Effects of ultrasonic and graft treatments on grafting degree, structure, functionality, and digestibility of rapeseed protein isolate-dextran conjugates

Protein from rapeseed for food applications: Extraction, sensory quality, functional and nutritional properties

The application of rapeseed protein in human foods is limited by residual antinutritive components and poor sensory quality. The effects of five extraction protocols on rapeseed protein yield, sensory, functional and nutritional properties were systematically evaluated in this study. In particular, the potential of weakly acidic salt (pH 6.5, 150 mmol·L-1 MgCl2) extraction as a mild method for recovering edible rapeseed protein was investigated compared with conventional alkali extraction. All salt-extracted proteins showed above 40 % extraction yield and low antinutritional factor contents. They also had ideal amino acid patterns and better in vitro gastroduodenal digestibility than alkaline-extracted proteins. Additionally, the lighter color and odor, as well as better solubility, emulsion activity, foaming property, and water/oil holding capacity were found in weakly acidic salt extraction-ultrafiltered proteins. These findings suggest that weakly acidic salt extraction-ultrafiltration could be used for obtaining edible rapeseed protein, while extraction yield should be improved for scale application.

Conjugation of gum Arabic and lentil protein hydrolysates through Maillard reaction: Antioxidant activity, volatile compounds, functional and sensory properties

Lentil protein hydrolysates (LPH) and lentil protein hydrolysates cross-linked (LPHC) were grafted with gum Arabic (GA) through a wet Maillard reaction at 100°C for 2 h and called MLPH and MLPHC. The samples were assessed for absorption, degree of grafting (DG), surface hydrophobicity, antioxidant activity, molecular weight (MW) profile, chemical alteration, volatile compounds, functional and sensory properties. Results showed that Maillard grafting led to increase in absorption and DG (maximum value: MLPHC), and led to the reduction of the surface hydrophobicity and antioxidant activity (minimum value: MLPHC). MW profiles indicated that MLPH and MLPHC formed new bands at MW >250 kDa. Regarding the Fourier transform infrared spectroscopy (FTIR), Maillard conjugation led to the occurrence of peaks at 1759 and 1765 cm-1, while the intensities of amide I bands at 1637 and 1659 cm-1 and amide II bands at 1498 and 1495 cm-1 were decreased. Hydrolysis, cross-linking, and especially Maillard grafting provided well-balanced content of volatile components. Indeed, the proportions of alcohols, ketones, aldehydes, and acids were changed, thereby, the inherent grassy and planty tastes were diminished while new umami taste was developed. Maillard grafting led to significant improvement of functional properties, while MLPH and MLPHC indicated the highest emulsifying activity at pH 10.0 (73.76 and 70.12 m2/g, respectively) and stability (369.64 and 288.22 min), foaming capacity (88.57% and 142.86%) and stability (60.57% and 72%). Sensory analysis has demonstrated that umami taste was highly developed in MLPH and MLPHC, which can be well considered as meat proteins and flavor enhancers such as monosodium glutamate (MSG).

Effects of the Roasting-Assisted Aqueous Ethanol Extraction of Peanut Oil on the Structure and Functional Properties of Dreg Proteins

The effects of the roasting-assisted aqueous ethanol extraction of peanut oil on the structure and functional properties of dreg proteins were investigated to interpret the high free oil yield and provide a basis for the full utilization of peanut protein resources. The roasting-assisted aqueous ethanol extraction of peanut oil obtained a free oil yield of 97.74% and a protein retention rate of 75.80% in the dreg. The water-holding capacity of dreg proteins increased significantly, and the oil-holding capacity and surface hydrophobicity decreased significantly, reducing the binding ability with oil and thus facilitating the release of oil. Although the relative crystallinity and denaturation enthalpy of the dreg proteins decreased slightly, the denaturation temperatures remained unchanged. Infrared and Raman spectra identified decreases in the C-H stretching vibration, Fermi resonance and α-helix, and increases in random coil, β-sheet and β-turn, showing a slight decrease in the overall ordering of proteins. After the roasting treatment, 62.57-135.33% of the protein functional properties were still preserved. Therefore, the roasting-assisted aqueous ethanol extraction of peanut oil is beneficial for fully utilizing the oil and protein resources in peanuts.

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.

Techno-functional attributes of oilseed proteins: influence of extraction and modification techniques

Plant-based protein isolates and concentrates are nowadays becoming popular due to their nutritional, functional as well as religious concerns. Among plant proteins, oilseeds, a vital source of valuable proteins, are continuously being explored for producing protein isolates/concentrates. This article delineates the overview of conventional as well as novel methods for the extraction of protein and their potential impact on its hydration, surface properties, and rheological characteristics. Moreover, proteins undergo several modifications using physical, chemical, and biological techniques to enhance their functionality by altering their microstructure and physical performance. The modified proteins hold a pronounced scope in novel food formulations. An overview of these protein modification approaches and their effects on the functional properties of proteins have also been presented in this review.

