Ultrasonic-assisted pH shift-induced interfacial remodeling for enhancing the emulsifying and foaming properties of perilla protein isolate

Insights into digestibility, biological activity, and peptide profiling of flaxseed protein isolates treated by ultrasound coupled with alkali cycling

This study aims to investigate the effects of ultrasound coupled with alkali cycling on the structural properties, digestion characteristics, biological activity, and peptide profiling of flaxseed protein isolates (FPI). The digestibility of FPI obtained by ultrasound coupled with pH 10/12 cycling (UFPI-10/12) (74.56 % and 79.12 %) was significantly higher than that of native FPI (64.40 %), and UFPI-10 showed higher hydrolysis degree (35.76 %) than FPI (30.65 %) after intestinal digestion. The combined treatment induced transition from α-helix to β-sheet with an orderly structure. Large FPI aggregates broke down into small-sized FPI particles, which induced the increase of specific surface area of particles. This might expose more cutting sites and contact area with enzymes. Furthermore, UFPI-10 showed high antioxidant activity (29.18 %) and lipid-lowering activity (70.52 %). Peptide profiling revealed that UFPI-10 exhibited a higher proportion of 300-600 Da peptides and significantly higher abundance of antioxidant peptides than native FPI, which might promote its antioxidant activity. Those results suggest that the combined treatment is a promising modification method to improve the digestion characteristics and biological activity of FPI. This work provides new ideas for widespread use of FPI as an active stabilizer in food systems.

Rapid quantitative analysis of soybean protein isolates secondary structure by two-dimensional correlation infrared spectroscopy through pH perturbation

The infrared spectroscopy (IR) signal of protein is prone to being covered by impurity signals, and the accuracy of the secondary structure content calculated using spectral data is poor. To tackle this challenge, a rapid high-precision quantitative model for protein secondary structure was proposed. Firstly, a two-dimensional correlation calculation was performed based on 60 groups of soybean protein isolates (SPI) infrared spectroscopy data, resulting in a two-dimensional correlation infrared spectroscopy (2DCOS-IR). Subsequently, the optimal characteristic bands of the four secondary structures were extracted from the 2DCOS-IR. Ultimately, partial least squares (PLS), long short-term memory (LSTM), and bidirectional long short-term memory (BILSTM) algorithms were used to model the extracted characteristic bands and predict the content of SPI secondary structure. The findings suggested that BILSTM combined with 2DCOS-IR model (2DCOS-BILSTM) exhibited superior predictive performance. The prediction sets for α-helix, β-sheet, β-turn, and random coil were designated as 0.9257, 0.9077, 0.9476, and 0.8443, respectively, and their corresponding RMSEP values were 0.26, 0.48, 0.20, and 0.15. This strategy enhances the precision of IR and facilitates the rapid identification of secondary structure components within SPI, which is vital for the advancement of protein industrial production.

A comprehensive review on the recent trends in extractions, pretreatments and modifications of plant-based proteins

Plant-based proteins offer sustainable and nutritious alternatives to animal proteins with their techno-functional attributes influencing product quality and designer food development. Due to the inherent complexities of plant proteins, proper extraction and modifications are vital for their effective utilization. This review highlights the emerging sources of plant-based proteins, and the recent statistics of the techniques employed for pretreatment, extraction, and modifications. The pretreatment, extraction and modification approach to modify plant proteins have been classified, addressed, and the recent applications of such methodologies are duly indicated. Furthermore, this study furnishes novel perspectives regarding the potential impacts of emerging technologies on the intricate dynamics of plant proteins. A thorough review of 100 articles (2018-2024) shows the researchers' keen interest in investigating novel plant proteins and how they can be used; seeds being the main source for protein extraction, followed by legumes. Use of by-products as a protein source is increasing rapidly, which is noteworthy. Protein studies still lack knowledge on protein fraction, antinutrients, and pretreatments. The use of physical methods and their combination with other techniques are increasing for effective and environmentally friendly extraction and modification of plant proteins. Several studies explore the effect of protein changes on their function and nutrition, especially with a goal of replacing ingredients with plant proteins that have improved or enhanced qualities. However, the next step is to investigate the sophisticated modification methods for deeper insights into food safety and toxicity.

