BLBS102-c42 BLBS102-Simpson March 21, 2012 14:27 Trim: 276mm X 219mm Printer Name: Yet to Come
800 Part 8: Food Safety and Food Allegensand bind to ‘receptors’ on other cells in the body, causing typical
allergic symptoms.
The severity of an allergic reaction depends on how sensitised
the person is and the amount of the allergenic component in-
gested. Histamine released from mast cells is usually complete
within 30 minutes after the allergen–IgE antibody interaction.
The release of mediators (other than histamine) is slower and
their effects are more prolonged. Allergic reactions may, thus,
sometimes occur in two phases. The first stage or first symptoms
disappear on their own or with medication only to recur in 4–6
hours. Reactions may range from mild to severe life-threatening
conditions, and may manifest as gastrointestinal disorders (nau-
sea, vomiting, diarrhoea and abdominal cramping), or involve
the skin, leading to urticaria or hives, dermatitis, eczema, an-
gioderma, pruritis or itching. It may also involve the respiratory
tract, in which case the individual may suffer from rhinitis,
asthma or laryngeal oedema. Systemic anaphylaxis represents
the most dramatic and potentially catastrophic manifestation of
immediate hypersensitivity. Virtually, every organ in the body
can be affected, although reactions involving the pulmonary, cir-
culatory, cutaneous, neurological and gastrointestinal tract are
the most common (Anderson 1986).
About 1–2% of the total population are affected by IgE-
mediated food allergies (Chafen et al. 2010). The most vul-
nerable group are infants and young children, with 5–8% infants
under 3 years being affected (Sampson and McCaskill 1985,
Motala and Lockey 2004, Sicherer 2010). More than 170 dif-
ferent foods have been implicated in immediate hypersensitivity
reactions (Hefle et al. 1996, Taylor 2000).Delayed Hypersensitivity ReactionsUnlike the immediate hypersensitivity reactions described
above, symptoms associated with delayed hypersensitivity in-
duced by T-cells may appear after several hours to even days
following consumption of the offending food. Delayed allergic
reactions to food are relatively more difficult to identify un-
less the suspected food is eliminated from the diet for at least
several weeks and then slowly reintroduced followed by moni-
toring for the onset of any physical, emotional or mental changes
(Anderson 1986). These reactions are mediated by tissue-bound
immune cells, and the acuteness of the reaction may be less than
that of the immediate reactions (Taylor 2000). An example of
delayed hypersensitivity reaction to food is celiac disease (CD),
which is described in greater detail below.Food IntoleranceFood intolerances are abnormal reactions to food or food compo-
nents that do not involve the immune system (Breneman 1987).
They are generally less severe, shorter in duration and more
localised than immunological reactions. Food intolerances are
the most common types of food sensitivities and specific ex-
amples include the metabolic food disorders and anaphylactoid
responses described below.Metabolic Food DisordersMetabolic food disorders arise from inherited genetic deficien-
cies that reduce the capacity of afflicted individuals to efficiently
metabolise food components. One such example is lactose in-
tolerance, which is caused by an inherited deficiency of the
digestive enzyme lactase, which hydrolyses lactose in milk and
milk products into galactose and glucose for further process-
ing within the body. As a result, the undigested lactose cannot
be absorbed by the small intestine and passes into the colon
where bacteria metabolise it into carbon dioxide (CO 2 ) and wa-
ter (H 2 O), leading to bloating, abdominal cramping and frothy
diarrhoea (Taylor 2000).
Another example is phenylketonuria, a metabolic disorder in
which afflicted individuals are deficient in the hepatic enzyme
phenylalanine hydroxylase, which metabolises phenylalanine
into tyrosine. Thus, phenylalanine and phenylpyruvate accumu-
late in the body, and if left untreated, it could affect the central
nervous system and cause mental retardation and/or brain dam-
age in infants and children.
A third example of food intolerance due to a genetic defi-
ciency is favism, where individuals are intolerant to fava beans
or the pollen from theVicia fabaplant. Persons with this intoler-
ance have an inherited deficiency of the erythrocyte glucose-6-
phosphate dehydrogenase (G6PDH) enzyme, which is essen-
tial to protect erythrocyte membranes against oxidative damage
(Taylor 2000). This deficiency is crucial as several endoge-
nous oxidants present in broad beans, for example, vicine and
convicine, are capable of damaging erythrocyte membranes
in G6PDH-deficient individuals, resulting in acute haemolytic
anaemia with pallor, fatigue, dyspnoea, nausea, abdominal and/
or back pain, fever and chills. It may even lead to more serious
symptoms such as haemoglobinuria, jaundice and renal failure,
but these situations are rare. Symptoms occur quite rapidly, usu-
ally within 5–24 hours following consumption of fava beans.Anaphylactoid ResponsesAnaphylactoid responses are due to the non-immunologic re-
lease of chemical mediators, such as histamine, from mast cells
(Sampson et al. 1992). The specific substances that cause this
reaction are not well known, and the reactions are often confused
with true food allergies because they display similar symptoms.
Anaphylactic shock is one of the most startling symptoms asso-
ciated with food allergies, and such food intolerances, and may
affect the gastrointestinal tract, skin, respiratory tract and the
cardiovascular system. It can cause severe hypotension, and if
not treated properly, it may lead to death within minutes after
ingesting the offending food (Taylor 2000).
The rest of this chapter will focus on describing some of the
properties of the nine most common food allergens and methods
for detecting allergens.MILK ALLERGENS
Milk is a nutritional biological fluid secreted from the mammary
gland of female mammalians, and it is primarily intended to