A Review of the Utilization of Canola Protein as an Emulsifier in the Development of Food Emulsions

Canola is the second-largest cultivated oilseed crop in the world and produces meal consisting of about 35-40% proteins. Despite this, less than 1% of the global plant-based protein market is taken up by canola protein. The reason behind such underutilization of canola protein and its rapeseed counterpart could be the harsh conditions of the industrial oil extraction process, the dark colour of the meal, the presence of various antinutrients, the variability in the protein composition based on the source, and the different properties of the two major protein components. Although academic research has shown immense potential for the use of canola protein and its rapeseed counterpart in emulsion development and stabilization, there is still a vast knowledge gap in efficiently utilizing canola proteins as an effective emulsifier in the development of various emulsion-based foods and beverages. In this context, this review paper summarizes the last 15 years of research on canola and rapeseed proteins as food emulsifiers. It discusses the protein extraction methods, modifications made to improve emulsification, emulsion composition, preparation protocols, and emulsion stability results. The need for further improvement in the scope of the research and reducing the knowledge gap is also highlighted, which could be useful for the food industry to rationally select canola proteins and optimize the processing parameters to obtain products with desirable attributes.

A novel strategy for improving the stability of myofibrillar protein emulsions at low ionic strength using high-intensity ultrasound combined with non-enzymatic glycation

Poor emulsification of myofibrillar proteins (MPs) limits the production of meat protein emulsion-type products, and it is related to the myosin self-assembles in low-salt settings. The effect of high-intensity ultrasound (HIU) pretreatment combined with non-enzymatic glycation on MP-stabilized emulsions in low-salt settings was investigated in this study, and the potential mechanism was revealed. The results indicated that, compared to using either HIU or glycation treatment alone, HIU pretreatment in combination with glycation significantly improves the physical stability of emulsions while increasing the distribution uniformity and reducing the droplet particle size from 18.05 μm to 2.54 μm (P < 0.05). Correspondingly, the emulsion prepared using this approach exhibited a relatively high absolute zeta potential (-23.58 mV) and a high interfacial protein content (38.78 %) (P < 0.05), promoting molecular rearrangement and forming a continuous and stable interfacial layer. HIU pretreatment combined with glycation could offer reinforced electrostatic repulsion and steric hindrance to depolymerize self-assembled filamentous polymers, thus enhancing the stability of droplets. Additionally, the thermal sensitivity of the glycated MPs pretreated by HIU was remarkably reduced, thus improving the thermal stability of the corresponding emulsions.

Alternative Processing Options for Improving the Proteins Functionality by Maillard Conjugation

Conjugation of the proteins with carbohydrates, occurring in the early stages of the Maillard reactions, received increased attention because of the high potential to ensure the improvement of the biological activity and functional properties of the proteins of different origins. The Maillard conjugates are conventionally formed through wet or dry heating, but the use of alternative technologies involving ultrasound, microwave, pulsed electric fields, high-pressure, or electrodynamic treatments appears to be efficient in accelerating the reaction steps and limiting the formation of toxic compounds. An overview of the mechanisms of these processing technologies, the main parameters influencing the Maillard conjugate formation, as well as their advantages and disadvantages, is provided in this paper. Different strategies employing these alternative technologies are reported in the literature: as pretreatment of the proteins, either alone or in admixture with the carbohydrates, followed by conventional heating, as a single alternative treatment step, or as a combination of heating and alternative processing. The desired functional properties of the proteins can be achieved by selecting the appropriate processing strategy and optimizing the reaction parameters. Moreover, alternative technologies can be exploited to obtain Maillard conjugates with remarkable biological activity in terms of antioxidant, antimicrobial, antihypertensive, anti-inflammatory, antimutagenic, or bifidogenic properties.

Intestine-targeted high internal phase Pickering emulsion formulated using silkworm pupa protein via ultrasonic treatment

High internal phase Pickering emulsions (HIPPEs) stabilized by food grade particles have received much attention as deliver vehicles for bioactives in recent years. In this study, ultrasonic treatment was conducted to regulate the size of silkworm pupa protein (SPP) particles, fabricating oil-in-water (O/W) HIPPEs with intestinal releasability. Briefly, the pretreated SPP and SPP-stabilized HIPPEs were characterized, and the targeting release was investigated using in vitro gastrointestinal simulations and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Results revealed ultrasonic treatment time was the key factor regulating emulsification performance and stability of HIPPEs. Optimized SPP particles were obtained based on their size and zeta potential of 152.67 nm and 26.77 mV, respectively. With ultrasonic treatment, the hydrophobic groups in the secondary structure of SPP were exposed, facilitating the formation of a stable oil-water interface for HIPPEs. Additionally, SPP-stabilized HIPPE showed high stable against the gastric digestion. The SPP with 70 kDa molecular weight, which was the major interfacial proteins of the HIPPE, can be hydrolyzed by intestinal digestive enzymes, enabling the intestine-targeted release of the emulsion. Overall, in the present study, a facile method was developed to stabilize HIPPEs using solo SPP with ultrasonic treatment to protect and deliver hydrophobic bioactive ingredients.

