Raman spectroscopic determination of structural changes in meat batters upon soy protein addition and heat treatment

Magnetic fields improve the gel properties of myofibrillar proteins in low-salt myofibrillar protein emulsion systems

The effect of magnetic field on the properties of emulsified gels containing myofibrillar protein (MP-emulsified gels) with different salt concentration (0, 0.2, 0.4, 0.6 mol/L) were investigated. The results demonstrated that the magnetic field treatment (4 °C, 3.8 mT, 3 h) made the emulsion droplets smaller and more uniform. At the same time, the magnetic field treatment improved the gel strength and WHC (water holding capacity) of MP-emulsified gels by 88.89 % and 3.5 % at 0.2 mol/L NaCl, and it also ameliorated the network structure of emulsified gel. Raman spectra showed that magnetic field treatment induced the transformation of β-structure into α-helix structure in MP-emulsified gel. Under high salt conditions (0.4 mol/L ∼ 0.6 mol/L), the magnetic field promoted the exposure of aliphatic residues in the tertiary structure and influences the hydrophobic interaction between molecules. In conclusion, Magnetic field treatment (4 °C, 3.8 mT, 3 h) improved MP-emulsified gels properties, offering a promising strategy for low-salt meat products.

Effect of Non-Meat Protein Addition on the 3D Printing Performance of Chicken Meat

In this study, three types of non-meat proteins, including soybean protein, wheat gluten, and whey protein, were used as additives to improve the 3D printing performance of chicken meat. The effects of non-meat proteins on rheological behavior, textural properties, moisture characteristics, and the microstructure of gels were investigated. Chicken meat paste without non-meat proteins added was taken as a control. Rheological results showed that the addition of non-meat proteins increased the apparent viscosity and the storage modulus of chicken meat paste. Textural properties of gels, including hardness, chewiness, cohesiveness, springiness, and resilience were also improved. The microstructure of gels with non-meat protein addition became denser and more compact, with improved connectivity. Nuclear magnetic resonance showed that the signals of bound water, immobilized water, and free water moved to the left towards lower relaxation time (p < 0.05) and part of immobile water and free water changed to bound water. The samples containing 15% soybean protein exhibited good shape-forming and shape-keeping capacities. There was an obvious increase in hardness (1991.40 ± 88.22 g), springiness (0.92 ± 0.00), cohesiveness (0.72 ± 0.01), gumminess (1299.14 ± 21.21), and resilience (0.34 ± 0.01) in these samples. The cooking loss of samples containing 15% soybean protein was 2.46 ± 0.36%, which was significantly lower than that of other treatments (p < 0.05). In summary, 15% soybean protein-added samples showed great potential for 3D printing.

Impact of Five Soy Proteins on Lean Chicken Breast Systems with Varying Moisture Contents: Cooking Loss, Texture, Microstructure, and T2 NMR

With increasing global meat consumption, meat-plant hybrid products have gained interest as a sustainable alternative. Soy proteins have been used in small quantities (2-3%) as meat extenders, yet limited data exist on their use at higher levels. Here, five commercial soy proteins (four isolates: SPI-A to -D; one concentrate: SPC) were used for meat replacement in lean meat batters with 0/40/80% added water. Cooking loss, texture, light micrographs, and T2 relaxation were analyzed. At 33% and 66% meat replacement, soy protein treatments maintained comparable or reduced cooking loss; SPI-D and SPC were the least and most effective, respectively. Complete replacement eliminated cooking loss in 0% and 40% water systems but failed to form self-supporting gels in the 80% system. At 33% replacement, SPI-A to -C generally increased hardness, whereas increasing the replacement level further to 66% decreased it. In the 0% and 80% systems, SPI-A treatments exhibited hardness comparable to controls, SPI-D treatments drastically reduced hardness, and SPC treatments maintained greater hardness than the controls even at 66% replacement. Micrographs offered potential explanations for these macroscopic measurements. NMR T2 data indicated that soy proteins restricted water mobility both pre- and post-cooking. Specifically, in the 40% and 80% systems, the T22 peaks (expelled liquid) of the hybrid samples containing 33% SPI-A were ~350 ms and 760 ms, compared to ~570 ms and 1170 ms for the meat controls, respectively. In conclusion, most soy proteins (except SPI-D) enhanced water binding, with SPI-A showing optimal texture and SPC showing promise as a more economical alternative.

