Improving the physical and oxidative stability of emulsions based on the interfacial electrostatic effects between porcine bone protein hydrolysates and porcine bone protein hydrolysate-rutin conjugates

Preparation of oil-in-water emulsions stabilized by faba bean protein-grape leaf polyphenol conjugates: pH-, salt-, heat-, and freeze-thaw-stability

BACKGROUND

Plant proteins are being increasingly utilized as functional ingredients in foods because of their potential health, sustainability, and environmental benefits. However, their functionality is often worse than the synthetic or animal-derived ingredients they are meant to replace. The functional performance of plant proteins can be improved by conjugating them with polyphenols. In this study, the formation and stability of oil-in-water emulsions prepared using faba bean protein-grape leaf polyphenol (FP-GLP) conjugates as emulsifiers. Initially, FP-GLP conjugates were formed using an ultrasound-assisted alkali treatment. Then, corn oil-in-water emulsions were prepared using high-intensity sonication (60% amplitude, 10 min) and the impacts of conjugate concentration, pH, ionic strength, freezing-thawing, and heating on their physicochemical properties and stability were determined.

RESULTS

Microscopy and light scattering analysis showed that oil-in-water emulsions containing small oil droplets could be formed at conjugate concentrations of 2% and higher. The addition of salt reduced the electrostatic repulsion between the droplets, which increased their susceptibility to aggregation. Indeed, appreciable droplet aggregation was observed at ≥ 50 mmol/L sodium chloride. The freeze-thaw stability of emulsions prepared with protein-polyphenol conjugates was better than those prepared using the proteins alone. In addition, the emulsions stabilized by the conjugates had a higher viscosity than those prepared by proteins alone.

CONCLUSION

This study showed that FP-GLP conjugates are effective plant-based emulsifiers for forming and stabilizing oil-in-water emulsions. Indeed, emulsions formed using these conjugates showed improved resistance to pH changes, heating, freezing, and salt addition. © 2024 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

The effect of rice protein-polyphenols covalent and non-covalent interactions on the structure, functionality and in vitro digestion properties of rice protein

The characteristics of the crosslinking between rice protein (RP) and ferulic acid (FA), gallic acid (GA), or tannin acid (TA) by covalent binding of Laccase and non-covalent binding were evaluated. The RP-polyphenol complexes greatly improved the functionality of RP. The covalent effect with higher polyphenol binding equivalence showed higher emulsion activity than the non-covalent effect. The solubility, and antioxidant activity of covalent binding were higher than that of non-covalent binding in the RP-FA group, but there was a contrasting behavior in the RP-GA group. The RP-FA was most soluble in conjugates, while the RP-GA had the highest solubility in mixtures. It was found that the covalent complexes were more stable in the intestinal tract. The content of polyphenols in the RP-TA group was rapidly increased at the later intestinal digestion, which indicated the high polyphenol-protective effect in this group. Meanwhile, the RP-TA group showed high reducing power but low digestibility.

Impact of quercetin conjugation using alkaline and free radical methods with tandem ultrasonication on the functional properties of camel whey and its hydrolysates

The structural and functional properties of whey-quercetin and whey hydrolysate-quercetin conjugates synthesized using alkaline and free radical-mediated methods (AM and FRM) coupled with sonication were studied. FTIR showed new peaks at 3000-3500 cm-1 (N-H stretching regions) and the 1000-1100 cm-1 region with the conjugates. Conjugation increased the random coils and α-helix content while decreasing the β-sheets and turns. It also increased the particle size and surface hydrophobicity which was significantly (p < 0.05) higher in AM than FRM conjugates. AM conjugates had higher radical scavenging activity but lower quercetin content than FRM conjugates. Overall, the functional properties of whey-quercetin conjugates were better than whey hydrolysate-quercetin conjugates. However, hydrolysate conjugates had significantly higher denaturation temperatures irrespective of the method of production. Sonication improved the radical scavenging activity and quercetin content of FRM conjugates while it decreased both for AM conjugates. This study suggested that whey-quercetin conjugates generally had better quality than whey hydrolysate conjugates and sonication tended to further improve these properties. This study highlights the potential for using camel whey or whey hydrolysate-quercetin conjugates to enhance the functional properties of food products in the food industry.

Characterization of the covalent binding of cyanidin-3-glucoside to bovine serum albumin and its inhibition mechanism for advanced nonenzymatic glycosylation reactions

Nonenzymatic glycosylation of proteins can generate advanced glycosylation end products, which are closely associated with the pathogenesis of certain chronic physiological diseases and aging. In this study, we characterized the covalent binding of cyanidin-3-glucoside (C3G) to bovine serum albumin (BSA) and investigated the mechanism by which this covalent binding inhibits the nonenzymatic glycosylation of BSA. The results indicated that the covalent interaction between C3G and BSA stabilized the protein's secondary structure. Through liquid chromatography-electrospray ionization tandem mass spectrometry analysis, we identified the covalent binding sites of C3G on BSA as lysine, arginine, asparagine, glutamine, and cysteine residues. This covalent interaction significantly suppressed the nonenzymatic glycosylation of BSA, consequently reducing the formation of nonenzymatic glycosylation products. C3G competitively binds to nonenzymatic glycosylation sites (e.g., lysine and arginine) on BSA, thereby impeding the glycosylation process and preventing the misfolding and structural alterations of BSA induced by fructose. Furthermore, the covalent attachment of C3G to BSA preserves the secondary structure of BSA and hinders subsequent nonenzymatic glycosylation events.

