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Removal of Allergens in Some Food Products Using Ultrasound


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Food allergy is an abnormal immunological, usually immunoglobulin E-related, reaction resulting from exposure through ingestion of, skin contact with, or inhalation of exogenous food macromolecules (typically proteins) known as allergens or antigens. Until now, avoidance of food has been practiced by allergic patients to protect themselves from this health problem. However, with the number of novel food products and ingredients launched on the market by the industry, it is a challenge for allergic patients to keep track of all the ingredients in the food products. In addition, cross-contamination of food allergens from one product to another and mislabeling pose health risks and sometimes can be fatal to allergic patients. A number of thermal and nonthermal food processing interventions have been tested on various allergenic foods to reduce their allergenicity. However, complicated food matrices and varied detection methods make it very challenging to apply a particular technology for reducing allergenicity. This chapter highlights the application of ultrasound to the potential reduction of food allergenicity.
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Chapter 11
Removal of Allergens in Some
Food Products Using
Balunkeswar Nayak
, Zhenxing Li
, Ishfaq Ahmed
, Hong Lin
University of Maine, Orono, ME, United States;
Ocean University of China, Qingdao, P.R. China
Food allergy refers to an abnormal or exaggerated immune response triggered
by eating specific foods or food additives. It was defined by an expert panel of
the National Institute of Allergy and Infectious Diseases as “an adverse health
effect [that] occurs reproducibly on exposure to proteins, or antigens, which
are components of food matrices, thereby causing a specific immune
response.” Allergic reactions to food may be caused by cells in the immune
system or antibodies in the blood (Boyce et al., 2010). Food allergy is among
the most common disorders and has tended to increase in prevalence in the
past decades thus becoming a significant public health concern. Novel proteins
and innovations in food formulations could lead to new cases of allergies. It is
very important to understand the basic terms used, the mechanism of food
allergy in humans, and the detection of allergens before applying any inter-
vention technology for the reduction of food allergens.
About 170 foods or food components have been documented as being
potentially allergenic. According to the Food Allergen Labeling and Consumer
Protection Act of 2004, only eight major foods or food groups, namely eggs,
milk, fish, shellfish, tree nuts, peanuts, soybeans, and wheat, account for
approximately 90% of all the allergic reactions. Milk and eggs are ubiqui-
tously prominent worldwide, whereas the adverse reactions caused by other
common allergenic foods vary based on geographic region. Radauer et al.
(2008) and Sathe et al. (2016) attempted to classify selected major food
allergens based on their sequence analogy and domain architecture. Most of
the allergens are water-soluble glycoproteins with molecular masses of
10e70 kDa that are illustrated by three main attributes: (1) ability to sensitize
a genetically influenced individual by activating the creation of IgE antibodies,
Ultrasound: Advances in Food Processing and Preservation.
Copyright ©2017 Elsevier Inc. All rights reserved. 267
(2) ability to bind those specific IgE antibodies, and (3) ability to cause an
adverse immunological reaction following IgE binding.
These adverse reactions can be toxic and nontoxic (Fig. 11.1). Among the
nontoxic reactions, those that are not immune-mediated are termed food
intolerance. Nonimmune adverse reactions mostly occur in people having
enzyme defects (i.e., vasoactive amines or lactose intolerance caused by a
deficiency of lactase, the enzyme responsible for digesting milk lactose). Such
adverse reactions are more prevalent than immune-mediated reactions. Phar-
macological reactions, another type of food intolerance, are caused by
chemical components of foods, such as tyramine in aged cheese or theobro-
mine in chocolate. Certain food additives such as potassium and sodium sul-
fites, metabisulfites, gaseous sulfur dioxides, and monosodium glutamate are
also examples of molecules that could cause adverse pharmacological
reactions in susceptible people. On the other hand, the immunological
response encompasses all forms of immune-mediated reactions, including
those caused by the innate and the adaptive immune system (Fig. 11.1).
Nonetheless, immune-mediated reactions are responsible for significant
morbidity and health care costs and can even lead to severe life-threatening
reactions (Sicherer and Sampson, 2014; De Silva et al., 2014; Longo et al.,
2013). The symptoms of food allergies include gastrointestinal, respiratory,
cardiovascular, and cutaneous symptoms and in the worst case can lead to
anaphylactic shock. Symptoms that become visible soon, within 1 h or less of
Adverse reactions to food
Adaptive Immune
Type I
Type II
Type III
Type IV
Innate Immune Responses:
Complements, Innate
Immune cells, Toll-like
Immune mediated Non-immune mediated
(e.g., lactose intolerance)
(e.g., vasoactive amines,
capsaicin, ethanol, methyl
FIGURE 11.1 Classification of immune-response adverse reactions to food.
268 Ultrasound: Advances in Food Processing and Preservation
exposure, are termed immediate-type reactions; those occurring between 1 and
6 h are termed accelerated reactions, and a delayed reaction may occur even
some days after ingestion of the food.
11.1.1 Types of Food Allergy
Food allergy is classified into four basic types, type I, type II, type III, and type
IV (Coombs and Gell, 1975). The most common and prevalent type of
immune-mediated adverse reaction to food protein is type 1 reactions, which
are characterized by the creation of immunoglobulin E (IgE) antibodies
following sensitization of basophils or mast cells, which is the main process
involved in triggering allergic immune response. In general, these key events
are called sensitization and effecter phases (Fig. 11.2). Sensitization entails
antigen-presenting cells; T cells; Th2 cytokines such as interleukin (IL)-4,
IL-13, and IL-5; IgE production; and cross-linking of allergens with B-cell
FIGURE 11.2 Sensitization and effector phases involved in the development of IgE-mediated
food allergy. Ig, immunoglobulin; IL, interleukin; MHC, major histocompatibility complex.
Removal of Allergens in Some Food Products Using Ultrasound Chapter j11 269
receptors. Sensitization takes place when antigen-presenting cells (i.e.,
dendritic and B cells) find allergenic segments or epitopes in the protein
fraction of food or food ingredients. After that, allergen antigens are trans-
ferred to MHC class II molecules and antigen interactions with T cells may
take place. This arrangement triggers allergen-specific T cells, which subse-
quently generate Th2 cytokines, and encourages the creation of IgE antibodies
by allergen-specific B cells. The IgE antibodies may attach to the IgE receptor
FcεRI on mast cell and basophil membranes, thereby creating sensitized cells
(He et al., 2013).
On the other hand, proteins that undergo complete digestion do not have
the potential to cause sensitization and may encourage tolerance (Vila et al.,
2001; Barone et al., 2000). However, indigestible proteins can lead to the
production of IgE and sensitization (Untersmayr and Jensen-Jarolim, 2006).
The movement of proteins all the way through the intestinal epithelium may
take place via either the transcellular route or the paracellular route (Reitsma
et al., 2014). The effector phase starts after the cross-linking of the same
allergen with two adjacent IgE molecules on sensitized basophils and mast
cells. Afterward, the triggered cells release proinflammatory mediators or
cytokines, which subsequently lead to allergic reactions (He et al., 2013).
IgE-associated food allergies affect 1%e3% of adults and 3%e8% of
children in developed countries. The IgE antibodies lead to instant allergic
reactions (within 2 h) after eating the food, and classic symptoms such as
swelling, itchy rash, and in some cases diarrhea and vomiting could occur. The
severity of the symptoms can vary among patients and in some situations could
cause a life-threatening health condition, such as difficulty in breathing and
collapse (anaphylaxis). The detection of food allergenespecific IgE in body
fluids and serum, as well as the assessment of IgE-mediated cellular and
in vivo responses, is used to identify patients with IgE-associated food allergy.
Eggs, milk, nuts, peanuts, wheat, fish, sesame, fruits, and vegetables are the
main causes of IgE-associated food allergy. Patients acquire tolerance to a few
foods among these, i.e., eggs, milk, and wheat, whereas allergies to tree nuts,
peanuts, and fish mostly endure for a lifetime.
The immunoglobulins produced by the body in response to an antigen must
bind initially with the antigen to induce an immune response. The binding sites
of the allergens are called epitopes. The epitopes can be part of a continuous
amino acid chain, which are called linear epitopes, or be a portion of the three-
dimensional folding of a protein, called conformational epitopes. The
disruption of epitopes is often required to alter the reactivity of binding sites of
allergens. Linear epitopes can be altered by fragmentation or genetic modifi-
cation of the amino acid sequence, whereas the conformational epitopes can be
obliterated by altering the structure of the allergen via denaturation, cross-
linking, aggregation, or chemical modification. The aforementioned methods
are used to inhibit allergic reactions, as the IgE antibodies may no longer be
able to recognize the allergen.
270 Ultrasound: Advances in Food Processing and Preservation
Similarly, food antigenespecific IgG is considered responsible for initi-
ating adverse reactions via type II or type III hypersensitivity. Type II is a
cytotoxic reaction between a cell- or tissue-bound antigen and an IgG or IgM
antibody. The clinical cases in which this arises include immune cytopenias
such as immune thrombocytopenia and autoimmune hemolytic anemia. In
contrast, type III is an immune-complex reaction between IgG antibody and
circulating antigen, and takes place in the walls of blood vessels, kidneys,
joints, and skin, exhibiting as serum sickness or in a few cases extrinsic
allergic alveolitis, although no concrete experimental proof is available to
support food allergies relevant to these reactions in patients. Therefore, several
researchers robustly discourage the testing for food antigenespecific IgG for
diagnosing food allergy (Bock, 2010; Stapel et al., 2008).
