Proteins, How They Interact With the Immune System and How They Are Affected by Food Processing

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Allergic reactions can seem very unpredictable, which is unsettling. Although you don’t need a degree in biochemistry to known that you have experienced one, having a basic idea of how proteins are put together and how they are affected by certain types of processing can help to explain why a certain food will bother you one time, but not another, and why different people are not affected by the same things.

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How a protein is made

Proteins are complex biological molecules that are essential for life. There are thousands of them in each cell of every living creature, all carrying out a wide range of crucial functions like providing energy, growing and repairing tissue, making hormones and neurotransmitters and boosting the immune system.

Amino acids; the building blocks of proteins

Proteins are made up of amino acids. There are over 500 amino acids in nature, but only 20 are considered ‘common’ or ‘standard’. These particular amino acids are encoded directly by the genetic code of living organisms who then use them to synthesise proteins.

As far as humans are concerned, these standard amino acids can be divided into 2 main categories; 11 non-essential amino acids (that our bodies can manufacture) and 9 essential amino acids (that we must get from our foods).

Although these 20 amino acids are widely known, there are another two genetically encoded, ‘rare’, ‘non-standard’ amino acids that life uses to build proteins.

Selenocysteine—aka ‘the 21^st amino acid’—is also used by most life forms, including humans who need it to make selenoproteins which are needed for multiple processes including antioxidant defence, thyroid hormone metabolism and immune function. Unlike the 20 common amino acids, selenocysteine is not directly coded in the universal genetic code but is inserted into proteins using a specialised mechanism called translational recoding.

Pyrrolysine (Pyl, O)—aka ‘the 22nd amino acid’—is made in a similar manner and can be found in certain methanogenic archaea and some bacteria..

Other amino acids are created by making changes to a protein’s side chains after it is built (post-translational modifications). One of the most important protein post-translational modifications is glycosylation—the attachment of sugar molecules—which happens in over half of all proteins and is primarily used to improve a protein’s structural stability and assist in folding

Amino acids share a common core structure, which consists of a central carbon atom—aka the alpha (α) carbon—bonded to an amino group (NH2), a carboxyl group (COOH) and a hydrogen atom. There is also another atom or group of atoms bonded to the alpha carbon, known as the R group, the variable group or the side-chain.

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The side chain is the alterable parts of an amino acid that distinguishes it from other amino acids and helps to determine its shape and function.

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An amino acid’s common core structure allows it to link to others in a long chain known as a polypeptide backbone. When amino acids link together, they attach by making peptide bonds between the amino group of one amino acid and the carboxyl group of another. This produces one strong peptide link between the two amino acids and one water molecule.

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Amino acids form bonds between each other that result in four distinct levels of structure. These levels are essential for determining the final 3D shape and function of the protein.

Protein primary structure

Amino acids are the building blocks of polypeptides which are, in turn, the fundamental building blocks for proteins. Polypeptides typically contain 50 or more amino acids. The particular sequence of amino acids in a polypeptide chain is the protein’s primary structure.

An amino acid can be repeated many times within a single polypeptide chain. These repetitions can occur consecutively or periodically throughout the protein sequence. As each of the individual amino acids can theoretically occur at any position in the polypeptide chain, a chain made up of just 5 of the 20 common amino acids could have 3,200,200 (20 x 20 x 20 x 20 x 20) possible versions. A chain with 50 amino acids could therefore produce an enormous number of different chains; in fact, one molecule of any kind would require more atoms to build than exist in the universe. In practice, however, to ensure the survival of the cell that it’s in, a polypeptide chain has to be able to adopt a stable 3D conformation, and this is only possible with certain amino acid combinations.

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The sequence of amino acids is determined by the DNA of the gene that encodes that specific protein. Just changing the order of one amino acid can affect a protein’s structure and, therefore, its function. For example, people with sickle cell anaemia have inherited DNA that replaces 1 of the around 150 amino acids that make up 1 of 4 polypeptide chains in a haemoglobin molecule. This results in haemoglobin molecules that become sticky when they release oxygen. They end up end up sticking together and stacking into long, rigid, rod-like chains that warp the red blood cell that they are in, which then makes the blood cell incapable of passing through small blood vessels.

