Structuration mechanism of β-lactoglobulin – acacia gum assemblies in presence of quercetin

The impact of ultrasonic-assisted extraction on the in vitro hypoglycemic activity of peach gum polysaccharide in relation to its conformational conversion

BACKGROUND

Peach gum (PG) is an exudate of the peach tree (Prunus persica of the Rosaceae family), which consists primarily of polysaccharides with a large molecular weight and branching structure. Consequently, PG can only swell in water and does not dissolve easily, which severely limits its application. Current conventional extraction methods for PG polysaccharide (PGPS) are time consuming and inefficient. This study investigated the impact of ultrasonic-assisted extraction (UAE) on PGPS structure and conformation, and their relationship to hypoglycemic activity in vitro.

RESULTS

In comparison with conventional aqueous extraction, UAE enhanced PGPS yielded from 28.07-32.83% to 80.37-84.90% (w/w) in 2 h. It drastically decreased the molecular size and conformational parameters of PGPS, including weight-average molecular weight (Mw), number-average molecular weight (Mn), z-average radius of gyration (Rg), hydrodynamic radius (Rh) and instrinsic viscosity ([η]) values. Peach gum polysaccharide conformation converted extended molecules to flexible random coil chains or compact spheres with no obvious primary structure alteration. Furthermore, UAE altered the flow behavior of PGPS solution from that of a non-Newtonian fluid to that of a Newtonian fluid. As a result, PGPS treated with UAE displayed weaker inhibitory activity than untreated PGPS, mostly because UAE weakens the binding strength of PGPS to α-glucosidase. However, this negative effect of UAE on PGPS activity was compensated by the increased solubility of polysaccharide. This enabled PGPS to achieve a wider range of doses.

CONCLUSION

Ultrasonic-assisted extraction is capable of degrading PGPS efficiently while preserving its primary structure, resulting in a Newtonian fluid solution. The degraded PGPS conformations displayed a consistent correlation with their inhibitory effect on α-glucosidase activity. © 2024 Society of Chemical Industry.

Determination of the critical aggregation concentration in water of Gum Arabic functionalized with curcumin oxidation products by micro-scale thermophoresis approach

Gum Arabic underwent enzymatic modification with curcumin oxidation products, prompting self-assembly in water at lower concentrations than native gum Arabic, which was fully soluble. The resulting particles displayed a narrow size distribution, suggestive of a micellization mechanism akin to Critical Micellization Concentration (CMC) in surfactants or Critical Aggregation Concentration (CAC) in polymers. Accurately determining CAC is vital for utilizing polymers in molecule encapsulation, but precise measurement is challenging, requiring multiple techniques. Initially, CAC was probed via turbidity measurements, dynamic light scattering (DLS), and isothermal calorimetric titration (ITC), yielding a range of 0.0015 to 0.01 %. Micro-scale thermophoresis (MST) was then employed for the first time to define CAC more precisely, facilitated by the intrinsic fluorescence of modified gum Arabic. Using MST, CAC was pinpointed at 0.001 % (w/v), a novel approach. Furthermore, MST revealed a low EC50 value of 0.007 % (w/t) for self-assembly, signifying uniformity among GAC sub-units and assembly stability upon dilution.

Fabrication and characterization of complex coacervates utilizing gelatin and carboxymethyl starch

BACKGROUND

Modified polysaccharides have greatly expanded applications in comparison with native polysaccharides due to their improved compatibility and interactions with proteins and active compounds in food-related areas. Nonetheless, there is a noticeable dearth of research concerning the utilization of carboxymethyl starch (CMS) as a microcapsule wall material in food processing, despite its common use in pharmaceutical delivery. The development of an economical and safe embedding carrier using CMS and gelatin (GE) holds immense importance within the food-processing industry. In this work, the potential of innovative coacervates formed by the combination of GE and CMS as a reliable, stable, and biodegradable embedding carrier is evaluated by turbidity measurements, thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and rheological measurements.

RESULTS

The results indicate that GE-CMS coacervates primarily resulted from electrostatic interactions and hydrogen bonding. The optimal coacervation was observed at pH 4.6 and with a GE/CMS blend ratio of 3:1 (w/w). However, the addition of NaCl reduced coacervation and made it less sensitive to temperature changes (35-55 °C). In comparison with individual GE or CMS, the coacervates exhibited higher thermal stability, as shown by TGA. X-ray diffraction analysis shows that the GE-CMS coacervates maintained an amorphous structure. Rheological testing reveals that the GE-CMS coacervates exhibited shear-thinning behavior and gel-like properties.