On the other hand, type IV hypersensitivity entails food antigenespecific
T-cell responses that can affect the gut mucosa and subsequently result in
disorders such as celiac disease. Such reactions are mostly gastrointestinal
(constipation. diarrhea, vomiting) and/or skin problems (atopic eczema). The
T-cell immune response is likely to be a delayed reaction, in which symptoms
are first visible in 4e28 h after ingesting the food. Celiac disease is charac-
terized by an allergic reaction against the components of wheat gluten,
comprising alkali- or acid-soluble glutenins and alcohol-soluble gliadins, in
conjunction with an autoimmune fraction. Type IV hypersensitivity reactions
could also occur because of food protein-induced enterocolitis causing
inflammation of the small and large intestine by directly activating the innate
immune system. Certain milk oligosaccharides and wheat amylase trypsin
inhibitors can induce inflammation of the intestines through activation of the
Toll-like receptor.
11.1.2 Prevalence of Food Allergy
The diagnosis of food allergy should be done by a food challenge test (the gold
standard), which is conducted as a double-blind placebo-controlled food
challenge test, except for cases in which severe food allergic reaction can be
recognized clearly. However, this practice is not followed nowadays, as it is
time-consuming and laborious. Alternatively, the food allergy prevalence
among the population can be estimated on the basis of interviews/question-
naires (self-reported food allergy) and can also be extended to the skin prick
test or allergen-specific IgE serology tests. The exact incidence of food
allergies has not been fully known, as discrepancies are found in studies in
which food allergies were self-reported versus those diagnosed by various
assays (e.g., skin test, provocation, or serologic tests).
A metaanalysis was carried out to evaluate the prevalence of food allergy in
Europe that included 30 articles published in the period from January 2000 to
September 30, 2012 (Nwaru et al., 2014). The prevalence of perceived food
allergy to any food was observed to be 5.0% in adults and 6.8% in children.
Removal of Allergens in Some Food Products Using Ultrasound Chapter j11 271
The overall prevalence of challenge-proven food allergy was 0.89% in adults
and 0.99% in children. With regard to sensitization, its prevalence was 2.7%
and 10.1% on the basis of skin prick or allergen-specific IgE tests, respectively.
The prevalence of food allergy among the US population is more than 2% but
less than 10% (Chafen et al., 2010). A 2013 research study conducted by the
National Health and Nutrition Examination Survey reported that the preva-
lence of self-reported food allergy in the United States was 9.7% in adults and
6.5% in children. In this study, the main allergens reported were milk, shell-
fish, and peanuts (McGowan and Keet, 2013). In Asia, the prevalence of
challenge-proven food and self-reported food allergies ranged from 1.1% to
3.8% and from 4.8% to 16.7%, respectively. In the Asian population, fish
seems to be the most reported allergen in comparison with other geographic
locations, which has been attributed to the large consumption of seafood in this
region. In Latin America, fruits and vegetables, such as beans, onions, oranges,
tomatoes, and lettuce, and meats and seafood were the most reported allergens
(Hu et al., 2010; Ho et al., 2012; Chen et al., 2011; Lao-araya and Trakulti-
vakorn, 2012; Wu et al., 2012; Lee et al., 2013).
The severity and prevalence of food allergies seem to be greater than ever.
The severity, frequency, and type of allergic symptoms in patients are influ-
enced by various factors such as genetics; dietary exposures; environmental,
behavioral, and cultural factors; and study designs or methodologies. The
hygiene hypothesis states that the reduction in family size and enhancements
in personal hygiene have led to the increased prevalence of IgE-mediated
allergies in people. Conversely, a diet of organic foods containing lactoba-
cilli and restrictive use of vaccines, antipyretics, and antibiotics (anthro-
posophical lifestyle) have a contributing role in minimizing the incidence of
allergies. The exclusion of the culprit food is the best remedy for both food
intolerance and allergy, although absolute exclusion of the food from the diet
is hard in modern days as allergenic foods are used as ingredients in a variety
of food products.
11.1.3 Detection of Food Allergens
Food allergen detection has been attaining significant attention from 2000 to
till date from both regulatory agencies and food industries. Food allergen
diagnosis is based on history, dietary analysis, challenge tests, skin tests, and
measuring specific IgE in the blood serum. The various methods employed for
assessing food allergenicity to qualify or quantify allergens are imperative in
establishing the efficiency of various processing techniques for altering the
reactivity of food allergens. Most food allergies are IgE based, and allergen
reactivity is frequently depicted by its potential to bind IgE antibodies
(Hengel Arjon, 2007).
The most common method used for detecting allergenicity of an antigen
includes in vitro, in vivo, and ex vivo tests. These tests are used to detect the
272 Ultrasound: Advances in Food Processing and Preservation
presence of food-specific IgE (sensitization). In vitro tests have many bene-
ficial aspects as they are cheap, rapid, and harmless when human subjects are
employed. On the other hand, in vivo assays provide more accurate results in
comparison with in vitro assays. But, it can be costly and time-consuming to
utilize human or animal subjects and the assays may pose threats to human
subjects (Besler, 2001).
Ultrasound technology is an emerging technology that is used extensively for
food processing and preservation. It is used successfully to deactivate
enzymes, aid extraction, homogenize emulsions, and accelerate dehydration,
ripening, and aging processes (Villamiel and Jong, 2000; Dolatowski et al.,
2007). However, the application of ultrasound in the reduction of food aller-
genicity is yet in its infancy. High-intensity ultrasound is operated by me-
chanical waves within a frequency range of 20e100 kHz (Feng et al., 2011).
The high energy causes physical and chemical modifications by promoting
formation of sonication bubbles in foods and leads to intermittent compression
and rarefaction until collapse at critical bubble sizes. The increased temper-
ature and pressure (up to 5000 K and 1000 atm, respectively) in the vicinity of
the collapsed cavities is the basis for altering the conformation of allergens and
their reactivity. Moreover, regions of high-velocity gradients and high shear
stress can create microstreams that stimulate chemical and mechanical effects,
resulting in the alteration of the native protein structure into a molten globule
state, formation of new intra-/intermolecular interactions, and even degrada-
tion (Soria and Villamiel, 2010; Lee et al., 2009).
The structures of allergenic food proteins are modified differently by
unfolding, aggregation, cross-linking, and sometimes oxidation and glyco-
sylation by different processing methods. Conformational changes through
disruption of the linear or conformational epitopes in the proteins by pro-
cessing methods can directly influence the allergenicity of food products. The
linear epitopes are affected by acidic or enzymatic hydrolysis, whereas the
conformational epitopes can be exposed or hidden by unfolding or aggregation
of allergenic proteins (Rahaman et al., 2015). Allergenicity and antigenic
integrity are sometimes used by many investigators without proper clarifica-
tion. The integrity of epitopes is recognized by IgG or IgE antibodies, whereas
allergenicity is the ability of food proteins to induce allergenic sensitization
(Verhoeckx et al., 2015). Thermal and nonthermal processing will modify the
allergenic proteins and influence the ability of antibodies to bind the modified
proteins; especially the IgE antibodies find it difficult to elicit an allergic
reaction or stimulate the production of an IgE-mediated food allergy. Modi-
fication of proteins by ultrasound is primarily attributed to the cavitation
phenomenon. The cavitation effects generated by bubble collapse may be
Removal of Allergens in Some Food Products Using Ultrasound Chapter j11 273
responsible for modifying proteins structurally and altering their functionality
(Mawson et al., 2011). Briefly, acoustic waves produced by ultrasound travel
through a medium resulting in a series of compression and rarefaction events.
Attractive forces between molecules in a liquid phase exceed during rarefac-
tion, at high power levels, and form bubbles owing to cavitation. Interference
of each bubble with its neighbor causes a collapse, and the release of energy
increases temperature and pressure in the medium. The cavitation collapse in
aqueous media also generates shear forces that can produce mechanical and
chemical effects. With low intensities (or high frequencies), acoustic stream-
ing is the main mechanism (Leighton, 2007). Acoustic streaming is the motion
and mixing within the fluid without formation of bubbles (Alzamora et al.,
2011). Higher intensities (low frequencies) induce acoustic cavitation (Povey
and Mason, 1998) due to the generation, growth, and collapse of large bubbles,
which cause the liberation of higher energies. In addition, the extreme agita-
tion created by microstreaming could disrupt Van der Waals interactions and
hydrogen bonds in polypeptides, causing protein denaturation (Tian et al.,
2004). Limited studies have been reported on the influence of ultrasound on
food allergens.
