Characterisation of gluten-free dough mixes from traditional food crops with reduced starch digestibility for baking applications

Abstract

Gluten-free (GF) baking is challenging because gluten, which is absent, gives wheat-based doughs their elasticity, structure, and ability to retain gas. Developing gluten-free dough mixes requires a strategic selection of substitute ingredients that can mimic gluten's functional properties. This calls for the use of various starches, flours, hydrocolloids, and proteins to achieve desirable dough rheology and final product characteristics. The challenge lies in optimizing the interactions between these ingredients to create a cohesive and elastic dough structure that can withstand processing and deliver acceptable sensory attributes. The choice of suitable ingredients and their proportions is crucial for achieving a balance between dough stability, gas retention, and crumb structure. Therefore, food scientists and technologists find it challenging to create baked foods that are gluten-free. For glutenfree products to be more widely accepted by consumers, these ingredients must ensure that they resemble typical bakery goods as much as possible. Amadumbe, millet, and psyllium offer unique properties that can be harnessed to create gluten-free dough mixes. Amadumbe, a starchy root crop rich in resistant starch, can reduce the glycemic load of baked goods. Millet is a gluten-free grain with high nutritional value, providing vital amino acids, minerals, and antioxidants. Psyllium, a soluble fibre, has been shown to improve dough handling, increase viscosity, and improve the textural properties of gluten-free baked goods. The combination of these ingredients can address the textural and nutritional deficiencies often associated with gluten free products. The focus of this research was the characterization of gluten-free dough mixes with reduced starch digestibility for baking applications. This was done by A; investigating the effect of hydrothermal treatments: annealing (ANN) and heat-moisture treatment (HMT) combined with 3% psyllium husk fibre (PHF), on the structural, rheological, pasting, and digestibility properties of maize starch with varying amylose content. B; evaluation of the functional and digestibility profiles of a gluten-free (GF) premix blend made from amadumbe and millet, supplemented with psyllium fibre, and C; the optimized gluten-free flour blend was tested for its dough-forming ability and baking quality. Hydrothermal treatments: annealing (ANN) and heat-moisture treatment (HMT), combined with 3% psyllium fibre supplementation, significantly (p < 0.05) enhanced the rheological, pasting, and starch digestibility profiles. However, hydrothermal treatment alone caused minimal to no change in these functional properties. The results demonstrated that fibre supplementation of both HMT- and ANNtreated starches increased peak viscosity, trough viscosity, final viscosity, and setback viscosity, with ANN exhibiting significantly higher values. ANN fibre-supplemented normal maize starch showed the largest increase in storage modulus (G'), according to rheological analysis. Profiling of starch digestibility revealed that fibre-supplemented high amylose maize starch produced the greatest levels of resistant starch (RS). These findings highlight the importance of developing healthier starches that promote well-being by reducing digestibility and increasing resistance to enzymatic breakdown. This will support the creation of low-glycemic, fibre-rich products. The results of the investigation proved useful in establishing the criteria for the amadumbe-millet and psyllium flours used to produce glutenfree composite blends. The evaluation of processed gluten-free (GF) flour blends made from amadumbe, millet, and psyllium flours revealed that the inclusion of psyllium fibre significantly improved the pasting properties (PV, FV, BV) two-fold. The rheological properties showed enhanced viscoelasticity of the dough, as indicated by the storage modulus (G') consistently being greater than the loss modulus (G") across the frequency range. Starch structural analysis using X-ray diffraction (XRD) indicated that all blends exhibited a typical A-type crystalline structure. The analysis of starch digestibility showed a significant increase in resistant starch (RS) and a decrease in rapidly digestible starch (RDS) due to the presence of psyllium fibre. Results obtained from this study suggest that fibre-supplemented gluten-free flours have great potential for baking, owing to their improved functional properties and reduced digestibility profile. The optimized gluten-free blend of amadumbe, millet, and psyllium (in a ratio of 70-30-3) was further evaluated for its dough-forming properties by examining water absorption capacity (WAC), oil absorption capacity (OAC), rheological properties, and textural properties. All the tests performed showed improvement with the inclusion of fibre. To assess the baking quality of the bread, textural analysis and sensory evaluation were conducted. Sensory evaluation assessed the amadumbe-milletpsyllium bread (AMP1) with a commercially available gluten-free bread. The results for overall acceptance indicated comparable findings (6.62±1.86) for AMP1 bread and (6.91±1.63) for the commercial gluten-free bread. However, starch digestibility results showed a reduction in resistant starch (RS) content, which was attributed to the increased baking temperature and time. This research contributes to the advancement of gluten-free bread with enhanced nutrition, texture and shelf life, meeting the growing demands of health-conscious consumers and gluten-intolerant individuals. Therefore, this study furnishes valuable insights for food scientists, bakers, and ingredient manufacturers, guiding the preparation of novel gluten-free products with enhanced nutritional and sensory attributes.