Brazilian study finds dietary fibre significantly ramps up the quality of gluten-free bread

23-Jul-2021 - Last updated on 23-Jul-2021 at 09:53 GMT

Psyllium is a natural bioactive soluble fibre made from husks of the seeds of the Plantago ovata plant. Pic: GettyImages/bdspn

Remove gluten and the most crucial ingredient for a dough’s rheology, the breadmaking processes, characteristics like structure and mouthfeel, along with a longer shelf life, has effectively been removed. But with gluten intolerance a global epidemic today, the demand for gluten-free (GF) products is ever increasing.

Gluten is the protein complex found in cereals like wheat, rye and barley that is responsible for the elastic texture of dough. Unfortunately, its key role in breadmaking and bread quality cannot be replaced by a single ingredient.

That’s what makes formulating products like gluten-free bread (GFB) is so challenging for food scientists and producers, particularly as the demand for premium products is growing in tandem with the number of individuals adopting a gluten-free lifestyle.

According to research undertaken by Brazilian scientists from the Federal University of São Paulo (UNIFESP) – published in a Special Issue ‘Improvement of the Nutritional and Sensory Quality of Gluten-Free Bread’ of Foods in April 2021 – there has been a dramatic rise in the number of people adhering to the GF diet, partly due to an increased prevalence of gluten-related disorders like celiac disease – “which has become a notorious public health problem worldwide” – but mainly driven by the widespread belief that a GF diet is healthier and more suitable for weight management.

Celiac disease is a chronic dysfunction of genetic origin that affects 1.4% of the world population and can lead to multisystem disorders, with severe complications if left untreated.

Wheat allergy is an immune reaction to the proteins in wheat.

Non-celiac gluten sensitivity, on the other hand, isn’t an autoimmune condition, but is caused by gluten or other components of wheat such as rapidly fermentable carbohydrates. Its symptoms are often similar to celiac disease, but less severe.

“Three conditions are currently recognised as grounds for prescribing a gluten-free diet: celiac disease, wheat allergy and non-celiac gluten sensitivity,” said Vanessa Dias Capriles, lead researcher of the study, a nutritionist and a professor at UNIFESP.

The challenge of making GFBs

While the development of premium GF products is ongoing and successfully evolving, GF breads, for example, typically have a shorter shelf life than gluten-bearing breads. This is because of starch retrogradation, the migration of water from the crumb to the crust, as well as the starchy raw materials and high water content used – two factors that accelerate staling and increase susceptibility to microbially driven deterioration.

“The development of these products is a major technological challenge,” added Prof Capriles.

“Bread made with wheat flour has been an important human food for millennia. The sense impressions it causes are deeply ingrained in people's lifestyle. That’s why it’s important to develop enhanced versions of these products. Market research shows that consumers are dissatisfied with the appearance, aroma, variety and convenience of the products currently available.”

Gluten-free bread is also often nutritionally poor.

“Generally speaking, it’s made with refined starch such as rice bran combined with corn, potato and cassava starch. It contains little fibre, proteins, vitamins or minerals, and relatively large amounts of fat. It’s not enriched with micronutrients in many countries,” said Prof Capriles.

Overcoming the challenges

The research underway at UNIFESP – with the support from the São Paulo Research Foundation (FAPESP) via Young Investigator and Multiuser Equipment Grants – is focused on ways to overcome these challenges, specifically to improve the overall nutritional value of GF products; to increase their acceptability to consumers; and to develop technologically feasible solutions.

The Brazilian scientists created more than 15 formulations they considered optimal, using different techniques, 50%-100% GF wholemeal flour to ramp up the fibre content, along with added proteins, vitamins and minerals. Fresh bread characterisation consisted of the loaf-specific volume, crumb moisture, crumb firmness, crumb grain, and height/width ratio of the central slice, and sensory acceptability.

Dietary fibres

The use of soluble dietary fibres is known to improve the physical properties, sensory acceptance, shelf life, nutritional content and glycaemic response of GFB, so the Brazilian scientists analysed a range of raw materials, including wholemeal flour from cereals such as rice, sorghum and millet; pseudo-cereals such as amaranth, quinoa and buckwheat; and others such as chickpeas, dry beans and pine nuts.

Ingredients

For the research, the team source psyllium husk powder (Vitacel Psyllium P95) from JRS Latinoamericana, rice flour from Urbano Agroindustrial, cassava starch from General Mills Brasil Alimentos, calcium propionate from Pantec Aditivos e Ingredientes para a Indústria and bread spray mould inhibitors from Conserv, along with commercial wheat flour from J. Macedo (for the WBs), water, eggs, sugar, soybean oil, salt, and dry yeast.

Psyllium – a natural bioactive soluble fibre made from husks of the seeds of the Plantago ovata plant – achieved the most positive results.

Psyllium is hygroscopic and expands into a gelatinous mass when mixed with water, presenting water-binding, gelling and structure-building properties that can increase the dough viscosity, strengthen the boundaries of the expanding cells, increase gas retention during baking, and improve the volume. It also reduces the loss of crumb moisture, softness, cohesiveness and springiness during storage, thus improving the structure, texture, appearance, acceptance and shelf life of GFB.

Every 100g of psyllium supplies 80g of soluble fibre, and is known to help with constipation and satiety, glycemia, cholesterol control, diabetes and atherosclerosis.

Particularly impressive results were achieved by teaming psyllium with chickpea flour.

“We succeeded in producing bread with 17% psyllium,” said Prof Capriles.

“Because it absorbs water, dough made with psyllium can be moulded into many shapes, just like rolls and loaves made with conventional wheat flour.

"In more recent studies, we associated psyllium with chickpea flour and obtained surprisingly good results. Besides high acceptability and nutritiousness, its advantages include a low glycaemic response [it does not raise blood sugar significantly] and heightened satiety in healthy people.

“Another very interesting point is that it maintained its acceptability even after being stored at room temperature for seven days.”

Conclusion and way forward

The results showed that psyllium improved GFB structure, mouthfeel and acceptability of GFB, with no significant differences in the acceptability of psyllium-enriched GFBs and wheat breads (WB). During storage, the control GFB had a crumb firmness that was eightfold higher than that of WB. The longest delay in GFB staling was observed with the addition of 17.14% psyllium, maintaining acceptability during storage comparable to that of the WB counterparts.

The next steps, according to Prof Capriles, is to find industry partners to take the formula from conception to commercialisation, as well as moving ahead with the research and development on a collaborative basis.