11.2.1 Soy
Amponsah and Nayak (2016) investigated the effects of ultrasound-assisted
extraction (UAE) on the recovery and detection of allergenic proteins from
various soy matrices (e.g., soy flour, soy protein isolate, and soy milk). The
investigators also used several buffers [phosphate-buffered saline (PBS),
Laemmli buffer, and urea] to determine the recovery of allergenic soy proteins
after the UAE. The recovery of total proteins from soy flour and soy protein
isolate was higher at 23C than at 4C using UAE, and urea provided
maximum recovery of proteins compared to Laemmli and PBS at both tem-
peratures (Amponsah and Nayak, 2016). However, recovery of total proteins
from soy milk was higher using UAE with Laemmli buffer. The same in-
vestigators reported that protein solubility was increased by the application of
ultrasonic energy and caused protein to undergo physical disruption and
chemical modification (Fig. 11.3). Tan et al. (2011) also reported that recov-
ery/yield and structural/functional properties of the protein were influenced by
extraction process parameters such as pH, salt concentration, and ionic
strength of the medium of extraction. Additionally, Jambrak et al. (2009)
reported an increase in the solubility of soy proteins after ultrasound treatment
(20, 40, and 500 kHz) for 15 min in soy protein isolates (SPI) and soy protein
concentrate (SPC). Karki et al. (2010) also investigated the use of high-power
ultrasound prior to soy protein extraction to simultaneously enhance protein
and sugar release in the extract and concluded that sonication at high ampli-
tude for 120 s gave the highest increase in protein yield of 46% compared with
nonsonicated samples (control). In another study, Albillos et al. (2011)
274 Ultrasound: Advances in Food Processing and Preservation
sonicated protein extracts from roasted almonds in a temperature-controlled
water bath and reported that ultrasonic treatment improved protein extrac-
tion from almonds roasted at 260C and 400C. Choudhary et al. (2013)
reported a reduction of 24% in soy protein allergenicity by the application of
high-intensity ultrasound treatment by a 37-kHz ultrasonic processor for
10 min. Ultrasound treatment at 37 kHz resulted in a reduction of allergenicity
of soy proteins by disrupting the secondary structure of the proteins
(Choudhary et al., 2013).
FIGURE 11.3 Protein profiles of extracts obtained from conventional extraction (lanes A/A0eC/C0),
MAE at 60Ce70C(lanes D/D0eF/F0), and UAE at 23C(lanes G/G0eI/I0) with PBS, Laemmli,
and urea buffers, respectively. Lanes AeI, reduced conditions; A0eI0, nonreduced conditions;
J, molecular weight marker. (A) Soy flour; (B) soy protein isolate (SPI), and (C) soy milk. Bands
around 75 and 50 kDa correspond to b-conglycinin and bands around 37 kDa correspond to
glycinin (33 kDa) and the 34-kDa P34 allergenic soy protein. Adapted from Amponsah, A., Nayak,
B., 2016. Effects of microwave and ultrasound assisted extraction on the recovery of soy proteins for
soy allergen detection. Journal of Food Science 81 (11), T2876eT2885.
Removal of Allergens in Some Food Products Using Ultrasound Chapter j11 275
11.2.2 Milk
The application of ultrasound (at 20 kHz and 125 mm amplitude for 60 min)
had a great positive impact on dairy processing as it maintained the nutritional
value of milk and did not increase the allergenic potential of b-lactoglobulin
(Stanic-Vucinic et al., 2012). The investigators observed an increase in the
polymerization of b-lactoglobulin with treatment time. Sixty minutes of
treatment time provided a significant number of high-mass polymers due to
bonds formed because of disulfide exchange, resulting in the formation of new
intermolecular bonds. The use of ultrasound also formed localized high tem-
perature that induced aggregation of up to 50% of the protein at 60 min.
However, ultrasound application under controlled temperature conditions
resulted in only dimer formation, unlike uncontrolled conditions. Most
importantly, circular dichroism measurements confirmed that ultrasound
generated a structure with a higher percentage of a-helical forms and random
coils, whereas untreated samples had exhibited predominantly b-strand
behavior. The calculation of secondary structure fractions confirmed that
different times of ultrasound exposure resulted in different compositions of
secondary structure after refolding. However, the conformational changes due
to ultrasound affected IgE binding of b-lactoglobulin very slightly as observed
by immunoblot and immunoprint. In a separate study, Chandrapala et al.
(2011) observed a 5%e9% decrease in b-strands, but an increase of 10% in the
a-helical form of whey protein concentrate when treated with ultrasound for
60 min.
Modification of proteins structurally and their allergenicity also depend on
the intensity of tandem use of ultrasonic treatment (e.g., ultrasonic treatment
combined with heat). It was reported that denaturation of a-lactalbumin and
b-lactoglobulin in milk was higher when treated with high-intensity ultrasound
in combination with heat (Villamiel and Jong, 2000). This type of synergism
between heat and ultrasound was attributed the reduction in viscosity of the
heated milk, resulting in a better penetration of the ultrasound into the liquid.
However, the high-intensity ultrasound application at 20 kHz and 500 W
power was not efficient at minimizing the allergenicity of milk proteins
(Choudhary et al., 2013).
11.2.3 Peanuts
IgE-binding affinity of Ara h1 and Ara h2, two major peanut allergens, was
moderately reduced (w10%) by ultrasound treatments (at 50 Hz for 5 h)
compared to ultrasonication and protease digestion (trypsin/a-chymotrypsin),
which significantly decreased IgE reactivity and increased the solubility of
proteins (Li et al., 2013). The investigators reported that ultrasonic treatment
loosened the structure of peanut protein, cleaved peptide bonds by shear force,
and also enhanced the efficiency of enzymatic hydrolysis treatment.
276 Ultrasound: Advances in Food Processing and Preservation
11.2.4 Shrimp and Crustaceans
Shellfish are responsible for inducing allergic reactions in most parts of the
world. Generally, shellfish allergy is severe, lifelong, and potentially fatal
¨thrich and Ballmer-Weber, 2001). Shellfish proteins are more heat stable,
which can lead to shellfish hypersensitivity. The main heat-stable shrimp
allergen is a 34- to 38-kDa protein called tropomyosin, also named Pen a 1 or
Sa-II, and is the main cause of food-related complications, i.e., hypersensi-
tivity (Reese et al., 1999;Nagpal et al., 1989). Tropomyosin has an important
role in muscle contraction, regulation of cellular structure, and motility.
Myosin light chain (20-kDa) and arginine kinase (40-kDa) are the other two
allergens that have been recognized, yet most shrimp allergenicity is attributed
to tropomyosin (Shiomi et al., 2008; Ayuso et al., 2008). Shrimp allergy,
in general, is a type I hypersensitivity. The first encounter with a shrimp
allergen will sensitize the individual to future exposures (Leungi and Chu,
1998). The most common symptoms of shrimp allergies include hives, itching,
swelling of the tongue and lips, gastrointestinal symptoms, pulmonary
symptoms, and anaphylactic shock (Jeong et al., 2006). The best way to
prevent shrimp-induced allergies is complete avoidance. However, complete
avoidance is usually difficult because of the addition of food allergens as
ingredients in common foods or unintentional cross-contamination. Therefore,
it is important to develop methods to inactivate or remove food allergens from
food products.
In general, processing is considered a potentially efficient way to decrease
the allergenicity of shrimp. Relevant literature on the influence of ultrasound
on shrimp and crustacean allergens is very scanty. Li et al. (2006) performed a
study on the effects of high-intensity ultrasound on isolated shrimp protein
and shrimp extract. High-intensity ultrasound treatment led to a substantial
reduction in the allergenicity by reducing IgE binding to both crude
shrimp protein extracts and isolated tropomyosin. These findings were also
corroborated by immunoblot and ELISA analysis. The isolated proteins and
shrimp extract were treated with a frequency of 30 Hz for 130e180 min.
The IgE binding capacity of isolated shrimp protein was decreased by
81.3%e88.5% after ELISA, whereas only a 68.9% reduction in the IgE
binding potential was found in shrimp extracts. Furthermore, during allergen
isolate treatment, new protein fractions with low molecular weights were
formed as time elapsed. Therefore, disintegration of shrimp protein may
take place during high-intensity ultrasound treatment (Li et al., 2006). Yang
et al. (2006) investigated whether the combined application of papain and
ultrasound aids in tenderization of shrimp by minimizing the shear force.
Li et al. (2011) examined the influence of power ultrasound on the allerge-
nicity and textural attributes of raw and boiled shrimp. Ultrasound treatment
significantly reduced the allergenicity of the boiled shrimp compared to raw
Removal of Allergens in Some Food Products Using Ultrasound Chapter j11 277
Crustaceans are also considered a main cause of allergic reactions
because of their high consumption, especially in coastal areas. Crustaceans
are favored by many people because of their nutritive value and delicacy
(Wild and Lehrer, 2005). The major allergen found in crabs is tropomyosin,
which is a myofibrillar protein having two identical subunits of 35e38 kDa
molecular mass and an isoelectric point of 4.5. Tropomyosin has high
stability compared to other proteins and can tolerate grinding, heat, and other
processing methods (Motoyama et al., 2006, 2007). Lee and Park (2004)
reported that common whelk allergens were digested by SGF, but remained
unchanged after thermal processing. This indicates that the key crustacean
allergen is heat stable. Yu et al. (2011) evaluated three different processing
methods (boiling, high-pressure steaming, and combined ultrasound and
boiling) for the degradation of tropomyosin and reduction of its IgE-binding
capacity in crabs, so that it could be easily decomposed during gastrointes-
tinal digestion. SDSePAGE showed very little impact on the digestive
stability of tropomyosin extracted from processed crab in the case of boiling
treatment. On the other hand, high-pressure steaming and combined
ultrasound and boiling enhanced the digestion of tropomyosin. Similarly,
inhibition ELISA and Western blotting also indicated that the reactivity of
IgE/IgG binding of tropomyosin was partially reduced after treatment with
high-pressure steaming and combined ultrasound and boiling. These findings
suggest that ultrasound treatment could be used to reduce the reactivity of
IgG/IgE binding of tropomyosin, promote tropomyosin degradation in
simulated gastrointestinal digestion, and reduce the occurrence of allergic
The application of ultrasound is a new interventional method targeted toward
reducing the allergenicity of certain food products. Unlike other thermal
treatments such as baking, boiling, roasting, and pasteurization and
nonthermal treatments such as high-pressure processing, very few allergenic
food products have been processed using ultrasound. Therefore, limited
information is available on the application of ultrasound for processing food
products to reduce food allergenicity. As a common practice, ultrasound is
used as a pretreatment method in most cases, prior to food processing oper-
ations. It is also used to extract phytochemicals or other compounds of interest
from food materials. A few investigators have used ultrasound to modify
allergenic proteins structurally and then detect them using a number of in vitro
and in vivo methods. Most of the investigators observed that ultrasound helped
in breaking up the structural integrity of the food products as well as protein
structures depending on the intensity of application. Recovery of total protein
as in the case of soy products may increase after ultrasound treatment, but the
allergenicity is not necessarily reduced in the processed soy products.
