Whey protein isolate-low acyl gellan gum Maillard-based conjugates with tailored technological functionality and antioxidant activity

Mechanistic insights into the interaction of Lycium barbarum polysaccharide with whey protein isolate: Functional and structural characterization

Protein-polysaccharide interactions are crucial for food system structure and stability. This study investigates the interaction of Lycium barbarum polysaccharide (LBP) at 0-2.00 % concentrations with whey protein isolate (WPI), focusing on functionality and structural changes. LBP covalently grafted onto WPI, as confirmed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), forming WPI-LBP complexes with a maximum degree of grafting (DG) of 44.58 % at 2.00 % LBP. This grafting reduced WPI's surface hydrophobicity (H0) and improved solubility, emulsifying properties, and digestibility under certain conditions, with optimal antioxidant activity at 1.00 % LBP. Multispectral analysis and microscopy showed LBP grafting alters WPI's secondary, tertiary, crystalline, and micro/nanostructures. The comprehensive analysis indicates that the interaction between LBP and WPI involves covalent bonding, hydrogen bonding, hydrophobic interactions, and electrostatic forces, as supported by zeta potential and chemical forces results. These findings suggest LBP-protein complexes as promising food materials for enhancing functionality and stability in the food industry.

Structural and functional modifications of quinoa protein via hyaluronic acid-induced Maillard reaction

In recent years, quinoa protein (QP) has attracted attention for its balanced amino acids composition, but its limited techno-functional properties continue to pose challenges for its utilization. Non-enzymatic Maillard glycation is considered as a promising strategy to expand the utilization of plant proteins in food processing due to its cost-effectiveness, spontaneous nature, and the lack of need for additives to initiate the reaction. Furthermore, the use of hyaluronic acid (HA) as an ingredient in food products is becoming increasingly accepted and popular. Therefore, the present study aims to prepare QP-HA glyconjugates by wet heating and to investigate the effects of sugar/protein ratios and reaction times on the structural features and functional properties of QP. The results showed that heating time and sugar/protein concentration ratio obviously affected the degree of grafting, structure and hydrophobicity of the conjugates. The random coil content of QP-HA increased significantly, resulting in a more flexible structure after Maillard glycation. After 3 h of glycation reaction, the QP-HA conjugates showed better emulsification, solubility, thermal stability and antioxidant activity compared to QP. Accordingly, these results indicate that polysaccharide-induced Maillard reaction is a potentially attractive approach for selective functionality enhancement and nutraceutical development of QP, which provides a new way to expand the application range of QP.

Insight into structural changes in heat-induced whey protein-fucoidan hydrogel by SR-IR and molecular docking techniques

This study aimed to investigate the structural changes in heat-induced polymerized whey protein (PWP)-fucoidan (FCN) hydrogels with different FCN concentration (0 % to 0.75 %, w/v). The interaction of PWP and FCN were traced by simultaneous rheology and Fourier transform infrared spectroscopy spectra (SR-IR) technology. The particle size and absolute zeta potential of PWP-FCN increased significantly (p < 0.05) with higher FCN concentrations, indicating that the formation of PWP-FCN enhanced the stability of the system. The gelation time of PWP-FCN was shortened from 1328 s to 881 s as the FCN concentration increased from 0 to 0.75 % (w/v) paralleled the increased apparent viscosity. The endothermic peak temperature of the hydrogels increased from 95.28 °C to 102.26 °C demonstrating the improved thermal stability due to FCN. The intrinsic fluorescence, surface hydrophobicity, and free thiol groups of PWP-FCN all indicated that FCN could interact with PWP through hydrophobic interactions, which changed the tertiary structure of PWP, and increased the density of PWP-FCN network. Cryogenic scanning electron microscopy (Cryo-SEM) and SEM images showed that the interactions between PWP and FCN resulted to rough and wrinkled microstructure of samples. Results of SR-IR and molecular docking assay both indicated that FCN could also interact with PWP through hydrogen bonds. In summary, FCN could promote the gelation process and the physicochemical properties of PWP-FCN hydrogel. Results of this study could provide theoretical basis for the application of protein-polysaccharide hydrogels in food field.

Structural characteristics and antioxidant activity of binary compounds formed by covalent modification of plant derived recombinant lactoferrin (OsrhLF) with four typical carbohydrates

Lactoferrin is crucial for the mammalian immune system, but the extraction of bovine lactoferrin (bLF) is low, and human lactoferrin in breast milk is costly. Although there are some reports on heterologous expression of lactoferrin, limited knowledge is available. In this study, structural characteristics and antioxidant activity of binary compounds formed by covalent modification of plant derived recombinant human lactoferrin (OsrhLF) with four typical carbohydrates including sodium alginate (SA), maltodextrin (Mal), pectin (Pec), and lactose (Lac). Results indicated that the structure of both bLF and OsrhLF unfolded, with side chain lysine or terminal amino acids forming CN bonds with aldehydes, altering their structure and improving stability and hydrophilicity. Compared with OsrhLF, the thermal denaturation temperatures of H-OsrhLF-Mal and H-OsrhLF-Lac increased by 56.8 °C and 58.4 °C, respectively. OsrhLF exhibited superior surface hydrophilicity and thermal stability compared to bLF, with Mal showing the most significant effect, aiding future functional food applications.

