Effect of chemical structure of selected phenolic acids on the structure of gluten proteins

The mechanism of purple sweet potato anthocyanin extract to reduce the digestion rate and improve the starch digestion characteristics based on dough system

Current studies have predominantly focused on the in vitro interactions between starch and anthocyanins, neglecting the complexity of actual food composition systems. In this study, purple sweet potato anthocyanin extract (PSPAE)-dough mixture was constructed with the aim of refining the mechanism by which anthocyanins improved starch digestive properties. Animal experiments demonstrated that the dough containing PSPAE (250 mg/kg) significantly reduced peak blood glucose levels in mice by 39.69 %. Further analysis of the dough mixture properties-including texture, particle size, pasting characteristics, microstructure, infrared spectrum, and crystallinity-helped elucidate how PSPAE impedes starch digestion. The incorporation of 600 mg of PSPAE into the dough led to a 40.45 % reduction in the volume mean diameter compared to the blank dough. Textural and microstructural examinations suggested that PSPAE obstruct the interaction forces between starch molecules by filling gluten protein pores or wrapping starch molecules. This denser microstructure likely contributes to enhanced starch resistance. Additionally, alterations in dough crystallinity revealed that PSPAE encourages the reorganization of linear starch molecules, boosting the content of resistant starch and thereby reducing starch digestibility. This study enriches the mechanism of PSPAE in ameliorating diabetes symptoms and provides theoretical insights for the development of functional foods aimed at diabetes management.

Establishing a novel covalent complex of wheat gluten with tea polyphenols: Structure, digestion, and action mechanism

Plant-based proteins represent a more sustainable alternative, the approaches to modify and enhance their functionality and application are focused on. Covalent interaction could significantly modify the structure and function properties of protein. This study investigated the effects of covalent interaction between wheat gluten and tea polyphenols on the structure, aggregation, stability, and digestive properties of their covalent complex, as well as the possible action mechanism. The results showed that tea polyphenols could interact with gluten via covalent bonds (CN and/or CS), while tea polyphenols also acted as a bridge connecting gluten molecules, thus making covalent complex to show the larger particle sizes. This covalent interaction significantly changed the secondary structure, tertiary structure, and surface hydrophobicity of gluten. Moreover, covalent complex exhibited the high polyphenols bioaccessibility during in vitro digestion. The peptide bonds of covalent complex were mainly broken in gastric digestion, while the covalent bonds between tea polyphenols and gluten were completely destroyed in intestinal digestion. In addition, their digestates exhibited excellent antioxidant capability. All results suggest that wheat gluten have potential to prepare functional carrier for transporting active compounds and protecting them during digestion.

Ultrasound-enhanced covalent reaction of gliadin: the inhibition of antigenicity and its potential mechanisms

BACKGROUND

Wheat proteins can be divided into water/salt-soluble protein (albumin/globulin) and water/salt-insoluble protein (gliadins and glutenins (Glu)) according to solubility. Gliadins (Glia) are one of the major allergens in wheat. The inhibition of Glia antigenicity by conventional processing techniques was not satisfactory.

RESULTS

In this study, free radical oxidation was used to induce covalent reactions. The effects of covalent reactions by high-intensity ultrasound (HIU) of different powers was compared. The enhancement of covalent grafting effectiveness between gliadin and (-)-epigallo-catechin 3-gallate (EGCG) was confirmed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, matrix-assisted laser desorption/ionization-time-of-flight-mass spectrometry and Folin-Ciocalteu tests. HIU caused protein deconvolution and disrupted the intrastrand disulfide bonds that maintain the tertiary structure, causing a shift in the side chain structure, as proved by Fourier, fluorescence and Raman spectroscopic analysis. Comparatively, the antigenic response of the conjugates formed in the sonication environment was significantly weaker, while these conjugates were more readily hydrolyzed and less antigenic during simulated gastrointestinal fluid digestion.

CONCLUSION

HIU-enhanced free radical oxidation caused further transformation of the spatial structure of Glia, which hid or destroyed the antigenic epitope, effectively inhibiting protein antigenicity. This study widened the application of polyphenol modification in the inhibition of wheat allergens. © 2024 Society of Chemical Industry.

Regulating the physicochemical, structural characteristics and digestibility of potato starch by complexing with different phenolic acids

The effects of ferulic acid (FA), protocatechuic acid (PA), and gallic acid (GA) on the physicochemical characteristics, structural properties, and in vitro digestion of gelatinized potato starch (PS) were investigated. Rapid viscosity analysis revealed that the gelatinized viscosity parameters of PS decreased after complexing with different phenolic acids. Dynamic rheology results showed that phenolic acids could reduce the values of G' and G″ of PS-phenolic acid complexes, demonstrating that the addition of phenolic acids weakened the viscoelasticity of starch gel. Fourier-transform infrared spectra and X-ray diffraction results elucidated that phenolic acids primarily reduced the degree of short-range ordered structure of starch through non-covalent interactions. The decrease in thermal stability and the more porous microstructure of the complexes confirmed that phenolic acids could interfere with the gel structure of the starch. The addition of different phenolic acids decreased the rapidly digestible starch (RDS) content and increased the resistant starch (RS) content, with GA exhibiting the best inhibitory capacity on starch in vitro digestibility, which might be associated with the number of hydroxy groups in phenolic acids. These results revealed that phenolic acids could affect the physicochemical characteristics of PS and regulate its digestion and might be a potential choice for producing slow digestibility starch foods.

