Control of wheat starch rheological properties and gel structure through modulating granule structure change by reconstituted gluten fractions

Role of pea protein isolate in modulating pea starch digestibility: insights from physicochemical and microstructural analysis

BACKGROUND

Understanding the interactions between protein and starch is crucial in revealing the mechanisms by which protein influences starch digestibility. The present study investigated the impact of different contents of pea protein isolate (PPI) on the physicochemical properties and digestibility of pea starch (PS).

RESULTS

The results demonstrated that as the content of PPI increased from 0% to 12%, and the digestion of PS decreased by 12.3%. Rheological analysis indicated that PPI primarily interacted with molecular chains of PS through hydrogen bonds. Increasing the content of PPI resulted in a 30.6% decrease in the hardness of the composite gels, accompanied by a 10% reduction in the short-ordered structure of PS. This hindered the formation of molecular aggregation and resulted in a loose and disordered gel network structure. The microstructure confirmed that the attachment of PPI to PS served as a physical barrier, impeding starch digestibility.

CONCLUSION

In summary, the primary mechanism by which PPI inhibited PS digestion involved steric hindrance exerted by PPI and its interaction with PS via hydrogen bonds. These findings contribute to a better understanding of the interaction mechanisms between PS and PPI and offer insights for the optimal utilization of pea resources. © 2024 Society of Chemical Industry.

Rheological, thermal, and structural properties of heat-induced gluten gel: Effects of starch with varying degrees of debranching

This study evaluated the effects of starch with varying degree of debranching on the rheological, thermal, and structural properties of heat-induced gluten gel. As the duration of starch debranching treatment increased from 0 to 8 h, the viscoelasticity of the gel containing debranched starch (DBS) improved. Compared with the gluten gel (G), the gel strength of the G + DBS (8 h) sample increased by 65.2 %. The degradation temperature of gluten was minimally affected by DBS, while the weight loss rate increased by 4.4 %. Furthermore, the α-helical structure of gluten decreased, concomitant with an increase in β-sheet content. Notably, DBS treated for 8 h exhibited more hydrogen bonds with the tyrosine of gluten and triggered disulfide bridge conformation to transition from g-g-g to t-g-g, thereby reducing the stability of the molecular conformation of gluten proteins, as evidenced by the decreased height and width of the molecular chains observed in atomic force microscopy images. Overall, the composite gel structure induced by DBS exhibited a more continuous and homogeneous owing to the improved compatibility between DBS and gluten proteins, favoring the formation of a robust gel. These findings provide valuable insights for utilizing DBS to enhance gluten gel properties.

Effects of soaking glutinous sorghum grains on physicochemical properties of starch

Glutinous sorghum grains were soaked (60-80 °C, 2-8 h) to explore the effects of soaking, an essential step in industrial processing of brewing, on starch. As the soaking temperature increased, the peak viscosity and crystallinity of starch gradually decreased, while the enzymatic hydrolysis rate and storage modulus first increased and then decreased. At 70 °C, the content of amylose, the enzymatic hydrolysis rate of starch, and the final viscosity first increase and then decrease with the increase of soaking time, reaching their maximum at 6 h, increased by 53.1 %, 11.0 %, and 10.4 %, respectively, as compared with the non-soaked sample. At 80 °C (4 h), the laser confocal microscopy images showed a network structure formed between the denatured protein chains and the leached-out amylose chains. The molecular weights of starch before and after soaking were all in the range of 3.82-8.98 × 107 g/mol. Since 70 °C is lower than that of starch gelatinization and protein denaturation, when soaking for 6 h, the enzymatic hydrolysis rate of starch is the highest, and the growth of miscellaneous bacteria is inhibited, which is beneficial for subsequent processing technology. The result provides a theoretical basis for the intelligent control of glutinous sorghum brewing.