Comparison of sea buckthorn fruit oil nanoemulsions stabilized by protein-polysaccharide conjugates prepared using β-glucan from various sources

To understand the influence of β-glucans structure on the emulsifying properties of protein-polysaccharide conjugates, sodium caseinate (NaCas) was utilized to form glycosylation conjugates with varying degrees of glycosylation (10.68-17.50%) using three β-glucans from bacteria, yeast, and oats. This process induced alterations in the secondary structure of protein. The nanoemulsions prepared with the glycosylated conjugates exhibited superior stability compared to those formulated solely with NaCas, particularly under conditions of drastic pH fluctuations and extended storage periods. The nanoemulsion prepared with the NaCas-Salecan conjugate demonstrated exceptional stability at pH 4 and 6, or storage for 20 days. Additionally, it significantly attenuated the oxidation of unsaturated fatty acids and exhibited the lowest levels of aggregation, flocculation, and free fatty acid release rate during in vitro digestion. This study suggested the potential of the NaCas-Salecan conjugates in enhancing the stability of nanoemulsions and facilitating the colorectal-targeted delivery of sea buckthorn fruit oil.

Preparation, characterization and functional evaluation of soy protein isolate-peach gum conjugates prepared by wet heating Maillard reaction

This study was conducted to formulate a conjugate of soy protein isolate (SPI) and peach gum (PG) with improved functional properties, interacting at mass ratios of 1:1, 1:2, 1:3, 2:1, and 2:3 by Maillard reaction via wet heating method. Conjugation efficiency was confirmed by grafting degree (DG) and browning index (BI). Results indicated that DG increased with increasing concentration of PG, and decreased with increasing pH, whereas no remarkable change was observed with increasing reaction time. The conjugates were optimized at a ratio of 1:3. SDS-PAGE confirmed conjugate formation, Fourier transform infrared spectroscopy (FTIR) and circular dichroism (CD) verified conjugate secondary structural changes, and scanning electron microscopy (SEM) indicated significant overall structural changes. The functional properties, solubility, emulsifying stability, water holding, foaming, and antioxidant activity were significantly improved. This study revealed the wet heating method as an effective approach to improve the functional properties of soy protein.

Effects of enzymatic hydrolysis combined with glycation on the emulsification characteristics and emulsion stability of peanut protein isolate

Peanut protein isolate (PPI) has high nutritional value, but its poor function limits its application in the food industry. In this study, peanut protein isolate was modified by enzymatic hydrolysis combined with glycation. The structure, emulsification and interface properties of peanut protein isolate hydrolysate (HPPI) and dextran (Dex) conjugate (HPPI-Dex) were studied. In addition, the physicochemical properties, rheological properties, and stability of the emulsion were also investigated. The results showed that the graft degree increased with the increase of Dex ratio. Fourier transform infrared spectroscopy (FTIR) confirmed that the glycation of HPPI and Dex occurred. The microstructure showed that the structure of HPPI-Dex was expanded, and the molecular flexibility was enhanced. When the ratio of HPPI to Dex was 1:3, the emulsifying activity and the interface pressure of glycated HPPI reached the highest value, and the emulsifying activity (61.08 m2/g) of HPPI-Dex was 5.28 times that of PPI. The HPPI-Dex stabilized emulsions had good physicochemical properties and rheological properties. In addition, HPPI-Dex stabilized emulsions had high stability under heat treatment, salt ion treatment and freeze-thaw cycle. According to confocal laser scanning microscopy (CLSM), the dispersion of HPPI-Dex stabilized emulsions was better after 28 days of storage. This study provides a theoretical basis for developing peanut protein emulsifier and further expanding the application of peanut protein in food industry.

The non-covalent and covalent interactions of whey proteins and saccharides: influencing factor and utilization in food

During the application of Whey proteins (WPs), they often have complex interactions with saccharides (Ss), another important biopolymer in food substrate. The texture and sensory qualities of foods containing WPs and Ss are largely influenced by the interactions of WPs-Ss. Moreover, the combination of WPs and Ss is possible to produce many excellent functional properties including emulsifying properties and thermal stability. However, the interactions between WPs-Ss are complex and susceptible to some processing conditions. In addition, with different interaction ways, they can be applied in different fields. Therefore, the non-covalent interaction mechanisms between WPs-Ss are firstly summarized in detail, including electrostatic interaction, hydrogen bond, hydrophobic interaction, van der Waals force. Furthermore, the existence modes of WPs-Ss are introduced, including complex coacervates, soluble complexes, segregation, and co-solubility. The covalent interactions of WPs-Ss in food applications are often formed by Maillard reaction (dry or wet heat reaction) and occasionally through enzyme induction. Then, two common influencing factors, pH and temperature, on non-covalent/covalent bonds are introduced. Finally, the applications of WPs-Ss complexes and conjugations in improving WP stability, delivery system, and emulsification are described. This review can improve our understanding of the interactions between WPs-Ss and further promote their wider application.