Effect of chickpea protein modified with combined heating and high-pressure homogenization on enhancing the gelation of reduced phosphate myofibrillar protein

The effects of chickpea protein (CP) modified by heating and/or high-pressure homogenization (HPH) on the gelling properties of myofibrillar protein under reduced phosphate conditions (5 mM sodium triphosphate, STPP) were investigated. The results showed that heating and HPH dual-modified CP could decrease the cooking loss by 29.57 %, elevate the water holding capacity by 17.08 %, and increase the gel strength by 126.88 %, which conferred myofibrillar protein with gelation performance comparable with, or even surpassing, that of the high-phosphate (10 mM STPP) control. This gelation behavior improvement could be attributed to enhanced myosin tail-tail interactions, decreased myosin thermal stability, elevated trans-gauche-trans disulfide conformation, strengthened hydrophobic interactions and hydrogen bonding, the uncoiling of α-helical structures, the formation of well-networked myofibrillar protein gel, and the disulfide linkages between the myosin heavy chain, actin, and CP subunits. Therefore, the dual-modified CP could be a promising phosphate alternative to develop healthier meat products.

Plant-based protein emulsions with soy protein isolate and gluten improve freeze-thaw stability and shelf life of pork meatballs

This study investigated the effects of oil-in-water emulsions used as fat substitutes on the physicochemical properties of meatballs during frozen storage. Different formulations of fat replacers were prepared, including pork fat as the control (C), oil and water (OW), oil-in-water emulsion (E), emulsion with soy protein isolate (SE), emulsion with gluten (GE), and emulsion with soy protein isolate and gluten (SG). These fat substitutes were applied to a meatball paste. The samples were stored at -18 °C for 30 and 60 days, and their physicochemical properties were analyzed after thawing at 4 °C for 12 h. The SE formulation had the highest values for both water content and liquid holding capacity during frozen storage (P < 0.05). SE, GE, and SG showed significantly higher hardness, cohesiveness, springiness, gumminess, and chewiness than those of E during storage (P < 0.05). The vegetable protein addition treatments maintained a compact structure throughout storage. SE, GE, and SG prevented lipid and protein oxidation during frozen storage. These results demonstrated that SE, GE, and SG offer significant advantages in improving the freeze-thaw stability, liquid holding capacity, and oxidation stability of pork meatballs during long-term frozen storage. Therefore, our study suggest that plant-based protein emulsions can effectively replace animal fats while maintaining product quality, offering valuable implications for the meat processing industry.

Deacetylation enhances the structure and gelation properties of konjac glucomannan/soy protein isolate cold-set gels

This study aimed to investigate the effect of the deacetylated konjac glucomannan (DKGM), with varying degree of deacetylation (DD), on the physicochemical and structural properties of transglutaminase-induced soy protein isolate (SPI) cold-set gels. Compared with native konjac glucomannan (KGM), DKGM significantly enhanced the gel strength, water-holding capacity, and thermal stability of the composite gels, with DK3 (DKGM with 65.85 % deacetylation) showing the most significant improvement. The secondary and tertiary structures of SPI in the DK3 group were the most stable. Compared with the KGM group, the DK3 group showed a 58.32 % increase in hydrophobic interaction and a 37.98 % decrease in free sulfhydryl content. The microstructure results demonstrated that DK3 was uniformly dispersed within the SPI network, promoting the formation of a continuous and dense network structure. This was mainly due to DK3 having a moderate particle size and low viscosity. Therefore, DKGM with a moderate DD is conducive to forming a more ordered and dense gel network structure, imparting optimal gel performance to the SPI cold-set gel.

Effect of Soy Protein Isolate on the Quality Characteristics of Silver Carp Surimi Gel during Cold Storage

This study mainly investigated the effect of soy protein isolate (SPI) on the gel quality of silver carp surimi under different storage conditions (storage temperatures of 4 °C, -20 °C, and -40 °C, and storage times of 0, 15, and 30 d). The results found that 10% SPI could inhibit the growth of ice crystals, improve the water distribution, enhance the water holding capacity of the gels, and strengthen the interaction between surimi and proteins. Compared to the control group, the composite silver carp surimi gel exhibited superior quality in texture, chemical interactions, and rheological properties during cold storage. Fourier transform infrared spectroscopy revealed an increasing trend in α-helix and β-turn content and a decreasing trend of β-sheet and random coil content. As storage time increased, the gel deterioration during cold storage inhibitory effect of the treatment group was superior to the control group, with the best results observed at -40 °C storage conditions. Overall, SPI was a good choice for maintaining the quality of silver carp surimi gel during cold storage, which could significantly reduce the changes in the textural properties during cold storage with improved water holding capacity.