Effects of emerging food pretreatment and drying techniques on protein structures, functional and nutritional properties: An updated review

Protein is one of the most important components of food which significantly contributes to the structure, functionality, and sensory properties which may affect consumer acceptability of processed products. Conventional thermal processing affects protein structure and induce undesirable degradation of food quality. This review provides an overview of emerging pretreatment and drying technologies (plasma treatment, ultrasound treatment, electrohydrodynamic, radio frequency, microwave, and superheated steam drying) in food processing by assessing protein structural changes to enhance functional and nutritional properties. In addition, mechanisms and principles of these modern technologies are described while challenges and opportunities for the development of these techniques in the drying process are also critically analyzed. Plasma discharges can lead to oxidative reactions and cross-linking of proteins that can change the structure of proteins. Microwave heating contributes to the occurrence of isopeptide or disulfide bonds which promotes α-helix and β-turn formation. These emerging technologies can be adopted to improve protein surface by exposing more hydrophobic groups which restrict water interaction. It is expected that these innovative processing technologies should become a preferred choice in the food industry for better food quality. Moreover, there are some limitations for industrial scale application of these emerging technologies that need to be addressed.

Study on the hypolipidemic activity of rapeseed protein-derived peptides

Hyperlipidaemia, a common chronic disease, is the cause of cardiovascular diseases such as myocardial infarction and atherosclerosis. Generally, drugs for lowering blood lipids have disadvantages such as short or poor efficacy, high toxicity, and side effects. Rapeseed active peptides are excellent substitutes for lipid-lowering drugs because of their high biological safety, strong penetration, and easy absorption by the human body. This study separated and purified the rapeseed peptides using gel chromatography and mass spectrometry. Rapeseed peptides amino acid sequences were determined to obtain Glu-Phe-Leu-Glu-Leu-Leu (EFLELL) peptides with good hypolipidaemic activity and IC₅₀ values of 0.1973 ± 0.05 mM (sodium taurocholate), 0.375 ± 0.03 mM (sodium cholate), and 0.203 ± 0.06 mM (sodium glycine cholate). The EFLELL hypolipidaemic activity was evaluated, and its mechanism of action was investigated using cell lines. Rapeseed peptide treatment significantly decreased the total cholesterol (T-CHO), triglyceride (TG), and low-density lipoprotein cholesterol (LDL-C) levels, and the protein and gene expression levels of proprotein convertase subtilisin/kexin type 9 (PCSK9) and low-density lipoprotein cholesterol (LDLR) suggested the mechanism. Molecular docking revealed that the binding energy between rapeseed peptide and LDLR-PCSK9 molecules was -6.3 kcal/mol and -8.1 kcal/mol. In conclusion, the rapeseed peptide EFLELL exerts a favourable hypolipidaemic effect by modulating the LDLR-PCSK9 signalling pathway.

Conjugation of soy protein isolate with carboxymethyl cellulose through dielectric barrier discharge (DBD) plasma

The present study aimed to evaluate the physicochemical properties of dielectric barrier discharge (DBD) plasma grafted carboxymethyl cellulose (CMC) and soy protein isolate (SPI). Therefore, the mixture of SPI and CMC was treated at 16, 18 and 20 kV for 5, 10 and 15 min with DBD plasma. The results of FTIR, XRD, FESEM and SDS-PAGE confirmed the SPI-CMC conjugate formation after plasma treatment, and a glycation degree of about 21 % was obtained after 15 min treatment at 18 kV. Significantly higher levels of emulsifying activity and stability, as well as solubility, were obtained for the conjugates, as compared with the SPI-CMC mixture. Also, the smaller droplet sizes were observed in emulsions obtained from conjugate produced at 18 kV for 5 min, which had the most stability after 14 days of storage at 4 °C. Eventually, it was detected that DBD plasma could graft SPI and CMC in a short time.

Novel Colloidal Food Ingredients: Protein Complexes and Conjugates

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

Enhancing the foaming properties of brewer's spent grain protein by ultrasound treatment and glycation reaction

The denaturation state and relatively poor solubility of brewer's spent grain protein (BSGP) have limited its industrial application. Ultrasound treatment and glycation reaction were applied to improve the structural and foaming properties of BSGP. The results showed that all ultrasound, glycation, and ultrasound-assisted glycation treatments increased the solubility and surface hydrophobicity of BSGP while decreasing its zeta potential, surface tension and particle size. Meanwhile, all these treatments resulted in a more disordered and flexible conformation of BSGP, as observed by CD spectroscopy and SEM. After grafting, the result of FTIR spectroscopy confirmed the covalent binding of -OH between maltose and BSGP. Ultrasound-assisted glycation treatment further improved the free SH and S-S content, which might be due to -OH oxidation, indicating that ultrasound promoted the glycation reaction. Furthermore, all these treatments significantly increased the foaming capacity (FC) and foam stability (FS) of BSGP. Notably, BSGP treated with ultrasound showed the best foaming properties, increasing the FC from 82.22% to 165.10% and the FS from 10.60% to 131.20%, respectively. In particular, the foam collapse rate of BSGP treated with ultrasound-assisted glycation was lower than that of ultrasound or traditional wet-heating glycation treatment. The enhanced hydrogen bonding ability and hydrophobic interaction between protein molecules caused by ultrasound and glycation might be responsible for the improved foaming properties of BSGP. Thus, ultrasound and glycation reactions were efficient methods for producing BSGP-maltose conjugates with superior foaming properties.