278 Ultrasound: Advances in Food Processing and Preservation
However, in some other cases, ultrasound reduced the allergenicity of food
products, such as roasted peanut extracts. It is recommended that more
allergenic foods in solid as well as liquid form should be tested for modifi-
cation of proteins and assessed for any reduction in allergenicity to help the
industry and human beings.
BOX 11.1 In Vitro Tests for Food Allergen Detection
The discovery of IgE allowed various immune assays to enable direct and objective
measurements of the specificity and extent of the immune response. The
in vitro assays utilize enzyme-linked immunosorbent assay (ELISA), sodium dodecyl
sulfateepolyacrylamide gel electrophoresis (SDSePAGE), radio-allergosorbent tests
(RAST), enzyme-allergosorbent tests (EAST), ImmunoCAP assays (Phadia, Uppsala,
Sweden), and immunoblotting to determine the presence and reactivity of allergens.
RAST and EAST are similar and the enzyme activity evaluated correlates to the
antibodies affixed to enzymes (Sampson, 1999). Among all the in vitro techniques,
immunoassays are used most frequently. Particularly, SDSePAGE, ELISA, and immu-
noblots are corroborated by federal agencies to detect major food allergens such as
milk, peanut, hazelnut, egg white, soybean, and wheat proteins (Merget et al., 1993).
Histamine Release Tests
In the histamine release assay basophils sensitized with an allergen are challenged,
which can result in cross-linking of surface-bound specific IgE antibodies, thereby
leading to release of histamine from the cells. Histamine can be determined immu-
nochemically by the Immunotech radioimmunoassay, fluorimetrically by coupling to
a fluorophore (o-phthaldialdehyde), or by using an automated fluorimetrichistamine
assay. The histamine release method uses glass-fiber-coated plates for histamine
separation from other components of the assay. The histamine concentration is
measured and a doseeresponse curve can be prepared and analyzed by comparing
with an appropriate standard. The liberated histamine content can also be articulated
as a percentage of the total level of histamines of unchallenged cells. On the other
hand, a passive sensitization technique can be applied instead of using blood from
sensitized patients. The basophils of a nonsensitized individual are used and the
receptor-bound IgE that is already present is taken from the donor basophils’ surface,
and subsequently the cells are passively sensitized with human serum havingrelevant
and specific IgE antibodies (Skov et al., 1997;Poulsen, 2001).
Basophils make up less than 0.5% of the leukocytes in the blood and are
extremely difficult to purify (Gibbs, 2008). Moreover, fresh blood cells from
nonallergic donors or allergic donors are required in case of passive sensitization
for each experiment, and after collection, the blood samples must be processed
immediately, which may present logistical hindrances. Another disadvantage is
that about 10% of basophil donors are nonresponsive, which leads to less reliable
results in terms of detecting individual responsiveness (Palmer et al., 2005). A
stable cell line that could be passively sensitized with serum IgE from allergic
patients could be used to overcome these problems.
Simulated Gastric Fluid (SGF) Assay
The resistance offered by some proteins, particularly transgenic proteins, to pro-
teolytic digestion in SGF can induce allergic reactions. It is assumed that
Removal of Allergens in Some Food Products Using Ultrasound Chapter j11 279
Box 11.1 In Vitro Tests for Food Allergen Detectiondcont’d
nutritionally desirable proteins, when consumed, should be digested rapidly, so
that they can exert fewer adverse health effects. Under acidic conditions (pH 1.2 to
2.0), the stability offered by transgenic proteins to pepsin digestion is usually
presumed to be an effective test to assess the allergenic risk associated with
transgenic proteins (Astwood et al., 1996). However, the relationship between the
digestive stability of a protein in SGF and allergenicity is not always absolute, as
there are reports indicating no correlation between allergenicity and digestive
stability (Fu et al., 2002).
SGF is designed in such a way as to mimic the mammalian gastrointestinal
system. Several factors, such as mechanical breakdown of food tissues, buffering
effect of food ingredients, range of stomach pH, gastric lipase in physiological
amounts, addition of surfactants (phospholipids), peristalsis, etc., can play a role.
Many researchers have reported their findings in support of the utilization of the
SGF assay. The pepsin activity recommended by many researchers ranges from
5000 to 20,000 units/mg of the test protein. The ratio of pepsin to protein (3:1),
pepsin concentration (3.2 mg/mL), pH (1.2 and 2.0), and different times of
incubation at 37C provide similar results (Flow Chart 11.1). Sometimes, the
nature of the substrate affects the pepsin activity, with a fairly broad range of pH
between 1.2 and 3.5. However, a small shift in these factors can hamper the
pepsin digestion of several allergens.
Although the SGF assay does not exactly mimic in vivo digestion, it still presents
results similar to those of in vivo digestion by the mammalian system (Verma and
Singh, 2013). The lack of consideration of the allergen prevalence in food, food
matrix interactions, or food processing effects is the main reason behind the vague
predictive potential of the SGF assay. The interaction of food matrix might play a
major role, as food components may sequester some of the proteins away from the
pepsin and acid in the gastric fluid. The purified kiwi allergen Act c 2 was digested
instantly in SGF, but digestion was stopped by fruit pectin both in vivo and in vitro.
Similarly, the association of protein with starch granules in transgenic corn
protected it against digestion in SGF. Therefore, the evaluation of purified protein
allergenicity in the SGF assay may not always present the desired results.
Simulated Intestinal Fluid (SIF) Assay
It is believed that allergenic proteins are not generally digested completely in the
proteolytic system of the human gastrointestinal system and can be absorbed
through the mucosa of the intestine. Thus, a novel protein is subjected to digestion
in SIF and SGF. Pancreatin is used to prepare SIF for the development of the SIF
assay. For the preparation of the assay, 1 g/100 mL pancreatin is dissolved in
0.05 M KH
at a pH of 7.5. The SIF aliquot is placed in a microcentrifuge tube
and incubated for 10 min at 37C in a water bath. The test protein at a level of
5 mg/mL should be put into the microcentrifuge tubes to initiate the reaction.
Laemmli buffer should be added to each tube at different time intervals (i.e., 0, 0.5,
5, 15, 60, and 120 min). SDSePAGE analysis in conjunction with densitometry
is carried out to compare the degradation at the different time intervals (Flow
Chart 11.2).
The assay conditions can influence the relative protein digestibility in SIF. The
relative amounts of test protein and enzyme employed in an SIF assay influence
280 Ultrasound: Advances in Food Processing and Preservation
Box 11.1 In Vitro Tests for Food Allergen Detectiondcont’d
the outcome for a particular protein. Changes in pH and the ratio of enzyme to
protein affects protein digestibility. Various guidelines have been considered for
SIF or SGF digestibility as a predictive tool for estimating the allergenic capability
of proteins. However, it is necessary to develop standardized assay conditions that
can be accepted globally. Some of the major allergens, like cow’s milk, lacto-
peroxidase, conalbumin, soybean, and peanut, are stable in SIF for 120 min.
Similarly, papain and bromelain exhibit higher stability in SIF. Ovomucoid and
lysozyme, well-known allergens in egg, showed higher stability (up to 60 and
120 min, respectively) in SIF (Fu et al., 2002). Hence, the in vitro digestion assay
can be employed to establish the allergenicity of a novel protein. Occasionally,
small portions of degraded protein in the gastrointestinal tract are enough to
stimulate allergenic reactions.
The radio-allergosorbent tests employs antibodies that are bound to radioisotopes
to measure serum IgE. The allergen is adsorbed to a solid phase and a serum
sample is used to incubate it. The IgE antibodies in the serum are specific to the
selected allergen and are cross-linked with the immobilized allergen. A secondary
antibody, which is conjugated to a radioisotope, reacts with the IgE antibodies, and
subsequently radioactivity is assessed. Furthermore, the findings are quantified via
a standard curve (Falagiani et al., 1994).
The enzyme-allergosorbent tests employs the same principle as the RAST,
although the antibodies used in EAST detection are conjugated to enzymes (i.e.,
alkaline phosphatase) and as a result enzyme activity is evaluated (Merget et al.,
1993). RAST and EAST are advantageous, as multiple samples can be tested at the
same time and there is no need for the patient’s presence during the test (Poulsen,
2001). Yet, qualitative discrepancies during the solid-phase and sample prepara-
tion among analysts could impose quantification issues. Moreover, IgG antibodies
may intrude during the analysis, as they vie with IgE antibodies for analogous
allergenic determinants (Falagiani et al., 1994).