Granular hydrogels with tunable properties prepared from gum Arabic and protein microgels

Granular hydrogels have emerged as a new class of materials for 3D printing, tissue engineering, and food applications due to their extrudability, porosity, and modularity. This work introduces a convenient method to prepare granular hydrogel with tunable properties by modulating the interaction between gum Arabic (GA) and whey protein isolate (WPI) microgels. As the concentration of GA increased, the appearance of the hydrogel changed from fluid liquid to moldable solid, and the microstructure changed from a macro-porous structure with thin walls to a dense structure formed by the accumulation of spherical particles. At a GA concentration of 0.5 %, the hydrogels remained fluid. Granular hydrogels containing 1.0 % GA showed mechanical properties similar to those of tofu (compressive strength: 10.8 ± 0.5 kPa, Young's modulus: 16.7 ± 0.4 kPa), while granular hydrogels containing 1.5 % GA showed mechanical properties similar to those of hawthorn sticks and sausages (compressive strength: 300.4 ± 5.8 kPa; Young's modulus: 200.5 ± 3.4 kPa). The hydrogel with 2.0 % GA was similar to hawthorn sticks, with satisfactory bite resistance and elasticity. Such tunability has led to various application potentials in the food industry to meet consumer demand for healthy, nutritious, and diverse textures.

Bioactive foamulsion gels: a unique structure prepared with gellan gum and Acanthophyllum glandulosum extract

BACKGROUND

Foamulsions have become increasingly popular in the food industry due to their ability to enhance the textural, sensory and health-promoting properties of food products. This study was therefore aimed to design and prepare a novel gelled structure, foamulsion gel containing 0-600 g L-1 oil, with gellan gum (GG; 7, 10 and 13 g L-1) and saponin-rich antioxidant Acanthophyllum glandulosum extract (AGE; 2, 6 and 10 g L-1).

RESULTS

The interaction between components was confirmed by infrared spectroscopy. The overrun and porosity of the foamulsion gels increased with antioxidant AGE (1.30 times) and reduced with oil (up to ca 70% and 30%, respectively) and GG levels. The systems were highly stable, and no water or oil was released during the physical stability experiments. Microscopic images showed that the size of air cells was significantly larger than that of oil droplets. The foamulsion gels based on 13 g L-1 GG and 10 g L-1 AGE had markedly higher elastic (G') and viscous (G'') moduli than other samples, and exhibited an elastic and solid-like behavior (G' > G''). The highest gel firmness was found in oil-free sample, and the presence of oil resulted in a lower firmness induced by the larger size and lubrication effect of oil droplets.

CONCLUSION

As a result, the interactions between AGE, GG and oil could lead to the creation of new aerated structures known as bioactive foamulsion gels. These gels exhibit excellent foamability, stability and viscoelasticity and may find applications in the development of novel, healthy and low-calorie aerated foods. © 2024 Society of Chemical Industry.

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.

Antioxidant and antibrowning properties of Maillard reaction products in food and biological systems

Oxidative damage refers to the harm caused to biological systems by reactive oxygen species such as free radicals. This damage can contribute to a range of diseases and aging processes in organisms. Moreover, oxidative deterioration of lipids is a serious problem because it reduces the shelf life of food products, degrades their nutritional value, and produces reaction products that could be toxic. Antioxidants are effective compounds for preventing lipid oxidation, and synthetic antioxidants are frequently added to foods due to their high effectiveness and low cost. However, the safety of these antioxidants is a subject that is being discussed in the public more and more. Synthetic antioxidants have been found to have potential negative effects on health due to their ability to accumulate in tissues and disrupt natural antioxidant systems. During thermal processing and storage, foods containing reducing sugars and amino compounds frequently produce Maillard reaction products (MRPs). Through the chelation of metal ions, scavenging of reactive oxygen species, destruction of hydrogen peroxide, and suppression of radical chain reaction, MRPs exhibit excellent antioxidant properties in a variety of food products and biological systems. Also, the capacity of MRPs to chelate metals makes them as a potential inhibitor of the enzymatic browning in fruits and vegetables. In this book chapter, the methods used for the evaluation of antioxidant activity of MRPs are provided. Moreover, the antioxidant and antibrowning activities of MRPs in food and biological systems is discussed. MRPs can generally be isolated and used as commercial preparations of natural antioxidants.

High internal phase emulsions stabilized by whey protein covalently modified with carboxymethyl cellulose: Enhanced environmental stability, storage stability and bioaccessibility

In this work, the effects of whey protein-carboxymethyl cellulose (WP-CMC) conjugates on the environmental stability, in vitro digestion stability, storage stability and bioaccessibility of high internal phase emulsions (HIPEs) were investigated. Compared to the HIPEs stabilized by the mixture of WP and CMC, the HIPEs stabilized by WP-CMC were less sensitive to environmental changes by particle size and zeta-potential, and showed better stability and bioavailability of pine nut oil as well as β-carotene during simulated gastrointestinal digestion. In addition, the inclusion function and pine nut oil oxidative stability of the HIPEs stabilized by WP-CMC were better during 16 days of storage than those of the pine nut oil and HIPEs stabilized by the mixture of WP and CMC, and also expressed higher storage stability of β-carotene. These results suggested that the conjugate-stabilized emulsions developed in this study have potential applications as protectors and carriers of liposoluble active ingredients.

