On Tuesday 13 February, the UK celebrated "pancake day", the colloquial name for the religious festival of Shrove Tuesday, which marks the last day before the fasting period of Lent. For centuries it was traditional in the UK to use up any household dairy produce to make pancakes on Shrove Tuesday before the Lenten fast began. Pancake day still remains a firm fixture in the UK's cultural calendar.
Gluten - friend or foe?
One of the key ingredients of a pancake batter – whether that be for making a European-style crêpe or its thicker, fluffier American cousin – is flour. The most common type of flour found in a modern Western diet is wheat flour, which contains a structural protein known as gluten. "Gluten" is actually a collective term referring to the combination of two different protein classes, glutelins and prolamins (e.g. gliadin), which are naturally found in cereal grains including wheat, oats, barley and rye. Gluten has notable viscoelastic and adhesive properties, which impart the characteristic elasticity of dough and enables dough to rise during the baking process.
However, gluten proteins are also allergens and can induce an immune response in certain people. In severe cases affected individuals may develop coeliac disease, a chronic autoimmune condition predominantly affecting the small intestine. When exposed to gluten, coeliac sufferers produce several types of autoantibodies that affect various organs. In particular, these antibodies cause an inflammation of the bowel and shortening of the villi – tiny protrusions of the epithelium of the small intestine which increase its surface area – which leads not only to discomfort and chronic diarrhoea, but also a reduction in absorption of nutrients in the intestine. In turn, this can lead to conditions characterised by nutrient deficiencies, such as anaemia.
It is estimated that around 1-2% of the UK population suffers from coeliac disease and as many as 6% suffer from some form of gluten sensitivity (including an inability to digest gluten) which affects their physical and/or mental health.
Advent of the gluten-free diet
The history of the gluten-free movement can be traced back to the 1920s, when Anton Schär, an Innsbruck doctor, conducted studies on children who eliminated wheat from their diet. After noticing that children with digestive problems responded favourably to his studies, Schär set up a health food company that specialised in selling gluten-free foods.
The Dutch paediatrician Willem-Karel Dicke made similar observations on coeliac patients during the "Hunger Winter" famine of 1944: in the absence of wheat products, he observed an improvement in the condition of many of his patients, who then relapsed when wheat-containing products became available again at the end of World War II in 1945. Follow-up studies identified the gliadin protein as the trigger of the patients' inflammatory responses.
And thus, a gluten-free diet, excluding all of the commonly available bakery products, subsequently became the only known cure for coeliac disease.
Gluten-free alternatives for bakery products
The holy grail of gluten-free is to produce bakery products that are indistinguishable in structure, texture and taste from gluten-containing products, so that the small but significant minority of people who develop a gluten sensitivity can continue to enjoy these foods.
Innovators have adopted several different approaches to meeting this challenge. Early attempts (as described in e.g. EP0035978 or WO 2006/107809) involved preparing bakery products from flours that do not contain any gluten, including flour produced from non-glutinous rice, maize starch and potato flour. However, products derived from these flours typically lack the necessary structure and texture of corresponding gluten-containing products. Issues also arise when processing gluten-free flours. Notably, more water must typically be added to dough made from gluten-free flour, which results in stickiness. Some of these alternative flours are also low in fibre content, and therefore a diet which relies heavily on products made from these flours can cause other digestive system issues.
Alternative approaches involve directly manipulating wheat flour in order to reduce its gluten content to below an acceptable level for coeliacs (the current regulatory threshold for advertising a product as "gluten-free" in the EU is less than 20 parts per million (ppm) gluten).
One common – and trendy – technique in bread manufacture that helps to reduce the gluten content of wheat flour is fermentation, used to produce sourdough. Sourdoughs are obtained from a mix of flour and water that is fermented by yeasts and lactic acid bacteria of the genus Lactobacillus. The bacteria help to eliminate particularly toxic components of gluten, in particular gliadin, from the dough via hydrolysis. However, not all types of lactic acid bacteria can reduce the gluten levels to the required 20 ppm. EP3653058 is a patent directed to a particularly effective process for removing gliadin from a flour/water dough comprising (i) an enzymatic hydrolysis step to hydrolyse gliadin, (ii) fermenting the mixture using specific lactic acid bacteria that can remove the peptides and amino acids generated by the hydrolysis step under controlled pH conditions, and (iii) a drying step. This process is said to reduce the amount of gliadin present by 98%, and even more if steps (i) and (ii) are repeated.
Another approach to modifying wheat flour is suggested in EP2269464, which involves heat treating wheat flour in the presence of moisture. The specific conditions employed allow for denaturation of the gluten proteins (i.e. disruption of the weak intramolecular forces which hold the proteins in their characteristic 3D shape) but crucially do not disrupt the granular state of the starch in the flour. The resulting bakery products are said to contain less than 20 ppm gluten, and to have improved sensory properties compared to alternative gluten-free products.
There have also been innovative developments in relation to the shelf life of gluten-free products. Gluten proteins are typically responsible for retention of moisture content in bakery products, and as such, gluten-free alternatives can often deteriorate in texture more rapidly and consequently have a shorter shelf-life. As described by Haghighat-Kharazi and co-workers, one way to counter this is to incorporate microencapsulated maltogenic amylase into the dough mixture. Maltoamylase is an enzyme that degrades the protein amylopectin after baking; the crystallisation of amylopectin is thought to contribute significantly to the staling process. Additionally, it is thought that the ability of maltoamylase to increase the dextrin levels in baked bread has a secondary effect, as dextrins hinder the crystallisation of amylopectin.Despite these - and other - advances in the gluten-free field, there remain several major challenges to be solved in the development of gluten-free bakery products. In particular, to address a disparity in taste and texture compared with gluten-containing products, manufacturers often add additional sugars and fats to gluten-free products, which give rise to other potential dietary and health risks. The development of products and methods which avoid these downsides remains an active area of research.
A brave new gluten-free world?
Although gluten-free options have improved beyond recognition over the past 30 years, we are still some way off a genuine like-for-like replacement of gluten-containing bakery products. One thing is certain, however: the gluten-free market is booming. Global sales of gluten-free products were estimated to be USD 5.6 billion in 2020, and are set to hit USD 8.3 billion by 2025. For those companies with exciting innovations in this sector, there are plenty of financial opportunities.
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