The bonds that make up the primary structure of a protein are very strong.

Protein secondary structure

The secondary structure of a protein involves local folding within the polypeptide thanks to hydrogen bonds that form between atoms in non-adjacent amine and carboxyl groups. The two most common shapes are the alpha-helix and the beta-pleated sheet.

Most proteins contain both alpha helices and beta pleated sheets, though some may contain just one or the other, or even neither.

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The bonds that make up the secondary structure of a protein tend to be of moderate strength.

Protein tertiary structure

The tertiary structure is the overall 3D shape of a polypeptide chain. It generally gets this shape from bonds that form between the side chains of the amino acids. The birch pollen protein, bet v 1, a major birch allergen, is an example of a protein with tertiary structure. Its structural similarity to certain food proteins—e.g. apple’s Mal d 1, celery’s Api g 1, soy’s Gly m 4, peanut’s Ara h 8 and hazelnut’s Cor a 1—is what causes cross-reactions in people with pollen food syndrome.

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The bonds that form tertiary structures tend to be weaker than those that form the primary and secondary structures, although there are lots of them and they can sometimes be stabilised by a strong type of bond (a disulfide bridge). As a rule of thumb, however, tertiary structures are more easily broken (denatured) by heat or acid than primary and secondary structures.

Protein quaternary structure

The final, quaternary structure of a protein is how its multiple polypeptide chains assemble together. Many proteins are only made up of a single polypeptide chain and are therefore limited to 3 levels of structure. Only proteins with multiple polypeptide chains (aka subunits) can have a quaternary structure. Examples of food proteins with quaternary structure include casein micelles in milk and glutenin in wheat.

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The quaternary structure is held together by the same type of (relatively weak) bonds that form the tertiary structure.

How the immune system recognises a protein

A person’s immune system recognises potentially troublesome molecules—antigens—using IgE antibodies.

IgE antibodies recognise allergens by binding to specific, limited regions on the allergen’s surface called epitopes.

The part of an antibody that recognises and binds to an antigen is called the paratope (or theantigen-binding site). It’s a small region located at the tip of the antibody’s variable region, so called because the amino acid sequence in this region of an antibody is very different to the same region of other antibodies, enabling each antibody to recognise and bind to a large number of different antigens.

Each paratope is unique and specifically recognises and binds to a particular epitope on an antigen, like a lock-and-key mechanism, where the paratope is the lock and the epitope its unique key (because it can unlock the cell’s defence mechanism). The precise fit between the paratope and epitope allows the immune system to selectively target specific antigens, thereby minimising unintended reactions against the body’s own proteins.

The vast majority of antibodies have two identical paratopes, but some can have two different paratopes, allowing the antibody to bind two different antigens simultaneously.

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There are 2 types of epitope; linear (aka sequential, continuous) and conformational (aka non-sequential, discontinuous). The main difference between them is the spatial relation between the amino acids that make them up.

Linear epitopes are continuous sequences of amino acids on a polypeptide chain—i.e. they involve the protein’s primary structure). They are typically 5–15 amino acids in length. Linear epitopes represent around 10% of all epitopes that IgE antibodies are designed to recognise.

Conformational epitopes are formed by amino acids that are far apart in the primary protein sequence but are brought close together because of the 3D folding of the protein (its tertiary structure). They are typically 15–22 amino acids in length—or rather, the antibody generally comes into contact with around 15 to 22 amino acids, the actual epitope is larger—although 5 to 8 amino acids generally contribute to most of the binding energy. The vast majority of epitopes—around 90%—are conformational.

People with allergies often have IgE antibodies that recognise both linear epitopes and conformational epitopes.