Constructing myosin/high-density lipoprotein composite emulsions: Roles of pH on emulsification stability, rheological and structural properties

The emulsification activity of myosin plays a significant role in affecting quality of emulsified meat products. High-density lipoprotein (HDL) possesses strong emulsification activity and stability due to its structural characteristics, suggesting potential for its utilization in developing functional emulsified meat products. In order to explore the effect of HDL addition on emulsification stability, rheological properties and structural features of myosin (MS) emulsions, HDL-MS emulsion was prepared by mixing soybean oil with isolated HDL and MS, with pH adjustments ranging from 3.0 to 11.0. The results found that emulsification activity and stability in two emulsion groups consistently improved as pH increased. Under identical pH, HDL-MS emulsion exhibited superior emulsification behavior as compared to MS emulsion. The HDL-MS emulsion under pH of 7.0-11.0 formed a viscoelastic protein layer at the interface, adsorbing more proteins and retarding oil droplet diffusion, leading to enhanced oxidative stability, compared to the MS emulsion. Raman spectroscopy analysis showed more flexible conformational changes in the HDL-MS emulsion. Microstructural observations corroborated these findings, showing a more uniform distribution of droplet sizes in the HDL-MS emulsion with smaller particle sizes. Overall, these determinations suggested that the addition of HDL enhanced the emulsification behavior of MS emulsions, and the composite emulsions demonstrated heightened responsiveness under alkaline conditions. This establishes a theoretical basis for the practical utilization of HDL in emulsified meat products.

Encapsulation of Lactobacillus plantarum in W1/O/W2 double emulsions stabilized with the high-intensity ultrasound-treated pea protein and pectin

This study focuses on developing a water-in-oil-in-water (W1/O/W2) double emulsion system using high-intensity ultrasound (HIU)-treated pea protein isolate (HIU-PPI) and pectin to encapsulate Lactobacillus plantarum (L. plantarum). The effects of ultrasound treatment on pea protein isolate (PPI) characteristics such as solubility, particle size, emulsification, surface hydrophobicity, and surface free sulfhydryl group were examined, determining optimal HIU processing conditions was 400 W for 10 min. The developed W1/O/W2 double emulsion system based on HIU-PPI demonstrated effective encapsulation and protection of L. plantarum, especially at the HIU-PPI concentration of 4 %, achieving an encapsulation efficiency of 52.65 %. Incorporating both HIU-PPI and pectin as emulsifiers increased the particle size and significantly enhanced the emulsion's viscosity. The highest bacterial encapsulation efficiency of the emulsion, 59.94 %, was attained at a HIU to pectin concentration ratio of 3:1. These emulsions effectively encapsulate and protect L. plantarum, with the concentration of HIU-PPI being a critical factor in enhancing probiotic survival under simulated gastrointestinal digestion. However, the concurrent utilization of pectin and HIU-PPI as emulsifiers did not provide a notable advantage compared to the exclusive use of HIU-PPI in enhancing probiotic viability during in vitro simulated digestion. This research offers valuable perspectives for the food industry on harnessing environmentally friendly, plant-based proteins as emulsifiers in probiotic delivery systems. It underscores the potential of HIU-modified pea protein and pectin in developing functional food products that promote the health benefits of probiotics.

The Effect of Nanoscale Modification of Nisin by Different Milk-Derived Proteins on Its Physicochemical Properties and Antibacterial Activity

Nisin is used as a natural food preservative because of its broad-spectrum antimicrobial activity against Gram-positive bacteria. However, free nisin is susceptible to various factors that reduce its antimicrobial activity. Milk protein, a protein derived from milk, has self-assembly properties and is a good carrier of bioactive substances. In this study, lactoferrin-nisin nanoparticles (L-N), bovine serum albumin-nisin nanoparticles (B-N), and casein-nisin nanoparticles (C-N) were successfully prepared by a self-assembly technique, and then their properties were investigated. The studies revealed that lactoferrin (LF) and nisin formed L-N mainly through hydrophobic interactions and hydrogen bonding, and L-N had the best performance. The small particle size (29.83 ± 2.42 nm), dense reticular structure, and good thermal stability, storage stability, and emulsification of L-N laid a certain foundation for its application in food. Further bacteriostatic studies showed that L-N enhanced the bacteriostatic activity of nisin, with prominent inhibitory properties against Listeria monocytogenes, Staphylococcus aureus, and Bacillus cereus, which mainly disrupted the cell membrane of the bacteria. The above results broaden our understanding of milk protein-nisin nanoparticles, while the excellent antibacterial activity of L-N makes it promising for application as a novel food preservative, which will help to improve the bioavailability of nisin in food systems.

