Impact of calcium on the interactions between epigallocatechin-3-gallate and β-lactoglobulin

Novel Colloidal Food Ingredients: Protein Complexes and Conjugates

Food proteins, polysaccharides, and polyphenols are natural ingredients with different functional attributes. For instance, many proteins are good emulsifiers and gelling agents, many polysaccharides are good thickening and stabilizing agents, and many polyphenols are good antioxidants and antimicrobials. These three kinds of ingredients can be combined into protein, polysaccharide, and/or polyphenol conjugates or complexes using covalent or noncovalent interactions to create novel multifunctional colloidal ingredients with new or improved properties. In this review, the formation, functionality, and potential applications of protein conjugates and complexes are discussed. In particular, the utilization of these colloidal ingredients to stabilize emulsions, control lipid digestion, encapsulate bioactive ingredients, modify textures, and form films is highlighted. Finally, future research needs in this area are briefly proposed. The rational design of protein complexes and conjugates may lead to the development of new functional ingredients that can be used to create more nutritious, sustainable, and healthy foods.

Chemistry of Protein-Phenolic Interactions Toward the Microbiota and Microbial Infections

Along with health concerns, interest in plants as food and bioactive phytochemical sources has been increased in the last few decades. Phytochemicals as secondary plant metabolites have been the subject of many studies in different fields. Breakthrough for research interest on this topic is re-juvenilized with rising relevance in this global pandemics' era. The recent COVID-19 pandemic attracted the attention of people to viral infections and molecular mechanisms behind these infections. Thus, the core of the present review is the interaction of plant phytochemicals with proteins as these interactions can affect the functions of co-existing proteins, especially focusing on microbial proteins. To the best of our knowledge, there is no work covering the protein-phenolic interactions based on their effects on microbiota and microbial infections. The present review collects and defines the recent data, representing the interactions of phenolic compounds -primarily flavonoids and phenolic acids- with various proteins and explores how these molecular-level interactions account for the human health directly and/or indirectly, such as increased antioxidant properties and antimicrobial capabilities. Furthermore, it provides an insight about the further biological activities of interacted protein-phenolic structure from an antiviral activity perspective. The research on the protein-phenolic interaction mechanisms is of great value for guiding how to take advantage of synergistic effects of proteins and polyphenolics for future medical and nutritive approaches and related technologies.

Effect of non-covalent binding of phenolic derivatives with scallop (Patinopecten yessoensis) gonad protein isolates on protein structure and in vitro digestion characteristics

The present study was aimed to investigate the effects of non-covalent interactions between scallop gonad protein isolates (SGPIs) and different concentrations (20, 120 and 240 μmol/g, protein basis) of four phenolic compounds, such as (-)-epigallocatechin gallate (EGCG), epicatechin 3-gallate (ECG), epigallocatechin (EGC), and catechin (C), regarding the structural and functional properties of the complex. Total sulfhydryl and surface hydrophobicity in SGPIs decreased by nearly 72% and 65% with 240 μmol/g EGCG, similar but less appreciable changes were produced by EGC, ECG and C. Fluorescence quenching and thermodynamic parameters suggested that hydrogen bond and van der Waals dominated the interaction process between SGPIs and EGCG, and the interaction was further studied by molecular docking. Moreover, EGCG-treated SGPIs digests exerted higher ABTS+• scavenging activity than that of ECG and EGC-treated SGPIs. These findings are helpful to reveal the binding mechanism of phenolics and SGPIs, and provide a theoretical basis for the application of SGPIs-phenolic complexes as functional food additives.

On improving bioaccessibility and targeted release of curcumin-whey protein complex microparticles in food

Curcumin is a bioactive food component, with poor bioaccessibility due to low water solubility and stability. Spray drying retained and in fact enhanced curcumin-whey protein isolate (WPI) complexation via desolvation, lowering the amount of unbound curcumin to <5% wt after drying, forming microparticles with better water solubility, stability, and bioaccessibility than raw curcumin. The desolvated microparticles encapsulated 3.47 ± 0.05 mg/g curcumin, almost one order of magnitude higher than the un-desolvated sample 0.37 ± 0.03 mg/g. After incorporation into yogurt, the rapid-release formula liberated 87% curcumin, whereas the targeted-release one discharged 44% before entering the simulated intestinal condition. Most of the yogurt sensory properties were not adversely affected, except for colour and curcumin flavour. This study proposed a strategy in which food ingredients containing hydrophobic bioactive small molecules can be incorporated into a food matrix to improve bioaccessibility and targeted release, without affecting their sensory properties.

Effects of Tea-Polysaccharide Conjugates and Metal Ions on Precipitate Formation by Epigallocatechin Gallate and Caffeine, the Key Components of Green Tea Infusion

The mechanism of tea-infusion precipitation is not clear. Epigallocatechin gallate (EGCG) and caffeine (CAF) are the core components of green tea infusion precipitate. The critical precipitation concentration ( C_CPC) of EGCG-CAF mixed aqueous solutions was assayed through a turbidity assay performed at 25 °C and verified by a differential-scanning calorimeter (DSC) for reliability. Different concentrations of the green tea polysaccharide conjugate fraction (gTPC-D), with a molecular weight of 2.32 × 10⁵ Da, and of metal ions (K⁺, Mg²⁺, Ca²⁺, and Al³⁺) were respectively introduced into the mixed solution to study their effects on C_CPC. On the basis of the changed C_CPC, the clarification-precipitation phase diagrams of the mixed aqueous solutions were constructed. By calculating the integral area of the clarification phase, it was determined that the four metal ions and gTPC-D could accelerate precipitate formation with a dose-response relationship; among the metal ions, the effect of Al³⁺ is the strongest, followed by that of Ca²⁺.

Understanding the shielding effects of whey protein on mulberry anthocyanins: Insights from multispectral and molecular modelling investigations

Assembling between polyphenols and proteins has been recently spotlighted and this binding is of specific importance in food chemistry since these complexes are typically used in different foodstuffs. A study on the copigmentation among three encapsulation wall-materials, including maltodextrin, gum Arabic, and whey proteins, with mulberry anthocyanins (AC) proved that whey protein (WP) is an outstanding wall-material due to its wrapping and hyperchromicity effects. Additionally, high binding ability of WP with AC was shown to be responsible for its superior copigmentation effects. Accordingly, the underlying shielding mechanism of WP on AC based on their non-covalent assembling was deeply studied using multispectral and computational assays. The fluorometric results demonstrated that a static and heat-stable binding between WP and AC occurred, leading to modification in size, hydrophobicity, and secondary structures of WP. The docking results explained that WP-AC complex was mainly molded via hydrophobic effects of WP surface and subsequently be stabilized by H-bonding and van der Waals forces. These results may contribute to a better understanding on the enhanced colouring proprieties of anthocyanins by using whey proteins.

Antioxidant activity and nutrient release from polyphenol-enriched cheese in a simulated gastrointestinal environment

Polyphenol recovery during the in vitro intestinal digestion of cheese with tea extract.