Whey protein-pectin conjugates: Linking the improved emulsifying properties to molecular and physico-chemical characteristics

Characterization and emulsifying ability evaluation of whey protein-pectin conjugates formed by glycosylation

Glycosylation is a method that enhances the functional properties of proteins by covalently attaching sugars to them. This study aimed at preparing three conjugates (WP-HG, WP-SBP, and WP-RGI) by dry heating method to research the influence of different pectin structures on the functional properties of WP and characterize properties and structures of these conjugates. The research results manifested that the degree of glycosylation (DG) of HG, SBP and RGI were 13.13 % ± 0.07 %, 23.27 % ± 0.3 % and 36.39 % ± 0.3 % respectively, suggesting that the increase of the number of branch chains promoted the glycosylation reaction. The formation of the conjugate was identified by the FT-IR spectroscopy technique. And SEM showed that WP could covalently bind to pectin, resulting in a smoother and denser surface of the conjugates. The circular dichroism analysis exhibited that the glycosylation reaction altered the secondary structure of WP and decreased the α-Helix content. This structural change in the protein spatial conformation led to a decrease in the hydrophobicity of protein surface. But the addition of pectin further regulated the hydrophilic-hydrophobic ratio on the surface of the protein, thus improving the emulsification properties of WP. In addition, the glycosylation could improve the stability of the emulsion, giving it a smaller droplet size, higher Zeta-potential and more stable properties. In a word, this study pointed out the direction for the application of different pectin structures in the development of functional properties of glycosylation products in food ingredients.

Food protein glycation: A review focusing on stability and in vitro digestive characteristics of oil/water emulsions

Recently, increasing studies have shown that the functional properties of proteins, including emulsifying properties, antioxidant properties, solubility, and thermal stability, can be improved through glycation reaction under controlled reaction conditions. The use of glycated proteins to stabilize hydrophobic active substances and to explore the gastrointestinal fate of the stabilized hydrophobic substances has also become the hot spot. Therefore, in this review, the effects of glycation on the structure and function of food proteins and the physical stability and oxidative stability of protein-stabilized oil/water emulsions were comprehensively summarized and discussed. Also, this review sheds lights on the in vitro digestion characteristics and edible safety of emulsion stabilized by glycated protein. It can further serve as a research basis for understanding the role of structural features in the emulsification and stabilization of glycated proteins, as well as their utilization as emulsifiers in the food industry.

Lycopene-loaded emulsions stabilized by whey protein covalently modified with pectin or/and chlorogenic acid: Enhanced physicochemical stability and reduced bio-accessibility

Lycopene-loaded emulsions were formulated with whey protein isolate (WPI) covalently modified with high methoxylated pectin (HMP) or/and chlorogenic acid (CA) prepared by dry heating or/and alkali grafting. Covalent WPI products were confirmed by SDS-PAGE and degree of graft/CA binding equivalent values. The α-helix and β-sheet percentage, surface hydrophobicity and fluorescence intensity of WPI decreased significantly (p < 0.05) upon binding. Both binary and ternary complexes enhanced the stability of the emulsions, and lycopene retained more after UV irradiation, thermal treatment, storage, compared with emulsions stabilized by WPI, with the best protection by both ternary complexes. In vitro simulated digestion results showed that free fatty acids were released in the order of WPI > WPI-HMP > WPI-CA > WPI-HMP-CA ≈ WPI-CA-HMP. Bio-accessibility analysis showed the same trend as the fatty acid release rate. These results may provide a theoretical basis for applications of conjugating protein with polysaccharide or/and polyphenol emulsions.

Changes in structural and functional properties of whey protein cross-linked by polyphenol oxidase

The natural whey protein is unstable, to achieve more efficient utilization, the functional properties of whey protein were modified by changing its structure, and enzymatic cross-linking is one of the common methods in dairy products to change the functional characterization. This study was conducted with objective to evaluate the structural and functional of whey protein which was cross-linked by polyphenol oxidase from Agaricus bisporus. Whey protein was cross-linked by polyphenol oxidase, and the polymers and dimers were revealed by SDS-PAGE and LC-MS/MS, the structural alterations of the polymers were analyzed by UV-vis, fluorescence spectroscopy and SEM, and the effects of functional properties of whey protein after cross-linked were also explored. Results showed that dimer and high polymer of β-lactoglobulin were formed, the secondary structure of whey protein was exhibited a significant variation, and the microstructure changed obviously. Moreover, the foaming and antioxidant activity of whey protein was enhanced although the emulsifying was reduced after cross-linked. These findings emphasize the feasible application of enzymatic cross-linking in improving the functional properties of whey protein, and provide a new direction for changing the traditional processing technology of whey protein and developing high-quality products.