Interfacial engineering method to regulate the performances of bilayer emulsions co-stabilized by casein/butyrylated dextrin nanoparticles and chitosan

In present study, bilayer emulsions with different interfacial structures stabilized by casein/butyrylated dextrin nanoparticles (CDNP), chitosan (CS) and chitosan nanoparticles (CSNP) were prepared to overcome the limitations of conventional emulsions. The effects of chitosan morphology and incorporation sequences on the bilayer emulsions were examined. Bilayer emulsions prepared with CDNP as the inner layer and CS/CSNP as the outer layer were observed to have smaller droplet sizes (1.39 ± 86.74 um and 1.45 ± 7.87 um). Bilayer emulsions prepared with CDNP as the inner layer and CS as the outer layer exhibited the lowest creaming index (2.38 %) after 14 days of storage, indicating excellent stability. Furthermore, bilayer emulsion prepared with CDNP as the inner layer and CS as the outer layer also exhibited a uniform water distribution, excellent protein oxidative stability, and uniformly distributed droplets by the measurement of Low-field NMR, intrinsic tryptophan fluorescence and laser confocal laser scanning microscopy. These results indicated that the study provided a theoretical basis for the development and design of bilayer emulsions with different interfacial structures. This study also provides a new material for the preparation of delivery systems that protect biologically active compounds. Bilayer emulsions are promising for applications in traditional and manufactured food products.

Insights into the emulsifying effect and oxidation stability of myofibrillar protein-diacylglycerol emulsions containing catechin at different ionic strengths

The purpose of this study was to investigate the effects of different ionic strengths on the emulsifying and oxidation stabilities of myofibrillar protein-diacylglycerol emulsions containing catechin (MP-DAG-C), in which lard, unpurified glycerolytic lard (UGL), and purified glycerolytic lard (PGL) were used as oil phases in this study, respectively. Results revealed that emulsifying ability was significantly improved by UGL and PGL (P < 0.05). Meanwhile, the emulsifying activity and stability, absolute ξ-potential value, shear viscosity, and dynamic rheological characteristic of emulsions increased with the increase of ionic strength (P < 0.05) remarkablely, which reached the maximum value at 0.6-M sodium chloride (NaCl). The droplets of emulsions at 0.6-M ionic strength were smallest and distributed most uniformly compared to other NaCl conditions. The formation of thiobarbituric acid substances and carbonyls increased, and the total sulfydryl contents decreased as the extension of storage days (P < 0.05). However, the oxidation stability of MP-DAG-C emulsions was insignificantly decreased by ionic strengths (P > 0.05). The above results showed that MP-DAG-C emulsions could keep excellent emulsifying effects and oxidation stability under high ionic strengths. This study provides data support for the application of MP-DAG-C emulsions in emulsified meat products, which is benefit for promoting the development of high-quality emulsified meat products.

Investigating the effect of catechin on the emulsification and oxidation stability of myofibrillar protein-diacylglycerol emulsions

The effects of catechin on the emulsification and oxidation stability of myofibrillar protein-diacylglycerol (MP-DAG) emulsions were investigated. Lard samples, namely, lard, unpurified glycerolytic lard (UGL), and purified glycerolytic lard (PGL), were used as oil phases. The emulsifying effects of UGL- and PGL-based emulsions were superior to those of lard-based emulsions (P < 0.05). The emulsifying properties of MP-DAG emulsions increased initially and then decreased with a rise in the catechin concentration, with 20-μmol/g catechin exhibiting optimal emulsification activity and stability (P < 0.05). The droplets were tinier and evenly distributed, and the absolute ξ-potential values and rheological characteristics reached their maximum at a catechin concentration of 20 μmol/g. The formation of thiobarbituric acid-reactive substances and carbonyls declined significantly with the growth of catechin levels (P < 0.05), which confirmed that the oxidation of MPs and lipids was reduced efficiently by catechin. This study provides an idea for improving the emulsification and oxidation stability of MP-DAG emulsions, which offers a theoretical basis for the application of MP-DAG emulsions in meat products.

Artificial oil bodies: A review on composition, properties, biotechnological applications, and improvement methods

In order to simulate the structure of natural oil body, artificial oil bodies (AOBs) are fabricated by the integration of oleosins, triacylglycerols (TAGs) and phospholipids (PLs) in vitro. Recently, AOBs have gained great research interest both in the food and biological fields due to its ability to act as a novel delivery system for bioactive compounds and as a carrier for target proteins. This review aims to summarize the composition and the preparation methods of AOBs, examine the factors influencing their stability. Moreover, this contribution focusses on exploring the application of AOBs to encapsulate functional ingredients that are prone to oxidation as well as improve efficiency involved in protein purification, renaturation and immobilization by reducing the complex steps. In addition, the improvement measures to further enhance the stability and efficacy of AOBs are also discussed. The application of AOBs is expected to be a big step towards replacing existing bioreactors and delivery systems.

