Effect of zein extrusion and starch type on the rheological behavior of gluten-free dough

A fundamental rheological approach to determine the optimum water absorption capacity of a model gluten-free dough system: soy flour dough

BACKGROUND

Determining the optimum water absorption capacity of gluten-free flours for an improved breadmaking process has been a challenge because there is no standard method. In the present study, large amplitude oscillatory shear (LAOS) tests were performed to explore the impact of different levels of added water on non-linear viscoelastic response of soy flour dough in comparison to wheat flour dough at a consistency of 500 BU.

RESULTS

Among the LAOS parameters, large strain modulus (G'L) and large strain rate viscosity (η'L) were found to better probe the impact of added water amount on non-linear viscoelastic properties of soy flour dough. Although soy flour dough with 160:100 (water: soy flour, v/w) and wheat flour dough had overlapping η*(ω) in the linear viscoelastic region, LAOS sweeps revealed similar tan δ, G'L and η'L values along with similar elastic and viscous Lissajous-Bowditch curves at γ0 = 200% for soy flour dough with 175:100 (water: soy flour, v/w) to those of wheat flour dough.

CONCLUSION

Considering the large deformations involved in breadmaking process and the poor capability of the linear viscoelastic measures to predict loaf volume, the present study suggests using the LAOS parameters to determine the optimum water absorption capacity and to optimize the strain-stiffening and shear-thinning behaviors of gluten-free flours to improve end-product quality. © 2025 Society of Chemical Industry.

Structural, physicochemical and technofunctional properties of corn gluten meal modified by extrusion

This study aimed to evaluate the influence of sample moisture, extrusion temperature, and extruder screw speed on the hydration properties of corn gluten meal (CG), optimize process condition for the highest protein solubility at pH 7 (PS7) and WAC, and assess the effect of the optimized extrusion process on the structural, chemical, physical, and technofunctional properties of CG proteins. Extrusion was carried out at different sample moisture (20%-40%), temperatures (120-160 °C), and screw speeds (33-117 rpm) using a complete factorial design with two central points. All extrusion conditions resulted in reduced hydration properties. Extrusion with 20% sample moisture, 120 °C and 117 rpm resulted in the lowest loss of water absorption capacity and protein solubility at pH 7 (optimized condition). After optimized extrusion, the GC became darker and showed greater activity and protein emulsifying capacity and lower foaming capacity. Furthermore, CG proteins had reduced solubility at different pHs. Changes in technofunctional properties resulted from changes in protein structure after extrusion. The new protein structure is stabilized by non-covalent bonds (hydrogen bonds and hydrophobic interactions) and disulfide bonds. Extruded corn gluten has the potential to be used as an ingredient in bakery, emulsified meat products, salad dressings, vegetable pates, and desserts.

Textural improvement of pea protein-based high-moisture extrudates with corn zein and rice starch

High moisture extrusion allows the production of plant protein-based products, including meat analogues. Building upon our previous findings showing that zein mixed with rice starch provides the necessary textural properties to formulations, different pea protein-based formulations with varying amounts of zein and rice starch or wheat gluten (as control) were produced using high moisture extrusion and the rheological, textural, and microstructural characteristics were evaluated and associated with the secondary structure of proteins. Samples containing wheat gluten presented desirable rheological and mechanical properties in terms of texturization, which was evidenced by the generation of a layered and three-dimensional viscoelastic network. The addition of rice starch to zein significantly increased the viscoelasticity of the samples due to enhanced development of non-covalent interactions that led to higher and more stable β-sheets content and to the formation of a fibrous and layered microstructure and a 3D network nearly like those obtained with gluten. The sole replacement of pea protein by zein was not enough to develop these desired characteristics, demonstrating the importance of the non-covalent interactions between rice starch and zein for the generation of these properties. Overall, zein and rice starch improved texturization of pea protein-based gluten-free analogues made by high moisture extrusion.

