Conformational changes induced by cellulose nanocrystals in collaboration with calcium ion improve solubility of pea protein isolate.

The low solubility of pea protein isolate (PPI) greatly limits its functional properties and its wide application in food field. Thus, this study investigated the effects and mechanisms of cellulose nanocrystals (CNC) (0.1-0.4 %) and CaCl2 (0.4-1.6 mM) on the solubility of PPI. The results showed that the synergistic effect of CNC (0.3 %) and Ca2+ (1.2 mM) increased the solubility of PPI by 242.31 %. CNC and Ca2+ changed the molecular conformation of PPI, enhanced intermolecular forces, and thus induced changes in the molecular morphology of PPI. Meanwhile, the turbidity of PPI decreased, while surface hydrophobicity, the absolute zeta potential value, viscoelasticity, ß-sheet ratio, and thermal properties increased. CNC bound to PPI molecules through van der Waals force and hydrogen bond. Ca2+ could strengthen the crosslinking between CNC and PPI. In summary, it is proposed a valuable combination method to improve the solubility of PPI, and it is believed that this research is of great significance for expanding the application fields of PPI and modifying plant proteins.

Investigation of the effect of ultrasonication on starch-fatty acid complexes and the stabilization mechanism.

The complexation of physically modified starch with fatty acids is favorable for the production of resistant starch. However, there is a lack of information on the effect of ultrasonication (UC) on the structure and properties of starch complexes and the molecular mechanism of the stabilization. Here, the multi-scale structure and in vitro digestive properties of starch-fatty acid complexes before and after UC were investigated, and the stabilization mechanisms of starch and fatty acids were explored. The results showed that the physicochemical properties and multi-scale structure of the starch-fatty acid complexes significantly changed with the type of fatty acids. The solubility and swelling power of the starch-fatty acid complexes were significantly decreased after UC (P < 0.05), which facilitated the binding of starch with fatty acids. The XRD results revealed that after the addition of fatty acids, the starch-fatty acid complexes showed typical V-shaped complexes. In addition, the starch-fatty acid complexes showed a significant increase in complexing index, improved short-range ordering and enhanced thermal stability. However, the differences in the structure and properties of the fatty acids themselves resulted in no significant improvement in the multi-scale structure of maize starch-palmitic acid by UC. In terms of digestibility, especially the complexes after UC were more compact in structure, which increased the difficulty of enzymatic digestion and thus slowed down the digestion process. DFT calculations and combined with FT-IR analysis showed that non-covalent interactions such as hydrogen bonding and hydrophobic interactions were the main driving force for the formation of the complexes, with binding energies (lauric acid, myristic acid and palmitic acid) of -30.50, -22.14 and -14.10 kcal/mol, respectively. Molecular dynamics simulations further confirmed the molecular mechanism of inclusion complex formation and stabilization. This study is important for the regulation of starchy foods by controlling processing conditions, and provides important information on the role of fatty acids in the regulation of starch complexes and the binding mechanism.

Remodeling mechanism of gel network structure of soy protein isolate amyloid fibrils mediated by cellulose nanocrystals.

The differences in the gelling properties of soy protein isolate (SPI) and soy protein isolate amyloid fibrils (SAFs) as well as the role of cellulose nanocrystals (CNC) in regulating their gel behaviors were investigated in this study. The binding of CNC to ß-conglycinin (7S), glycinin (11S), and SAFs was predominantly driven by non-covalent interactions. CNC addition reduced the particle size, turbidity, subunit segments, and crystallinity of SPI and SAFs, promoted the conversion of α-helix to ß-sheet, improved the thermal stability, exposed more tyrosine and tryptophan residues, and enhanced the intermolecular interactions. A more regular and ordered lamellar network structure was formed in the SAFs-CNC composite gel, which could be conducive to the improvement of gel quality. This study would provide theoretical reference for the understanding of the regulatory mechanism of protein amyloid fibrils gelation as well as the high-value utilization of SAFs-CNC complex as a functional protein-based material or food ingredient in food field.

Insight into the solubilization mechanism of wheat gluten by protease modification from conformational change and molecular interaction perspective.

The low solubility limits the utilization of other functional characteristics of wheat gluten (WG). This study effectively improved the solubility of WG through protease modification and explored the potential mechanism of protease modification to enhance the solubility of WG, further stimulating the potential application of WG in the food industry. Solubility of WG modified with alkaline protease, complex protease, and neutral protease was enhanced by 98.99%, 54.59%, and 51.68%, respectively. Notably, the content of ß-sheet was reduced while the combined effect of hydrogen bond and ionic bond were increased after protease modification. Meanwhile, the reduced molecular size and viscoelasticity as well as the elevated surface hydrophobicity, thermostability, water absorption capacity, and crystallinity were observed in modified WG. Moreover, molecular docking indicated that protease was specifically bound to the amino acid residues of WG through hydrogen bonding, hydrophobic interaction, and salt bridge.

Synergistic effect and mechanism of cellulose nanocrystals and calcium ion on the film-forming properties of pea protein isolate.

The current serious environmental problems have greatly encouraged the design and development of food packaging materials with environmental protection, green, and safety. This study aims to explore the synergistic effect and corresponding mechanism of cellulose nanocrystals (CNC) and CaCl2 to enhance the film-forming properties of pea protein isolate (PPI). The combination of 0.5 % CNC and 4.5 mM CaCl2 resulted in a 76.6 % increase in tensile strength when compared with pure PPI-based film. Meanwhile, this combination effectively improved the barrier performance, surface hydrophobicity, water resistance, and biodegradability of PPI-based film. The greater crystallinity, viscoelasticity, lower water mobility, and improved protein spatial conformation were also observed in CNC/CaCl2 composite film. Compared with the control, the main degradation temperature of composite film was increased from 326.23 °C to 335.43 °C. The CNC chains bonded with amino acid residue of pea protein at specific sites via non-covalent forces (e.g., hydrogen bonds, Van der Waals forces). Meanwhile, Ca2+ promoted the ordered protein aggregation at suitable rate and degree, accompanied by the formation of more disulfide bonds. Furthermore, proper Ca2+ could strengthen the cross-linking and interaction between CNC and protein, thereby establishing a stable network structure. The prepared composite films are expected to be used for strawberry preservation.

Complexation between rice starch and cellulose nanocrystal from black tea residues: Gelatinization properties and digestibility in vitro.

In this work, cellulose nanocrystal (CNC) was extracted from black tea waste and its effects on the physicochemical properties of rice starch were explored. It was revealed that CNC improved the viscosity of starch during pasting and inhibited its short-term retrogradation. The addition of CNC changed the gelatinization enthalpy and improved the shear resistance, viscoelasticity, and short-range ordering of starch paste, which meant that CNC made the starch paste system more stable. The interaction of CNC with starch was analyzed using quantum chemistry methods, and it was demonstrated that the hydrogen bonds were formed between starch molecules and the hydroxyl groups of CNC. In addition, the digestibility of starch gels containing CNC was significantly decreased because CNC could dissociate and act as an inhibitor of amylase. This study further expanded the understanding of the interactions between CNC and starch during processing, which could provide a reference for the application of CNC in starch-based foods and the development of functional foods with a low glycemic index.