BLBS102-c42 BLBS102-Simpson March 21, 2012 14:27 Trim: 276mm X 219mm Printer Name: Yet to Come
42 Food Allergens 799finfish), crustaceans (e.g. shrimp, prawns, crab, lobster and crayfish)
and molluscs (e.g. snails, oysters, clams, squid, octopus and cuttle-
fish), gluten-containing cereals (i.e. wheat, rye, barley and their
hybridised strains and products), sesame and mustard. Symptoms
of food allergic reactions and the threshold dose required to pro-
voke allergic reaction markedly vary among sensitised individuals.
Food production practices, processing conditions and matrix effects
can also modify the molecular structure of food allergens and their
potential immunogenic properties which can make allergens diffi-
cult to detect even when present in foods. This chapter provides an
overview of the different types of food hypersensitivities includ-
ing a distinction between food allergies and food intolerance, the
properties of the nine priority food allergens, current approaches for
the management of food allergens and a summary of some of the
current methods used in food allergen detection.INTRODUCTION
Humans require food to survive. In addition to basic nutri-
tion, food consumption provides a sense of satisfaction and
culinary pleasure and also serves as a source of social enter-
tainment. However, for a small percentage of the population,
consumption of certain foods even in small quantities can re-
sult in life-threatening allergic reactions. Approximately 4–8%
of young children and 2–4% of adults in developed countries
suffer from food allergies (Kanny et al. 2001, Munoz-Furlong
et al. 2004, Sampson 2004, Sicherer et al. 2004, Breiteneder
and Mills 2005). Although over 170 foods are known to cause
food allergies, nine foods (and their derived products) are to-
day considered to be major allergens accounting for over 90%
of all food allergic reactions. These priority allergens include
milk, eggs, soya beans, peanuts, tree nuts (e.g. almonds, wal-
nuts, pecans, cashews, Brazil nuts, hazel nuts, pistachios, pine
nuts, macadamia nuts, chestnuts and hickory nuts), seafood such
as fish (i.e. both saltwater and freshwater finfish), crustacea (e.g.
shrimp, prawns, crab, lobster and crayfish) and molluscs (e.g.
snails, oysters, clams, squid, octopus and cuttlefish), gluten-
containing cereals (i.e. wheat, rye, barley and their hybridised
strains and products), sesame and mustard.
Food allergy is thus emerging as a growing public health prob-
lem. Unfortunately, the management of food allergens along the
food value chain and the diagnosis of food allergic diseases con-
tinue to pose a challenge to the food industry as well as health
care professionals. The factors responsible for this are varied.
Multiple foods can induce food allergic reactions, and the thresh-
old dose required to provoke allergic reaction markedly varies
for different patients; thus, small quantities of foods can cause se-
vere reactions in sensitised individuals, whereas other sensitised
individuals can tolerate quantities of the allergen that are orders
of magnitude higher. Additionally, symptoms of food allergies
vary tremendously among sensitised individuals, and food pro-
duction practices, processing conditions and matrix effects can
alter the molecular structure of food allergens and their potential
immunogenic properties and detection. In this chapter, we will
provide an overview of the different types of food hypersensi-
tivities, including a distinction between food allergies and foodintolerance, the properties of the nine priority food allergens,
current approaches for the management of food allergens and a
summary of some of the current methods used for food allergen
detection.FOOD HYPERSENSITIVITY
Food AllergyFood allergy is an immunological reaction resulting from the
ingestion, inhalation or atopic contact of food. Immunological
reactions can be mediated by IgE antibodies or other immune
cells such as T cells. Some workers define food allergy specifi-
cally as being those immunological responses mediated by im-
munoglobulin E (IgE) antibodies, whereas others use the broader
definition of immunological response, which include T-cell me-
diated responses as well. In this chapter, the latter definition will
be used.
In general, any protein-containing food can elicit an aller-
gic response in sensitised individuals. Allergenic proteins in
foods may be enzymes, enzyme inhibitors, structural proteins
or binding proteins with varied biological functions (Stewart
and Thompson 1996, Valenta et al. 1999, Chapman et al. 2000,
Martin and Chapman 2001). The pathogenesis of food allergy
begins with a sensitisation phase during which time the body
recognises one or more proteins in a particular food source as
a foreign invader and begins to mount an immune-defensive re-
sponse. Subsequent consumption of the offending food can result
in an allergic response that may manifest in one of two forms,
that is, immediate or delayed response as described below.Immediate Hypersensitivity ReactionsImmediate hypersensitivity reactions are mediated by a specific
class of antibodies known as IgE. Symptoms of an IgE-mediated
food allergy develop within a few minutes to a few hours after
an individual has ingested the offending food (Taylor 2000).
During the sensitisation phase, the body produces IgE antibod-
ies, which recognise allergenic fragments from the offending
food. After production, IgE antibodies circulate in the blood
and bind to basophiles and to the surface of mast cells (Taylor
2000). Mast cells and basophiles contain granules packed with
potent inflammatory mediators such as histamine, cytokines and
other chemotactic factors. When an allergic person encounters
an allergen to which the person has previously produced IgE
antibodies, the allergen combines with the IgE antibody on the
surface of the mast cells and basophiles. This triggers a com-
plex series of reactions that result in the release of histamine
and other chemical mediators (prostaglandin D2, tryptase, hep-
arin, etc.) from the granules inside the mast cells and basophiles
(Taylor and Lehrer 1996, Lu et al. 2007). Histamine as well as
the other chemical mediators has been shown to be the agents
responsible for producing symptoms of allergy. The release of
some of these mediators occurs rapidly, within 5 minutes after
the interaction between the allergen and the IgE antibody (Taylor
2000). Once released, these compounds enter the blood stream