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A single allergen can contain multiple, different types of epitopes. The number (density) of epitopes on an allergen’s surface help to determine the efficiency of the IgE binding and the severity of the symptoms; the more epitopes there are, the more severe a reaction is likely to be.

In fact, an allergen’s surface can be almost entirely covered in epitopes. However, only a few IgE antibodies usually bind to a single molecule; the immune system operates on an ‘all-or-nothing’ activation threshold and it generally takes only a fraction of the total cell-bound IgE to be cross-linked to activate a mast cell or a basophil.

Because an allergic reaction requires at least two IgE antibodies to be cross-linked by a single allergen molecule:

• an allergen molecule needs to have at least two epitope sites that can be reached by IgE antibodies for it to be able to provoke a reaction
• the proximity of the epitopes helps to determine the severity of the symptoms; the closer the epitopes are to each other, the greater their ability to create dense clusters of cross-linked antibodies on a mast cell’s surface, therefore the stronger the mast cell’s degranulation and the more severe the allergic reaction

People who are sensitised to multiple allergens within one food (known as polysensitisation) may be more likely to have a persistent food allergy. Multiple allergens would provide ongoing stimulation for the immune system, encouraging it to produce IgE antibodies against that food, especially if the allergens are resistant to heat and digestion like, for example, peanut storage proteins. People will polysensitisation may also have to undergo immunotherapy treatment for longer before seeing a positive result.

The simplified steps of an allergic reaction

Allergic reactions happen when IgE antibodies recognise specific allergens and cause immune system cells—notably mast cells (in barrier tissues like the respiratory tract, intestinal tract and skin) and basophils (in blood)— to ‘degranulate’ and release their inflammatory mediators. One of these mediators is histamine, which is the one that causes the symptoms associated with allergic reactions.

It works like this:

1. During the sensitisation phase of an allergic reaction, the immune system encounters an allergen (typically a protein*) for the first time and identifies it as a threat
2. Immune system B cells produce IgE antibodies designed to recognise that specific allergen
3. These IgE antibodies travel through the body and attach themselves to the surface of mast cells and basophils via ‘high-affinity receptors’, sensitising the cells and effectively priming them for future reactions. This binding is incredibly strong, meaning that the antibodies often remain attached to the cell for its whole lifetime, effectively creating a lasting memory of allergen exposure
4. When the a person is exposed to the same allergen again, the IgE antibodies recognise the allergen and bind to it
5. For a reaction to happen, at least two IgE antibodies must connect to an allergen, a process known as cross-linking;
   1. When two or more adjacent IgE antibodies cross-link to an allergen, the allergen acts as a bridge between the high-affinity receptors attaching the antibodies to the immune system cell, bringing the receptors closer together on the cell’s surface and creating a ‘cluster’
   2. This clustering acts as the cell’s ‘on switch’, triggering intracellular signals and causing the cell to release its inflammatory mediators
6. The more IgE antibodies are able to cross-link, the faster and more intense the mast cell response

*Although the vast majority of the allergens—particularly food allergens—that we know about are proteins or glycoproteins (proteins with oligosaccharide (sugar) chains attached to the amino acid side-chains), some are carbohydrates, the best known among these being galactose-alpha-1,3-galactose—alpha gal—the allergen that causes reactions to red meat.

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As cross-linking is necessary for a reaction to occur, the more epitopes a person’s IgE antibodies recognise, the greater their chances of binding to an allergen and cross-linking, even at low doses. And the more antibodies are able to cross-link, the more mast cells will be triggered and the more inflammatory mediators, including histamine, will be released. Therefore:

Sensitisation to multiple epitopes is associated with a greater chance of having a symptomatic allergy, as well as a tendency to react to smaller amounts of allergen and to experience severe symptoms that involve multiple organs.

Why cooking food helps some people but makes things worse for others

Cooking makes things better for some people with food allergies by denaturing the food proteins that their immune systems react to. Denaturation describes the process during which proteins lose their original (aka ‘native’) three-dimensional structure due to external stress.