Effects of ultrasonic-assisted pH shift treatment on physicochemical properties of electrospinning nanofibers made from rapeseed protein isolates

Electrospinning nanofibers (NFs) made from natural proteins have drawn increasing attention recently. Rapeseed meal is a by-product that rich in protein but not fully utilized due to poor properties. Therefore, modification of rapeseed protein isolates (RPI) is necessary to expand applications. In this study, pH shift alone or ultrasonic-assisted pH shift treatment was adopted, the solubility of RPI, along with the conductivity and viscosity of the electrospinning solution were detected. Moreover, the microstructure and functional characteristics of the electrospinning NFs, as well as the antibacterial activity of clove essential oil loaded-NFs were investigated. The tested parameters were remarkably improved after different treatments compared with the control, and synergistic effects were observed, especially under alkaline conditions. Hence, pH_12.5 + US showed the maximum value of solubility, conductivity, and viscosity, which was more than 7-fold, 3-fold, and almost 1-fold higher than the control respectively. Additionally, SEM and AFM images showed a finer and smoother surface of NFs after treatments, and the finest diameter of 216.7 nm was obtained after pH_12.5 + US treatment in comparison with 450.0 nm in control. FTIR spectroscopy of NFs demonstrated spatial structure changes of RPI, and improved thermal stability and mechanical strength of NFs were achieved after different treatments. Furthermore, an inhibition zone with a diameter of 22.8 mm was observed from the composite NFs. This study indicated the effectiveness of ultrasonic-assisted pH shift treatment on the physicochemical properties improvement and functional enhancement of NFs made from RPI, as well as the potential antibacterial application of the composite NFs in the future.

Enhancement of pea protein solubility and thermal stability for acidic beverage applications via endogenous Maillard-induced glycation and chromatography purification

A clean-label process to endogenously glycate and purify pea protein was investigated. The production of maltodextrin from pea starch with a specific dextrose equivalent (DE) was optimized. The produced maltodextrin (14.6 DE) was used to initiate a limited and controlled Maillard-induced glycation of pea protein. The partially glycated pea protein (PG-PP) was subjected to hydrophobic interaction chromatography to remove unreacted carbohydrate, followed by characterization of the purified product. The extent of Maillard-induced glycation was monitored by assessing changes in color, free amino groups, and protein/glycoprotein profiles. The purified PG-PP was evaluated for thermal denaturation, surface properties, protein secondary structure, protein solubility, thermal stability, and digestibility. Maillard-induced glycation was limited to initial stages and resulted in a moderate blockage of amine groups (∼30%). The purified PG-PP had a relatively low surface hydrophobicity, a markedly enhanced protein solubility (∼90%) at pH 3.4, and a nonimpacted protein in vitro digestibility (∼100%). This work provided the impetus needed for future scale-up and process optimization for the production of value-added pea protein ingredient intended for high protein beverage applications.

Structural Characteristics and Emulsifying Properties of Soy Protein Isolate Glycated with Galacto-Oligosaccharides under High-Pressure Homogenization

This study explored the Maillard reaction process during the glycation of soy protein isolate (SPI) with galacto-oligosaccharides (GOSs) under high-pressure homogenization (HPH) and its effects on the emulsifying properties of SPI. SPI-GOS glycation under moderate pressure (80 MPa) significantly inhibited the occurrence and extent of the Maillard reaction (p < 0.05), but homogenization pressures in the range of 80−140 MPa gradually promoted this reaction. HPH caused a decrease in the surface hydrophobicity of the glycated protein, an increase in the abundance of free sulfhydryl groups, unfolding of the protein molecular structure, and the formation of new covalent bonds (C=O, C=N). Additionally, the particle size of emulsions created with SPI-GOS conjugates was reduced under HPH, thus improving the emulsifying properties of SPI. A reduction in particle size (117 nm), enhanced zeta potential (−23 mV), and uniform droplet size were observed for the emulsion created with the SPI-GOS conjugate prepared at 120 MPa. The conformational changes in the glycated protein supported the improved emulsification function. All results were significantly different (p < 0.05). The study findings indicate that HPH provides a potential method for controlling glycation and improving the emulsifying properties of SPI.

Dextran Conjugation Improves the Structural and Functional Properties of Heat-Treated Protein Isolate from Cinnamomum camphora Seed Kernel

The Cinnamomum camphora seed kernel (CCSK), with high contents of medium-chain oil (~59%) and protein (~19%), is an excellent source for a plant-based food ingredient. To broaden the application of the protein isolate (PI) from CCSK in the food industry, the Maillard reaction products (MRPs) were prepared by PI and dextran (DX) under mild wet-heating conditions (60 °C, 5 h), and the structural and functional properties of the PI-DX conjugates were investigated. The covalent bond between PI and DX was confirmed by the degree of grafting and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Compared with the heated PI, the PI-DX conjugates had more ordered structure, with the decreased random coil content. The changes in tertiary structure of PI-DX conjugates were reflected by the results of intrinsic fluorescence and surface hydrophobicity. Moreover, PI-DX conjugates showed better solubility, emulsifying properties, thermal stability and antioxidant activities. These results provided a theoretical basis for the development of PI-based MRPs with desirable characteristics.