Effect of various oligosaccharides on casein solubility and other functional properties: Via Maillard reaction

This study explored the improvement of casein (CN)'s properties by conjugating it with oligosaccharides, namely, fructooligosaccharide (FOS), galactooligosaccharide (GOS), isomaltooligosaccharide (IMO), and xylo-oligosaccharide (XOS) via Maillard reaction to identify the most optimal oligosaccharides and modification conditions. The degree of grafting was 30.5 ± 0.41 % for CN-FOS, 33.7 ± 0.62 % for CN-GOS, 38.9 ± 0.51 % for CN-IMO, and 43.7 ± 0.54 % for CN-XOS. With the degree of grafting rising, more oligosaccharides were conjugated, causing greater changes in CN properties. The CN-XOS underwent significant alterations, as the introduction of oligosaccharides led to a decrease in particle size by around 51 nm. Furthermore, the hydroxyl groups caused a reduction in surface hydrophobicity, which in turn decreased the proportion of hydrophobic groups. The solubility of CN-XOS increased significantly at pH 3, by approximately 30.99 %. Additionally, the conjugation of oligosaccharides substantially boosted the rates of DPPH, ABTS, and -OH radical scavenging by 4.61 times, 2.20 times, and 2.58 times, respectively, and also improved the thermal stability of the modified CN. Moreover, the process lowered the protein digestibility, possibly enhancing its applicability as an active substance transporter. This research offers additional theoretical backing for altering CN with oligosaccharides and implementing it in the food and pharmaceutical sectors.

Effect of polysaccharide addition on food physical properties: A review

The texture, flavor, performance and nutrition of foods are affected by their physical properties during processing, cooking, storage, and shelf life. In addition to chemical, physical, and enzymatic modification methods, polysaccharide addition is also considered a safe, effective, and convenient food modification strategy. However, thus far, literature review on the effects of polysaccharides on the physical properties of foods is few. Therefore, the present work reviews the effects of polysaccharides on water retention capacity, rheological property, suspension ability, viscoelasticity, emulsifying property, gelling property, stability, and starch regeneration and digestion. Furthermore, the existing problems and future recommendations during food physical property modification by polysaccharides are presented. This work aims to provide some theoretical references for future research, development, and application of polysaccharides on food physical property modification.

Comprehensive structural and functional characterization of a new protein-polysaccharide conjugate between grass pea protein (Lathyrus sativus) and xanthan gum produced by wet heating

The purpose of this work was to use a controlled wet-heating process to promote Maillard reaction (MR) between grass pea protein (GPPI) and xanthan gum (XG), and then analyse structural, functional and antioxidant properties of the conjugate (GPPI-XGCs). During heating, the degree of glycation of all conjugated samples was raised (up to 37.43 %) and, after heating for 24 h, the lightness of the samples decreased by 24.75 %. Circular dichroism showed changes in secondary structure with lower content of α-helix and random coil in conjugates. XRD patterns showed that MR destroyed the crystalline structure of the protein. In addition, Lys and Arg content of the produced conjugates decreased by 16.94 % and 6.17 %, respectively. Functional properties including foaming capacity and stability were increased by 45.17 % and 37.17 %, and solubility reached 98.88 %, due to the protein unfolding driven by MR. GPPI-XGCs showed significantly higher antioxidant activities with maximum ABTS-RS value of 49.57 %. This study revealed how MR can improve GPPI's properties, which can aid the food industry in producing a wide range of plant-based foods. Especially, among other characteristics, the foaming properties were significantly improved and the final product can be introduced as a promising foaming agent to be used in food formulation.

Effect of ultrasonic assisted grafting on the structural and functional properties of mung bean protein isolate conjugated with maltodextrin through maillard reaction

Four different methods of maillard reaction including ultrasound (150 W, 10 min) assisted, classical wet heating (80 °C, 60min), moderate water bath heating (60°C, 12 to 30 h) and dry state method (60 °C, 79 % relative humidity and 48 h) were used to Mung bean protein isolate - Maltodexrtin conjugates (MPI-MD) preparation. The samples prepared under ultrasound and wet heating were chosen for further analysis according to degree of graft and UV-absorbance at 420 nm. Higher glycosylation at short time and lower browning were obtained under ultrasound treatment. Covalent attachment in conjugates confirmed by SDS-polyacrylamide gel electrophoresis. The structural analysis revealed prominent unfolding effect of ultrasound waves on the protein's molecules. The decrease of α-helix content was related to the exposure of buried amino group residues during reaction. Glycation of MPI under ultrasound caused changes in tertiary structure of protein and leads to decrease in the fluorescence intensity compared with native and wet heating treatments. FTIR spectra confirmed the conjugation of the MPI and MD and suggested that protein structure was changed and ultrasound promoted the graft reaction more than wet heating treatment. Conjugated MPI showed higher emulsification and solubility index than MPI, moreover the effect of ultrasonic waves on ameliorated functional properties was impressive than those for wet heating treatment. Overall, this study showed use of ultrasonication in maillard reaction was a suitable method for producing MPI- MD conjugates and improved the efficiency of graft reaction and functional properties of grafts.