During denaturation, the weak bonds and interactions that maintain a protein’s shape are broken, affecting the protein’s secondary, tertiary and quaternary structures, but—generally—not its primary structure. As the bonds between atoms are destroyed, the protein unfolds and is no longer able to carry out its original function. More importantly, if you have allergies, denaturation destroys at least some of a protein’s epitopes.

The denaturation of food proteins is often irreversible—for example, when you cook an egg, the albumin protein in the egg white unfolds. These unfolded proteins interact, clump together (coagulate) and solidify; this is what you are seeing when the transparent egg white turns white.

Sometimes, however, denaturation can be reversed (a process known as renaturation)—for example, when you heat milk, its 3D-shaped (‘globular’) whey proteins are denatured. But when milk is allowed to cool to room temperature, the whey proteins slowly refold and return to their original structure, as long as the heat was not high enough to cause permanent coagulation. Likewise, food proteins that have been denatured with mild pressure can often regain their original shape.

Proteins can be denatured by various processes, including:

• Heating: heat provides kinetic energy that vibrates a protein’s molecules violently, breaking the weak bonds—such as hydrogen bonds—that maintains its 3D shape, causing it to unfold or unravel
• Acidification: acids contain a lot of free, positively charged hydrogen ions. These interact with protein in a couple of ways:
  • They interact with the amino acids’ negatively charged carboxylate groups (COO–), destroying the strong electrostatic forces of attraction between the oppositely charged ions holding the protein in its shape
  • They interfere with the weak hydrogen bonds that maintain the protein’s secondary and tertiary structures
• Hydrostatic pressure: pressure in the presence of water interacts with protein in several ways:
  • It forces water molecules into the protein’s cavities, where it disrupts internal hydrophobic interactions holding the protein together, causing it to unfold
  • It disrupts ionic bonds (i.e. it breaks the electrostatic interactions between charged particles)
  • It disrupts both intra- and intermolecular hydrogen bonds, typically leading to the destruction of alpha-helices and the formation of beta-pleated sheets and random coils

Conformational epitopes are often relatively easily destroyed by heating, using vinegar (an acid) and digestion (the human stomach environment is normally highly acidic). Commercial food processing often includes more extreme forms of processing (e.g. high temperatures and high pressure), which is even more likely to destroy conformational epitopes, as well as other, cutting edge and emerging techniques such as ultrasound, UV radiation and cold plasma, whose effects on allergens is still being investigated.

Linear epitopes—which correspond to the proteins’ primary structures—are typically not destroyed, which is why people whose IgE antibodies recognise linear epitopes are unlikely to be helped by cooking and digestion. Even the high temperatures and pressures used in commercial food processing are generally not violent enough to disrupt the strong bonds that form linear epitopes.

However, although denaturation can be helpful for people who have IgE antibodies that recognise existing epitopes, it can cause problems for other people allergic to that food.

This is because cooking can produce neotopes—i.e. new epitopes. Neotopes are epitopes that are created during the processing, modification or denaturation of a protein.

Proteins with a natural 3D structure contain hidden/masked epitopes —also known as cryptotopes (i.e. cryptic epitopes)—on the inside. When a protein is denatured and unfolds, the epitopes that were previously hidden within the structure are now exposed and can be recognised by IgE antibodies.

These newly exposed epitopes are often linear epitopes, as the unravelled protein displays its own linear, amino acid sequence. But they can also be conformational epitopes.

Neotopes allow IgE antibodies to bind to new areas of a protein that did not exist in the raw food, provoking allergic reactions that might otherwise not have occurred when the protein was in its natural state and potentially making the cooked food more likely to provoke a reaction in some people.

The revelation of neotopes during the denaturation of proteins helps to explain why some people can, for example, react to cooked peas but not to raw peas, or why some types of shellfish are more allergenic after being cooked.