Ultrasound-assisted modification of soybean protein isolate with L-histidine: Relationship between structure and function

Herein, the effects of ultrasound-assisted L-histidine (L-His) on the physicochemical properties and conformation of soybean protein isolate (SPI) were investigated. Particle size, zeta potential, turbidity, and solubility were used to evaluate protein aggregation, and the relationship between structural and functional changes of the proteins was characterized using spectral analysis, surface hydrophobicity, emulsification, and antioxidant properties. After ultrasound-assisted L-His treatment, SPI exhibited a smaller particle size, higher solubility, and more homogeneous micromorphology owing to the decrease in alpha-helix content and subsequent increases in zeta potential and active sulfhydryl content. In addition, spectral analysis showed that L-His and SPI could form a complex, which changed the microenvironment of the amino acid residues in SPI, thus improving its emulsification and antioxidant properties. At the concentration of L-His was 0.3 % w/w, the nanocomplex had a smaller particle size (140.03 nm), higher ζ-potential (-23.63 mV), and higher emulsification stability (22.48 min).

Molecular regulation of rapeseed protein for improving its techno-functional properties

To improve the techno-functional properties of rapeseed protein (RP), this work tried to regulate the molecular structure of RP via inducing the co-assembly of RP with zein and whey protein (WP). The results showed that WP and zein mainly regulate the folding process of RP through hydrophobic and disulfide bonds, thereby altering the structural conformation and forming stable complex RP (CRP). WP addition not only increased the number of surface charges and hydrophilicity of proteins, but also decreased their sizes, improved the water solubility, as well as the availability of active groups. These changes significantly increased the foaming capacity (from 60 % to 147 %) and in vitro gastric digestion rate (from 10 % to 60 %) of CRP. Besides, WP also contributed to the formation of gels and the regulation of their textural profiles. Comparatively, zein improved the hydrophobicity of CRP and balanced degree of intermolecular forces, which effectively increased the emulsifying activity index of CRP from 22 m2/g to 90 m2/g. Zein decreased the hardness, springiness and water-holding capacity of gel, but increased its gumminess and chewiness. Overall, both WP and zein effectively changed the structural conformation of RP, and improved its techno-functional properties, which provides an effective strategy to modify protein.

Effect of oil extraction methods on walnut oil quality characteristics and the functional properties of walnut protein isolate

Walnut oils were obtained by supercritical carbon dioxide extraction (SCB), cold-pressing (CP), hexane extraction (HE), and subcritical butane extraction (SBE), and walnut protein isolates (WPI) from the walnut cakes were performed. The results indicate that SCB has the highest oil yield for walnut oil, which was 62.72%, and the total content of trace nutrients (total tocopherols, total phytosterols, and total phenolic compounds) in SCB-walnut oil was also the highest at 2186.75 mg/kg, approximately 1.05 times higher than CP-walnut oil and 1.21 times higher than SBE-walnut oil. Meanwhile, the treatment of WPI with SCB results in a decrease in β-Sheet and α-Helix structures and an increase in β-Turn and Random coil structures. Thereby increasing its oil-holding capacity (OHC) and solubility by approximately 1.16 times and 1.27 times compared to CP, respectively. Interestingly, SCB as a green oil production technology, also has good prospects for retaining WPI functionality characteristics.

Structure and functionality of whey protein, pea protein, and mixed whey and pea proteins treated by pH shift or high-intensity ultrasound

Three modifications (pH shift, ultrasound, combined pH shift and ultrasound) induced alterations in pure whey protein isolate (WPI), pea protein isolate (PPI), and mixed whey and pea protein (WPI-PPI) were investigated. The processing effect was related to the protein type and technique used. Solubility of WPI remained unchanged by various treatments. Particle size was enlarged by pH shift while reduced by ultrasound and combined approach. All methods exposed more surface hydrophobic groups on WPI, while pH shift and joint processing was detrimental to its emulsifying activity. The PPI and mixture exhibited similar responses toward the modifications. Solubility of PPI and the blend enhanced in the sequence of pH shift and ultrasound > ultrasound > pH shift. Individual approach expanded while co-handling diminished the particle diameter. Treatments also caused more disclosure of hydrophobic regions in PPI and WPI-PPI and emulsifying activity was ameliorated in the order of pH shift and ultrasound > ultrasound > pH shift.