Hydro- and aerogels from quince seed gum and gelatin solutions

The composite hydro/aerogels were designed using gelatin and quince seed gum (QSG) at total polymer concentration (TPC) of 1, 1.5 and 2% and gelatin/QSG ratio of 1:0, 1:0.5 and 1:1. The gel syneresis decreased significantly with increase in TPC and QSG. Although, hydrogels with 2% TPC had remarkably higher gel strength and elasticity than 1% TPC ones, the addition of high levels of QSG to the gelatin (i.e., gelatin/QSG 1:1) led to a decrease in its gel strength (∼0.97-fold) and elasticity (∼3,463-fold). The temperature-sweep test showed higher melting points in gelatin/QSG hydrogels (>60 °C) compared to the gelatin ones (∼58 °C). Additionally, QSG addition to the gelatin led to more porous networks with higher gel strength, thermal stability, and crystallinity, as observed by scanning electron microscopy, differential scanning calorimetry, and X-ray diffractometer. Therefore, QSG could be used as a natural hydrocolloid to modify gelatin functionality.

Behavior of protein-polysaccharide conjugate-stabilized food emulsions under various destabilization conditions

The sensitivity of protein-stabilized emulsions to flocculation, coalescence, and phase separation under destabilization conditions (i.e., heating, aging, pH, ionic strength, and freeze-thawing) may limit the widespread use of proteins as effective emulsifiers. Therefore, there is a great interest in modulating and improving the technological functionality of food proteins by conjugating them with polysaccharides, through the Maillard reaction. The present review article highlights the current approaches of protein-polysaccharide conjugate formation, their interfacial properties, and the behavior of protein-polysaccharide conjugate stabilized emulsions under various destabilization conditions, including long-term storage, heating and freeze-thawing treatments, acidic conditions, high ionic strength, and oxidation. Protein-polysaccharide conjugates are capable of forming a thick and cohesive macromolecular layer around oil droplets in food emulsions and stabilizing them against flocculation and coalescence under unfavorable conditions, through steric and electrostatic repulsion. The protein-polysaccharide conjugates could be therefore industrially used to design emulsion-based functional foods with high physicochemical stability.

A novel approach for the development of edible oleofoams using double network oleogelation systems

Whipped oleogels (oleofoams) are commonly stabilized by crystalline particles. Still, external factors like temperature fluctuations could change the state of the crystals (phase transitions), leading to the destabilization and disruption of oleofoams. Herein, a double network oleogelation system comprised of a primary crystalline network (using glycerol monostearate) and a secondary colloidal network (stabilized by soy protein isolate-anionic polysaccharides Mailard conjugates) is proposed as a novel strategy to overcome these challenges. It was observed that the incorporation of the secondary network resulted in a lower over-run, but a higher melting point, elasticity, foam stability, and more uniform bubble size distribution. This was explained by the strong interfacial stabilization provided by the colloidal network that can protect the crystalline particle against coarsening and oil drainage. These double network oleofoams, which could retain 41-48 % air (oleogel-based), display great potential for utilization in low-calorie lipid-based products.

Ultrasound treatment enhanced the functional properties of phycocyanin with phlorotannin from Ascophyllum nodosum

Introduction

Phycocyanin offers advantageous biological effects, including immune-regulatory, anticancer, antioxidant, and anti-inflammation capabilities. While PC, as a natural pigment molecule, is different from synthetic pigment, it can be easily degradable under high temperature and light conditions.

Methods

In this work, the impact of ultrasound treatment on the complex of PC and phlorotannin structural and functional characteristics was carefully investigated. The interaction between PC and phlorotannin after ultrasound treatment was studied by UV–Vis, fluorescence spectroscopy, circular dichroism (CD) spectroscopy, fourier transform infrared (FTIR) spectroscopy. Additionally, the antioxidant potential and in vitro digestibility of the complexes were assessed.

Results

The result was manifested as the UV–Vis spectrum reduction effect, fluorescence quenching effect and weak conformational change of the CD spectrum of PC. PC was identified as amorphous based on the X-ray diffraction (XRD) data and that phlorotannin was embedded into the PC matrix. The differential scanning calorimetry (DSC) results showed that ultrasound treatment and the addition of phlorotannin could improve the denaturation peak temperatures (Td) of PC to 78.7°C. In vitro digestion and free radical scavenging experiments showed that appropriate ultrasound treatment and the addition of phlorotannin were more resistant to simulated gastrointestinal conditions and could improve DPPH and ABTS+ free radical scavenging performance.

Discussion

Ultrasound treatment and the addition of phlorotannin changed the structural and functional properties of PC. These results demonstrated the feasibility of ultrasound-assisted phlorotannin from A. nodosum in improving the functional properties of PC and provided a possibility for the application of PC-polyphenol complexes as functional food ingredients or as bioactive materials.