Neotopes can also be formed when several proteins combine to form aggregates. This is what happens when milk is heated and then cools; when milk is heated, the whey proteins, which have a tertiary structure, unfold. As the milk cools, the unfolded whey proteins bind together (aggregate) or combine with the caseins, forming new, multi-subunit particles. These newly aggregated structures may include new epitopes that did not exist in the original milk.

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When a food protein is exposed to prolonged, high-temperature cooking, changes to its original structure can make it more allergenic for other reasons. This happens, for example, during the Maillard reaction—responsible for the delicious flavours produced when foods are browned during cooking.

The Maillard reaction is a complicated, barely-understood, multi-stage process during which the amino groups in proteins react with carbonyl groups of reducing sugars (which is a carbohydrate capable of donating electrons to another molecule, like glucose, fructose, lactose or maltose). This destroys the proteins’ original structures and forms new, complex products called advanced glycation end products (AGEs). Peanut-related research has shown that these AGEs may contain new binding sites for IgE antibodies, as well as being more resistant to both heat and digestion by stomach enzymes than the original proteins, thus greatly improving their chances of causing allergic reactions.

In fact, research has shown that, thanks to the Maillard reaction, roasted peanuts are more allergenic than boiled peanuts and are able to bind to IgE antibodies 90 times more strongly than raw peanuts.

The effects of the Maillard reaction are strongly dependent on the processing methods and the foods involved and are therefore variable and difficult to predict, sometimes producing a reduction in allergenicity or no change at all.

The fact is, different food proteins do not react to processing in the same way, and they also react differently in the presence of other food proteins.

Heating an egg, for example, is known to make it less likely to provoke reactions in a subset of people with egg allergy, but not in all the egg-allergic. This is because the heating affects the various egg proteins/allergens differently.

Ovomucoid and ovalbumin are widely considered to be the most important and dominant allergens in egg white. Ovomucoid (which just happens to be known for its high number of IgE-binding linear epitopes) is very stable to both heating and digestion. Ovalbumin, on the other hand, is vulnerable to heating (and also happens to be known for its high number of IgE-binding conformational epitopes). Cooking an egg is much more likely to help people who are sensitised to ovalbumin than people who are sensitised to ovomucoid.

For example, if you want to make a boiled egg significantly less likely to provoke an allergic reaction, you need to boil it for 45 minutes before the ovomucoid aggregates and IgE antibodies can no longer recognise its conformational and linear epitopes. Ovalbumin, however, is already less likely to provoke a reaction after 10 minutes of boiling.

Similarly, when egg is baked in muffin form for half an hour on 180°C/350°F, the heating affects both allergens but, whereas there is a 1,942-fold reduction in the amount of allergenic ovalbumin in the muffin after that length of time, there is only a 72-fold reduction in the ovomucoid concentration.

However, many egg-allergic people can actually eat muffins; this is because of the food matrix. The food matrix is the structural network created when proteins, fats and carbohydrates in a food interact with each other.

Muffins consist of more than egg alone, and it’s how the egg proteins react with the other food molecules in the muffin that helps people who are sensitised to ovomucoid. The food matrix of a muffin can lessen the likelihood of reactions by:

• creating larger food molecules that hide/bury their epitopes from IgE antibody detection
• inducing the Maillard reaction between proteins and sugars in the muffin mix, which tends to destroy or mask conformational epitopes in egg and milk products
• forming a matrix with wheat which prevents proteins from unfolding to bind with IgE antibodies

However, the effect produced by a food matrix is highly variable and depends on the ingredients and how they are processed. For example, a plain, wheat flour and egg muffin is likely to be tolerated by the majority of the egg-allergic, which is why you will find it on the first step of the egg ladder. But if you use rice flour to make it instead, or swap out some wheat flour for banana, you risk making a food that’s more likely to provoke a reaction.

(Even that’s not entirely straightforward: there’s actually more ovalbumin available to cause a reaction in a wheat flour muffin than in baked egg alone. Luckily, the 3D structure of ovalbumin is more likely to be destroyed by the heat during baking than ovomucoid which is, itself, less likely to be able to bind to IgE antibodies and cause a reaction when baked in a wheat matrix.)