Regulation of interfacial mechanics of soy protein via co-extraction with flaxseed protein for efficient fabrication of foams and emulsions

Enrichment of plant proteins with functionality is of great importance for expanding their application in food formulations. This study proposed an innovation to co-enrich soy protein and flaxseed protein to act as efficient interfacial stabilizers for generating foams and emulsions. The structure, interfacial properties, and functionalities of the soy protein-flaxseed protein natural nanoparticles (SFNPs) obtained by alkali extraction-isoelectric precipitation (AE) and salt extraction-dialysis (SE) methods were investigated. Overall, the foamability of AE-SFNPs (194.67 %) was 1.45-fold that of SE-SFNPs, due to their more flexible structure, smaller particle size, and suitable surface wettability, promoting diffusion and adsorption at the air-water interface. AE-SFNPs showed higher emulsion stability (140.89 min), probably because the adsorbed AE-SFNPs with smaller size displayed soft particle-like properties and stronger interfacial flexibility, and therefore could densely and evenly arrange at the interface, facilitating the formation of a stiff and solid-like interfacial layer, beneficial for more stable emulsion formation. The findings may innovatively expand the applications of SFNPs as food ingredients.

Aggregate Size Modulates the Oil/Water Interfacial Behavior of Myofibrillar Proteins: Toward the Thicker Interface Film and Disulfide Bond

Myofibrillar protein (MP) aggregate models have been established to elucidate the correlation between their aggregate sizes and interfacial properties. The interfacial layer thickness was measured by the polystyrene latex method and quartz crystal microbalance with dissipation measurement. Interfacial conformations were then characterized in situ (front-surface fluorescence spectroscopy) and ex situ (reactive sulfhydryl group and secondary structure measurement following MP displacement). The viscoelasticity of the interfacial film and its resistance to surfactant-induced competitive displacement were reflected by the dilatational rheology and dynamic interfacial tension with the bulk phase exchange. Finally, we compared the findings of competitive displacement before/after adding a sulfhydryl-blocking agent, N-ethylmaleimide, to highlight the role of S-S linkage on interfacial film formation and stability. We substantiated that the aggregate size of the MP governed their interfacial properties. Small-sized aggregates exhibited more ordered secondary structures on the oil-water interface, which was conducive to the adsorption ratio of the protein and the adsorption dynamics. Although larger aggregates lowered the diffusion rate during interfacial film formation, they allowed the thicker and more viscoelastic interfacial film to be constructed afterward through more disulfide bond formation, resulting in greater resistance to surfactant-induced competitive displacement.

Modification of whey protein isolate by ultrasound-assisted pH shift for complexation with carboxymethylcellulose: Structure and interfacial properties

The application of whey protein isolate (WPI) is limited because of its compact spherical structure. In this study, ultrasound-assisted pH shift was employed to modify WPI for complexation with carboxymethylcellulose (CMC). The foaming and emulsifying properties of WPI/CMC complexes were investigated. The results demonstrate that the pretreatment of ultrasound-assisted pH 12 shift increased the content of free sulfhydryl groups from 16.5 μmol/g to 34.7 μmol/g and enhanced protein hydrophobicity from 311.4 to 370.6 (p < 0.05). Compared to the complexes formed by untreated WPI and CMC, the complexes pretreated with ultrasound-assisted pH 12 shift had a smaller size of 293.4 nm and a more uniform distribution. Furthermore, WPI/CMC complexes pretreated by ultrasound-assisted pH 12 shift exhibited higher emulsifying activity and emulsion stability index, which were increased by 8.9 % and 42.6 % respectively, in comparison with the control group (p < 0.05). A positive correlation was found between the surface hydrophobicity of WPI and emulsifying activity of WPI/CMC complexes. Ultrasound-assisted pH 2 shift improved the foaming capacity of complexes by 28.3 % over the control (p < 0.05). All the results indicate that the interfacial properties of WPI/CMC complexes can be improved significantly by the combination of pH shift and ultrasound.