Continuous cyclic wet heating glycation to prepare myofibrillar protein-glucose conjugates: A study on the structures, solubility and emulsifying properties

Myofibrillar protein (MP) is often modified by various strategies to obtain better functional properties, which are crucial to the quality of meat products. This study prepared MP-glucose conjugates with high degrees of grafting (DG) by continuous cyclic wet heating glycation, and explored the changes in the structural and functional properties. The determination of DG, amino acid contents and Fourier transform infrared spectroscopy (FT-IR) confirmed the occurrence of glycation. The conjugates lost α-helix structures, and their intrinsic fluorescence intensity decreased while their surface hydrophobicity increased, which reflected the conformational unfolding and stretching behaviour of the molecules. Glycation resulted in a smaller particle size and lower ζ-potential, delaying molecular cross-linking during heating, thereby significantly reducing the apparent viscosity of the solutions and improving the solubility and emulsifying properties of MP. The results can provide new ideas and approaches for understanding glycation, and enrich the theoretical basis of the structure-function relationship of MP.

Ultrasound-assisted preparation of lactoferrin-EGCG conjugates and their application in forming and stabilizing algae oil emulsions

The aim of this study was to prepare lactoferrin-epigallocatechin-3-gallate (LF-EGCG) conjugates and to determine their ability to protect emulsified algal oil against aggregation and oxidation. LF-EGCG conjugates were formed using an ultrasound-assisted alkaline treatment. The ultrasonic treatment significantly improved the grafting efficiency of LF and EGCG and shortened the reaction time from 24 h to 40 min. Fourier transform infrared spectroscopy and circular dichroism spectroscopy analyses showed that the covalent/non-covalent complexes could be formed between LF and EGCG, with the CO and CN groups playing an important role. The formation of the conjugates reduced the α-helix content and increased the random coil content of the LF. Moreover, the antioxidant activity of LF was significantly enhanced after conjugation with EGCG. LF-EGCG conjugates as emulsifiers were better at inhibiting oil droplet aggregation and oxidation than LF alone. This study demonstrates that ultrasound-assisted formation of protein-polyphenol conjugates can enhance the functional properties of the proteins, thereby extending their application as functional ingredients in nutritionally fortified foods.

Effect of ultrasound on the glycosylation reaction of pea protein isolate-arabinose: Structure and emulsifying properties

This study investigated the effects of different ultrasonic power and ultrasonic time on the structure and emulsifying properties of pea protein isolate (PPI)-arabinose conjugates. An examination of the absorbance and color development of PPI-d-arabinose (Ara) conjugates found that compared with traditional heating, the degree of glycosylation of protein reached the maximum when the ultrasonic treatment power was 150 and the treatment time was 30 min. Structural analysis revealed that the content of disordered structures (β-turn and random coil) of the protein conjugates increased, the maximum emission wavelength of the fluorescence spectrum was red-shifted, and the UV second-order derivative values decreased. The protein structure unfolded, exposing more hydrophobic groups on the molecular surface. Ultrasonic treatment improved the emulsification of protein conjugates. The emulsifying activity index (EAI) increased to 19.7 and 19.3 m²/g, and the emulsifying stability index (ESI) also increased. The contact angle and zeta potential also demonstrate that ultrasonic power has a positive effect on emulsion stability. Based on examining the thermal stability of the emulsion, the ultrasonic treatment increased the thermal denaturation resistance of the protein. This result confirms that mild sonication can increase the degree of glycosylation reaction and improve the emulsification properties of protein-Ara conjugates, providing a theoretical basis for developing foods with excellent emulsification properties.

Enhancing thermal and emulsifying resilience of pomegranate fruit protein with gum Arabic conjugation

In this study, a controlled Maillard reaction was carried out to conjugate gum Arabic (GA) polymer to pomegranate protein isolate (PPI). The Maillard conjugates (MCs) were visualized by SEM and authenticity of the conjugates was assessed by NMR, FTIR, and XRD. To reveal the effect of the Maillard conjugation on the quality attributes of PPI, functional properties, thermal stability, and emulsifying behaviors of PPI and MCs were investigated. The oil binding capacity of conjugated protein (370.52%) was higher than that of protein alone (208.19%). While GA and PPI were completely degraded or decomposed at a temperature of 1000 °C, the MCs retained approximately half of the initial mass. MCs displayed higher emulsifying activity (42.71 m²/g) and emulsifying stability (90.17 (ESI30)), compared to PPI (32.61 m²/g) and (72.25 (ESI30)). Stability coefficient was significantly improved and reached from 0.64 R to 0.95 R with the usage of MCs in the emulsions. A lower centrifugal precipitation rate was determined in MCs emulsions (28.26%) compared to PPI emulsions (45.42%). Utilization of MCs instead of protein alone as a stabilizer in the oil-in-water emulsions was a logical approach for increasing their stability against environmental degradations including freeze-thaw cycle, pH, ionic, and temperature stress.

