Effect of the Food Matrix and

Processing on the Allergenic

Activity of Foods

Overview

• Introduction

• Development of Food Processing

• Processing-Induced Modification of Food

Proteins

• Impact of Processing on Food Allergens

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

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

Introduction

• The effects of thermal processing on

allergenicity of foods is difficult

– Many time-temperature combinations

– Impact of water activity

– Different methods

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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

Processing-Induced Modification of Food Proteins

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

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

Middleton 8th edition

• 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

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)

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

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

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

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

Impact of Processing on Food Allergens

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

Middleton 8th edition

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

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

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.

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

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

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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

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

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

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

Middleton 8th edition

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

Middleton 8th edition

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

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

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

Pollen-fruit

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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

Middleton 8th edition

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

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

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