Insight on the emulsifying mechanisms of low-salt type emulsions stabilized by Maillard conjugates: Myofibrillar protein peptide-dextrin with different degrees of hydrolysis

In this study, we investigated the emulsifying properties and stabilisation mechanisms of low-salt type emulsions stabilised by MP-base conjugates prepared via the Maillard reaction between DX and MP peptides (MPP). Mild hydrolysis by Alcalase promoted a well-controlled Maillard reaction in dry conditions. Combining hydrolysis and Maillard reaction caused the dissociation and unfolding of highly aggregated MP structures; the ordered secondary structure was lost and the hydrophobic residue was exposed. The MPP-DX conjugates greatly improved the emulsifying ability and stability in the low-salt system; the resulting emulsion exhibited a small droplet size and homogeneous microstructure with desirable storage stability. Further, the glycation products were found to effectively suppress gravity-induced creaming. The MPP-DX glycoconjugate developed with 5% DG, exhibiting strongest flocculation and creaming stability, was determined as the optimal emulsifying agent for low-salt type emulsions. These findings provide a theoretical basis for developing low-salt meat products and/or emulsion-based foods.

Preparation, structural characterization and properties of feruloyl oligosaccharide-rice protein hydrolysate conjugates

Rice protein hydrolysate (RPH) and feruloyl oligosaccharides (FOs) were conjugated under the catalysis of laccase and free radical, and the structure and properties of the resultant conjugates were studied. Electrophoresis analysis demonstrated that conjugation with FOs increased the molecular weight of some fractions in RPH, which confirmed the formation of both conjugates. The conjugation degree of laccase-induced conjugate and radical-induced conjugate was 60.45% and 22.70%, respectively. Laccase-catalyzed conjugation decreased the tyrosine residue content of RPH but had no significant effect on the free amino group content, which suggested that tyrosine residues were the conjugation site in the laccase-induced conjugate. However, radical-catalyzed conjugation decreased both the free amino group content and the tyrosine residue content, which indicated that both free amino groups and tyrosine residues were the conjugation site in the radical-induced conjugate. The ultraviolet, fluorescence and circular dichroism spectroscopy analysis revealed that conjugation with FOs significantly altered the secondary and tertiary structure of RPH. In addition, conjugation with FOs increased the solubility and antioxidant activity of RPH but decreased the emulsifying activity and stability. Particularly, the radical-induced conjugate had greater anti-aggregation capacity and antioxidant activity but lower emulsifying activity and stability than the laccase-induced conjugate, which might be due to that their conjugation site and degree were different.

Unravelling the interaction between α-SOH and myofibrillar protein based on spectroscopy and molecular dynamics simulation

This work systematically investigated the dose-response interaction between hydroxy-α-sanshool (α-SOH) and pork myofibrillar proteins (MPs) via spectroscopy, molecular docking, and molecular dynamics simulation methods. Results showed that MPs bound with low α-SOH can enhance the surface hydrophobicity and particle size of MPs, whereas high concentrations were exactly the opposite. The main interaction force in α-SOH/MPs complex changed from hydrophobic to hydrogen bonding with increased α-SOH. α-SOH causes tryptophan quenching and bring about a red shift at low concentration, as well as to promote α-helix conversion into β-sheet in MPs. Simultaneously, molecular docking and dynamics simulations verified that hydrogen bonding and hydrophobic forces were the main contributors to α-SOH/MPs complex, indicating that the binding of α-SOH with MPs proceeded spontaneously with high intensity, in which TYR286 contributed the most significant energy. Therefore, revealing the binding mechanism of α-SOH and MPs can contribute to the deep processing of numbing meat products.

Construction of protein-, polysaccharide- and polyphenol-based conjugates as delivery systems

Natural polymers, such as polysaccharides and proteins, have been used to prepare several delivery systems owing to their abundance, bioactivity, and biodegradability. They are usually modified or combined with small molecules to form the delivery systems needed to meet different needs in food systems. This paper reviews the interactions of proteins, polysaccharides, and polyphenols in the bulk phase and discusses the design strategies, coupling techniques, and their applications as conjugates in emulsion delivery systems, including traditional, Pickering, multilayer, and high internal-phase emulsions. Furthermore, it explores the prospects of the application of conjugates in food preservation, food development, and nanocarrier development. Currently, there are seven methods for composite delivery systems including the Maillard reaction, carbodiimide cross-linking, alkali treatment, enzymatic cross-linking, free radical induction, genipin cross-linking, and Schiff base chemical cross-linking to prepare binary and ternary conjugates of proteins, polysaccharides, and polyphenols. To design an effective target complex and its delivery system, it is helpful to understand the physicochemical properties of these biomolecules and their interactions in the bulk phase. This review summarizes the knowledge on the interaction of biological complexes in the bulk phase, preparation methods, and the preparation of stable emulsion delivery system.

Insight into covalent conjugates of β-lactoglobulin with rutin: Characterizing allergenicity, digestibility, and antioxidant properties in vitro

β-lactoglobulin (β-LG) is an essential nutrient in milk, but it is the primary allergen causing dairy allergy in humans. Currently, researchers are focusing on using flavonoids to covalently modify β-LG for improving its functionality. However, the impact and underlying mechanisms of rutin covalent modification on the functional properties and allergenicity of β-LG remain unclear. Here, we aim to investigate the changes in allergenicity, digestive characteristics, and antioxidant properties of β-LG after covalent modification using a combination of spectroscopy, enzyme-linked immunosorbent assay (ELISA), simulated digestion, and antioxidant assays. The results indicate that rutin forms covalent bonds with the free amino group, sulfhydryl group, and tryptophan of β-LG, leading to alterations in the secondary structure of β-LG. Furthermore, the modified β-LG exhibits improved antioxidant capacity and decreased allergenicity, along with reduced resistance to pancreatin digestion in vitro. This study provides novel insights and strategies to expand the functional application of β-LG.