Impacts of ethanol-plasticization and extrusion on development of zein network and structure of zein-starch dough

To improve the viscoelasticity of zein in gluten-free dough, ethanol-plasticization and extrusion modification were employed. The peak viscosity of UZS (unextruded zein-starch) flour and EZS (extruded zein-starch) flour with ethanol (10 %, v/v) increased from 1340.0 to 1996.5 mPa·s and 1336.3 to 2291.5 mPa·s, and the bound bromophenol blue increased from 7.1 μg to 10.6 μg and 5.3 μg to 5.9 μg, respectively. Ethanol-plasticization enhanced zein's hydrophobic interactions and promoted zein network development, thus improving dough compatibility. However, the dense structure of the extruded zein made ethanol inaccessible to the interior, and the structural improvement on extruded zein-starch dough was limited. A model was developed to explain the influences of extrusion and ethanol-plasticization on the behavior of zein in the dough. Extrusion reduces the fiber-forming ability of zein, while ethanol-plasticization facilitates extensive fibrous network formation. This study provides a sound basis for the development of zein in gluten-free foods.

Breaking the temperature limitation of zein-rice starch dough by microwave pre-gelatinization: Morphological, structural and rheological properties of the dough

Zein has gluten-like viscoelasticity, but its use is limited due to high glass transition temperature (Tg). To break the temperature limitation of zein-starch dough, microwave heating was used to pre-gelatinize a partial of the starch with zein, and then the remaining was added and kneaded to form a dough. Pre-gelatinized doughs formed by rice starch (PRS), zein-starch (PUZS), and extruded zein-starch (PEZS) were included in this study. The thermal, morphological, rheological, and secondary structural properties of the dough were investigated. The results showed that zein and starch formed a composite gel network and firmly bound starch granules, which improved the dough properties with a smooth surface and compact internal structure, increased strain tolerance, and decreased stiffness. Unextruded zein was distributed uniformly and had strong interactions with the starch. Extruded zein tended to form large particles and had limited interaction with starch but improved dough extensibility. Microwave pre-gelatinization increased the stability of the secondary structure of zein and maintained the viscoelasticity of dough below zein's Tg, which provided a safe and effective way to break the temperature limitation of zein as a structural protein used in foods.

Development of Protein Rich Pregelatinized Whole Grain Cereal Bar Enriched With Nontraditional Ingredient: Nutritional, Phytochemical, Textural, and Sensory Characterization

This study was aimed to use extrusion cooking as a pretreatment for non-conventional seeds (Indian horse chestnut flour) to blend them with whole grain flours (whole wheat flour, whole barley flour, and whole corn flour) for the development of a pregelatinized cereal bar (PCB). In this study, date paste (7.5-17.5%) and walnut grits (2.5-12.5%) were incorporated at varying levels to prepare PCB. The PCB was evaluated for its nutritional, color, textural (both three-point bending test and TPA), antioxidant activity, and sensory attributes. The flexural modulus, rupture stress, and fracture strain of PCB increased with the incorporation of a higher proportion of date paste. The protein and fiber content in PCB increased from 7.74 to 9.13% and 4.81 to 5.59% with the incorporation of walnut grits and date paste, respectively. The DPPH, total phenolic content, and water activity of PCB were determined, which progressively enhanced with increased levels of walnut grits and date paste. The correlation between sensory attributes and instrumental texture on PCB was also investigated. The correlation results showed a significant (p < 0.05) positive correlation between texture analysis and sensory hardness, springiness, adhesiveness, and negatively correlated to instrumental and sensory cohesiveness. For sensorial attributes, all PCB samples presented average scores of 7/10 and 4/5 for buying intention. Therefore, whole grain extrudates, date paste, and walnut grits can be efficiently used to develop PCB with improved nutritional, nutraceutical, and economic values.

Effects of Hydrothermal and Microwave Dual Treatment and Zein on the Enzymolysis of High Amylose Corn Starch