CONCLUSION

Overall, attaining electroneutrality in the mixture boosts the formation of a denser structure and enhances rheological properties, leading to promising applications in food, biomaterials, cosmetics, and pharmaceutical products. © 2023 Society of Chemical Industry.

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.

Fabrication and characterization of gelatin-EGCG-pectin ternary complex: formation mechanism, emulsion stability, and structure

BACKGROUND

Protein-polyphenol-polysaccharide ternary complex particles have better emulsion interfacial stability compared to protein-polysaccharide binary complexes. However, knowledge is scarce when it comes to the fabrication of protein-polyphenol-polysaccharide ternary complexes as interfacial stabilizers and the interactions between the three substances. In the present work, ternary complexes were prepared using gelatin, high methoxyl pectin, and epigallocatechin gallate (EGCG) as raw materials. The effect of different influencing factors on the formation process of ternary complexes was investigated by varying different parameters. physicochemical stability, emulsifying properties, and structural characteristics were analyzed.

RESULTS

The ternary complex had a smaller particle size (275 nm) and polydispersity index (0.112) when the mass concentration ratio of gelatin to high methoxyl pectin was 9:1, addition of EGCG was 0.05%, pH value was 3.0, and ionic strength was 10 mmol L^-1 . Meanwhile, the complex had the highest emulsifying stability index (691.75 min) and emulsifying activity index (22.96 m²  g^-1 ). Scanning electron microscopical observation demonstrated that the addition of EGCG promoted the dispersion of ternary complex more uniformly, and effectively reduced the agglomeration phenomenon. The discrepancy in fluorescence intensity suggested that interactions between EGCG and gelatin occurred, which altered the protein spatial conformation of gelatin. Fourier transform infrared spectroscopic analysis elucidated that hydrogen bond interaction was the primary non-covalent interaction between EGCG and gelatin-high methoxyl pectin binary complex.

CONCLUSION

The aforementioned results purposed to provide some theoretical reference and basis for the rational design of stable protein-polyphenol-polysaccharide ternary complexes. © 2022 Society of Chemical Industry.

Formation mechanism of binary complex based on β-lactoglobulin and propylene glycol alginate with different molecular weights: Structural characterization and delivery of curcumin

The complexation of protein and polysaccharide has shown considerable potential for the encapsulation of functional food components. In this work, propylene glycol alginate (PGA) molecules with different molecular weights (100, 500, and 2,000 kDa) were prepared through H2O2 oxidation, which were further combined with β-lactoglobulin nanoparticles (β-lgNPs) to form PGA-β-lgNPs complexes for the delivery of curcumin (Cur). Results showed that the depolymerization of PGA molecule was resulted from the breakage of glycosidic bonds in the main chain, and the depolymerization rate of PGA molecule depended on the reaction time, temperature, solution pH and H2O2 concentration. As the increasing molecular weight of PGA, the particle size, zeta-potential and turbidity of the complexes were obviously increased. The formation of PGA/β-lgNPs complexes was mainly driven by non-covalent interaction, including electrostatic gravitational interaction, hydrogen bonding and hydrophobic effect. Interestingly, the difference in the molecular weight of PGA also led to significantly differences in the micro-morphology of the complexes, as PGA with a high molecular weight (2,000 kDa) generated the formation of a “fruit-tree” shaped structure, whereas PGA with relatively low molecular weight (100 and 500 kDa) led to spherical particles with a “core-shell” structure. In addition, the incorporation of PGA molecules into β-lgNPs dispersion also contributed to the improvement in the encapsulation efficiency of Cur as well as physicochemical stability of β-lgNPs, and PGA with a higher molecular weight was confirmed with a better effect. Findings in the current work may help to further understand the effect of molecular weight of polysaccharide on the physical and structural properties as well as effectiveness as delivery systems of polysaccharide-protein complexes, providing for the possibility for the design and development of more efficient carriers for bioactive compounds in food system.