The concept of the ImmunoCAP test is similar to that of EAST and RAST. However,
it shows higher sensitivity and improved results and is designed in such a way as to
minimize the hurdles seen in EAST and RAST (Johansson, 2004). The best part of
an ImmunoCAP test is the three-dimensional solid phase that reduces nonspecific
binding by means of non-IgE-binding antibodies. ImmunoCAP tests can be
conducted in less than 20 min and reagent preparation is designed in such a way
as to minimize conformational epitope losses (Hamilton and Williams, 2010;
Diaz-Vazquez et al., 2009).
Sodium dodecyl sulfateepolyacrylamide gel electrophoresis (SDSePAGE) is used
to evaluate the existence or absence of allergens or to measure changes in the
electrophoretic pattern of a protein (Shapiro et al., 1967). Fluctuations in the
molecular weight, like dimerization, can also be observed in SDSePAGE. Proteins
or allergens often get aggregated owing to treatment conditions and may enlarge in
Removal of Allergens in Some Food Products Using Ultrasound Chapter j11 281
Box 11.1 In Vitro Tests for Food Allergen Detectiondcont’d
size and so get stuck in the pores of the polyacrylamide gel or washed away. In
contrast, if treatment conditions lead to fragmentation of proteins, then the frag-
ments that are too small for the gel resolution will pass through the gel swiftly and
eventually result in buffer loss. In addition, the bands of proteins with stimulated
intramolecular cross-linking may have a smudged appearance in polyacrylamide
gels. The intramolecular cross-linking can hamper the protein from being wholly
linearized during the denaturing conditions. This analytical method is advanta-
geous, as it is cheap and results can be acquired in a short period of time.
However, SDSePAGE could not measure the IgE-binding reactivity of the allergens
(Taheri-Kafrani et al., 2009).
The analysis of allergens by immunoblotting includes Western blot and dot-blot
analysis. Western blot analysis involves the separation of proteins by molecular
weight via PAGE. Afterward, the proteins are transferred to a membrane of
nitrocellulose or polyvinylidene fluoride (PVDF) and subjected to antibody
assessment assays (Towbin et al., 1979). Western blotting has many benefits, as
protein bands can be analyzed individually for the determination of variations in a
specific allergen. This method of detection is relatively easy, fast, and inexpensive.
A shortcoming of Western blotting is that proteins are usually tested at their
primary or linear level and conformational epitopes might not be represented
(Aalberse, 2000). Additionally, the new binding epitopes, which were once
invisible within the protein, may be exposed. It is important to point out that as
molecular weight is used to separate the proteins, so those that are too small or too
large for the gel or blotting membrane resolution may not be precisely evaluated.
In the case of dot-blot analysis, the samples are directly adsorbed onto a
membrane such as nitrocellulose and evaluated by using antibody detection
(Singh and Knox, 1985). In this analysis, conformational epitopes are not affected,
because no denaturing conditions are involved, although membrane adsorption
may lead to unfolding of proteins. The immunogenicity of the whole sample is
analyzed in this method, as proteins are not separated by molecular weight.
However, single proteins may also be determined, in case the sample contains
separated proteins. Likewise, the blotting membrane resolution is the limiting
factor for extremely low or high molecular weight proteins.
ELISA includes indirect ELISA and competitive inhibition ELISA (Ci-ELISA), which
is used to determine the IgE-binding capacity of the allergens. The method is used
to detect either single protein or entire sample reactivity, based on the antibodies
used. In this method proteins are adsorbed to the surface of the ELISA plate wells
and detected via suitable antibodies (Wachholz et al., 2005; Kemeny and Chantler,
1988). Sometimes, hydrophobic interactions could lead to the adherence of pro-
tein to the plate and can hinder or mask the conformational epitopes. Moreover,
strong hydrophobic interactions between protein and the polystyrene material may
cause denaturation and unfolding of the protein. Therefore, it is essential to choose
appropriate materials for performing ELISA (Butler et al., 1997).
282 Ultrasound: Advances in Food Processing and Preservation
BOX 11.2 In Vivo Tests for Detection of Food Allergens
In vivo assays include the skin prick test (SPT) and oral food challenge (OFC) to
detect food allergens.
Skin Prick Test
Skin Prick tests can be used to determine specific IgE sensitization. The skin is
marked for testing with a panel of appropriate allergens for the patient, selected on
the basis of the clinical history and knowledge of the allergens commonly found in
the locality. Positive and negative comparator tests using histamine and saline also
should be performed to prove that the skin is capable of demonstrating a positive
reaction and to prevent the interpretation of false-positive results occurring as a
result of dermatographism. It is necessary for the patient not to take any medi-
cations such as antihistamines prior to testing. The SPT is performed by injecting a
minute amount of allergen under the skin using a device, i.e., a lancet. This allows
the test protein to act together with IgE antibodies on the surface of skin mast cells.
Mast cells degranulate in the presence of food-specific IgE antibodies and release
mediators that result in localized wheal and flare. After 10e15 min the results are
interpreted by reference to the control tests. Saline and histamine are employed as
negative and positive controls, respectively. The development of a small red circle
or wheal greater than 3 mm on the skin indicates the sensitiveness of the patient
toward the allergen. However, wheal size can vary depending on allergen and
subject (Sampson, 1999; Merget et al., 1993). SPT cannot quantify the allergens
and is employed only to find the presence or absence of an allergy. This method is
not a perfect technique to determine allergy, however, as it can cause false-positive
wheals in patients with atopic dermatitis (Byrne et al., 2010). The subject must not
be given any drugs like antihistamines, which can influence the findings of the test.
Moreover, SPT is based on the quality of the allergen extract employed for testing,
so subjective results could vary among evaluators (Poulsen, 2001). The advantages
of SPT include good sensitivity, quick results, and the potential to test any antigen.
The disadvantages include possible danger of anaphylaxis, discomfort inherent in
the procedure, and the contraindicating influence of medications such as
decongestants, antihistamines, bronchodilators, beta blockers, and theophylline
(Sampson and Metcalfe, 1992).
Oral Food Challenge
Oral food challenge (OFC) test is considered to be the “gold standard” and pro-
vides more accurate results with regard to food allergy. In this study, it is necessary
for the subject to consume test foods. However, this practice could be hazardous
for the patient, because the patient is directly subjected to allergens. It can induce
severe reactions in the case of acute IgE-mediated reactions, enterocolitis syn-
drome, and severe atopic dermatitis. Especially those who are vulnerable to
anaphylaxis must not participate in this type of study (Byrne et al., 2010; Merget
et al., 1993). The safety of OFC studies was tested by Perry et al. (2004), who found
severe allergic reaction in 28% of the participants. The participants consuming
10 g of lyophilized protein without any visible symptoms are considered not
allergic, yet need to be validated further (Sampson, 1999). Such tests are often not
Removal of Allergens in Some Food Products Using Ultrasound Chapter j11 283
Box 11.2 In Vivo Tests for Detection of Food Allergensdcont’d
performed because of their high cost, complexity, and time requirements. None-
theless, animal models could be used to avoid such problems, but still these
models are not always comparable to the human body.
Animal Models
Animal models are used to develop a standardized allergen exposure protocol in
an animal rather than humans, as ethical concerns are related around performing
food allergen challenge studies in humans. Owing to the challenges in performing
experiments with humans in controlled studies, animal models are studied to
predict whether a novel protein has the potential to induce the production of IgE in
the animal. Additionally, their relevance to the human condition must also be
considered. Different allergen exposure models have been attempted in several
species, with each species having advantages over others. Rodents present many
advantages, as they are easily available, easy to handle, and genetically stable. The
rodent models can be evaluated for their response to a range of exposure sites.
Several strains can be evaluated for the relevance to the sensitivity of humans to a
given allergen (Madsen and Pilegaard, 2003). Additionally, rodents are helpful in
understanding allergen mechanisms owing to the availability of an enormous array
of reagents for the researchers. Mostly IgE binding is assessed to specify sensiti-
zation in animals; however, biomarkers of sensitization can also include cell
receptors and cytokines for rodent models. Similarly, other species, such as swine
and dog models, proffer closer approximations of clinical symptoms of humans.
The swine model is particularly useful for illustrating peanut allergen sensitivity
with greater correlations to human peanut allergy (Helm et al., 2002).
An authenticated allergen model that kindles the process of sensitization in
humans is not easy to perform because of the lack of well-defined allergic re-
sponses in animals that would remain consistent among allergens and could be
considered parallel with the human allergic response. From a mechanistic
perspective on optimizing novel allergy vaccines, the models need to reflect
especially the aspects related to human disease but not the natural process of
sensitization, while a very high correlation to the sensitization process occurring in
humans is needed for a predictive model. Furthermore, allergen preparation,
adjuvant selection, and the duration between sensitization and allergen challenge
are not easy to determine for all but only a small number of well-characterized
proteins. Moreover, the consistency across the study sites of an animal model’s
response to a well-studied allergen (i.e., ovalbumin) remains obscure. Studies on
animal models have led to improvement in animal models, such as including
appropriate positive and negative study controls, allergen preparation standardi-
zation, animal selection, and the proper genetic strain (Helm et al., 2003; Knippels
et al., 2004). The commonly used animal models permit the exploration of
mechanisms at the molecular and cellular levels to study therapeutic strategies
(Adel-Patient et al., 2005). Several model allergens over a wide range of sensi-
tivities can be accommodated by an animal model, yet in animals, the develop-
ment of a standardized protocol for food allergens still remains a challenge for
their use as a predictive tool.