The fact is, cooking food a certain way can help some people with allergies, but not everyone. Cooking methods and food brands that work for you may not work for your food-allergic counterpart. If you find a food product that you can tolerate, be mindful that you may react to another product (even if it’s the same food item but a different brand, because the ingredients or the processing used may be slightly different). Likewise, advising another person with a similar food allergy to eat a food product that you tolerate may not work for them.

Why fermentation helps some people with food allergies

People with food allergies can tolerate some food products that have been fermented.

Fermentation is a process by which microorganisms—typically bacteria, yeasts or moulds—break down complex organic compounds into simpler molecules as a way of producing energy. These microorganisms produce a range of enzymes (themselves proteins) that act as molecular scissors to break down the compounds; e.g. amylases (deal with carbohydrates), lipases (deal with fats) and proteases (deal with proteins).

The fermentation process can alter the structure of a protein and make it less allergenic in 2 ways:

1. The proteases produced by the microbes involved in fermentation break the food proteins into smaller peptide fragments and ‘free’ (individual) amino acids that are less likely to be recognised by IgE antibodies
2. Food fermentation typically involves lactic acid bacteria (LAB) which consume the sugars in food, producing lactic acid as their primary byproduct. This makes the environment more acidic and causes proteins to denature and unfold, destroying their 3D structure and thus breaking up or hiding epitopes, and revealing new epitopes that can be broken down further by enzymes

Unlike other types of food processing, fermentation can destroy both conformational and linear epitopes.

The effectiveness of the fermentation process depends on various different factors:

The specific microorganisms: different enzymes recognise and break (cleave) different bonds in different molecules. Different proteases, for example, recognise different amino acids and cut them in different places. They can be split into 2 main groups, depending on where they cleave bonds:

• Endopeptidases, which cleave internal peptide bonds.
• Exopeptidases, which cleave terminal peptide bonds and can be subdivided further into 2 main groups:
  • aminopeptidases, which cleave at amino terminal bonds (N terminus)
  • carboxypeptidases, which cleave at carboxy terminal bonds (C terminus)

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Of course, enzymes are character-less proteins, not adorable creatures with scissors. They’re also not Pacman-like creatures, but this video still does a nice job of showing you how enzymes react with substrates (like food proteins) to break them up.

Aminopeptidases tend to work on a broad range of polypeptides, but carboxypeptidases are more specialised and rely on the chemical properties of the amino acid at the end of the chain to bind and cleave it. There are also dipeptidases (cleave only dipeptides, short chains of 2 amino acids) and tripeptidases (cleave only tripeptides, short chains of 3 amino acids) which work on the fragments produced by the other proteases.

In biological systems, different kinds of proteases typically work together to get the job done; for example, in the human digestive system, endopeptidases (like pepsin and trypsin) first break large, complex proteins down into smaller polypeptide fragments which are then broken down further by exopeptidases to produce free amino acids and small peptides which can be absorbed in the gut.

All of which is a long way of saying that, when you ferment a food, using different individual or combinations of proteases will get you completely different mixtures of peptides and amino acids. Whether or not you end up reacting to a fermented food product will depends on whether the enzymes being used have managed to destroy the particular epitopes that you are sensitised to.

The specific food: microorganisms require carbon, nitrogen and minerals to thrive. Foods that lack these substances, such as foods that are low in proteins or minerals, can cause sluggish or ‘stuck’ fermentations. The type of sugar in the food is also important; simple sugars like glucose and fructose allow for rapid fermentation, whereas complex carbohydrates have to be broken down by enzymes first, slowing the process down.

The pH of the environment: microorganisms thrive under different conditions, and may work in different ways depending on the pH of the surroundings they find themselves in.