Modification of Ovalbumin by Maillard Reaction: Effect of Heating Temperature and Different Monosaccharides

Glycosylation is considered to be an effective way to improve the performance of protein emulsification. This study focused on the effects of the molecular structure and emulsifying properties of ovalbumin (OVA) by wet heating Maillard reaction with three types of monosaccharides (i.e., xylose, glucose, and galactose). Results showed that increasing reaction temperature from 55°C to 95°C could significantly improve the degree of grafting (DG), while glycosylated OVA conjugate with xylose at 95°C processed the highest DG of 28.46%. This reaction was further confirmed by the browning intensity determination. Analysis of Fourier transform infrared spectrophotometer, circular dichroism, and fluorescence spectra indicated that there were slight changes in the subunits and the conversion of α-helices to β-sheets, as well as the unfolded structures, thereby increasing the surface hydrophobicity and absolute zeta potential of obtained glycosylated OVA. Glycosylation endowed OVA with better emulsifying properties, especially the xylose glycosylated OVA was superior to that of glucose and galactose glycosylated OVA, which was mainly due to its shorter molecular chains with smaller steric hindrance for reaction. Furthermore, the enhancement of emulsifying properties may be attributed to the synergistic effect of stronger electrostatic repulsion of larger absolute zeta potential and the steric hindrance from thicker adsorbed layer, thereby inhibiting aggregation and flocculation of emulsion droplet.

Characterization of β-Glucan-Peanut Protein Isolate/Soy Protein Isolate Conjugates and Their Application on Low-Fat Sausage

Polysaccharide-protein conjugates can improve the functional properties and expand the application field. The emulsifying, thermal properties of WSG-PPI conjugates and WSG-SPI conjugates were improved, compared to WSG, PPI and SPI. The Maillard reaction was confirmed by Fourier transform infrared spectroscopy (FT-IR). Circular dichroism (CD) exhibited that the structure of the conjugates was more expanded. Cryo-SEM and AFM demonstrated that the WSG, WSG-PPI and WSG-SPI conjugates had a morphology of a chain. When the conjugates were added as fat substitutes to low-fat sausage, the cooking yield, hardness and chewiness increased. The objective of this research was to study the emulsifying property, thermal property and structural changes of β-glucan-peanut protein isolate (WSG-PPI) conjugates and β-glucan-soy protein isolate (WSG-SPI) conjugates prepared through wet-heated Maillard reaction, and their effect on the texture of low-fat sausage.

The modification of pomegranate polyphenol with ultrasound improves mechanical, antioxidant, and antibacterial properties of tuna skin collagen-chitosan film

To produce an edible film with high mechanical and physicochemical properties, Tuna skin collagen-chitosan (TSC-CTS) composite films were prepared by incorporating ultrasound (UT) and pomegranate polyphenols including gallic acid (GA), tannic acid (TA), and ellagic acid (EA), respectively. The tensile strength and the DPPH scavenging activity of the GA-UT-TSC-CTS film (ultrasound frequency of 28 ± 0.5 kHz, power of 100 W/L, sweep frequency cycle of 100 ms, duty ratio of 77% and time of 10 min; GA concentration of 1.0 g/L and reaction time of 10 min) were increased by 47.03% and 24.16 folds, respectively compared to the control (TSC-CTS film). Meanwhile, light transmittance and water vapor permeability of the GA-UT-TSC-CTS film were decreased by 29.26% and 15.70%, respectively. These positive modification results were attributed to the altered structure during the film formation process, which were verified by Fourier transform infrared spectroscopy (FTIR), circular dichroism (CD), X-ray diffraction (XRD), and thermogravimetry results. Moreover, the GA-UT-TSC-CTS film possessed moderate thermal stability and color indexes and improved antibacterial activity. The antibacterial effect of the film against Bacillus subtilis was the highest, followed by Escherichia coli, Listeria monocytogenes, and Staphylococcus aureus. Overall, the combination modification of gallic acid and ultrasound was an efficient modification method to improve the mechanical, antioxidant, and antibacterial properties of edible TSC-CTS films.

Molecular structure and functional properties of glycinin conjugated to κ-carrageenan and guar gum: A comparative study

Molecular structure and functional properties of glycinin conjugated to κ-carrageenan and guar gum using a dry-heating method were comparatively analyzed. Glycosylation was confirmed by analyzing the degree of grafting, protein subunit composition, infrared absorption profile, and changes in contents of protein secondary structures. K-carrageenan was proven to possess a greater susceptibility to be grafted to glycinin than guar gum due to its relatively low molecular weight and negatively charged characteristics. The improvement of solubility by glycosylation with guar gum near the isoelectric point of glycinin was better than that by glycosylation with κ-carrageenan. Glycinin glycosylated with both polysaccharides exhibited enhanced emulsifying activity and stability. The enhanced apparent viscosity, elastic modulus, and viscous modulus also demonstrated that glycosylation promoted the appearance of stable elastic network structure. In summary, glycosylation with these two polysaccharides conferred glycinin superior emulsifying and rheological properties, and κ-carrageenan exhibited a better performance compared to guar gum.

Pea protein isolate-inulin conjugates prepared by pH-shift treatment and ultrasonic-enhanced glycosylation: Structural and functional properties

The application of pea proteins in the food industry is often limited by their poor functional properties, such as solubility, emulsification, and gelation. To address this problem, a novel method of constructing pea protein-inulin conjugates with improved functional attributes was developed, which consisted of combining a high-intensity ultrasonic treatment with a pH-shift wet heating method. This combined method promoted the Maillard reaction, leading to a grafting degree that was 2.3-times higher than that of the traditional wet heating method. SDS-PAGE confirmed the formation of pea protein-inulin conjugates. The pea protein-inulin conjugates had higher solubility than pea proteins alone, especially around the isoelectric point of the protein. Furthermore, the thermal stability, antioxidant activity, foaming and emulsifying properties of the conjugates were better than those of the protein. This study shows that the combined ultrasound/pH-shift wet heating method is highly effective at improving the functional properties of pea proteins.