Manipulation of protein structure and bonding pattern to improve the gelling and textural quality of surimi gels from silver carp: incorporation of mosambi (Citrus limetta) peel extract

BACKGROUND

This investigation focused on the use of mosambi peel extract (MPE) fortification (at 0% to 1.50%, w/w) in silver carp surimi to improve the gelling, textural, and other physicochemical properties of the surimi.

RESULTS

The peels were extracted in ethanol (40-100% concentrations, v/v) and water. It was found that 100% ethanol had significantly (P < 0.05) higher yield and total phenolic, flavonoid, and tannin content. The fortification of MPE at optimum level (0.75%) improved the breaking force (55.1%) and gel strength (89.9%) significantly (P < 0.05) in comparison with 0% MPE gel samples. Moreover, 0.75% MPE-fortified gels had higher hydrogen and hydrophobic bonds, higher water-holding capacity, and lower sulfhydryl groups and free amino groups. The myosin heavy chain (MHC) bands in sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) disappeared completely in the MPE-fortified gels. Fortification with MPE affected the secondary structures of protein as shifting of peaks was observed in Fourier-transform infrared (FTIR) spectra. Scanning electron microscopy (SEM) images showed relatively organized finer and denser gel networks in MPE-treated gels.

CONCLUSION

The surimi gels fortified with 0.75% MPE demonstrated improved gelling properties, with an overall higher acceptability than the unfortified gels (0% MPE). The fortified gels also became enriched with bioactive polyphenols, which are generally not present in surimi. This study provides an efficient way to utilize mosambi peel to develop functional surimi and surimi-based products with improved gel ability. © 2023 Society of Chemical Industry.

Extraction, optimization, and functional quality evaluation of carotenoproteins from shrimp processing side streams through enzymatic process

The study aimed to develop an effective and eco-friendly enzymatic process to extract carotenoproteins from shrimp waste. The optimization of enzymatic hydrolysis conditions to maximize the degree of deproteinization (DDP) of carotenoprotein from shrimp head waste (SHW) and shrimp shell waste (SSW) was conducted separately using the Box-Behnken design of response surface methodology (RSM). To achieve a maximum DDP of 92.32% for SSW and 96.72% for SHW, the optimal hydrolysis conditions were determined as follows: temperature (SSW: 53.13 °C; SHW: 45.90 °C), pH (SSW: 7.13; SHW: 6.78), time (SSW: 90 min; SHW: 61.18 min), and enzyme/substrate ratio (SSW: 2 g/100 g; SHW: 1.18 g/100 g). The carotenoprotein effluent obtained was subjected to spray drying and subsequently assessed for color, nutritional, and functional characteristics. The carotenoprotein from shrimp shell (CpSS) contained a higher essential amino acid score than carotenoprotein from shrimp head (CpSH). CpSS had a higher whiteness index of 82.05, while CpSH had 64.04. Both CpSS and CpSH showed good functional properties viz solubility, emulsion, and foaming properties. The maximum solubility of CpSH and CpSS was determined to be 92.94% and 96.48% at pH 10.0, respectively. The highest emulsion capacity (CpSH: 81.33%, CpSS: 70.13%) and stability (CpSH: 57.06%, CpSS: 63.05%) were observed at 3% carotenoprotein concentration. Similarly, the highest values of foaming capacity (CpSH: 27.66%, CpSS: 105.5%) and stability (CpSH: 23.83%, CpSS: 105.33%) were also found at the same 3% carotenoprotein concentration. In conclusion, the carotenoproteins obtained from shrimp waste showed favorable attributes in terms of color, amino acid composition, and functional properties. These findings strongly suggest the potential applicability of CpSS and CpSH as valuable resources in various domains. CpSS, with its higher whiteness index, greater amino acid content, and superior functional characteristics, may find suitability as functional ingredients in human food products. Conversely, CpSH could be considered for incorporation into animal feed formulations.

Covalent modification of (+)-catechin to improve the physicochemical, rheological, and oxidative stability properties of rice bran protein emulsion

The aim of this study is the effects of (+)-catechin (CC) covalent cross-linking (CCCI) (0.05-0.25 %, w/v) on the physicochemical properties, rheological properties, and oxidative stability of rice bran protein (RBP) emulsion. Analysis of particle size, ζ-potential, circular dichroism, fluorescence spectroscopy, surface hydrophobicity, and emulsifying properties demonstrated that a concentration of 0.15 % (w/v) CCCI facilitated protein structure unfolding, resulting in reduced particle size, enhanced electrostatic repulsion, and improved emulsion stability. Moreover, the covalent complexes of RBP-0.15 %CC (w/v) exhibited increased viscosity and shear stress, reflected by the highest G' and G″ values, ultimately enhancing the oxidative stability. Furthermore, analysis using atomic force microscopy and confocal laser scanning microscopy revealed that the RBP-0.15 %CC complexes exhibited the smallest particle size (164 nm) and displayed greater homogeneity. An increase in CC concentration to 0.25 % (w/v) resulted in a higher emulsion aggregation. The emulsions stabilized by CCCI exhibited superior rheological properties and enhanced oxidation stability compared to the control. In conclusion, an appropriate amount of CC can enhance the rheology and oxidation stability of the RBP emulsion, while CCCI treatment holds potential for expanding the utility of RBP in various applications.