284 Ultrasound: Advances in Food Processing and Preservation
Box 11.2 In Vivo Tests for Detection of Food Allergensdcont’d
Mediator Release Assay
The mediator release assay imitates the type I allergic reaction mechanism
utilizing rat basophilic leukemia (RBL) cells, which express the human FcεR1
receptor in a recombinant manner (Vogel et al., 2005; Kaul et al., 2007). These
cells help in the binding of human IgE antibodies and possess all the functional
properties of basophils and mast cells. b-Hexosaminidase, which is found in the
granules and released along with histamine, has been selected as a surrogate
marker for histamine release. This enzyme hydrolyzes the added substrate,
thereby leading to coloration that can be analyzed via a spectrophotometer.
The mediator release assay allows the measurement of allergens in different
samples and the biological activity or potency of the allergens and the investi-
gation of cross-reactivities among the allergens. The potency of allergens can be
indicated by determining the requirement of doses for initiating efficient cell
degranulation and values corresponding to the allergen dose that induces up to
50% of the maximum release (EC
values). Generally, sera having a higher
percentage of allergen-specific versus total IgE antibodies can be used in this test.
In the case of sera obtained from peanut-allergic patients, the most effective sera
must have at least 15 kU/L of peanut-specific IgE and 50 kU/L of total IgE, and
have more than 10% peanut-specific IgE (Dibbern et al., 2003). In addition, the
concentration of FcεRI on the transfected RBL cell lines may be a limiting factor,
for example, RBL SX-38 cells have about 100,000 receptors/cell versus 500,000
receptors/cell on the basophils from allergic individuals (Wiegand et al., 1996;
MacGlashan, 2007). The low percentage of serum-specific IgE in conjunction
with low expression level of FcεRI on the RBL cells could lead to the loading of
most of the IgE receptors with nonspecific IgE antibodies. Many serum factors and
also the extent of the allergic subject’s clinical response severity have been
regarded as imperative factors to induce mediator release with these cell lines.
T-Cell Polarization Assay
T-cell polarization assays are employed to examine the reactivity mediated by
T cells toward allergens and allergenic proteins. Abnormal T-cell responses to
allergens predominated by extended Th2 cells lead to allergic diseases (Akdis
et al., 2004). Allergen-specific CD4
Th2 cells exude large quantities of IL-4 and
IL-13, which stimulate the creation of allergen-specific IgE antibodies, which
results in immediate allergic symptoms (Christensen et al., 2008; Akdis, 2009).
Allergen-specific Th2 cells can also take part directly in clinical late-phase
reactions in target organs such as skin and lung, in addition to this indirect
participation in immediate reactions (Bohle et al., 2006).
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SGF assay
SGF (0.32% pepsin, pH 1.2) at 37oC.
Test proteins
Incubation of test proteins in SGF from 30 sec-1
hr time periods
Stopping of pepsinolysis using NaHCO3 or NaOH
Observation of protein profile on SDS-PAGE
FLOW CHART 11.1 Simulated gastric fluid (SGF) assay protocol.
SIF assay
SIF (1g/100 mL of pancrean in
0.05 M KH2PO4, pH 7.5) at 37°C
Test proteins
Incubaon of test proteins in SIF for different
incubaon me periods
Stopping of reacons at different me points
Observaon of protein profile on SDS-PAGE
FLOW CHART 11.2 Simulated intestinal fluid (SIF) assay protocol.
286 Ultrasound: Advances in Food Processing and Preservation
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... In addition, reports showed that US affects food allergens (Wang et al. 2020;Nayak et al. 2017) and helps in the development of functional food ingredients (Ozuna et al. 2015). This chapter investigates the existing reports on the applications of US in food science and technology as well its influence on food bioactives. ...
... Food allergy is a situation where the immune system response is abnormal or excessive due to the consumption of specific foods and additives (Nayak et al. 2017). According to the National Institute of Allergy and Infectious Diseases (NIAID), food allergy is an adversative health effect that arises reproducibly on contact to proteins, or antigens, which are constituents of food mediums, thereby producing a specific immune response (Nayak et al. 2017). ...
... Food allergy is a situation where the immune system response is abnormal or excessive due to the consumption of specific foods and additives (Nayak et al. 2017). According to the National Institute of Allergy and Infectious Diseases (NIAID), food allergy is an adversative health effect that arises reproducibly on contact to proteins, or antigens, which are constituents of food mediums, thereby producing a specific immune response (Nayak et al. 2017). Reports from the literature show that approximately 170 foods or their constituents are allergenic (Nayak et al. 2017). ...
... In the last years, ultrasound has been studied as potential alternative non-thermal process to decrease food allergenicity (Nayak, Li, Ahmed, & Lin, 2017). Ultrasound can promote changes in both conformational and physical features of proteins, affecting emulsification and solubility properties which can alter its allergenicity (Zhu et al., 2018a). ...
... Ultrasound can promote changes in both conformational and physical features of proteins, affecting emulsification and solubility properties which can alter its allergenicity (Zhu et al., 2018a). Nevertheless, different results have been found since the effect of ultrasound differs with distinct food proteins (Nayak et al., 2017). Stefanović et al. (2014) obtained hydrolysates of egg white with lower molecular weight and potentially with decreased allergenicity, after combining ultrasound pre-hydrolysis treatment with proteases to improve functional properties of the proteins. ...
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Egg is a versatile ingredient and ubiquitous food. Nevertheless, egg proteins are a common cause of allergy mainly in childhood. Until now, egg eviction has been the best way to prevent this disorder, however processed food can contribute to mitigate allergies and to guarantee life quality of allergic individuals. This review focuses on discussing and highlighting recent advances in processes to reduce egg allergenicity as well as new approaches to egg allergy management. In recent times, different methods have been developed to reduce egg allergies, by hiding the epitopes or changing the native or conformational structure of the proteins. Despite processing food has not yet been a solution to completely remove the allergenic potential of egg proteins, innovative strategies, such as addition of phenolic compounds, have been developed with promising results.
... Processing techniques such as heat, enzymatic and acidic treatments, as well as other novel approaches such as high-pressure processing (HPP), irradiation, high-intensity ultrasound, pulsed ultraviolet (PUV) light and/or the combination of these technologies have been employed, being capable of altering the structure of food proteins in different ways. The possible structural modifications include unfolding, aggregation, crosslinking between the ingredients and chemical modifications, such as oxidation and glycation (Harder, Arthur, and Harder 2017;Lepski and Brockmeyer 2013;Nayak et al. 2017;Rahaman, Vasiljevic, and Ramchandran 2015;Yuan et al. 2017;Zhang, Deng, and Zhao 2017), which may influence allergenicity. Conformational epitopes can be exposed or hidden by unfolding or aggregation of proteins, respectively (Rahaman, Vasiljevic, and Ramchandran 2015), whereas sequential epitopes can be affected by acidic or enzymatic hydrolysis (Kasera et al. 2015) and Maillard reactions (Toda et al. 2014). ...
... Clearly, these processing-related structural and chemical changes will have the potential to influence the allergenicity of proteins as reflected by their tendency to bind to specific IgE. Several attempts have been made to understand how different methods of processing affect the immunoreactivity of crustacean allergens (Ahmed et al. 2018;Liu et al. 2017a;Lv et al. 2017a;Lv et al. 2017b;Nayak et al. 2017;Vanga, Singh, and Raghavan 2017;Vanga and Raghavan 2016;Verhoeckx et al. 2015;Zhang, Deng, and Zhao 2017). The influence of processing technologies on the immunoreactivity of crustacean allergens, as well as their advantages and limitations are summarized in Table 6. ...
Crustacean allergy has become a growing food safety concern at a global scale. In the past decades, various food processing approaches have been employed to develop food products with reduced allergenic potential. Thermal treatment can dramatically influence the allergenicity of crustaceans by either reducing or enhancing their allergenic potential. Maillard reaction, enzymatic and acid treatments have shown to be promising in mitigating crustacean allergenicity. Recently, novel processing technologies, namely high-pressure processing, high-intensity ultrasound, irradiation, pulsed ultraviolet light and hurdle technology have attracted special attention from the researchers and the food industry professionals owing to their benefits over the conventional methods. In this context, this review paper provides an updated overview of the current knowledge on how different food processing methods induce structural changes of crustacean allergens and, subsequently, influence their allergenic potential. Data on prevalence and clinical relevance of crustacean allergy are presented, as well as, the molecular characterization of crustacean allergens and the main analytical methods for their detection in processed foods.
... Most common symptoms of food allergies are gastrointestinal, respiratory, cardiovascular, and cutaneous symptoms and eventually an anaphylactic shock. Studies have reported eight major food groups, namely eggs, milk, fish, shellfish, tree nuts, peanuts, soybeans, and wheat that account for approximately 90% of all the allergic reactions (Nayak et al., 2017). ...