Study on the interaction and functional properties of Dolichos lablab L. protein-tea polyphenols complexes

Tea polyphenols (TP) and plant proteins are significant materials in the food industry, the interactions between them are beneficial for their stability, functional properties, and biological activity. In this study, the mechanism and interaction between Dolichos lablab L. protein (DLP) obtained from nine treatments and three tea polyphenol monomers (EGCG, ECG, and EGC) were investigated. The results showed that the fluorescence of DLP was noticeably quenched and exhibited static quenching after the addition of polyphenols. DLP exhibited 1-2 binding sites for EGCG and ECG, but weakly binding to EGC (<1). The binding sites of DLP-TP were found to be in close proximity to the tyrosine residues, primarily interacting through hydrophobic interactions, van der Waals forces, and hydrogen bonds. The antioxidant capacity of DLP-TP compound was significantly improved after digestion. ECG showed a strong resistance to intestinal digestion. Compared with ECG (653.456 μg/mL), the content of free tea polyphenols of 20/40 kHz-ECG after digestion was 732.42 μg/mL. DLP-TP complexes significantly improved the storage stability, thermal stability, and bioaccessibility of tea polyphenols. The interaction between TP and DLP, as a protein-polyphenol complex, has great potential for application in preparing emulsion delivery systems due to their antioxidant activity and improved stability.

Composition, functional properties, health benefits and applications of oilseed proteins: A systematic review

Common oilseeds, such as soybean, peanut, rapeseed, sunflower seed, sesame seed and chia seed, are key sources of edible vegetable oils. Their defatted meals are excellent natural sources of plant proteins that can meet consumers' demand for health and sustainable substitutes for animal proteins. Oilseed proteins and their derived peptides are also associated with many health benefits, including weight loss and reduced risks of diabetes, hypertension, metabolic syndrome and cardiovascular events. This review summarizes the current status of knowledge on the protein and amino acid composition of common oilseeds as well as the functional properties, nutrition, health benefits and food applications of oilseed protein. Currently, oilseeds are widely applied in the food industry regarding for their health benefits and good functional properties. However, most oilseed proteins are incomplete proteins and their functional properties are not promising compared to animal proteins. They are also limited in the food industry due to their off-flavor, allergenic and antinutritional factors. These properties can be improved by protein modification. Therefore, in order to make better use of oilseed proteins, methods for improving their nutrition value, bioactive activity, functional and sensory characteristics, as well as the strategies for reducing their allergenicity were also discussed in this paper. Finally, examples for the application of oilseed proteins in the food industry are presented. Limitations and future perspectives for developing oilseed proteins as food ingredients are also pointed out. This review aims to foster thinking and generate novel ideas for future research. It will also provide novel ideas and broad prospects for the application of oilseeds in the food industry.

Mechanism of ultrasonic combined with different fields on protein complex system and its effect on its functional characteristics and application: A review

In recent years, new food processing technologies (such as ultrasound, high-pressure homogenization, and pulsed electric fields) have gradually appeared in the public 's field of vision. These technologies have made outstanding contributions to changing the structure and function of protein complexes. As a relatively mature physical field, ultrasound has been widely used in food-related fields. However, with the gradual deepening of related research, it is found that the combination of different fields often makes some characteristics of the product better than the product under the action of a single field, which will not only lead to a broader application prospect of the product, but also make the product a better solution in some special fields. There are usually synergistic and antagonistic effects when multiple fields are combined, and these effects will also gradually enlarge the interaction between different components of the protein complex system. In this paper, while explaining the mechanism of ultrasonic combined with other fields affecting the steric hindrance and shielding site of protein complex system, we will further explain the effect of this effect on the function and application of protein complex system.

Ultrasound-assisted pH-shifting to construct a stable aqueous solution of paprika oleoresin using egg yolk low-density lipoprotein as a natural liposome-like nano-emulsifier

In this study, a stable aqueous solution of paprika oleoresin (PO, the natural colorant extracted from the fruit peel of Capsicum annuum L) was constructed. The solubility of PO in an alkline aqueous solution (pH 10.95-11.10) increased rapidly. However, the aqueous solution of PO (pH 12.00) was unstable, obvious stratification was observed, and the color retention rate was only 52.99% after 28 days of storage. Chicken egg yolk low-density lipoprotein (LDL) was added combined with ultrasonic treatment to improve the stability of LDL-PO solution. The method could decrease the turbidity by 17.5 %, reduce the average particle size of the LDL-PO solution (13.9%), and enhance the interaction and combination of LDL and PO. The prepared PO aqueous solution was used in yogurt, egg white gel, fish balls and soymilk, and it could significantly improve the color of products and provided potential health benefits.