Technological, nutritional, and biological properties of apricot kernel protein hydrolyzates affected by various commercial proteases

The effect of enzymatic hydrolysis of apricot kernel protein with different proteases (Alcalase, pancreatin, pepsin, and trypsin) on the amino acid content, degree of hydrolysis (DH), antioxidant, and antibacterial characteristics of the resulting hydrolyzates was investigated in this study. The composition of amino acids (hydrophobic: ~35%; antioxidant: ~13%), EAA/TAA ratio (~34%), and PER index (~1.85) indicates the ability of the hydrolyzate as a source of nutrients and antioxidants with high digestibility. Enzymatic hydrolysis with increasing DH (from 3.1 to a maximum of 37.9%) led to improved solubility (especially in the isoelectric range) and changes in water- and oil-holding capacity. The highest free radical scavenging activity of DPPH (83.3%), ABTS (88.1%), TEAC (2.38 mM), OH (72.5%), NO (65.7%), antioxidant activity in emulsion and formation of TBARS (0.36 mg MDA/L), total antioxidant (1.61), reducing power (1.17), chelation of iron (87.7%), copper (34.8%) ions, and inhibition of the growth of Escherichia coli (16.3 mm) and Bacillus cereus (15.4 mm) were affected by the type of enzymes (especially Alcalase). This research showed that apricot kernel hydrolyzate could serve as a nutrient source, emulsifier, stabilizer, antioxidant, and natural antibacterial agent in functional food formulations.

Structure relationship of non-covalent interactions between lotus seedpod oligomeric procyanidins and glycated casein hydrolysate during digestion

Procyanidin-amino acid interactions during transmembrane transport cause changes in the structural and physical properties of peptides, which limits further absorption of oligopeptide-advanced glycation end products (AGEs). In this study, glycated casein hydrolysates (GCSHs) were employed to investigate the structure and interaction mechanism of GCSH with lotus seedpod oligomeric procyanidin (LSOPC) complexes in an intestinal environment. LSOPC can interact with GCSH under certain conditions to form hydrogen bonds and hydrophobic interactions to form GCSH-LSOPC complexes. Results showed that procyanidin further leads to the transformation of a GCSH secondary structure and the increase of surface hydrophobicity (H0). The strongest non-covalent interaction between GCSH and (-)-epigallocatechin gallate (EGCG) was due to the polyhydroxy structure of EGCG. Binding site analysis showed that EGCG binds to the internal cavity of P1 to maintain the relative stability of the binding conformation. The antioxidant capacity of GCSH was remarkably elevated by GCSH-LSOPC. This study will provide a new reference for the accurate control of oligopeptide-AGEs absorption by LSOPC in vivo.

Effect of ultrasound treatment on interactions of whey protein isolate with rutin

Rutin is a biologically active polyphenol, but its poor water solubility and low bioavailability limit its application to the food industry. We investigated the effect of ultrasound treatment on the properties of rutin (R) and whey protein isolate (WPI) using spectral and physicochemical analysis. The results revealed that there was covalent interaction between whey protein isolate with rutin, and the binding degree of whey isolate protein with rutin increased with ultrasound treatment. Additionally, solubility and surface hydrophobicity of WPI-R complex improved with ultrasonic treatment, and a maximum solubility of 81.9 % at 300 W ultrasonic power. The ultrasound treatment caused the complex to develop a more ordered secondary structure, resulting in a three-dimensional network structure with small and uniform pore sizes. This research could provide a theoretical reference for studying protein-polyphenol interactions and their applications in food delivery systems.

Blue agave inulin-soluble dietary fiber: effect on technological quality properties of pangasius mince emulsion-type sausage

BACKGROUND

The aim of the work was to investigate the influence of supplementing pangasius mince-based emulsion sausages with blue agave-derived inulin at 1% (T1), 2% (T2), 3% (T3), 4% (T4), and 5% (T5) on its technological quality attributes and acceptability.

RESULTS

The cooking yield of T-2, T-3, and T-4 sausages (96-97%) exhibited no significant difference (P > 0.05), which was higher than the other lots. The T-2 batter exhibited a significant difference with all other treatments, showing the lowest total expressible fluid (12.20%) value, indicating the highest emulsion stability of the batter. There was a significant effect on the diameter reduction of the cooked sausages as the level of inulin increased. Sodium dodecyl sulfate polyacrylamide gel electrophoresis revealed the proteolysis of raw mince without inulin and new bands in cooked sausage samples were observed. Increasing inulin content increased the hardness of the sausages from 2510.81 ± 114.31 g to 3415.54 ± 75.88. The differential scanning calorimetry melting temperatures of peak 2 of the T-1, T-2, T-3, and T-4 increased as the inulin content increased from 1 to 4%. The scanning electron microscope images exhibited a smooth appearance on the surface as the inulin level increased.