So, for example, soy milk makes better yoghurt than almond milk because it contains more carbohydrates and simple sugars, which provides lactic acid bacteria with the right resources for fermentation, resulting in an increased production of metabolites such as lactic acid which, in turn, lowers the pH of soy-based yogurts more quickly than almond-based yoghurts and ultimately produces yoghurt with a taste and consistency that is closer to traditional animal dairy products.

Additionally, fermenting at a temperature of around 30 °C favours a greater population growth of Lactobacillus delbrueckii, producing a yoghurt that is slightly less acidic than if you choose to ferment a temperature of around 45 °C, which favours the growth of Streptococcus thermophilus and produces a more aromatic product.

The acidity of the surrounding environment and the specific bacteria being used also affects the allergenicity the food product being produced.

Fermentation time matters too, especially when it comes to making a food that is less likely to provoke allergic reactions. The longer a microbe has to break down proteins in the food, the less likely those proteins are to retain the ability to bind IgE antibodies and cause reactions. This was demonstrated in a study in which 21 children sensitised to egg lysozyme were given Grana Padano cheese (which is prepared with lysozyme) to eat; 5 of the children reacted to cheese which had been aged for 12 months, whereas only 1 reacted to cheese that had been aged for 24 months.

Effective fermentation depends on so many different variables that food producers typically use several different enzymes and processes to make one product, especially if that product is supposed to be suitable for people with allergies or intolerances. A good case in point is infant formula. In order to break down cow’s milk proteins into smaller, digestible peptides and amino acids to make ‘hypoallergenic’ or ‘gentle’ formulas suitable for infants with milk allergies or intolerances, the formula has to undergo a complex production process involving a series of steps. These may include heat treatment, ultrafiltration and high hydrostatic pressure-assisted enzymatic hydrolysis, during which a commercial blend of enzymes such as Protamex and/or Flavourzyme may be used as the milk protein is subjected to both enzymatic hydrolysis and high pressure at the same time.

This last step combines the enzymes with the high pressure because it makes the process more effective; the high pressure physically unfolds the rigid milk proteins, making the polypeptide chains more accessible to the enzymes which can then break them down faster and more efficiently without the need for high temperatures which would damage the essential amino acids needed for the baby’s nutrition. This processing results in a product which will be tolerated by a majority of infants with milk allergies or intolerances. But not all.

Examples of common fermented foods that have been found to cause fewer allergic reactions include:

Yoghurt: the fermentation of milk with specific lactic acid bacteria considerably reduces its allergenicity because the microbes can break down both casein and whey proteins. Research involving milk-allergic children has found that many are able to tolerate yoghurt.

Cheese: cheese, specifically hard cheese that has been aged for a long time, like Parmigiano Reggiano which is matured for 36 months, has also been shown not to provoke reactions in a majority of milk-allergic children.

It’s results like these that have put hard cheese and yoghurt on the milk ladder.

Likewise, both soy sauce and miso, which are fermented with koji mould, have been found to be low in soybean allergens and unlikely to cause reactions in the majority of people allergic to soy. This is especially true of the darker versions of miso, which are allowed to fermented for the longest periods of time.

Saeujeot, a type of Korean fermented shrimp (and a key ingredient in traditional Korean kimchi) has also shown a reduced ability to provoke reactions in people allergic to shrimp.

Certain types of sourdough bread have also been found to cause fewer problems for people with food-related diseases; in one study, a 60-day diet of baked goods made with fully hydrolysed wheat flour (made using a longer fermentation period—of up to 2 days— than sourdough made with extensively hydrolysed flour) did not produce symptoms or tissue damage in people with coeliac disease.

It’s worth pointing out that none of these foods was tolerated by every person who tried it.

In the end, the lessons we can learn from fermentation are the same as those from other types of food processing; what may help you will not necessarily help someone else. Conversely, what doesn’t help someone else may help you so, if you have a food intolerance and not a potentially dangerous allergy, certain methods of food preparation or types of processed foods may be worth trying to see if you can tolerate them.

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