Insight into Organization of Gliadin and Glutenin Extracted from Gluten Modified by Phenolic Acids

The changes in the secondary structure of individual gluten protein fractions (gliadin and glutenin) caused by the supplementation of model dough with eight phenolic acids were analysed. Gliadins and glutenins were extracted from gluten samples obtained from overmixed dough. The changes in the gliadin secondary structure depended on the amount of phenolic acid added to the dough. Higher acid concentrations (0.1% and 0.2%) led to a significant reduction in the amount of α-helices and to the formation of aggregates, non-ordered secondary structures, and antiparallel β-sheets. After the addition of acids at a lower concentration (0.05%), the disaggregation of pseudo-β-sheet structures and the formation of β-turns, hydrogen-bonded β-turns, and antiparallel β-sheets were detected. In the case of glutenin, most of the phenolic acids induced the formation of intermolecular hydrogen bonds between the polypeptide chains, leading to glutenin aggregation. When phenolic acids were added at a concentration of 0.05%, the process of protein folding and regular secondary structure formation was also observed. In this system, antiparallel β-sheets and β-turns were created at the expense of pseudo-β-sheets.

Bioactive components and nutritional properties of fiber-rich cookies produced with different parts of oleaster (Elaeagnus angustifolia L.)

BACKGROUND

Oleaster (Elaeagnus angustifolia L.) possesses exocarp and endocarp layers enriched with abundant phytochemicals and fiber. Flours produced in different parts of oleaster were used in cookie formulation to improve the bioactive components and nutritional properties of cookies.

RESULTS

The rheological properties of composite flours containing varying levels of oleaster exocarp flour (O'EX-F) and endocarp flour (O'EN-F), ranging from 0% to 30%, were assessed using Mixolab (Chopin Technologies, Villeneuve-la-Garenne, France). The physical, chemical, nutritional, and sensory properties of cookies made with these flours were also analyzed. The substitution of O'EX-F and O'EN-F in the cookies enhanced redness and total color differences at the same time as decreasing hardness and improving the spread ratio. Furthermore, using these flours elevated the dietary fiber content of the cookies, particularly in terms of soluble and total dietary fiber. O'EX-F and O'EN-F also significantly increased free, bound, and total phenolic contents, as well as antioxidant capacity. Sensory evaluation of cookies with 10% and 20% O'EX-F and O'EN-F indicated greater appreciation than control cookies. Incorporating 20% O'EX-F and 20% O'EN-F into cookies resulted in a notable increase in Ca, Mg, K, Fe, and Zn levels.

CONCLUSION

The utilization of O'EX-F and O'EN-F, which contain a wealth of bioactive components, has significantly impacted the dough of rheology. Including these ingredients in cookie formulations has demonstrated improvements in ash, dietary fiber content, phenolics, antioxidant activity, and overall technological quality at the same time as providing distinctive sensory properties. The present study has contributed a new composite flour to the existing literature and has facilitated the development of novel cookie products for the functional food industry. © 2023 Society of Chemical Industry.

Sonochemical Effects on the Preparation, Structure and Function of Gliadin-(-)-Epigallo-Catechin 3-Gallate Conjugates

It is essential to understand the mechanism of action of ultrasound synergistic free radical oxidation to promote covalent reactions between proteins and polyphenols. (-)-epigallo-catechin 3-gallate (EGCG) with rich bioactivity could be used to increase the functional properties of cereal protein-gliadin (GL). This study systematically explored the role of ultrasound treatment (US) on the binding mechanisms of GL and EGCG. Electrophoresis and high-performance liquid chromatography (HPLC) confirmed the greater molecular mass of the covalent complexes in the ultrasound environment. Quantitative analysis by the phenol content revealed that the ultrasound environment increased the EGCG content in the covalent complex by 15.08 mg/g of protein. The changes in the spatial structure of the proteins were indicated by Fourier infrared and ultraviolet spectroscopy. Additionally, scanning electron microscopy (SEM) and atomic force microscopy (AFM) found that US disrupted the aggregation of GL and the clustered structure of the covalent complexes. The results demonstrated that the water solubility of ultrasonic conjugates was significantly increased by 8.8-64.19%, the digestion rate was more efficient, and the radical scavenging capacity was twice that of GL. This research contributes to the theoretical basis for broadening the application of polyphenols in modifying protein.