Effects of three different polysaccharides on the sol gel-behavior, rheological, and structural properties of tapioca starch

The sol-gel behavior of tapioca starch (TS) plays a crucial role in the processing and quality control of flour-based products. However, natural tapioca starch has low gel strength and poor viscosity, which tremendously limits its application. To solve this problem, this study investigated the effects of κ-carrageenan (KC), konjac gum (KGM), and Mesona chinensis Benth polysaccharide (MCP) on the pasting behavior, rheological, and structural properties of tapioca starch. KC, KGM, and MCP significantly increased the viscosity of TS. With the exception of high-concentration KGM (0.5 %), all other blending systems showed decrease in setback. This may be attributed to the stronger effect of the high-concentration KC (0.5 %) and MCP (0.5 %) functional groups interacting with starch. KC, KGM, and MCP effectively improved the dynamic modulus (G' and G") of TS gel and were effective in increasing the gel strength and hardness of TS. The FT-IR analysis indicated that the short-range order of TS was mainly influenced by polysaccharides through non-covalent bonding interactions. Furthermore, it was confirmed that three polysaccharides could form dense structures by hydrogen bonding with TS. Similarly, more stable structure and pore size were observed in the microstructure diagram.

Interaction with wheat starch affect the aggregation behavior and digestibility of gluten proteins

Understanding the interplay between gluten and wheat starch is crucial for elucidating the digestibility mechanism of gluten in wheat-based products. However, this mechanism remains under-investigated. This study sought to elucidate the influence of starch-induced protein structural modifications on gluten digestion. Our findings revealed that starch considerably enhanced gluten digestion. In the presence of starch, gluten protein digestibility increased from 10.91 % (in the control group with a gluten-to-starch ratio of 1:0) to 14.40 % (in the complex with a gluten-to-corn starch ratio of 1:1). The diminished gluten protein digestibility due to starch may be ascribed to modifications in protein configuration and aggregation behavior. Morphological studies suggested that starch not only functioned as filler particles but also diluted the gluten matrix. A protein network assessment further affirmed that both the junction density and branching rate of gluten proteins decreased notably by 29.9 % and 25.1 %, respectively. Conversely, lacunarity increased by 1.92-fold, compromising the cohesiveness and connectivity of the gluten matrix. Elevated starch concentrations suppressed the formation of disulfide bonds, impeding gluten protein aggregation. Concurrently, gluten-starch interactions were governed by hydrogen bonds and hydrophobic associations. In summary, starch augmented gluten protein digestibility by curtailing their polymerization. This revelation might offer novel perspectives on optimizing gluten protein digestion and utilization.

Glutenin-gliadin ratio changes combining heat-moisture treatment significantly influences the in vitro digestibility of starch in recombinant wheat flours

This study aimed to investigate the effect of heat-moisture treatment (HMT) on the in vitro digestibility of recombinant wheat flours characterizing by gluten proteins differ in glutenin-gliadin ratio. Compared with the untreated flours in our previous study, HMT improved the digestion resistance of starch in flours with different glutenin-gliadin ratios. For the HMT strong-gluten flour, the proportional increase of glutenin led to an excessively strong and fragile gluten network that unstable under HMT, which weakened the wrapping of gluten network around starch granules and reduced the long- and short-range order of starch, resulting in the conversion of resistant starch (RS) and slowly digestible starch (SDS) to rapidly digestible starch (RDS); however, the quantitative increase of gliadin induced the conversion of SDS to RS due to the enhanced protein-starch interactions as well as the improved long- and short-range order of starch during HMT. For the HMT weak-gluten flour, the changes of glutenin-gliadin ratio aggravated the broken of protein network and starch granules during HMT, thus improving the starch digestibility in varying degrees. In conclusion, the relative crystallinity of starch mainly affected the content of resistant starch, while the content of slowly digestible starch was more influenced by protein-starch interactions.