A Ferrofluid with High Specific Absorption Rate Prepared in a Single Step Using a Biopolymer

An exhaustive characterization of the physicochemical properties of gum arabic (GA)-coated Fe₃O₄ magnetic nanoparticles was conducted in this work. These nanoparticles were obtained via the in-situ coprecipitation method (a fast single-step method) in two GA:Fe ratios, 10:1 and 20:1, respectively. Several experimental techniques were applied in the characterization process, all of them described below. Using Transmission Electron Microcopy images, they were shown to have spherical-like morphology with 11 nm diameter. The Fourier Transform Infrared spectra confirmed the attachment of the GA on the surface of the magnetic nanoparticles (MNPs), providing good colloidal stability from pH 7 to 8. The thickness of the coatings (1.7 nm and 1.1 nm) was determined using thermogravimetric measurements. A high specific absorption rate and superparamagnetic properties were determined using alternant and static magnetic fields, respectively. The GA-coated MNPs were non-cytotoxic, according to tests on HT-29 human intestine cells. Additionally, HT-29 cells were exposed to magnetic fluid hyperthermia at 530 kHz, and the induction of cell death by the magnetic field, due to the heating of GA-coated MNP, was observed.

Effect of protein-fatty acid interactions on the formation of starch-lipid-protein complexes

The effect of interactions between beta-lactoglobulin (βLG) and lauric acid (LA) on the formation of ternary maize starch-LA-protein complexes was investigated. Analysis of the secondary structure of βLG by FTIR and changes in fluorescence λmax and intensity indicated that βLG and LA interacted during heating and cooling in a Rapid Visco Analyser (RVA). Results from RVA, DSC and Raman spectroscopy analyses showed that increasing the concentration of βLG from 25 to 200 mg increased the amount of ternary starch-LA-βLG complexes formed. There was little difference in the amounts of the ternary complexes formed when the amount of βLG was 25-150 mg, but a greater amount of starch-LA-βLG complexes was formed when 200 mg of βLG was pre-mixed with LA. From this study, we concluded that prior interaction between βLG and LA had no significant effect on the formation of ternary starch-LA-βLG complexes.

Effects of cooling rate and complexing temperature on the formation of starch-lauric acid-β-lactoglobulin complexes

The aim of present study was to investigate the effects of cooling rate (3, 5, 10, 15 °C/min) and complexing temperature (50, 60, 70, 80 and 90 °C) on the formation of complexes between wheat starch (WS), lauric acid (LA) and β-lactoglobulin (βLG) in Rapid Visco Analyser (RVA). Higher cooling rate resulted in the higher viscosity peak and final viscosity of WS-LA or WS-LA-βLG complexes than the lower cooling rate during setback of RVA procedure. Results from differential scanning calorimetry (DSC) and Raman spectroscopy showed that larger amount of complexes with lower thermal transition temperatures were formed at higher cooling rate. Higher complexing temperature led to the formation of more complexes with higher thermal transition temperatures. XRD patterns of binary and ternary complexes presented no differences at different cooling rates or different complexing temperatures. We conclude that both higher cooling rate and complexing temperature facilitate the formation of WS-LA and WS-LA-βLG complexes.

Assembly of propylene glycol alginate/β-lactoglobulin composite hydrogels induced by ethanol for co-delivery of probiotics and curcumin

Probiotics and curcumin can exhibit synergistic biological activities on the basis of a gut-brain axis, but are sensitive to environmental conditions, making it a challenge for their co-utilization. To meet the demand for high efficiency and convenience, both probiotics and curcumin were encapsulated within a propylene glycol alginate-based hydrogel delivery system, which was assembled using an ethanol-induced approach. The composite hydrogel was effective at sustaining the release of curcumin and protecting LGG cells in simulated gastrointestinal tract conditions. Moreover, it could also largely reduce the chemical degradation of curcumin and increase the survival of LGG during light exposure and long-term storage: up to 91.3 % of curcumin and 9.72 log CFU cm^-3 remained present throughout 4 weeks of storage. Results in this work demonstrate a low-energy and green approach to assemble a composite hydrogel with remarkable biocompatibility, which is considered as a desired delivery vehicle for co-delivery of probiotics and curcumin.