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Implementation of ultrasonic for the extraction of bioactive compounds and retention of physico-chemical properties is an important technology. This technology applies physical and chemical phenomena for the extraction of compounds. Ultrasonic assisted extraction causes less damaging effect on quality properties of food as compared to the conventional extraction technique. The present review article focuses on the degradation of various bioactive compounds as a result of ultra-sonication which include vitamins, carotenoids and phenolic compounds. This review article also discusses the influence of ultrasonic extraction on the physico-chemical properties of extracted food products. In addition, the paper explores the effect of ultrasonication on food allergenicity through changes in solubility, hydrophobicity, molecular weight as well as conformational changes of the allergens, a direct result of increase in temperature and pressure during cavitation process.
... Regarding proteins, US could induce changes in native form: conformational changes, damage to secondary structure, re-structuration of disulfide bond or generation of other intra/inter molecular interactions (Chizoba Ekezie et al. 2018). Studies on proteins in FV after US have focused mostly on its extraction yield and allergenicity (Nayak 2017). Only one study carried on by Li et al. (2017) evaluated the effect of US (40 kHz, 350 W) on total soluble proteins of straw mushrooms. ...
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Ultrasound (US) processing has emerged as a novel food preservation technology. This strategy has proved antimicrobial effects due to cavitation, which is the formation, growth, and collapse of bubbles that generate a localized mechanical and chemical energy. This technology can be applied by water so introducing it in the washing step to obtain safe fresh or fresh-cut products could be promising. The current review provides an overview of the current knowledge and recent findings on the use of US, alone or in combination with other mild physical technologies or chemical agents, to reduce microbial loads, and to better retain their quality attributes including color and texture, as well as the content of bioactive compounds such as antioxidant, phenolic compounds, or vitamins of minimally processed fruits and vegetables. As the effects of US depends on several factors related with treatment parameters, target microorganism, and matrix characteristics, further research efforts should be directed on optimizing US processes in accordance with their further application.
... Unfortunately, conventional techniques (e.g., chemical and biological methods) cannot effectively address the concerns as mentioned above due to the resistance of these chemical compounds and undesirable changes in physicochemical properties of food products (Gan et al. 2003;Nayak et al. 2017). Moreover, the removing pesticide and allergens from food and agricultural products is a relatively new concept and has attracted the attention of many researchers around the world (Heo et al. 2014;Misra et al. 2014b;Zhang et al. 2017;Zhou et al. 2018). ...
Food contaminants are challenging the food industry due to the inefficiency of conventional decontamination techniques. Cold plasma as an emerging technique for the degradation of food contaminants attracted notable attention. The current study overviews the plasma-induced degradation of food contaminants, discusses the mechanisms involved, points its benefits and drawbacks out, highlights the research needed in this area, and explores future trends. According to the literature, cold plasma efficiently degraded many common pesticides (e.g. parathion, paraoxon, omethoate, dichlorvos, malathion, azoxystrobin, cyprodinil, fludioxonil, cypermethrin, and chlorpyrifos) and food allergens (e.g. tropomyosin, b-conglycinin, glycinin, trypsin inhibitor, and Kunitztype trypsin inhibitor). These degradations occurred primarily due to the presence of reactive oxygen species (ROS) and reactive nitrogen species (RNS) in the plasma that attack the chemical bonds of food contaminants. The type of pesticide degrades are highly dependent on the concentrations of plasma-generated ROS and RNS. Research showed that several parameters, such as plasma generation device, plasma exposure time, plasma power, and the carrier gas composition, influence the type and concentration of reactive species (e.g. ROS and RNS) and the overall efficiency of cold plasma degradation for a specific pesticide or allergen. • Highlights • Cold plasma can be used for degradation of many types of pesticides and allergens. • Plasma-generated reactive species and UV can interact with pesticides and allergens. • The scaled up removal of pesticides and allergens by plasma can be challenging.
... There was significantly decreased shrimp allergenicity (IgE-binding capacity) by 74.7% after 180min ultrasonic processing compared to untreated samples. A study of soybean protein demonstrated that high-intensity ultrasound treatment at 37 kHz for 10 min effectively disrupted the secondary structure of soy proteins resulting in a decrease of 24% in soy protein allergenicity (Nayak, Li, Ahmed, & Lin, 2017). In peanuts, the IgE-binding activity of peanut protein extracts was decreased by 10% after a high-intensity ultrasound processing at 50 Hz for 1 hr compared to untreated peanut samples (Li, Yu, Ahmedna, & Goktepe, 2013). ...
Kiwifruit is rich in bioactive components including dietary fibers, carbohydrates, natural sugars, vitamins, minerals, omega‐3 fatty acids, and antioxidants. These components are beneficial to boost the human immune system and prevent cancer and heart diseases. However, kiwifruit is emerging as one of the most common elicitors of food allergies worldwide. Kiwifruit allergy results from an abnormal immune response to kiwifruit proteins and occur after consuming this fruit. Symptoms range from the oral allergy syndrome (OAS) to the life‐threatening anaphylaxis. Thirteen different allergens have been identified in green kiwifruit and, among these allergens, Act d 1, Act d 2, Act d 8, Act d 11, and Act d 12 are defined as the “major allergens.” Act d 1 and Act d 2 are ripening‐related allergens and are found in abundance in fully ripe kiwifruit. Structures of several kiwifruit allergens may be altered under high temperatures or strong acidic conditions. This review discusses the pathogenesis, clinical features, and diagnosis of kiwifruit allergy and evaluates food processing methods including thermal, ultrasound, and chemical processing which may be used to reduce the allergenicity of kiwifruit. Management and medical treatments for kiwifruit allergy are also summarized.
... 6 Similarly, several research studies have been focused on altering the structure of food proteins by various approaches in order to improve their functionality and shelf-life stability and reduce allergenicity. [7][8][9][10][11][12][13] However, few methods can be widely applied in actual processing. ...
β-lactoglobulin (β-LG) is recognized as the major milk allergen. In this study, the effects of transglutaminase (TGase) and glucosamine (GlcN)-catalyzed glycosylation and glycation on the conformational structure and allergenicity of β-lactoglobulin (β-LG) were investigated. The formations of cross-linked peptides were demonstrated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and GlcN-conjugated modification was identified using matrix-assisted laser desorption ionization-time of flight-mass spectrometry (MALDI-TOF-MS). Structural analysis revealed that glycosylation and glycation of β-LG induced unfolding of the primary protein structure followed by loss of secondary structure. As revealed by the circular dichroism (CD) spectroscopies, glycosylated β-LG exhibited highest increase in the β-sheets from 32.6 % to 40.4 % (25 °C) and 44.2 % (37 °C), and the percentage of α-helices decreased from 17.7 % to 14.4 % (25 °C) and 12.3 % (37 °C), respectively. The tertiary and quaternary structures of β-LG also changed significantly during glycosylation and glycation, along with reduced free amino groups and variation in surface hydrophobicity. Immunoblotting and indirect enzyme-linked immuno sorbent assay (ELISA) analyses demonstrated that the lowest IgG- and IgE-binding capacities of β-LG were obtained following glycosylation at 37 °C, which were 52.7 % and 56.3 % lower than that of the native protein in a respective way. The reduction in the antigenicity and potential allergenicity of glycosylated β-LG were more pronounced compared to TGase treated- and glycated β-LG, which correlated well with the structural changes. These results suggest that TGase-catalyzed glycosylation has more potential compared to glycation for mitigating the allergenic potential of milk products.
Tropomyosin (TM) is a major allergen in crustaceans, which often causes allergy and is fatal to some consumers. Currently, the most effective treatment is to avoid ingesting TM, although most adverse events occur in accidental ingestion. In this review, the molecular characterization, epitopes, cross-reactivity, and pathogenesis of TM are introduced and elucidated. Modification of TM by traditional processing methods such as heat treatment and enzymatic hydrolysis, and innovative processing technologies including high-pressure treatment, cold plasma (CP), ultrasound, pulsed electric field (PEF), pulsed ultraviolet, microwave and irradiation are discussed in detail. Particularly, enzymolysis, PEF, and CP technologies show great potential for modifying TM and more studies are needed to verify their effectiveness for the seafood industry. Possible mechanisms and the advantages/disadvantages of these technologies for the mitigation of TM allergenicity are also highlighted. Further work should be conducted to investigate the allergenicity caused by protein segments such as epitopes, examine the interaction sites between the allergen and the processing techniques and reveal the reduction mechanism of allergenicity.
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Allergenicity to crustaceans is a global food safety concern in spite of acceptance of delicacies like shrimps, crabs and lobsters. They are also the leading causative of food induced anaphylaxis. Major percentage of allergic reactions are triggered by allergic protein, tropomyosin and the others such as arginine kinase, sarcoplasmic calcium-binding protein, myosin light chain, troponin C, hemocyanin are also involved. Prevalence of crustacean allergenicty, allergens reported in different crusta�ceans and their cross reactivities are discussed in this reviews. Besides the effect of various thermal and non-thermal processing techniques in managing the crustacean allergen is also discussed. In com�parison to the enhanced allergenicity effects re�ported by thermal techniques, novel non-thermal techniques like high pressure processing, gamma irradiation, enzymic hydrolysis, high intensity ultra�sound, pulsed ultraviolet light etc have promising effects on allergenicity reduction by structural modifications in the proteins. The advantages of combined treatments in hurdle technology ap�proaches can make effective mitigation of crustacean allergenicity and can be suitably optimized for hypoallergic food development.
