Protein-polyphenol functional ingredients: The foaming properties of lactoferrin are enhanced by forming complexes with procyanidin

Improving foam performance using colloidal protein-polyphenol complexes: Lactoferrin and tannic acid

In this study, colloidal complexes were prepared from bovine lactoferrin (BLF) and tannic acid (TA) and then their ability to form and stabilize foams was characterized. The molecular interactions between BLF and TA were studied using fluorescence and molecular docking analysis, which suggested that hydrophobic forces were primarily involved in holding the complexes together. The production of colloidal BLF-TA complexes was supported by increases in turbidity and mean particle diameter, quenching of intrinsic fluorescence, decrease in surface hydrophobicity, and change in conformation. When used alone, BLF exhibited good foam formation but poor foam stability properties. In contrast, BLF-TA complexes exhibited good foam stability but poor foamability properties. The change in foaming properties of the proteins was closely related to their interactions with the polyphenols. These findings may be useful for the development of novel functional ingredients to construct food foams with good physicochemical and nutritional attributes.

Molecular modeling of lactoferrin for food and nutraceutical applications: insights from in silico techniques

Lactoferrin is a protein, primarily found in milk that has attracted the interest of the food industries due to its health properties. Nevertheless, the instability of lactoferrin has limited its commercial application. Recent studies have focused on encapsulation to enhance the stability of lactoferrin. However, the molecular insights underlying the changes of structural properties of lactoferrin and the interaction with protectants remain poorly understood. Computational approaches have proven useful in understanding the structural properties of molecules and the key binding with other constituents. In this review, comprehensive information on the structure and function of lactoferrin and the binding with various molecules for food purposes are reviewed, with a special emphasis on the use of molecular dynamics simulations. The results demonstrate the application of modeling and simulations to determine key residues of lactoferrin responsible for its stability and interactions with other biomolecular components under various conditions, which are also associated with its functional benefits. These have also been extended into the potential creation of enhanced lactoferrin for commercial purposes. This review provides valuable strategies in designing novel nutraceuticals for food science practitioners and those who have interests in acquiring familiarity with the application of computational modeling for food and health purposes.

Review on the Regulation of Plant Polyphenols on the Stability of Polyunsaturated-Fatty-Acid-Enriched Emulsions: Partitioning Kinetic and Interfacial Engineering

The plant polyphenols are normally presented as natural functional antioxidants, which also possess the potential ability to improve the physicochemical stability of polyunsaturated fatty acid (PUFA)-enriched emulsions by interface engineering. This review discussed the potential effects of polyphenols on the stability of PUFA-enriched emulsions from the perspective of the molecular thermodynamic antioxidative analysis, the kinetic of interfacial partitioning, and the covalent and non-covalent interactions with emulsifiers. Recently, research studies have proven that the interfacial structure of emulsions can be concurrently optimized via promoting interfacial partitioning of polyphenols and further increasing interfacial thickness and strength. Moreover, the applied limitations of polyphenols in PUFA-enriched emulsions were summarized, and then some valuable and constructive viewpoints were put forward in this review to provide guidance for the use of polyphenols in constructing PUFA-enriched emulsions.

Non-covalent interaction of soy protein isolate and catechin: Mechanism and effects on protein conformation

Understanding the molecular mechanism behind protein-polyphenol interactions is critical for the application of protein-polyphenol compounds in foods. The purpose of this research was to investigate the non-covalent interaction mechanism between soy protein isolate (SPI) and catechin and its effect on protein conformation. We observed that particle size, ζ-potential, and polyphenol bound equivalents of SPI increased significantly after non-covalent modification with catechin. These changes caused SPI to aggregate and form a network-like structure. Fourier transform infrared spectroscopy (FTIR) indicated that increased catechin concentrations caused SPI to become looser and more disordered as its α-helix and β-sheet transformed into β-turn and random coil. Furthermore, internal structure of SPI was opened and its hydrophobic groups were exposed to a polar environment, which was demonstrated by decreased surface hydrophobicity. Thermodynamic analysis and molecular docking results showed that the main forces present between SPI and catechin were hydrophobic interactions and hydrogen bonds.

Bioactives and extracts affect the physico-chemical properties of concentrated whey protein isolate dispersions

Non-covalent complexation interactions are known to occur between bioactive compounds and proteins. While formulating with these components can have positive outcomes such as stabilization of colors and actives, it can also result in changes to the structures and physical properties of proteins, affecting product functionality and sensory attributes. Previous experiments reported measurable changes in the physico-chemical properties of whey protein isolate (WPI) dispersions upon formulation with Aronia berry extract, ascribing changes to protein-polyphenol (PP) interactions in the systems. Pure gallotannin, beet extract, and cranberry extract, providing a diverse variety structures and sizes, were selected for further experimentation and comparison with the effects of Aronia extract. Concentrated dispersions with varying WPI:sucrose ratios, formulated with several bioactives contents from multiple different sources were analyzed to identify the effects of different bioactives on physico-chemical properties of dispersions. Dispersions formulated with cranberry extract demonstrated the largest increases in surface tensions, viscosities, and particle sizes, while those formulated with beet extract were the least affected by the presence of bioactives, suggesting that different bioactives and extracts had varying propensities for complexation interactions with WPI, despite their relatively low levels of addition (0, 0.5, and 1%).

