem 2006;54: 5098-104

36. Middleton 8th edition

37. Prolamin superfamily
•2S albumin and LTP allergens appear to be more thermostable than many other types of allergens
•Peanuts, tree nuts, Brazil nuts, and sesame seeds heated to temperatures >110° C, the 2S albumin begins to unfold
•Peach LTP, Pru p 3 retain its allergenic activity in commercial juices and after ultrafiltration
Johnson PE, et al. Mol Nutr Food Res 2010;54: 1701-10
Brenna O, et al. J Agric Food Chem 2004;8:493-7

38. Prolamin superfamily
•Severe heat treatment (100C, 2 hr)
–Minor changes in protein structure
–Decrease in IgE-binding and biological activity
•Glycation had a protective effect
•The presence of sugars in fruits may contribute to the thermostability of the allergenic activity of LTP in heat- processed foods
Sancho AI, et al. Allergy 2005;60: 1262-8

39. BET V 1 Superfamily
•Group of proteins with a shared β-barrel structure that possess a central lipid-binding tunnel, belongs to PR group 10 proteins
•Initially sensitized to Bet v 1 from birch pollen and related proteins from other pollens
•IgE-binding epitopes on Bet v 1 sites on the native proteins on fresh fruits and vegetables

40. Pollen-fruit
Middleton 8th edition

41. BET V 1 Superfamily
•Generally thermolabile
•Purified protein is stable after heating to 90 c
•Processed fruits and vegetables lost the native structure
•Can consume cooked fruits and vegetables
•Apples
–Preparing an apple for a fresh fruit salad can be enough to prevent it from eliciting intense oral itching

42. Middleton 8th edition

43. BET V 1 Superfamily
Celery
•Celery remains allergenic even after extended thermal treatment (76.07 min,100 C)
•Celery spice is allergenic for patients with an allergy to raw celery
Ballmer-Weber BK, et al. Allergy 2002;57:228-35

44. Tropomyosin
•Crustacean and molluscan shellfish species
•α-helical structural protein
•Found in both muscle and nonmuscle cells
•The greasy back shrimp (Met e 1): heat-stable
•Boiling may enhance the allergenicity of shrimp for certain individuals
•Boiled extracts induced larger wheals than raw extracts
Carnes J, et alAnn Allergy Asthma Immunol 2007;98:349-54

45. Parvalbumins
•White muscle of fish
•Thermal processing usually reduces but does not abolish the allergenic activity of fish
•Enhance the allergenic activity in a few people
•Severe thermal processing; canning reduces its allergenic activity more extensively than boiling
Bernhisel-Broadbent J, et al. J Allergy Clin Immunol 1992;90:622-9