Physicochemical properties of whey protein isolate and alkaline soluble polysaccharide from sugar beet pulp conjugates formed by Maillard reaction and genipin crosslinking reaction: A comparison study

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Emulsifying activity of ASP2 was obviously improved by graftingwith WPI.

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ASP2 self-crosslinking could be excuted by both maillard reaction and genipin crosslinking reaction.

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WPI linked with carbonyl group contributed more efficiency to emulsifying activity of PPC than linked with amino group of ASP2.

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Calcium bridge effect could not be efficiently inhibited by grafting ASP2 with WPI.

This study aim to investigate the effect of alkaline soluble polysaccharide from sugar beet pulp (ASP2) grafted with whey protein isolate (WPI) by two linking models (grafting on amino group or carbonyl group) on its emulsifying properties. Results demonstrated that the d_4,3 value of WPI, M−AW, M−AA, G-AW and G-AA stabilized emulsions was 0.18 μm, 0.28 μm, 0.72 μm, 0.56 μm and 0.83 μm, respectively, suggesting the higher emulsifying activity of the products prepared by Maillard reaction compared with the products obtained from genipin crosslinking reaction. After storage, the d_4,3 increment was 1.05 μm, 0.21 μm, 0.31 μm, 0.2 μm and 0.15 μm for WPI, M−AW, M−AA, G-AW and G-AA stabilized emulsions, respectively, indicating that the new generated polymers held stronger emulsifying stability compared with WPI. However, the aggregates emerged in high calcium emulsions system indicated that grafting with WPI could not efficiently reduce the sensitivity of ASP2 to calcium.

The complex of whey protein and pectin: Interactions, functional properties and applications in food colloidal systems - A review

This review describes the mechanism of non-covalent/covalent interaction of whey protein-pectin (WPP) complexes, including electrostatic interaction, steric hindrance, cross-linking and Maillard reaction. The interaction between whey protein and pectin determines the form of the complex in the system, i.e. co-dissolution, precipitation, separation, complex coacervation and compounding. The interaction of WPP is affected by environmental conditions and its own properties, including several factors such as pH, polymer concentration and ratio, temperature, and ionic strength. In addition, the functional properties of WPP complexes are discussed through illustrative examples. The complexes with good emulsification, heat stability, gelling properties and biological activity have promising application prospects. WPP complexes have been widely studied for application in food colloidal systems, including protein beverages, delivery systems for bioactive substances, fat substitutes and food preservation films/coatings. The understanding of the interaction and functional properties of WPP complexes provides theoretical support for the improvement and design of new food colloidal systems.

Structure and Applications of Pectin in Food, Biomedical, and Pharmaceutical Industry: A Review

Pectin is a biocompatible polysaccharide with intrinsic biological activity, which may exhibit different structures depending on its source or extraction method. The extraction of pectin from various industrial by-products presents itself as a green option for the valorization of agro-industrial residues by producing a high commercial value product. Pectin is susceptible to physical, chemical, and/or enzymatic changes. The numerous functional groups present in its structure can stimulate different functionalities, and certain modifications can enable pectin for countless applications in food, agriculture, drugs, and biomedicine. It is currently a trend to use pectin to produce edible coating to protect foodstuff, antimicrobial bio-based films, nanoparticles, healing agents, and cancer treatment. Advances in methodology, use of different sources of extraction, and knowledge about structural modification have significantly expanded the properties, yields, and applications of this polysaccharide. Recently, structurally modified pectin has shown better functional properties and bioactivities than the native one. In addition, pectin can be used in conjunction with a wide variety of biopolymers with differentiated properties and specific functionalities. In this context, this review presents the structural characteristics and properties of pectin and information on the modification of this polysaccharide, its respective applications, perspectives, and future challenges.