Graphical Abstract

Non-covalent interaction between pea protein isolate and catechin: effects on protein structure and functional properties

The aim of this study was to investigate the effects of non-covalent interaction between pea protein isolate (PPI) and different concentrations (0.05–0.25%, w/v) of catechin (CT) on the structural and functional characteristics of protein.

Fabrication and performance evaluation of pectin-fish gelatin-resveratrol preservative films

Resveratrol-loaded fish gelatin (FG)-low methoxyl pectin (LMP) composite films with different FG:LMP mass ratios were prepared and evaluated as food packaging materials. With increasing FG contents, the water solubility of the films decreased. Moreover, the UV (315-400 nm) blocking efficiency and opacity increased with increasing LMP contents. The elongation of the films at breaking and tensile strengths were adjusted using the ratio of FG and LMP. The lowest water vapour permeability was observed at an FG:LMP mass ratio of 2:1. All films exhibited good antioxidant properties and significantly delayed oil deterioration when used for beef tallow preservation. The release behaviour of resveratrol in 95% ethanol as a food simulant was determined by film composition. The fabricated films exhibit significant potential for beef tallow preservation applications. Furthermore, LMP can improve the stability of resveratrol-FG complexes and compete with resveratrol for binding FG to accelerate resveratrol release.

Conjoint application of ultrasonication and redox pair mediated free radical method enhances the functional and bioactive properties of camel whey-quercetin conjugates

Ultrasonication, redox-pair generated free radical method and their combination (Ultrasonication/redox-pair method) was used for production of camel whey-quercetin conjugates. FTIR and SDS-PAGE confirmed successful production of whey-quercetin conjugates using ultrasonication and ultrasonication/redox-pair method. FTIR suggested existence of covalent (appearance of new peak at 3399 cm-1) and non-covalent linkages (shifting of peak at 3271 cm-1, 1655 cm-1 (amide I), 1534 cm-1 and 1422 cm-1 (Amide II)) in the whey-quercetin conjugates. Moreover, SDS-PAGE of conjugates produced by ultrasonication as well redox-pair method indicated shifting of protein bands slightly towards high molecular weight due to increase in the mass of proteins due to the binding of polyphenols. All conjugates showed improved techno-functional and bioactive properties in comparison to whey proteins. Conjugates produced through ultrasonication showed smaller particle size, improved solubility, emulsifying and foaming properties while conjugates produced through ultrasonication/redox-pair method depicted superior antioxidant properties in comparison to whey. Furthermore, conjugated samples showed higher inhibition of enzymatic markers involved in diabetes and obesity with highest potential recorded in conjugates produced using ultrasonication. Therefore, ultrasonication can be successfully used individually as well as in combination with redox-pair for production of whey-quercetin conjugates with enhanced bioactive and techno-functional properties.

Characteristics of the interaction mechanisms of procyanidin B1 and procyanidin B2 with protein tyrosine phosphatase-1B: Analysis by kinetics, spectroscopy methods and molecular docking

Protein tyrosine phosphatase-1B (PTP1B) is a novel and indispensable drug target for the treatment of type 2 diabetes mellitus (T2DM). Procyanidins are flavonoids that exhibit a significant hypoglycemic function. However, the potential inhibitory effects of procyanidins on PTP1B are unclear. In this study, the interaction mechanisms of PTP1B with procyanidin B1 (PB1) and procyanidin B2 (PB2) were investigated through kinetics analysis, UV-visible spectroscopy, fluorescence spectroscopy, circular dichroism spectroscopy and molecular docking. The results showed that PB1 and PB2 could inhibit the activity of PTP1B in a mixed inhibition mode, which was one of the reversible inhibition types. Multi-spectral analysis showed that PB1/PB2 formed complexes with PTP1B, which effectively quenched the intrinsic fluorescence of PTP1B based on the static mechanism. The values of the binding constants were K_S(PTP1B-PB1) = 4.06 × 10² L·mol^-1 and K_S(PTP1B-PB2) = 2.53 × 10² L·mol^-1, indicating that the binding affinity of PTP1B to PB1 was higher than that for PB2. PB1 and PB2 both changed the secondary structure of the enzyme, thereby decreasing the PTP1B activity. Thermodynamic investigations revealed that the binding of procyanidin B1 and B2 to PTP1B was spontaneous in both cases, and highlighted the key role of hydrophobic interactions. Molecular docking analysis provided further information regarding the interactions between PB1 or PB2 and the amino acid residues of PTP1B. Moreover, PB1 and PB2 were found to down-regulate the expression level of PTP1B in insulin-resistant HepG2 cells. These findings are the first to elucidate the inhibitory effects of PB1 and PB2 on PTP1B, and highlight the role of procyanidins as dietary supplements in regulating T2DM.