Non-thermal plasma modulation of the interaction between whey protein isolate and ginsenoside Rg1 to improve the rheological and oxidative properties of emulsion

Molecular interaction forces regulate the interfacial properties of oil-in-water emulsion and play a key role in the rheology and stability of the emulsion in the food industry. In this study, the effects of non-thermal plasma (NTP) treatment on the structural and functional properties of whey protein isolate (WPI) and its binding interaction with ginsenoside Rg₁ (GR₁) were investigated. The results based on surface hydrophobicity, infrared spectroscopy and fluorescence spectroscopy test showed that the NTP treatment induced the unfolding of the structure of WPI and promoted the binding affinity between WPI and GR₁. By comparing with untreated WPI (an α-helix content of 19.63 % and a β-sheet content of 31.66 %), there was a greater decrease in α-helix content and an increase in β-sheet content of WPI in N₂₀-WPI (α-helix = 9.63 %, β-sheet = 39.63 %) and N₂₀-WPI-GR₁ (α-helix = 4.98 %, β-sheet = 48.66 %) groups. Importantly, the NTP treatment increased the interfacial adsorption and antioxidant capacity of the WPI-GR1 complexes, which contributed to the improvement of the rheological properties and oxidation stability of the emulsion. As a result, the NTP treatment could markedly improve the rheological and antioxidative properties of the WPI-GR₁ complexes and the NTP-treated WPI-GR₁ emulsions was more stable than that untreated. The present research indicated that NTP-treated formation of protein-saponin complexes could enhance the functional properties of the proteins, thus expanding their application as functional ingradients in nutritionally fortified food.

Changes in the functional properties of casein conjugates prepared by Maillard reaction with pectin or arabinogalactan

The aim of this study was to prepare conjugates of casein (CA) with pectin (CP) or arabinogalactan (AG) by the Maillard reaction (wet-heating) and to investigate the effects of CP or AG on the structural and functional properties of casein. The results indicated that the highest grafting degree of CA with CP or AG was observed at 90 °C for 1.5 h or 1 h, respectively. Secondary structure showed that grafting with CP or AG reduced the α-helix level and increased the random coil level of CA. Glycosylation treatment of CA-CP and CA-AG exhibited lower surface hydrophobicity and higher absolute ζ-potential values, further significantly improving the functional properties of CA (e.g., solubility, foaming property, emulsifying property, thermal stability, and antioxidant activity). Accordingly, our results indicated that it is feasible for CP or AG to improve the functional properties of CA by the Maillard reaction.

Ultra-stable high internal phase emulsions stabilized by protein-anionic polysaccharide Maillard conjugates

This paper reports the production of O/W high internal phase emulsions (HIPEs) using protein-anionic polysaccharide Maillard conjugates. First, Maillard conjugates were prepared from soy protein isolate (SPI) or sodium caseinate (SC) proteins and Alyssum homolocarpum seed gum (AHSG) or kappa-carrageenan (kC) polysaccharides. The conjugation process was confirmed and monitored by UV spectrophotometry, Fourier transform infrared, circular dichroism, fluorescence spectroscopies, and differential scanning calorimetry. Under the optimized reaction conditions, SC-AHSG conjugates exhibited the highest glycation degree and emulsifying properties. Next, HIPEs were made using the optimized conjugates, and their microstructure, droplet size, and physical stability were evaluated. The emulsion stabilized by SC-AHSG conjugate had the lowest mean droplet size (363.07 ± 34.56 nm), orderly-packed oil droplets with monomodal distribution, the highest zeta potential (-27.70 ± 0.70 mV), high storage stability (no creaming or oil-off) and was ultra-stable against environmental stresses. Results of this research are helpful for development of emulsion-based foods with novel functionality.

Gellan gum conjugation with soy protein via Maillard-driven molecular interactions and subsequent clustering lead to conjugates with tuned technological functionality

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Soy protein isolate (SPI) was conjugated to low acyl gellan gum (LAGG).

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Conjugate formation was confirmed by glycation degree (DG) and structural changes.

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SPI-LAGG conjugates were classified into low, medium, and high DG clusters.

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A low DG was enough to enhance the techno-functional properties of SPI.

Soy proteins are frequently used in the food industry; however, they have rigid and compact structure with relatively poor interfacial properties and solubility. This study was therefore aimed to modify techno-functional characteristics of soy protein isolate (SPI; 0.1% w/v) by conjugating to low acyl gellan gum (LAGG; 0.1, 0.2, and 0.3% w/v), through the Maillard reaction (at 90 °C for 90 min). The SPI-LAGG conjugates were confirmed by changes in pH, glycation degree (DG; up to 48%), Fourier transform infrared spectroscopy, and sodium dodecyl sulphate polyacrylamide electrophoresis. The conjugates were then classified into three clusters of low, medium, and high DG, via K-means clustering method. The low DG conjugate had lower surface hydrophobicity and foaming capacity, and higher thermal stability, solubility, emulsifying properties, foam stability, and antioxidant activity compared to the other clusters. This indicated that a low DG is required to enhance the functional properties of proteins.