Effects of three glutenins extracted in acidic, neutral and alkaline urea solutions on the retrogradation of wheat amylose and amylopectin

Three glutenins (glutenin 1, glutenin 2, and glutenin 2) were extracted in acidic, neutral and alkaline urea solutions respectively. All of the three glutenins are rich in glutamic acid (Glu, >30 %) and proline (Pro, >20 %). Glutenin 1, extracted at pH 5, shows higher contents of hydrophilic amino acids as serine (Ser, 5.25 %), aspartic acid (Asp, 2.99 %), tyrosine (Tyr, 3.11 %), arginine (Arg, 2.09 %) and threonine (Thr, 2.11 %) than the other two glutenins. The retrogradation of three glutenins with amylose/amylopectin indicated that glutenin 1 showed significant inhibition effect on the retrogradation of wheat amylose. The characterizations of amylose retrograded with glutenin 1 by FT-IR, XRD, DSC and solid ¹³C NMR showed that new hydrogen bonds between Glu, Tyr and wheat amylose were formed, which prevented the formation of hydrogen bonds between amylose themselves. Glycosidic bonds between some hydroxyl groups of C6 in wheat amylose and certain hydroxyl groups of Ser and Thr in glutenin with specific chain length were present. The macromolecules with steric hindrance prevented the rearrangement of amylose into regular crystals. The retrogradation of wheat amylose was inhibited in this way. This study provides a key targeting step to control the retrogradation of amylose.

pH-shifting alters textural, thermal, and microstructural properties of mung bean starch-flaxseed protein composite gels

The objective of this study was to investigate the effect of pH-shifting on the textural and microstructural properties of mung bean starch (MBS)-flaxseed protein (FP) composite gels. Results showed that different pH-shifting treatments caused changes in hydrogen bond interactions and secondary structures in composite gels, leading to the formation of loose or compact gel networks. The pH 2-shifting modified protein and starch molecules with shorter chains tended to form smaller intermolecular aggregates, resulting in the formation of a looser gel network. For pH 12-shifting treatment, conformational change of FP caused the unfolding of protein and the exposure of more hydrophobic groups, which enhanced the hydrogen bond and hydrophobic interactions between polymers, contributing to the formation of a compact gel network. Furthermore, pH 12-shifting improved the water-holding capacity (WHC), storage modulus, and strength of gels, while pH 2-treated gels exhibited lower WHC, hardness, and gumminess due to the degradation of MBS and denaturation of FP caused by extreme acid condition. These findings suggest that pH-shifting can alter the gel properties of bi-polymeric starch-protein composite systems by affecting the secondary structures of proteins and the hydrogen bonding between the polymers, and provide a promising way for a wide application of FP in soft gel-type food production.

Physicochemical and Structural Properties of Gluten-Konjac glucomannan Conjugates Prepared by Maillard Reaction

Gluten (Glu) is important to wheat products by forming a three-dimensional matrix. This study aimed to investigate the physicochemical and structural properties of gluten after conjugation with konjac glucomannan (KGM) through the Maillard reaction. The study revealed that the degree of graft increased with the prolonged reaction time. The Glu-KGM conjugates were possessed of increased β-sheet but decreased α-helix and β-turn, as well as unfolding and loose tertiary structures as the reaction proceeded. Among three different proportions, the Glu-KGM 1:1 conjugate was proved to have the most excellent foaming and emulsifying properties, and could form more rigid and firm gelation structures, which could be related to the decreased particle size and increased zeta potential of the conjugate. Overall, the physicochemical and structural properties of gluten were significantly related to the KGM ratios as well as the reaction period.

Konjac glucomannan improves the gel properties of low salt myofibrillar protein through modifying protein conformation

Improving the characteristics of low salt proteins is the key to the gel properties of low-salt meat products which are demanded by people nowadays. The present study focused on the effects of KGM concentrations on the changes in structure and gelling properties of low-salt myofibrillar protein (MP). KGM addition (≤0.75 %) irrespective of salt concentration modified secondary and tertiary structures of MPs, enhanced the binding capacity of Troponin-T and Tropomyosin, augmented the gelling behavior of proteins, and remarkably improved the storage modulus (G') and gel strength of heat-induced MP gels. Interestingly, KGM addition in low salt condition showed the transformation of the all-gauche SS conformation into gauche-gauche-trans and trans-gauche-trans, and the partial transformation of α-helices into β-sheets. overall, KGM modified the structure of low salt MPs and thus improved the gel properties of low salt MPs. Therefore, KGM is recommended for low-salt meat processing to enhance the MP gelling potential.