The interaction between sodium alginate and myofibrillar proteins: The rheological and emulsifying properties of their mixture

The interaction between sodium alginate (SA) and turbot myofibrillar proteins (TMP) and the effects of SA concentration (0.1%-0.5%) on the rheological and emulsifying properties of the mixture at neutral pH were investigated. TMP and SA formed complexes through electrostatic repulsion and hydrophobic interaction. The FT-IR analysis indicated that hydrogen bonding was also related to the interaction. With the addition of SA, the electrostatic repulsion between molecules enhanced, which prevented protein aggregation and improved the stability of dispersions. The TMP/SA mixture showed non-Newtonian shear-thinning behavior. The viscosity gradually increased with the increasing SA concentration. TMP and SA formed an interconnected gel-like network structure with a predominant elastic behavior. The strength of network increased due to the strong repulsion between the two biopolymers. Both EAI and ESI of TMP significantly increased after SA addition. The addition of SA reduced droplet size of emulsions. The emulsions also showed pseudoplastic behavior. Addition of SA increased stability of emulsions by increasing viscosity of continuous phase. Complexation with SA effectively improved the rheological and emulsifying properties of fish myofibrillar proteins. These results contributed to the efficient utilization of marine fish proteins as functional ingredients in food products.

Quantitative analysis of binding affinities and characterization of β-lactoglobulin and λ-carrageenan as a function of pH

λ-Carrageenan (λcar) interacted with β-lactoglobulin (βlg) immediately to form βlg-λcar complexes when used as an additive in milk. The formation of complexes is the key process through which to explore the bioapplication of λcar, which is a complicated process and influenced by many factors. In this study, the formation process and effect of pH were ascertained by the binding affinity, hydrodynamic diameter, and secondary structure. Results showed that the interaction was spontaneously exothermic and the complexes were soluble. The binding affinities (Ka) decreased from 9.0 ± 1.3 × 10⁵ to 1.3 ± 0.8 × 10⁵  M^-1 , and the stoichiometry also decreased as the pH was increased from 4 to 7. Furthermore, DLS showed a larger hydrodynamic diameter of the complexes at lower pH. Moreover, the complexes induced a change in the secondary structural components of βlg at lower pH. PRACTICAL APPLICATIONS: The secondary structure of βlg was changed by the interaction of λcar, which resulted in βlg-λcar complexes under acidic conditions. The soluble βlg-λcar complexes showed a good stability against aggregation. Thus, they can enhance the textural properties and stability of acidic dairy drinks, and can be used to accurately formulate ingredients in the food ingredient industry.

Thermodynamic Study of Ion-Driven Aggregation of Cellulose Nanocrystals

The thermodynamics of interactions between cations of the second group of the periodic table and differently negatively charged cellulose nanocrystals was investigated using isothermal titration calorimetry (ITC). The interaction of cations with the negatively charged CNCs was found to be endothermic and driven by an increase in entropy upon adsorption of the ions, due to an increase in degrees of freedom gained by the surface bound water upon ion adsorption. The effect was pH-dependent, showing an increase in enthalpy for cellulose suspensions at near-neutral pH (6.5) when compared to acidic pH (2). Sulfated cellulose nanoparticles were found to readily interact with divalent ions at both pH levels. The adsorption on carboxylate nanocrystals was found to be pH dependent, showing that the carboxylic group needs to be in the deprotonated form to interact with divalent ions. For the combined system (sulfate and carboxylate present at the same time), at neutral pH, the adsorption enthalpy was higher than the value obtained from cellulose nanocrystals containing a single functional group, while the association constant was higher due to an increased favorable entropic contribution. The higher entropic contribution indicates a more restricted surface-bound water layer when multiple functionalities are present. The stoichiometric number n was nearly constant for all systems, showing that the adsorption depends almost completely on the ion valency and on the amount of ionic groups on the CNC surface, independent of the type of functional group on the CNC surface as long as it is deprotonated. In addition, we showed that the reduction in Gibbs free energy drives the ionotropic gelation of nanocellulose suspensions, and we show that ITC is able to detect gel formation at the same time as determining the critical association concentration.

Tree gum-based renewable materials: Sustainable applications in nanotechnology, biomedical and environmental fields

The prospective uses of tree gum polysaccharides and their nanostructures in various aspects of food, water, energy, biotechnology, environment and medicine industries, have garnered a great deal of attention recently. In addition to extensive applications of tree gums in food, there are substantial non-food applications of these commercial gums, which have gained widespread attention due to their availability, structural diversity and remarkable properties as 'green' bio-based renewable materials. Tree gums are obtainable as natural polysaccharides from various tree genera possessing exceptional properties, including their renewable, biocompatible, biodegradable, and non-toxic nature and their ability to undergo easy chemical modifications. This review focuses on non-food applications of several important commercially available gums (arabic, karaya, tragacanth, ghatti and kondagogu) for the greener synthesis and stabilization of metal/metal oxide NPs, production of electrospun fibers, environmental bioremediation, bio-catalysis, biosensors, coordination complexes of metal-hydrogels, and for antimicrobial and biomedical applications. Furthermore, polysaccharides acquired from botanical, seaweed, animal, and microbial origins are briefly compared with the characteristics of tree gum exudates.