Modification of functional properties of perilla protein isolate by high-intensity ultrasonic treatment and the stability of o/w emulsion

This study investigated the effects of ultrasonic treatment on the structural characteristics and functional properties of perilla protein isolate (PPI). Besides, the performance of the emulsions stabilized by ultrasonic-treated PPI was analyzed, aiming at exploring the potential mechanism of ultrasonic technology to improve emulsion stability. Results showed that ultrasonic treatment reduced the particle size, induced the exposure of hydrophobic groups and changes in the secondary structure and tertiary conformation of PPI. However, the molecular weight and the crystalline regions were remained unchanged. Apart from this, ultrasonic treatment improved the solubility, water/oil holding capacity, foaming and emulsifying capacity of PPI. Furthermore, the emulsions prepared by ultrasonic-treated PPI possessed the highest stability, which might be due to the smaller droplets size and reduced droplets attraction by higher proportion of interfacial adsorbed protein. This findings will provide a new insight into the application of ultrasonic to improve the stability of PPI-stabilized emulsions.

Preparation of tuna skin collagen-chitosan composite film improved by sweep frequency pulsed ultrasound technology

To produce a natural food packaging film from tuna skin collagen (TSC) and chitosan (CTS) and improve its mechanical and physicochemical properties, the sweep frequency pulsed ultrasound (SFPU) was introduced as a new technology and compared with the conventional method. The optimum preparation conditions of the SFPU-TSC-CTS film were sweep frequency of 28 ± 0.5 kHz, power density of 100 W/L, sweep frequency cycle of 100 ms, pulse duty ratio of 77%, and ultrasonic time of 10 min. Significant increases in the tensile strength (27.14%) and elongation at break (16.54%) and a significant decrease in the water vapor permeability (12.15%) were observed by sonication. Thus, a moderate SFPU treatment can significantly improve the moisture resistance and mechanical properties of the film. These enhancements were achieved by a more ordered and compact structure, a good crystallinity and a higher thermostability of SFPU-TSC-CTS film, which were verified by the Fourier transform infrared spectroscopy (FTIR), circular dichroism (CD), scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermal stability indexes. Moreover, SFPU-TSC-CTS film also presented good antioxidant and antibacterial activities. Therefore, SFPU was an effective auxiliary technology for improving the quality of food packaging film and can be deeply explored.

Molecular structure modification of ovalbumin through controlled glycosylation with dextran for its emulsibility improvement

Ovalbumin (OVA) is a high nutritious protein, but the poor emulsibility limited its application. The present study glycosylated OVA with dextran (Dex) by controlled wetheating (60-90 °C for 3 h). Temperature was an inductive factor for glycosylation degree (DG and browning intensity), and higher temperature could accelerate the reaction. Variations in molecular structure of OVA were analyzed by SDS-PAGE, FTIR, fluorescence spectroscopy and UV spectroscopy, which verified successes in the generation of glycoconjugate with more flexible structure. Emulsifying activity index (EAI) and emulsion stability index (ESI) for the emulsion of OVA-Dex glycoconjugates were significantly enhanced with the increasing of glycosylation temperature. Moreover, confocal laser scanning results revealed that the emulsion exhibited smaller size and more uniform distribution, and slower transmission profiles were checked by LUMiSizer centrifugal analysis as well, confirming the emulsibility improvement of OVA. Thus, controlled glycosylation reaction is an available method to improve the emulsifying properties of OVA.

Ultrasound-assisted alkaline proteinase extraction enhances the yield of pecan protein and modifies its functional properties

To enhance the extraction yield of pecan protein and modify its functional properties, this study investigated whether both ultrasound and enzyme have a synergistic impact on the extraction of pecan (Carya illinoinensis (Wangenh.) K. Koch) protein. The highest protein extraction rate (25.51%) was obtained under the conditions of 1415.43 W.cm-2, 15 min, pH 10.0, 50 °C, and 1% (w/w) alkaline proteinase. Owing to its high shear, mechanical energy and cavitation, the ultrasound process increased the solubility of the substrate making it readily accessible to the enzyme, thereby accelerating the chemical reaction and improving the yield of the protein. The optimized ultrasound-assisted enzymatic method (400 W, 20 kHz, 5 s/3s) effectively changed the secondary and tertiary structure of the pecan protein. The results of surface hydrophobicity, intrinsic fluorescence spectra, sulfhydryl content and scanning electron microscopy all indicated the unfolding of protein and exposure of hydrophobic groups and sulfhydryl groups. Moreover, the protein obtained by this method showed higher solubility (70.77%), higher emulsifying activity (120.56 m2/g), smaller particle size (326.7 nm), and better dispersion (0.305) than single ultrasound and non-ultrasound methods (p < 0.05). To conclude, ultrasound-assisted enzymatic method could be an appropriate technique to improve the yield and quality of the pecan protein. The study also provides a theoretical basis for the application of pecan protein in food processing.