The impact of konjac glucomannan on the physical and chemical stability of walnut oil-in-water emulsions coated by whey proteins

BACKGROUND

Walnut oil, which is rich in polyunsaturated fatty acids (PUFAs), can be incorporated into food emulsions to increase their nutritional value. However, these emulsions are highly susceptible to deterioration during storage due to lipid oxidation. Konjac glucomannan (KGM) is a neutral plant polysaccharide used as a stabilizer, thickener or gelling agent in foods. The goal of this study was to incorporate KGM into oil-in-water emulsions containing walnut oil droplets coated by whey protein isolate (WPI) and then determine its effects on their physical and oxidative stability.

RESULTS

At pH 3, inclusion of KGM (0.1-1 g kg^-1 ) reduced the positive surface potential on the droplets in the emulsions and modified the secondary structure of the adsorbed whey proteins, suggesting an interaction between KGM and WPI at the droplet surfaces. The physical stability of the emulsions was enhanced when 0.1-0.6 g kg^-1 KGM was added but reduced at higher levels. Lipid oxidation was inhibited in the emulsions in a dose-dependent manner when 0.2-0.6 g kg^-1 KGM was added but protein oxidation was promoted at higher KGM levels. The steric hindrance provided by the thick WPI-KGM interfaces, as well as the ability of the polysaccharides to modify the antioxidant properties of the adsorbed proteins, may account for these effects.

CONCLUSION

These results suggest that KGM can be used to inhibit lipid oxidation in emulsified foods containing protein-coated oil droplets. However, its level must be optimized because higher doses can result in droplet aggregation and protein oxidation. © 2022 Society of Chemical Industry.

The non-covalent interactions between whey protein and various food functional ingredients

In daily diet, Whey protein (WP) is often coexisted with various Food functional ingredients (FFI) such as proteins, polyphenols, polysaccharides and vitamins, which inevitably affect or interact with each other. Generally speaking, they may be interact by two different mechanisms: non-covalent and covalent interactions, of which the former is more common. We reviewed the non-covalent interactions between WP and various FFI, explained the effect of each WP-FFI interaction, and provided possible applications of WP-FFI complex in the food industry. The biological activity, physical and chemical stability of FFI, and the structure and functionalities of WP were enhanced through the non-covalent interactions. The development of non-covalent interactions between WP and FFI provides opportunities for the design of new ingredients and biopolymer complex, which can be applied in different fields. Future research will further focus on the influence of external or environmental factors in the food system and processing methods on interactions.

Effect of thermal treatment on aroma compound formation in yeast fermented pork hydrolysate supplemented with xylose and cysteine

BACKGROUND

The present study has revealed an innovative method of coupling enzyme hydrolysis, yeast fermentation and thermal treatment to transform pork trimmings into a seasoning product. The pork trimmings were first enzymatically hydrolysed and fermented into liquid pork hydrolysates, followed by adding xylose and cysteine, then heat treatment.

RESULTS

Approximately 28% of xylose and 7% of glucose were consumed, and amino acids increased by around 31% after thermal treatment. The heated yeast fermented pork hydrolysates possessed a characteristic 'savoury, roasted-meat and fruity sweet' aroma as a result of the formation of thermally induced sulfur-containing volatiles such as 2-furfurylthiol, as well as retention of yeast generated esters including isoamyl acetate and hexyl acetate.

CONCLUSION

The heat-treated fermented pork hydrolysates impart an attractive and innovative aroma because of yeast fermentation and heat treatment. The innovative heated fermented pork hydrolysates could be further processed into a nutritional and savoury pork broth and/or a meat sauce. © 2021 Society of Chemical Industry.

Effect of carbohydrate type on the structural and functional properties of Maillard-reacted black bean protein

Protein from black beans (Phaseolus vulgaris L.) has good solubility, emulsification, and antioxidant properties, with significant potential applications in the food industry. Maillard-reaction-mediated dry-heat glycosylation is a relatively safe modification method to improve the functional properties of black bean protein (BBP). Here, Maillard-reacted conjugates were prepared by applying 24-h dry-heating to induce a reaction between BBP and one of three carbohydrates (dextran, chitosan, and sodium alginate) at 70°C and 79% relative humidity. The resulting Maillard conjugates were designated as BBP-Dex, BBP-Ch, and BBP-SA, respectively. The formation of each Maillard conjugate was characterized by analyzing the grafting degree, free sulfhydryl (SH) groups content, and surface hydrophobicity, as well as the results of Fourier-transform infrared (FTIR) spectroscopy and fluorescence spectroscopy. The FTIR and fluorescence spectroscopy results provided information on the formation of the Maillard conjugates. The BBP-SA conjugate had a higher grafting degree and SH group content than the other two conjugates. The solubility, emulsifying properties, and antioxidant properties of the BBP were significantly improved after the Maillard reaction (p < 0.05). Moreover, the physicochemical and functional properties of the conjugates were superior to those of the BBP-carbohydrate mixtures, indicating that covalent interactions may be stronger than noncovalent interactions. This study provides theoretical guidance for future research on protein-carbohydrate conjugates. PRACTICAL APPLICATION: This study has great potential applications in the development of new multi-functional food ingredients and the realization of functional factor homeostasis, and provides scientific and theoretical bases for the application of protein-carbohydrate conjugate in the field of functional food.

