BLBS102-c42 BLBS102-Simpson March 21, 2012 14:27 Trim: 276mm X 219mm Printer Name: Yet to Come
42 Food Allergens 803have been reported after eating food contaminated with trace
amounts of milk protein, including breast milk from mothers
who consume cow’s milk (Gerrard and Shenassa 1983), meat
treated with casein to enhance texture (Yman et al. 1994), frozen
desserts that contain trace amounts of whey protein (Laoprasert
et al. 1998) and lactose-containing medications that contained
residual milk protein (Nowak-Wegrzyn et al. 2004).
Bindslev-Jensen et al. (2002) developed a statistical approach
to estimate threshold levels of four major food allergens. They
reported that the threshold dose required for a person to develop
an adverse reaction using a million CMP susceptible popula-
tion is 0.005 mg of cow’s milk or 7× 10 −^5 mg of milk pro-
tein (Bindslev-Jensen et al. 2002). Other workers have reported
threshold levels ranging between 3 and 180 mg (Morisset et al.
2003a, Taylor et al. 2002).Effect of Processing on the Allergenicity of
Cow’s Milk ProteinsProcessing techniques are routinely applied to raw milk in order
to reduce or eliminate microorganisms and enhance shelf life.
Some of the techniques such as homogenisation, pasteurisation
and sterilisation do not modify protein structure significantly,
whereas others such as hydrolysis and irradiation do. In gen-
eral, results from several studies have shown that cow’s milk
allergenicity could be decreased, increased or unchanged by
processing treatments such as pasteurisation or sterilisation and
homogenisation (Host and Samuelsson 1988).Heat treatmentThe effect of heating on milk protein allergenicity remains con-
troversial. Pasteurised milk has been reported to have higher al-
lergenicity than raw or homogenised milk (Host and Samuelsson
1988). Caseins are more thermostable, whereas BLG manifests
a thermolabile behaviour (Wal 2004). However, BLG may be
protected from denaturation when heated due to possible inter-
actions with caseins. Currently, heat denaturation is not accepted
as a satisfactory process to reduce the allergenicity of milk pro-
tein. On the contrary, application of heat treatment could lead to
the formation of neo-allergens.HydrolysisHydrolysis of milk proteins reduces their allergenicity to vary-
ing degrees. Several cow’s milk proteins, for example BLG,
are relatively resistant to degradation by proteolytic enzymes,
while others are considered very labile (e.g. caseins). Boza et al.
(1994) obtained an extensively hydrolysed hypoallergenic in-
fant formulae by using a combination of ultrafiltration process
and hydrolysis with enzymes from bacterial/fungal origin with
broad specificity. Extensively hydrolyzed formulas (eHF) suc-
cessfully protect the development of allergy symptoms in the
majority of CMA infants (Walker-Smith 2003). However, even
eHFs (molecular weight (MW) less than 1.5 kDa) can still in-
duce allergic response in infants with atopic family background
(Nentwich et al. 2001) and CMA infants (De Boissieu et al.1997). Moreover, eHF have also been criticised for their poor
functionality (Crittenden and Bennett 2005).RadiationLee et al. (2001) reported that the application of gamma irra-
diation toα-casein and BLG altered the epitope structure of
both milk proteins, probably due to agglomeration of the milk
proteins and consequent decrease in solubility. Further research
is needed to clearly elucidate the effect of irradiated milk on
allergenicity.High-Pressure TreatmentHigh pressure may reveal potentially immunogenic hydrophobic
regions to enzymes, resulting in better hydrolysis. Bonomi et al.
(2003) reported that enzymatic hydrolysis under high pressure
(600 MPa) produced non-immunogenic peptides. Other work-
ers have, however, reported an increase in antigenicity of milk
proteins on high-pressure treatment in the absence of hydrolysis
(Kleber et al. 2004, 2007). Thus, as with irradiation, further re-
search will be useful to ascertain the effect of high pressure on
milk protein allergenicity.EGG ALLERGENS
Egg protein is used as a protein nutritional standard because it
is highly nutritional and has all the essential amino acids in the
right amounts required by the human body. Moreover, with the
exception of vitamin C, eggs serve as a good source of vitamins
A, D, E, K, as well as the B vitamins. Whole egg and egg-
derived ingredients also possess excellent functional properties
(e.g. gelation, emulsification and foaming), which has resulted in
their extensive use in the formulation of various food products.
Egg consists of the white and yolk, both of which contain
allergenic proteins. Whole egg contains 12.8–13.4% protein,
10.5–11.8% fat, 0.3–1% carbohydrate and 0.8–1.0% ash on a wet
basis (Breeding and Beyer 2000). Proteins found in egg white
are ovalbumin, conalbumin, ovomucoid, lysozyme, ovomucin
and other minor albumen proteins such as avidin, ovoglobulins,
flavoprotein and ovoinhibitors. The egg yolk proteins are rich
in lipoproteins and phosophoproteins and primarily comprise of
lipovitellin, lipovitellenin, vitellin, vitellenin, phosvitin, trans-
ferrin,γ-globulin, serum albumin andα 2 -glycoprotein.Prevalence, Symptoms and ThresholdsAlthough the majority of people can tolerate eggs in their diet,
a small percentage of the population, mostly children, suffer se-
vere allergic reactions after consuming egg. Symptoms of egg
allergic reactions include vomiting, diarrhoea, gastrointestinal
pain, urticaria, angiodema, atopic dermatitis, asthma and rhico-
conjunctivitis (Martorell Aragon ́es et al. 2001).
Egg allergy prevalence in the general population is estimated
between 1.6 and 3.2%, making egg the second most important
cause of food allergic reactions next to peanut (Arede et al. 2000,
Mine and Yang 2008 and references within). In children, egg