Resistant starch (RS) type 2-high-amylose corn starch (HACS) was subjected to simultaneous hydrothermal (25% moisture content, 90 °C for 12 h) and microwave (35% moisture content, 40 W/g microwaving for 4 min) treatment and zein (at a zein to treated starch ratio of 1:5, 50 °C for 1 h) to improve its resistance to enzymolysis. Scanning electron microscopy (SEM) highlighted the aggregation and adhesion of the composite. The average particle size of the composite (27.65 μm) was exceeded that of both the HACS (12.52 μm) and the hydrothermal and microwave treated HACS (hydro-micro-HACS) (12.68 μm). The X-ray diffraction results revealed that the hydro-micro-HACS and composite remained B-type, while their crystallinity significantly decreased to 16.98% and 12.11%, respectively. The viscosity of the hydro-micro-HACS and composite at 50 °C was 25.41% and 35.36% lower than that of HACS. The differential scanning calorimetry (DSC) results demonstrated that the composite displayed a new endothermic peak at 95.79 °C, while the weight loss rate and decomposition temperature were 7.61% and 2.39% lower than HACS, respectively. The RS content in HACS, the hydro-micro-HACS, and composite was 47.12%, 57.28%, and 62.74%, respectively. In conclusion, hydrothermal and microwave treatment combined with zein provide an efficient physical strategy to enhance the RS type 2-HACS.

High Protein Substitutes for Gluten in Gluten-Free Bread

Gluten-free products have come into the market in order to alleviate health problems such as celiac disease. In this review, recent advances in gluten-free bread are described along with plant-based gluten-free proteins. A comparison with animal-based gluten-free proteins is made reporting on different high protein sources of animal origin. Sea microorganisms- and insect-based proteins are also mentioned, and the optimization of the structure of gluten-free bread with added high protein sources is highlighted along with protein digestibility issues. The latter is an issue for consideration that can be manipulated by a careful design of the mixture in terms of phenolic compounds, soluble carbohydrates and fibres, but also the baking process itself. Additionally, the presence of enzymes and different hydrocolloids are key factors controlling quality features of the final product.

Prolamin-based complexes: Structure design and food-related applications

Prolamins are a group of safe food additives that are biocompatible, biodegradable, and sustainable. Zein, gliadin, kafirin, and hordein are common prolamins that have been extensively studied, particularly as these form colloidal particles because of their amphiphilic properties. Prolamin-based binary/ternary complexes, which have stable physicochemical properties and superior functionality, are formed by combining prolamins with polysaccharides, polyphenols, water-soluble proteins, and surfactants. Although the combination of prolamins with other components has received attention, the relationship between the structural design of prolamin-based complexes and their functionalities remains uncertain. This review discusses the production methods of prolamin-based complexes, the factors influencing their structural characteristics, and their applications in the food industry. Further studies are needed to elucidate the structure-function relationships between prolamins and other biopolymers, as well as the toxicological effects of these complexes in food.

Methods for the Modification and Evaluation of Cereal Proteins for the Substitution of Wheat Gluten in Dough Systems

The substitution of wheat gluten in the food industry is a relevant research area because the only known treatment for celiac disease is abstinence from this protein complex. The use of gluten-free cereals in dough systems has demonstrated that the viscoelastic properties of gluten cannot be achieved without the modification of the protein fraction. The quality of the final product is determined by the ability of the modification to form a matrix similar to that of gluten and to reach this, different methods have been proposed and tested. These procedures can be classified into four main types: chemical, enzymatic, physical, and genetic. This article provides a comprehensive review of the most recent research done in protein modification of cereal and pseudocereals for gluten substitution. The reported effects and methodologies for studying the changes made with each type of modification are described; also, some opportunity areas for future works regarding the study of the effect of protein modifications on gluten-free products are presented.

A Systematic Review of Gluten-Free Dough and Bread: Dough Rheology, Bread Characteristics, and Improvement Strategies

High-quality, gluten-free doughs and bakery products are clearly more difficult to produce than wheat flour-based products. The poor quality of the breads that are currently available demonstrates that manufacturing remains a significant technological problem. This is mainly due to the absence of gluten, which has a huge negative impact on dough rheology and bread characteristics. Gluten replacement is still the major challenge in the development of doughs and baked goods. The literature documents various improvement strategies. The most active approach seeks to identify alternative ingredients that can mimic the viscoelastic properties of the gluten network, notably hydrocolloids, enzymes, emulsifiers, and alternative sources of protein. However, other innovative strategies, such as high pressure, using heat to dry flour, and sourdough fermentation, have been investigated. In this context, the first aim of this review is to summarize current knowledge regarding gluten-free doughs, breads, and bakery products. Secondly, as it is clear that the manufacture of gluten-free products remains a key challenge, it suggests some improvement strategies that can boost their nutritional, technological, and sensorial characteristics.