Rice starch and Co-proteins improve the rheological properties of zein dough

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.

Wheat Flour Quality Assessment by Fundamental Non-Linear Rheological Methods: A Critical Review

Wheat quality assessment involves physical, physicochemical, chemical, and sensory characterization of wheat kernels and the resulting wheat flour, dough, and bread. The physical tests conducted on wheat flour dough are mostly based on empirical methods. Empirical methods have been useful in industry and research to relate wheat flour quality to baking performance. However, these methods have the disadvantage of providing data in arbitrary units, which makes the fundamental interpretation of results difficult. Therefore, this review focuses on the use of fundamental rheological methods to determine wheat flour quality in terms of processing performance. During the transition from wheat flour to bread, wheat flour dough is mostly exposed to large deformations, and the quality of wheat flour determines its response to these large deformations and its baking quality. For this reason, this review only focuses on the application of fundamental rheological tests that are conducted in the non-linear viscoelastic region where wheat flour dough experiences large deformations.

Effects of coarse cereals on dough and Chinese steamed bread - a review

Chinese steamed breads (CSBs) are long-established staple foods in China. To enhance the nutritional value, coarse cereals such as oats, buckwheat, and quinoa have been added to the formulation for making CSBs. This review presents the nutritional value of various coarse cereals and analyses the interactions between the functional components of coarse cereals in the dough. The addition of coarse cereals leads to changes in the rheological, fermentation, and pasting aging properties of the dough, which further deteriorates the appearance and texture of CSBs. This review can provide some suggestions and guidelines for the production of staple and nutritious staple foods.

Effect of Proofing on the Rheology and Moisture Distribution of Corn Starch-Hydroxypropylmethylcellulose Gluten-Free Dough

Dough rheology, mainly enabled by gluten in the traditional dough, determines the end-products' quality, particularly by affecting gas production and retention capacities during proofing. Gluten-free dough has quite different rheological performance compared with gluten-containing dough. To deepen the understanding of gluten-free dough, variations of rheology and moisture distribution of corn starch-hydroxypropylmethylcellulose (CS-HPMC) gluten-free dough in the process of proofing were studied. Significant differences were found in terms of soluble carbohydrate composition, moisture distribution, and rheology. Arabinose, glucose, fructose, and mannose were the main composition of soluble carbohydrates in CS-HPMC dough, out of which glucose was preferentially utilized during proofing. Non-freezable water content and third relaxation time decreased from 44.24% and 2171.12 ms to 41.39% and 766.4 ms, respectively, whereas the amplitudes of T₂₃ increased from 0.03% to 0.19%, indicating reduced bounded water proportion and improved water mobility with proofing time. Frequency dependence and the maximum creep compliance increased, whereas zero shear viscosity reduced, suggesting decreased molecular interactions and flowability, but improved dough rigidity. In conclusion, the reduced soluble carbohydrates and improved water mobility decreased molecular entanglements and hydrogen bonding. Furthermore, yeast growth restricted a large amount of water, resulting in declined flowability and increased rigidity.

Effect of soy protein isolate on physical properties of quinoa dough and gluten-free bread quality characteristics

BACKGROUND

Quinoa is a good gluten-free resource for food processing, especially bread making, and can improve and prevent the development of complications associated with celiac disease (CD). However, lack of gluten affects quinoa bread quality. Previous research showed that soy protein isolate (SPI) could improve gluten-free bread quality to some extent. Therefore, this study investigated the effects of SPI on the physical properties of quinoa dough and gluten-free bread quality characteristics.

RESULTS

Results showed that, with appropriate SPI substitution, the farinograph properties of quinoa flour significantly improved (P < 0.05). The sample with 8% SPI substitution showed a better development time (DT, 3.30 ± 0.20 min), stability time (ST, 8.80 ± 0.10 min) and softening degree (SD, 8.80 ± 0.10 FU), which were close to those of wheat flour, although more water absorption (WA, 76.40 ± 2.10%) was needed than for wheat flour (66.30 ± 3.10%). The extensograph properties of quinoa flour also significantly improved after 8% SPI substitution (P < 0.05). Furthermore, SPI substitution increased G' moduli of quinoa dough and decreased tan δ to some extent, providing better rheological properties closer to those of wheat dough. SPI substitution also improved the quality and texture of quinoa bread and reduced the gap with wheat bread. When SPI substitution was 8%, the specific volume, hardness and springiness of quinoa bread were 2.29 ± 0.05 mL g^-1 , 1496.47 ± 85.21 g and 0.71 ± 0.03%, respectively.

CONCLUSION

These results suggested that SPI substitution would be an effective way to develop higher-quality gluten-free bread. © 2022 Society of Chemical Industry.

Modification of zein dough functionality using kafirin as a coprotein

Kafirin, sorghum prolamin, was investigated as a coprotein for zein as visco-elastic masses and in starch-based model doughs. Regular kafirin and kafirins from waxy and high protein digestibility (HD) sorghum crosses were studied. HPLC revealed that waxy-HD kafirin was of smaller molecular size and low in β-kafirin. It also had greater surface hydrophobicity. Kafirin addition to zein increased visco-elastic mass elasticity up to ≈50% stress-recovery, similar to wheat gluten. Waxy-HD kafirin gave the highest elasticity, possibly due to its hydrophobicity. Kafirin inclusion at 2:8 parts zein increased the tensile strength of model doughs. Maximum strength was, however, only 60% that of gluten-based dough. Kafirin from regular sorghum gave the highest strength, possibly because of greater disulphide-bonded polymerisation. Confocal laser scanning microscopy showed that zein-kafirin copolymers formed fairly linear fibrils in stretched doughs, indicating excellent compatibility between the proteins. Future research should establish how kafirin-zein copolymer performs in non-wheat flour products.