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The aim of this study was to examine the effect of power ultrasound on the allergenicity and texture properties of shrimp (Penaeus vannamei). For this purpose, raw and boiled shrimps were treated with power ultrasound (30 kHz, 800 W) at 0°C and 50°C for 0, 2, 8, 10, and 30 minutes. The results showed that the ultrasound treatment had a greater effect on the allergenicity of the boiled shrimps than of the raw ones, while with hardness it was vice versa. The allergenicity of the boiled shrimps treated at 0°C (treatment 3) and 50°C (treatment 4) decreased by nearly 50% and 40%, respectively, with 10 min of the treatment duration. As for the raw shrimps, with the treatment at 0°C (treatment 1) their allergenicity increased in the first 10 min and then decreased, while at 50°C (treatment 2), a slight reduction of 8% in allergenicity occurred. After treating with ultrasound for 30 min the hardness in treatment 1 increased to a peak-1.5-fold higher than the control, compared with 27% increase in treatment 2 and 15% increase in treatments 3 and 4. The results suggest that allergenicity can be reduced by power ultrasound with no change in the texture.
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Structural modifications influence the immune-reactivity of food proteins. We investigated effects of pH (3, 5, 7), temperature (80, 100, 120°C), and shear (100, 500, and 1,000 s(-1)) on conformational changes (monitored by surface hydrophobicity, total thiol content, Fourier transform infrared spectroscopy, and gel electrophoresis) and their relation to antigenicity (determined by indirect ELISA) of β-lactoglobulin (β-LG). Overall, heating at low pH (3) caused unfolding of proteins and fragmentation due to partial acid hydrolysis and thereby exposed β-strands that contributed to appearance of some hidden epitopes, resulting in higher antigenicity. Heating at pH 5 and 7 decreased the allergenic response due to covalently bonded molecular polymerization and aggregation, which destroyed or masked some epitopes. Shear alone had no effect on the antigenic response of β-LG but may have an effect in combination with pH or temperature. Overall, heating β-LG solutions to 120°C at pH 5 with shearing (100-1,000 s(-1)) resulted in minimal antigenicity. Structural modifications of β-LG via denaturation or disulfide- or thiol-mediated interactions can either enhance or decrease its antigenicity. Copyright © 2015 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.
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Food processing can have many beneficial effects. However, processing may also alter the allergenic properties of food proteins. A wide variety of processing methods is available and their use depends largely on the food to be processed. In this review the impact of processing (heat and non-heat treatment) on the allergenic potential of proteins, and on the antigenic (IgG-binding) and allergenic (IgE-binding) properties of proteins has been considered. A variety of allergenic foods (peanuts, tree nuts, cows' milk, hens' eggs, soy, wheat and mustard) have been reviewed. The overall conclusion drawn is that processing does not completely abolish the allergenic potential of allergens. Currently, only fermentation and hydrolysis may have potential to reduce allergenicity to such an extent that symptoms will not be elicited, while other methods might be promising but need more data. Literature on the effect of processing on allergenic potential and the ability to induce sensitisation is scarce. This is an important issue since processing may impact on the ability of proteins to cause the acquisition of allergic sensitisation, and the subject should be a focus of future research. Also, there remains a need to developed robust and integrated methods for the risk assessment of food allergenicity. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.
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In view of the imminent deficiency of protein sources for human consumption in the near future, new protein sources need to be identified. However, safety issues such as the risk of allergenicity are often a bottleneck, due to the absence of predictive, validated and accepted methods for risk assessment. The current strategy to assess the allergenic potential of proteins focuses mainly on homology, stability and cross-reactivity, although other factors such as intestinal transport might be of added value too. In this review, we present an overview of the knowledge of protein transport across the intestinal wall and the methods currently being used to measure this. A literature study reveals that protein transport in sensitised persons occurs para-cellularly with the involvement of mast cells, and trans-cellularly via enterocytes, while in non-sensitised persons micro-fold cells and enterocytes are considered most important. However, there is a lack of comparable systematic studies on transport of allergenic proteins. Knowledge of the multiple protein transport pathways and which model system can be useful to study these processes may be of added value in the risk assessment of food allergenicity.
The extraction of soy proteins for soy allergen detections is conventionally achieved with PBS buffer for at least 2 h at room temperature or 4 °C. This method has been reported to be inefficient due to time consumption and inadequate protein extraction resulting in false negative allergen detection and mislabeling of foods containing allergenic proteins. This study investigated the application of microwave (MAE) and ultrasound assisted extraction (UAE) techniques to extract and improve recovery of allergens from various soy matrices. Soy proteins were extracted from raw soy flour, soy protein isolate (SPI) and soy milk using MAE at 60, 70, and 100 °C for 5 and 10 min and UAE at 4 and 23 °C for extraction times of 1, 5, and 10 min with PBS, Laemmli and urea buffers. Extracts were analyzed for total proteins, protein profile, and antibody-based detection (ELISA) of soy proteins. Conventional extraction with each of the buffers was used as controls. Overall, proteins recovered from MAE and UAE samples were higher than recoveries from the controls in all soy matrices. Under all extraction conditions, Laemmli and urea buffer recovered more proteins than PBS. Electrophoresis analysis of protein showed bands around 75, 50, and 33 kDa indicating the presence of soy allergenic proteins β-conglycinin and glycinin, in all samples. Using sandwich ELISA, control and UAE extracts resulted in high soy protein detection but this reduced in MAE extracts.
Food allergy is receiving increased attention in recent years. Because there is currently no known cure for food allergy, avoiding the offending food is the best defense for sensitive individuals. Type I food allergy is mediated by food proteins, and thus, theoretically, any food protein is a potential allergen. Variability of an individual's immune system further complicates attempts to understand allergen-antibody interaction. In this article, we briefly review food allergy occurrence, prevalence, mechanisms, and detection. Efforts aimed at reducingeliminating allergens through food processing are discussed. Future research needs are addressed.
Animal Biotechnology introduces applications of animal biotechnology and implications for human health and welfare. It begins with an introduction to animal cell cultures and genome sequencing analysis and provides readers with a review of available cell and molecular tools. Topics here include the use of transgenic animal models, tissue engineering, nanobiotechnology, and proteomics. The book then delivers in-depth examples of applications in human health and prospects for the future, including cytogenetics and molecular genetics, xenografts, and treatment of HIV and cancers. All this is complemented by a discussion of the ethical and safety considerations in the field. Animal biotechnology is a broad field encompassing the polarities of fundamental and applied research, including molecular modeling, gene manipulation, development of diagnostics and vaccines, and manipulation of tissue. Given the tools that are currently available and the translational potential for these studies, animal biotechnology has become one of the most essential subjects for those studying life sciences.
Allergic reactions to food can have serious consequences. This systematic review summarizes evidence about the immediate management of reactions and longer-term approaches to minimize adverse impacts. Seven bibliographic databases were searched from their inception to September 30, 2012, for systematic reviews, randomized controlled trials, quasi-randomized controlled trials, controlled clinical trials, controlled before-and-after and interrupted time series studies. Experts were consulted for additional studies. There was no language or geographic restrictions. Two reviewers critically appraised the studies using the appropriate tools. Data were not suitable for meta-analysis due to heterogeneity so were narratively synthesized. Eighty-four studies were included, but two-thirds were at high risk of potential bias. There was little evidence about acute management for non-life-threatening reactions. H1-antihistamines may be of benefit, but this evidence was in part derived from studies on those with cross-reactive birch pollen allergy. Regarding long-term management, avoiding the allergenic food or substituting an alternative was commonly recommended, but apart from for infants with cow's milk allergy, there was little high-quality research on this management approach. To reduce symptoms in children with cow's milk allergy, there was evidence to recommend alternatives such as extensively hydrolyzed formula. Supplements such as probiotics have not proved helpful, but allergen-specific immunotherapy may be disease modifying and therefore warrants further exploration. Food allergy can be debilitating and affects a significant number of people. However, the evidence base about acute and longer-term management is weak and needs to be strengthened as a matter of priority.
This review focuses on advances and updates in the epidemiology, pathogenesis, diagnosis, and treatment of food allergy over the past 3 years since our last comprehensive review. On the basis of numerous studies, food allergy likely affects nearly 5% of adults and 8% of children, with growing evidence of an increase in prevalence. Potentially rectifiable risk factors include vitamin D insufficiency, unhealthful dietary fat, obesity, increased hygiene, and the timing of exposure to foods, but genetics and other lifestyle issues play a role as well. Interesting clinical insights into pathogenesis include discoveries regarding gene-environment interactions and an increasing understanding of the role of nonoral sensitizing exposures causing food allergy, such as delayed allergic reactions to carbohydrate moieties in mammalian meats caused by sensitization from homologous substances transferred during tick bites. Component-resolved diagnosis is being rapidly incorporated into clinical use, and sophisticated diagnostic tests that indicate severity and prognosis are on the horizon. Current management relies heavily on avoidance and emergency preparedness, and recent studies, guidelines, and resources provide insight into improving the safety and well-being of patients and their families. Incorporation of extensively heated (heat-denatured) forms of milk and egg into the diets of children who tolerate these foods, rather than strict avoidance, represents a significant shift in clinical approach. Recommendations about the prevention of food allergy and atopic disease through diet have changed radically, with rescinding of many recommendations about extensive and prolonged allergen avoidance. Numerous therapies have reached clinical trials, with some showing promise to dramatically alter treatment. Ongoing studies will elucidate improved prevention, diagnosis, and treatment.