Conformational changes and functional properties of whey protein isolate-polyphenol complexes formed by non-covalent interaction

The present study was conducted to evaluate the non-ovalent modifications of whey protein isolate (WPI) with gallic acid (GA), chlorogenic acid (CA) and epigallocatechin gallate (EGCG). The structural and functional properties of WPI before and after binding with GA, CA and EGCG were investigated. Results showed that free sulfhydryl groups and surface hydrophobicity significantly decreased in WPI after binding with phenolic compounds. Significant structural alterations in complexes were demonstrated, characterized by a red-shifted maximum emission wavelength in intrinsic fluorescence spectroscopy, and a significant decrease in α-helix and β-sheet and a remarkable increase in β-turn and random coil contents in fourier transform infrared (FTIR) spectroscopy. Moreover, the presence of three polyphenols induced enhanced solubility, foaming and emulsifying capacities of WPI. These findings suggest the feasible application of GA, CA and EGCG to improve the functional properties of WPI and the potential uses of WPI-polyphenol complexes in food industries.

Glycation of soy proteins leads to a range of fractions with various supramolecular assemblies and surface activities

Dry and subsequent wet heating were used to glycate soy proteins with dextran or glucose, followed by fractionation based on size and solubility. Dry heating led to protein glycation (formation of furosine, Nε-(carboxymethyl)-l-lysine, Nε-(carboxyethyl)-l-lysine, and protein-bound carbonyls) and aggregation (increased particle size); while subsequent wet heating induced partial unfolding and de-aggregation. The measurable free amino group content of soy proteins changed from 0.77 to 0.14, then to 0.62 mmol/g upon dry and subsequent wet heating; this non-monotonic evolution is probably due to protein structural changes, and shows that this content should be interpreted with caution as a glycation marker. After both heating steps, the smaller-sized water-soluble fractions showed higher surface activity than the larger insoluble ones, and dextran conjugates exhibited a higher surface activity than their glucose counterparts. We thereby achieved a comprehensive understanding of the properties of various fractions in plant protein fractions, which is essential when targeting applications.

Protein-Based Pickering High Internal Phase Emulsions as Nutraceutical Vehicles of and the Template for Advanced Materials: A Perspective Paper

Pickering high internal phase emulsions (HIPEs) are normally highly concentrated emulsions stabilized by colloidal particles with a minimum internal phase volume fraction of 0.74. They have received considerable attention in many fields, including pharmaceuticals, tissue engineering, foods, and personal care products. The aim of this perspective is to update the current knowledge on the field of protein-based Pickering HIPEs, emphasizing those aspects that need to be explored and clarified. Research progress in constructing HIPEs by protein-type colloid particles and promising research trends in basic research and potential applications were highlighted. Promising studies in this field include (1) clarifying bioavailability and evolution of activity of active ingredients in Pickering HIPEs by oral administration, (2) constructing a Pickering interfacial catalysis platform using protein colloidal particles, and (3) expanding the emerging applications of Pickering HIPEs in fields, such as partially hydrogenated oil replacers, probiotic encapsulation, and the template for porous materials.

Chemical features of the oligochitosan-glycated caseinate digest and its enhanced protection on barrier function of the acrylamide-injured IEC-6 cells

Whether caseinate oligochitosan-glycation of the transglutaminase-type followed by trypsin digestion could lead to better protection against the acrylamide-induced cell barrier damage was investigated. Compared with caseinate digest, glycated caseinate digest had similar amount of Lys and Arg but lower -NH₂ (0.557 versus 0.508 mol/kg protein) and total amide (1.12 versus 1.05 mol/kg protein) contents, and contained glucosamine at 5.74 g/kg protein. Acrylamide damaged barrier function of IEC-6 cells efficiently, leading to increased paracellular permeability and lactate dehydrogenase release, decreased trans-epithelial electrical resistance, and destroyed tight junction. The two digests alleviated these barrier dysfunctions via reversing index values. Three cellular proteins (ZO-1, occludin, and claudin-1) crucial to tight junction were up-regulated by the two digests. Furthermore, glycated caseinate digest was always more effective than caseinate digest to improve cell barrier function. This oligochitosan glycation is thus desired, as it ensures glycated protein digest with higher potential to protect intestinal barrier function.