Application of protein-polysaccharide Maillard conjugates as emulsifiers: Source, preparation and functional properties

The protein-polysaccharide conjugates formed by Maillard reaction can be used as novel emulsifiers in the food industry. Proteins and polysaccharides have extensive sources, and their emulsifying properties are highly dependent on their structural features. The Maillard conjugates can be prepared from conventional and novel methods, and these methods have different advantages and limitations in industrial applications. After an appropriate glycation, the conjugates show some modified or enhanced functional properties, including solubility, emulsifying property, thermal stability, foaming capacity, and gelation property. However, the research on the structure-function relationship of both proteins and polysaccharides is limited. It is necessary to well understand the characteristics of these biopolymers, and select appropriate conditions to control the process of Maillard reaction. Overall, the Maillard conjugates show great potential as the emulsifiers and stabilizers in the emulsion system. This review introduces the sources and structural characteristics of commonly used proteins and polysaccharides for Maillard reaction, outlines the methods (dry-heating, wet-heating, electrospinning, ultrasound, pulsed electric field, and microwave) for preparing Maillard conjugates and focuses on the improved functional properties (solubility, emulsifying, foaming and thermal properties) and the potential mechanisms.

The interfacial covalent bonding of whey protein hydrolysate and pectin under high temperature sterilization: Effect on emulsion stability

In this study, the effect of high-pressure steam sterilization (121 °C for 15 min) on whey protein hydrolysate-pectin solutions and emulsions was studied. The interaction and emulsification characteristics of pectin and whey protein concentrate (WPC) were evaluated from the solution system to the emulsion system. Enzymatic hydrolysis of WPC (WPH, 2 % and 8 % degree of hydrolysis) increased the covalent binding with pectin, which reduced the heat-induced aggregation of protein and improved emulsification. The thermodynamic incompatibility between WPC and pectin was not conducive to the covalent bonding under high temperature sterilization and produced serious aggregates, which also made a rapid increase in particle size (up to ∼3 μm), compared to WPH-pectin emulsion (∼ 400 nm). In addition, if emulsion was stirred during the sterilization, the creaming and protein aggregation could be avoided. By comparing low methoxy pectin (LMP) and high methoxy pectin (HMP), it was found that the whey protein-HMP complex had better emulsification stability, and the steric stabilization played a more important role in emulsion stability than the electrostatic repulsion. The changes of whey protein and pectin at the oil-water interface of the emulsion during the sterilization process may provide a reference for the sterilized bioactive ingredient delivery system.

Physicochemical stability and gastrointestinal fate of β-carotene-loaded oil-in-water emulsions stabilized by whey protein isolate-low acyl gellan gum conjugates

This study aimed to examine the effect of whey protein isolate-low acyl gellan gum (WPI-GG) conjugate on the physicochemical properties and digestibility of β-carotene-loaded oil-in-water emulsions. The WPI-GG conjugate-stabilized emulsions had lower droplet sizes with more homogenous distribution, more negative surface charge, and higher interfacial protein concentration and viscosity, compared to those stabilized by WPI-GG mixture and WPI. The emulsion droplets coated by the conjugate were also generally more stable to environmental stresses (i.e., storage, pH changes, ionic strength, freeze-thaw cycles, and thermal treatment) along with higher β-carotene retention than other systems. The stability to droplet aggregation during in vitro digestion was remarkably increased for the conjugate-stabilized emulsion. However, the β-carotene bioaccessibility was significantly affected when the conjugate was used to stabilize the emulsions, likely due to the thick interfacial layer, high viscosity, and negative charge of the corresponding emulsions that could inhibit droplet digestion and mixed micelle formation.

Fabrication and characterization of whey protein isolates- lotus seedpod proanthocyanin conjugate: Its potential application in oxidizable emulsions

Emulsified ω-3 polyunsaturated fatty acid have expanding application in different food matrix with improved water solubility while still prone to oxidation. Lotus seedpod proanthocyanidin (LSPC) was grafted to whey protein isolate (WPI) to create nature-derived antioxidant emulsifiers. ¹HNMR, SDS-PAGE and multiple spectrometry showed that the structure of protein was changed after grafting. DPPH and FRAP measurements showed that WPI-LSPC conjugate (90.53 ± 1.48% of DPPH scavenging, 691.85 ± 4.54 μg/mL for FRAP assay) possessed a much better antioxidant ability than WPI (17.06 ± 3.34% of DPPH scavenging, 10.43 ± 0.26 μg/mL for FRAP assay). Ultrasonic emulsification and DSC experiments showed that WPI-LSPC conjugate were more effective at forming and stabilizing the flaxseed oil emulsions than pure WPI, with higher thermostability. Likewise, low levels of primary and secondary oxidation products were formed for the conjugate than the pure protein in O/W systems after storage, again suggesting WPI-LSPC could be used as fine antioxidant emulsifiers in oxidizing delivery systems.