The formation of phycocyanin-EGCG complex for improving the color protection stability exposing to light

Phycocyanin (PC) is a natural pigment-protein complex in food dye applications. In this study, a phycocyanin-epigallocatechin gallate (EGCG) complex (PE) was prepared and the effects of EGCG on the structure and color stability of PC were evaluated. The fluorescence results showed that the binding number n was 62.1 ± 3.41 (EGCG/PC) and the binding constant K was 4.39 (±0.2) × 10⁵ M^-1, indicating a weak-binding interaction. Fourier transform-infrared analysis showed that EGCG caused structural changes in PC by partially uncoiling α-helix and increasing β-sheet content. The EGCG induced a PC association at a reaction molar ratio above 40:1 (EGCG/PC). Moreover, EGCG protected phycocyanobilin against color fading, making PE more stable relative to PC under 8-days storage in light. This study provides a novel scheme to stabilize PC by forming a complex with polyphenols, which will facilitate the PC application as a natural blue pigment in food.

Roles of Proteins/Enzymes from Animal Sources in Food Quality and Function

Animal proteins are good sources of protein for human, due to the composition of necessary amino acids. The quality of food depends significantly on the properties of protein inside, especially the gelation, transportation, and antimicrobial properties. Interestingly, various kinds of molecules co-exist with proteins in foodstuff, and the interactions between these can significantly affect the food quality. In food processing, these interactions have been used to improve the texture, color, taste, and shelf-life of animal food by affecting the gelation, antioxidation, and antimicrobial properties of proteins. Meanwhile, the binding properties of proteins contributed to the nutritional properties of food. In this review, proteins in meat, milk, eggs, and fishery products have been summarized, and polysaccharides, polyphenols, and other functional molecules have been applied during food processing to improve the nutritional and sensory quality of food. Specific interactions between functional molecules and proteins based on the crystal structures will be highlighted with an aim to improve the food quality in the future.

Spectroscopic and docking studies of the interaction mechanisms of xylitol with α-casein and κ-casein

The molecular interactions of xylitol (XY) with α-casein (α-CN) and κ-casein (κ-CN) at pH 7.4 as a function of temperature (298, 308, and 318 K) were characterized by multispectral techniques and molecular docking. The fluorescence results showed that XY strongly quenched the intrinsic fluorescence of α- and κ-CN by static quenching, as well as the presence of a single binding site for XY on both proteins with a binding constant value of ∼10⁵ L/mol. The binding affinity of both proteins for XY decreased with increasing temperature, and Van der Waals forces, hydrogen bonding and protonation were the key forces in the interactions. The addition of XY altered the polarity of the microenvironment of proteins and changed their secondary structure from ordered to disordered. The molecular docking results showed that XY had different binding sites to α- and κ-CN, with several amino acids involved in the binding processes.

Whey protein-polyphenol conjugates and complexes: Production, characterization, and applications

Whey proteins are widely used as functional ingredients in various food applications owing to their emulsifying, foaming, and gelling properties. However, their functional attributes are limited in some applications because of the dependence of their performance on pH, mineral levels, and temperature. Several approaches have been investigated to enhance the functional performance of whey proteins by interacting them with polyphenols via covalent bonds (conjugates) or non-covalent bonds (complexes). The interaction of the polyphenols to the whey proteins alters their molecular characteristics, techno-functional attributes, and biological properties. Analytical methods for characterizing the properties of whey protein-polyphenol complexes and conjugates are highlighted, and a variety of potential applications within the food industry are discussed, including as antioxidants, emulsifiers, and foaming agents. Finally, areas for future research are highlighted.

Lactoferrin-ginsenoside Rg3 complex ingredients: Study of interaction mechanism and preparation of oil-in-water emulsion

Revealing the interaction mechanism between bovine lactoferrin (LF) and 20(S)-ginsenoside Rg3 (Rg3), thereby introducing Rg3 to LF and even into stable emulsions will contribute significantly to food valorization and food industry. Adding Rg3 to LF caused slight absorbance increment and static fluorescence quench of LF, implying the successful combination. Synchronous fluorescence, three-dimensional fluorescence and circular dichroism spectroscopy indicated the conformation changing of LF after binding with Rg3. Thermodynamic analysis showed that the binding happened spontaneously to form a LF-Rg3 complex with a molar ratio of 1:1, which was mainly driven by hydrogen bonding and van der Waals force. Molecular docking simulation provided extensive information about the optimized binding sites and the involved interactions. Finally, we prepared stable LF-Rg3 oil-in-water emulsion, showing great potential in foods and beverages. This work prepares all-natural functional ingredients, and also diversifies the effective food molecule-based delivery systems for LF and Rg3.