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.

Co-Extraction of Flaxseed Protein and Polysaccharide with a High Emulsifying and Foaming Property: Enrichment through the Sequence Extraction Approach

A new focus with respect to the extraction of plant protein is that ingredient enrichment should target functionality instead of pursuing purity. Herein, the sequence aqueous extraction method was used to co-enrich five protein-polysaccharide natural fractions from flaxseed meal, and their composition, structure, and functional properties were investigated. The total recovery rate of flaxseed protein obtained by the sequence extraction approach was more than 80%, which was far higher than the existing reports. The defatted flaxseed meal was soaked by deionized water to obtain fraction 1 (supernatant), and the residue was further treated to get fraction 2 (supernatant) and 3 (precipitate) through weak alkali solubilization. Part of the fraction 2 was taken out, followed by adjusting its pH to 4.2. After centrifuging, the albumin-rich supernatant and precipitate with protein content of 73.05% were gained and labeled as fraction 4 and fraction 5. The solubility of fraction 2 and 4 exceeded 90%, and the foaming ability and stability of fraction 5 were 12.76 times and 9.89 times higher than commercial flaxseed protein, respectively. The emulsifying properties of fractions 1, 2, and 5 were all greater than that of commercial sodium caseinate, implying that these fractions could be utilized as high-efficiency emulsifiers. Cryo-SEM results showed that polysaccharides in fractions were beneficial to the formation of network structure and induced the formation of tighter and smoother interfacial layers, which could prevent emulsion flocculation, disproportionation, and coalescence. This study provides a reference to promote the high-value utilization of flaxseed meals.

The Impact of High-Intensity Ultrasound-Assisted Extraction on the Structural and Functional Properties of Hempseed Protein Isolate (HPI)

Hempseed protein has become a promising candidate as a future alternative protein source due to its high nutritional value. In the current study, hempseed protein isolate (HPI) was obtained using ultrasonic-assisted extraction with the aim to improve the functionality of HPI via protein structure modification. The solubility of HPI could be improved twofold under 20 kHz ultrasound processing compared to conventional alkaline extraction-isoelectric point precipitation. The protein solubility was gradually enhanced as the ultrasonic power improved, whereas excessive ultrasound intensity would cause a decline in protein solubility. Ultrasonic processing was found to have beneficial effects on the other functionalities of the extracted HPI, such as emulsifying and foaming properties. This improvement can be ascribed to the physical effects of acoustic cavitation that changed the secondary and tertiary structures of the protein to enhance surface hydrophobicity and decrease the particle size of the extracted protein aggregates. In addition, more available thiols were observed in US-treated samples, which could be another reason for improved functionality. However, the results of this study also revealed that prolonged high-power ultrasound exposure may eventually have a detrimental impact on HPI functional properties due to protein aggregation. Overall, this study suggests that high intensity ultrasound can enhance the functionality of HPI, which may ultimately improve its value in HPI-based food products.

Effect of Corn Starch Granules on Stabilizing the Foam Structure of Ultrasonically Modified Whey Isolate Protein

In this study, the mechanism of ultrasound combined with corn starch granules (CSG) treatment improved the foam properties of whey protein isolates (WPI) and was systematically investigated. The results showed that ultrasound combined with corn starch granules treatment increased foam capacity and stability by 15.38% and 41.40%, respectively. Compared with the control group, corn starch granules enhanced the surface charge (52.38%) and system turbidity (51.43%), which certainly provided the necessary conditions for the improvement of foam stabilization stability. In addition, corn starch granules as microgel particles increased the mechanical properties of the interfacial protein film, thus delaying the instability of foam. This research would provide new insights into the design of new protein-based foam foods in the future food industry.