CONCLUSION

The sausages incorporated with the 2% and 3% blue agave plant-derived inulin (T-2 and T-3) showed better sensory overall acceptability scores than the control. The results suggested that the blue agave plant-derived inulin could be efficiently utilized at the 2% and 3% levels to enhance the quality of emulsion-type pangasius sausage. © 2023 Society of Chemical Industry.

Covalent modification of soy protein hydrolysates by EGCG: Improves the emulsifying and antioxidant properties

In this study, the effect of EGCG conjugation on the emulsifying and antioxidant properties of SPHs was investigated to improve the functional characteristic of soy protein hydrolysates (SPHs) and develop a novel hydrolysates/peptides-EGCG conjugates. Enzymatic hydrolyzed SPHs (DH 5%, 8%, 10%) covalent with 1% EGCG to prepare conjugates at pH 9.0. The free amino group and tryptophan content of SPHs-EGCG conjugates significantly decreased, indicating the successful preparation of SPHs-EGCG conjugates. Additionally, 5% SPHs-EGCG conjugates showed the highest EGCG binding capacity. EGCG conjugation increased the particle sizes and charge of SPHs. Compared with non-covalent SPHs, the covalent modification of EGCG increased the emulsifying and antioxidant capacity, especially for 5% SPHs-EGCG, it exhibited much higher surface hydrophobicity, ESI (emulsifying stability index), EAI (emulsifying activity index), and antioxidant activity than others. This result revealed that SPHs and EGCG played a synergistic effect in improving the emulsifying and antioxidant capacity. Fluorescence spectroscopy analysis showed that the combination of EGCG conjugation significantly decreased the fluorescence intensity and caused maximum emission red-shift. The formation of a covalent bond between SPHs and EGCG was verified through Fourier transform infrared spectroscopy (FTIR), and the results also showed a significant increase in the α-helix and random coil contents of the conjugation, and a significant decrease in the β-sheet and β-turn contents. These results indicate that EGCG conjugation with SPHs induced the unfolding and stretching of protein flexibility. Overall, SPHs-EGCG conjugates can be applied as a promising emulsifier to fabricate emulsion systems and would be helpful in designing functional beverages containing polyphenols and peptides with enhanced functional nutritional properties.

Effects of Pineapple Peel Ethanolic Extract on the Physicochemical and Textural Properties of Surimi Prepared from Silver Carp (Hypophthalmichthys molitrix)

The effects of ethanolic pineapple peel extract (PPE) powder at various concentrations (0–1.50%, w/w) on the gelling properties of silver carp surimi were investigated. The pineapple peel extract produced with 0–100% ethanol, revealed that 100% ethanol had the highest bioactive properties. Surimi gels with added PPE powder demonstrated improved gel strength (504.13 ± 11.78 g.cm) and breaking force (511.64 ± 11.80 g) up to 1% PPE addition; however, as PPE concentration increased beyond 1%, the gel strength decreased. Similarly, with the addition of 1% PPE powder, more hydrophobic bonds and fewer sulfhydryl groups and free amino groups were seen. However, the gels with PPE powder added showed a slight reduction in the whiteness of the surimi gels. FTIR analysis indicated that the fortification with PPE powder brought about the secondary structure of myofibrillar proteins; peaks shifted to the β-sheet region (PPE gels) from the α-helix region (control). SEM analysis indicated that the gel with 1% PPE powder had a relatively organized, finer and denser gel architecture. Overall results suggested that the addition of PPE powder up to 1% to the surimi gels enhanced the gelling properties as well as the microstructure of the surimi.

Synergistic modification of pea protein structure using high-intensity ultrasound and pH-shifting technology to improve solubility and emulsification

The most important factors restricting research and application in the food industry are the poor solubility and emulsification of pea protein isolate (PPI). This study investigates the effect of high-intensity ultrasound (HIU, 0-600 W) and pH-shifting treatment, alone or combined, on the structure, solubility, and emulsification of PPI, as well as its potential mechanism. The results revealed that the PPI solubility significantly increases when treated with the combination, corresponding to a decrease in the protein particle size, especially at 500 W of HIU power (p < 0.05). Correspondingly, the emulsion prepared from it was less prone to phase separation during storage. According to the structural analysis, the structural changes caused by protein unfolding (i.e., the exposure of hydrophobic and polar sites and the loss of the α-helix) seemed to be the primary reasons for increased PPI solubility. In addition, confocal laser scanning microscopy indicated that the combination treatment accelerated the adsorption of PPI at the oil/water interface and strengthened the compactness of the interface film. Improved interfacial properties and intermolecular forces played a critical role in the resistance to droplet coalescence in PPI emulsion. In conclusion, ultrasound and pH-shifting treatments have a synergistic effect on improving the solubility and emulsification of PPI.