Modifying the plant proteins techno-functionalities by novel physical processing technologies: a review

Plant proteins have recently gained market demand and momentum due to their environmentally friendly origins and health advantages over their animal-derived counterparts. However, their lower techno-functionalities, digestibility, bioactivities, and anti-nutritional compounds have limited their application in foods. Increased demand for physically modified proteins with better techno-functionalities resulted in the application of different thermal and non-thermal treatments to modify plant proteins. Novel physical processing technologies (NPPT) considered 'emerging high-potential treatments for tomorrow' are required to alter protein functionality, enhance bioactive peptide formations, reduce anti-nutritional, reduce loss of nutrients, prevention of damage to heat liable proteins and clean label. NPPT can be promising substitutes for the lower energy-efficient and aggressive thermal treatments in plant protein modification. These facts captivated the interest of the scientific community in designing novel functional food systems. However, these improvements are not verifiable for all the plant proteins and depend immensely on the protein type and concentration, other environmental parameters (pH, ionic strength, temperature, and co-solutes), and NPPT conditions. This review addresses the most promising approaches of NPPT for the modification of techno-functionalities of plant proteins. New insights elaborating the effect of NPPTs on proteins' structural and functional behavior in relation to other food components are discussed. The combined application of NPPTs in the field of plant-based bioactive functionalities is also explored.

Effect of Physical and Enzymatic Pre-Treatment on the Nutritional and Functional Properties of Fermented Beverages Enriched with Cricket Proteins

The aim of this study was to evaluate the effects of γ-irradiation (IR), ultrasound (US), and combined treatments of ultrasound followed by γ-irradiation (US-IR), ultrasound followed by enzymatic hydrolysis with and without centrifugation (US-E and US-EWC, respectively), and ultrasound followed by γ-irradiation and enzymatic hydrolysis (US-IRE), on the digestibility and the nutritional value of fermented beverages containing probiotics. Results showed that US (20 min), IR (3 kGy) and US-IR (tUS = 20 min, dose = 3 kGy) treatments raised protein solubility from 11.5 to 21.5, 24.3 and 29.9%, respectively. According to our results, these treatments were accompanied by the increased amount of total sulfhydryl groups, surface hydrophobicity and changes to the secondary structure of the proteins measured by Fourier-transform infrared spectroscopy (FTIR). Fermented probiotic beverages, non-enriched (C) and enriched with untreated (Cr) or treated cricket protein with combined treatments were also evaluated for their in vitro protein digestibility. Results showed that the soluble fraction of US-IRE fermented beverage had the highest digestibility (94%) as compared to the whole fermented tested beverages. The peptides profile demonstrated that US-IRE had a low proportion of high molecular weight (MW) peptides (0.7%) and the highest proportion of low MW peptides by over 80% as compared to the other treatments.

Preparation of Heat-Sensitivity Proteins from Walnut Meal by Sweep Frequency Ultrasound-Assisted Alkali Extraction

Sweep frequency ultrasound- (SFU-) assisted alkali extraction was conducted to increase the yield and content of heat-sensitive protein of walnut meal under a relatively mild condition. The physicochemical and structural characteristics of the proteins obtained by SFU-assisted alkali extraction and the conventional alkali extraction were compared. It was found that the optimal parameters for the SFU-assisted extraction were the solid-liquid ratio of 1 : 12, pH value of 9, initial temperature of 25°C, ultrasonic frequency of 28 kHz, sweep frequency amplitude of 1.5 kHz, sweep frequency cycle of 100 ms, duty ratio of 77%, and ultrasonic time of 90 min. Under this condition, a vast improvement in the walnut protein yield (34.9%) and the walnut protein content (9.8%) was observed. Such improvement was due to the structural changes of the sonicated protein; e.g., SFU decreased the intermolecular/intramolecular hydrogen bond force of proteins and, therefore, caused more order secondary structures and more loosen microstructures. This helped to improve the thermoplastic and solubility of the heat-sensitivity protein. Thus, SFU treatment could be an effective auxiliary technology in the alkali extraction of heat-sensitivity walnut protein. It might also be a promising technology for the extraction of heat-sensitivity protein from other agricultural by-products.

Astaxanthin-loaded emulsion gels stabilized by Maillard reaction products of whey protein and flaxseed gum: Physicochemical characterization and in vitro digestibility

In order to evaluate the effect of ultrasound and Maillard reaction on the physicochemical properties and gastrointestinal fate of astaxanthin-loaded emulsion gels, the Maillard reaction products (MRPs) of whey protein and flaxseed gum (FG) were prepared by traditional or ultrasonic assisted wet-heating. The MRPs obtained by ultrasonic assisted wet-heating had higher grafting degree and more expanded structures evidenced by the browning intensity, fluorescence intensity and circular dichroism (CD) analysis, thus enhancing its functional properties like solubility and emulsifying capacity. The MRPs improved the water holding capacity, encapsulation efficiency, stability of emulsion gels, in which astaxanthin was wrapped as a model bioactive compound. During the simulated digestion process, the bioaccessibility of loaded astaxanthin reached 72.08% for the emulsion gels stabilized by MRPs. The results highlighted the potential of MRPs in improving functionality of protein and as a delivery carrier of bioactive compounds in food industry.