“What has been almost impossible to do so far is to keep the many small gas bubbles in the dough without the supporting gluten scaffold,” said Prof Dr Mario Jekle, head of the Department of Plant-Based Foods at the University of Hohenheim in Stuttgart.
While the development of gluten-free baked goods has improved in leaps and bounds over the years, food scientists are still hard at work to find an effective alternative that matches the outstanding properties of gluten.
The extraordinary web
In chemical-physical terms, gluten is a key protein in baking.
Think of it as a net that keeps dough airy until baking stabilises the open-pore structure. This web is capable of trapping gas bubbles during fermentation; the stronger it is, the more gas it can hold and the higher the rise. At the same time, the more the gluten develops, the stronger and longer those interconnected strands become, leading to more chewiness and toughness in the final product.
Hence the variation of flours for different applications. Although bread begins with many of the same ingredients as cakes, it has a completely different consistency. Bread flour has a protein percentage of 11%-13%, resulting in a product that is airy and satisfyingly chewy. It’s hard to imagine enjoying a chewy cake, so cake flour, with a protein percentage of 7%-9%, has a low gluten-development potential.
A common misconception is that gluten is part of flour. Yes, flour contains the two proteins - glutenin and gliadin - necessary to form gluten, but these only join to form that miraculous net when a liquid (water, milk) is added.
In gluten-free bakery, lathering up ingredients - creating friction to trap air - isn’t a problem. This can be achieved by stirring or using a leavening agent like yeast or baking powder.
What gluten-free bakery lacks is that supporting network to hold it all together.
However, gluten is a problematic protein - in varying degrees - for about 2%-3% of the global population.
“We now know three disease patterns that are related to gluten,” said Prof Dr Stephan Bischoff of the Institute of Clinical Nutrition at the University of Hohenheim.
Celiac disease is a widespread chronic condition, a mix of an allergy and autoimmune disease in which the body mistakenly reacts to gluten as if it were a poison.
Wheat allergy is triggered by gluten and similar peptides and is similarly widespread.
The third clinical picture is wheat sensitivity, the least researched to date, but essentially no antibodies are produced and there does not appear to be damage to the gut lining.
“It is not yet clear exactly what triggers wheat sensitivity and whether gluten also plays a role in this case. At our department, we are therefore working hard on this puzzle,” said the University’s Prof Dr Bischoff, a clinical nutritionist.
According to Coeliac UK, two further malaises can be added to the mix. Gluten ataxia is one of a number of neurological manifestations of coeliac disease, causing clumsiness, incoordination, slurred speech and sometimes jumpy vision. Dermatitis herpetiformis is the skin presentation of coeliac disease, associated with small blisters on the elbows and knees.
No matter the level of intensity, people who cannot stomach gluten have only one remedy in everyday life - to resort to gluten-free foods.
Revolutionising gluten-free bakery
The researchers at the University of Hohenheim are taking a new approach.
“Instead of supporting the dough with gluten, we focus on stabilising the interface between gas bubbles and dough with alternative proteins,” said Prof Dr Jekle.
His team is working on extracting protein from peas, rapeseed, rice and maize that can directly replace gluten protein. He also sees further potential in plant breeding, “If we define the requirements precisely, we can work with plant breeding to target new pea varieties whose proteins are even better suited to our approach.”
In another approach, the department is trying to link the natural proteins from rice, maize or oats with mucins (referred to as arabinoxylans) to form chains with gluten-like properties.
The scientists also found that naturally-occurring compounds called sapponins found in the cells of quinoa seed or mucilages of cereal hulls - along with the stems, leaves and flowers of daisies - additionally support the formation of an airy dough.
It is an approach with additional benefits as, in some cases, it can be used to enrich baked goods with valuable dietary fibre.
“To give an example: 30g of fibre a day is already good prevention against colon cancer, one of the three most common cancers in men and women,” said Prof Dr Bischoff.
The scientists are planning to investigate the use of arabinoxylans in other applications, like meat substitutes. The approach not only gives plant-based products a meat-like structure but additional nutrition from the dietary fibre. So far, there are no comparable products on the market, claim the scientists.
The bread rolls currently coming off the mini production line at the University’s Technical Centre for Food Science are still small - each comprising 30g of dough - but after being steamed and then baked, the results are light, golden and steaming.
The experiment - using a hand-width conveyor belt - combines technology with materials science and engineering. However, the challenge is the recipe, as the dough is completely gluten-free and should still produce a product that is fluffy and tastes good.
3D printed bread
The department is also working to ‘loosen’ the dough and combine it with the baking process in one step with the help of 3D printers. A nozzle builds up the pastry together with the pores in millimetre-thin layers, above which, a baking unit immediately solidifies each layer.
The process is somewhat similar to the way Salzwedel bakers have been baking the classic Baumkuchen (literally translated ‘tree cake’ or ‘log cake’) for 200 years. Using a ladle, the Baumkuchen batter is applied in millimetre-thin layers onto a rotating roller and baked layer by layer in front of an open flame.
“Our technology at the University of Hohenheim is, of course, much more sophisticated, flexible and can build many different structures,” said Prof Dr Jekle.
His team has been experimenting with 3D printing for several years and in principle, almost any food - from bakery to meat and plant-based - can be produced by this piece of equipment. It also has advantages that extend from personalised nutrition to sustainability and limiting food waste.
“With printed foods, I can personalise meals, meaning I can tailor the ratio of fats, carbohydrates, proteins and all other components to exactly meet the personal needs of individuals,” said Prof Dr Jekle.
“And I can also obtain some of the raw materials from residual materials that are created during food production, for example.”