Fabrication of emulsions prepared by rice bran protein hydrolysate and ferulic acid covalent conjugate: Focus on ultrasonic emulsification

The aim of the paper was to investigate the effect of ultrasonic emulsification treatment on the fabrication mechanism and stability of the emulsion. The covalent conjugate made with rice bran protein hydrolysate (RBPH) and ferulic acid (FA) was used as the emulsifier. The effects of high intensity ultrasound (HIU) power with different level (0 W, 150 W, 300 W, 450 W and 600 W) on the stability of emulsion were evaluated. The results showed that ultrasonic emulsification can significantly improve the stability of the emulsions (p < 0.05). The emulsion gained better stability and emulsifying property at 300 W. It was able to fabricate emulsion with smaller particle size, more uniform distribution and higher interfacial protein content. It was confirmed by fluorescent microscopy and cryo-scanning electron microscopy (cryo-SEM) furtherly. And it was also proved that the emulsion treated by proper HIU treatment at 300 W had better storage stability. Excessive HIU treatment (450 W, 600 W) had negative effects on the stability of emulsion. The stability of emulsion (300 W) against different environmental stresses was further explored, which established a theoretical basis for the industrial application of emulsion in food industry.

Fabrication and emulsifying properties of non-covalent complexes between soy protein isolate fibrils and soy soluble polysaccharides

Non-covalent complexes (SPIF/SSPS) of soy protein isolate fibrils (SPIF) and soy soluble polysaccharides (SSPS) were fabricated and used to stabilize oil-in-water (O/W) emulsions. FT-IR spectroscopy and zeta potential results demonstrated that the interactions between SPIF and SSPS mainly include hydrogen bonding and electrostatic interactions. The presence of SSPS decreased the particle size and surface hydrophobicity of SPIF, resulting in a decrease and redshift of the fluorescence intensity. During the interfacial adsorption process, SPIF/SSPS complexes had lower diffusion and penetration rates compared with pure SPIF because of their hydrophilic region, but the molecular reorganization rate increased. Emulsions stabilized with the SPIF/SSPS complex at 5 : 5 (i.e., 1 : 1) ratio had both an excellent emulsifying activity index (EAI) of 26.17 m2 g-1 and an excellent emulsifying stability index (ESI) of 93.01%, as well as the smallest emulsion droplet particle size of 1.74 μm. Meanwhile, no flocculation was observed in this emulsion which is attributed to the sufficient steric stabilization provided by the hydrophilic SSPS. After three weeks of storage, there was no phase separation observed in the emulsions stabilized by SPIF/SSPS complexes in 5 : 4 and 5 : 5 ratios and the Turbiscan stability indices were 17.86 and 15.14, respectively, much lower than the other emulsion formulations tested.

The fabrication of novel zein and resveratrol covalent conjugates: Enhanced thermal stability, emulsifying and antioxidant properties

Novel zein and resveratrol conjugates were fabricated by alkaline and free radical grafting reactions. The grafting efficiency and total phenolic content of alkaline treated conjugates were slightly higher than those of free radical grafting. Compared to native and alkaline treated zein, the sulfhydryl contents of conjugates were obviously decreased, confirming that nucleophilic addition of resveratrol to sulfhydryl group of zein formed stable CS covalent bonds. The conformation changes of zein modified by resveratrol were revealed by fourier transform infrared spectroscopy and fluorescence spectroscopy. Moreover, covalent modification changed isoelectric point of zein from 6.5 to 5.4 (alkaline) or 5.6 (free radical grafting), and broadening the pH application range of zein. It was worth mentioning that the conjugates showed much higher thermal stability, antioxidant activity, and emulsify activity than those of native zein. This study provides an effective way for the design of novel delivery systems to encapsulate bioactive substances.

Enhanced In Vitro Functionality and Food Application of Lactobacillus acidophilus Encapsulated in a Whey Protein Isolate and (-)-Epigallocatechin-3-Gallate Conjugate

The present study investigated the potential of free radical grafting conjugation of whey protein isolate (WPI) and (-)-epigallocatechin-3-gallate (EGCG), followed by freeze-drying, for the safe delivery of probiotic Lactobacillus acidophilus (LA) upon digestion and in food systems. WPI-EGCG-LA microspheres presented higher encapsulation efficiency (97%) than native WPI-LA (70%) and maltodextrin (MD-LA 75%). The physicochemical characteristics of all microspheres, including moisture content, water activity, and hygroscopicity, were within the acceptable range for the stability of industrial powders. Scanning electron microscopy of WPI-EGCG-LA revealed a glass-like structure, with a smoother and less porous surface area than WPI-LA and MD-LA, as a result of the strong binding affinity between WPIs and EGCG. Particle sizes ranged from 438.4 to 453.3 μm. The structural stability of WPI-EGCG-LA was further confirmed by Fourier transform infrared spectra, which revealed some changes in the protein secondary structure. Thermogravimetric and differential scanning calorimetry analysis showed that WPI-EGCG conjugates had higher thermal stability than native WPIs and MD. Additionally, cells encapsulated in WPI-EGCG conjugates demonstrated higher in vitro survivability and surface hydrophobicity compared to free or WPI- and MD-encapsulated cells. Furthermore, WPI-EGCG-LA microspheres exerted enhanced in vitro antioxidant (78%) and antidiabetic (52%) activities. Finally, the WPI-EGCG conjugates remarkably improved probiotic viability (8.55 ± 0.1 log cfu/g) during 30 days of storage in an apple juice drink of pH (3.2 ± 0.01). Hence, the WPI-EGCG conjugate represents a propitious carrier to enhance probiotic functional properties upon digestion and during storage in low-pH food products.