Nanoencapsulation of Polyphenols towards Dairy Beverage Incorporation

Phenolic compounds, while widely recognized for their biological potential, when added into food matrixes may interact with food constituents. One example of this is the interaction between phenolic compounds and proteins, that may result in the formation of complexes and alter the bioavailability of both phenolic compounds and the nutrient availability. Moreover, when adding compounds to improve the functionality of a food matrix, these interactions may compromise the perceived benefits of the additions. Nanoencapsulation has been considered one of the means to circumvent these interactions, as they may function as a physical barrier between the phenolic compounds and the matrix (preventing not only the loss of bioactivity, but eventual sensorial alterations of the foods), protect phenolic compounds through the gastrointestinal tract, and may enhance phenolic absorption through cellular endocytosis. However, despite these advantages the food industry is still limited in its nanotechnological solutions, as special care must be taken to use food-grade encapsulants which will not pose any deleterious effect towards human health. Therefore, this review aims to provide an encompassing view of the existing advantages and limitations of nanotechnology, associated with the inclusion of phenolic compounds in dairy beverages.

Fabrication mechanism and structural characteristics of the ternary aggregates by lactoferrin, pectin, and (-)-epigallocatechin gallate using multispectroscopic methods

The ternary aggregates were fabricated by lactoferrin (LF), pectin (high methylated pectin (HMP)/low methylated pectin (LMP)), and (-)-epigallocatechin gallate (EGCG) through three different fabrication methods at pH 5.0. The turbidity, particle size, and ζ-potential of ternary aggregates were influenced by the types of pectin, the concentration of EGCG, and fabrication methods. The fluorescence intensity of LF decreased with an increase in EGCG concentration for all ternary aggregates. Far-UV circular dichroism results indicated that EGCG could alter the secondary structure of LF with an increase in the proportion of β-sheet structure at the cost of unordered coil structure. According to near-UV circular dichroism results, EGCG could also modulate the tertiary structure of LF at the presence of pectin. In addition, EGCG could increase the viscoelasticity of the ternary aggregates with HMP, leading to better stability of the ternary aggregates. An opposite result was observed for the ternary aggregates with LMP. These findings should provide an insight into the fabrication mechanism and applications of ternary aggregates formed by protein, polysaccharide, and polyphenol in the food, pharmaceutical, and cosmetic industries.

Nature and consequences of non-covalent interactions between flavonoids and macronutrients in foods

Many of the potential health benefits of flavonoids have been associated with their specific chemical and biological properties including their ability to interact and bind non-covalently to macronutrients in foods. While flavonoid-protein interactions and binding have been the subject of intensive study, significantly less is understood about non-covalent interactions with carbohydrates and lipids. These interactions with macronutrients are likely to impact both the flavonoid properties in foods, such as their radical scavenging activity, and the food or beverage matrix itself, including their taste, texture and other sensorial properties. Overall, non-covalent binding of flavonoids with macronutrients is primarily driven by van der Waals interactions. From the flavonoid perspective, these interactions are modulated by characteristics such as degree of polymerization, molecular flexibility, number of external hydroxyl groups, or number of terminal galloyl groups. From the macronutrient standpoint, electrostatic and ionic interactions are generally predominant with carbohydrates, while hydrophobic interactions are generally predominant with lipids and mainly limited to interactions with flavonols. All of these interactions are involved in flavonoid-protein interactions. While primarily associated with undesirable characteristics in foods and beverages, such as astringency, negative impact on macronutrient digestibility and hazing, more recent efforts have attempted to leverage these interactions to develop controlled delivery systems or strategies to enhance flavonoids bioavailability. This paper aims at reviewing the fundamental bases for non-covalent interactions, their occurrence in food and beverage systems and their impact on the physico-chemical, organoleptic and some nutritional properties of food.