Influence of cadmium ion on denaturation kinetics of hen egg white-lysozyme under thermal and acidic conditions

To study the influence of Cd(II) ions on denaturation kinetics of hen egg white lysozyme (HEWL) under thermal and acidic conditions, spontaneous Raman spectroscopy in conjunction with Thioflavin-T fluorescence, AFM imaging, far-UV circular dichroism spectroscopy, and transmittance assays was conducted. Four distinctive Raman spectral markers for protein tertiary and secondary structures were recorded to follow the kinetics of conformational transformation. Through comparing variations of these markers in the presence or absence of Cd(II) ions, Cd(II) ions show an ability to efficiently accelerate the disruption of tertiary structure, and meanwhile, to promote the direct formation of organized β-sheets from the uncoiling of α-helices by skipping intermediate random coils. More significantly, with the action of Cd(II) ions, the initially resulting oligomers with disordered structures tend to assemble into aggregates with random structures like gels more than amyloid fibrils, along with a so-called "off-pathway" denaturation pathway. Our results advance the in-depth understanding of corresponding ion-specific effects.

Using Potassium Bicarbonate to Improve the Water-Holding Capacity, Gel and Rheology Characteristics of Reduced-Phosphate Silver Carp Batters

To study the use of partial or total potassium bicarbonate (PBC) to replace sodium tripolyphosphate (STPP) on reduced-phosphate silver carp batters, all the batters were composed of silver carp surimi, pork back fat, ice water, spices, sugar, and sodium chloride. Therein, the sample of T1 contained 4 g/kg STPP; T2 contained 1 g/kg PBC, 3 g/kg STPP; T3 contained 2 g/kg PBC, 2 g/kg STPP; T4 contained 3 g/kg PBC, 1 g/kg STPP; T5 contained 4 g/kg PBC, and they were all produced using a bowl chopper. The changes in pH, whiteness, water- and oil-holding capacity, gel and rheological properties, as well as protein conformation were investigated. The pH, cooking yield, water- and oil-holding capacity, texture properties, and the G' values at 90 °C of the reduced-phosphate silver carp batters with PBC significantly increased (p < 0.05) compared to the sample without PBC. Due to the increasing pH and enhanced ion strength, more β-sheet and β-turns structures were formed. Furthermore, by increasing PBC, the pH significantly increased (p < 0.05) and the cooked silver carp batters became darkened. Meanwhile, more CO₂ was generated, which destroyed the gel structure, leading the water- and oil-holding capacity, texture properties, and G' values at 90 °C to be increased and then decreased. Overall, using PBC partial as a substitute of STPP enables reduced-phosphate silver carp batter to have better gel characteristics and water-holding capacity by increasing its pH and changing its rheology characteristic and protein conformation.

Insoluble dietary fibers from Lentinus edodes stipes improve the gel properties of pork myofibrillar protein: A water distribution, microstructure and intermolecular interactions study

This paper investigated the effects of Lentinus edodes stipes insoluble dietary fiber (LESIDF, 0%-3.0%) on the quality and microscopic properties of pork myofibrillar protein (MP) gels. The results showed that the water holding capacity and gel strength of composite gels enhanced with increasing LESIDF (1.0%-2.5%), and reached the maximum at the level of 2.5%-3.0%. Disulfide and non-disulfide covalent bonds were major chemical forces maintaining the 3D network of LESIDF-MP composite gels. LESIDF also promoted the formation of ionic and hydrogen bonds, confirmed by the self-assembly of β-sheets to α-helices, leading to a compact gel network structure. The observation of paraffin section revealed that LESIDF could capture more water molecules in gels, which was consistent with the transformation of free water to immobilized water. Overall, the optimal addition of LESIDF was 2.5%-3.0%, which provided a good strategy for LESIDF as an agricultural by-product to improve the quality of gel meat products.

Evaluation of chickpea protein isolate as a partial replacement for phosphate in pork meat batters: Techno-functional properties and molecular characteristic modifications

The effects of chickpea protein isolate (CPI, 0.5-2 %, w/w) on the techno-functional properties of 50 % reduced-phosphate pork meat batters (RPMBs) were explored. The results showed that 1.5-2 % CPI significantly decreased the cooking loss but significantly increased the emulsion stability, hardness, gumminess, chewiness and yellowness (b*) of RPMBs (P < 0.05). CPI altered molecular characteristics of RPMBs, as demonstrated by the increased storage modulus (G'), the conversion of free water into immobilized water, the reduced intensities of the aliphatic residue Raman bands, the decreased α-helical structure and the formation of well-organized gel networks with evenly distributed small fat globules. Principal component analysis and Pearson's correlation analysis indicated that CPI-induced changes in RPMB techno-functional properties were closely related to molecular characteristics. Hierarchical cluster analysis suggested that RPMBs supplemented with 1.5-2 % CPI were highly similar in techno-functional properties to the high-phosphate group. Therefore, CPI may potentially be used to develop reduced-phosphate meat products.

Effect of High Pressure Homogenization-Modified Soy 11S Globulin on the Gel and Rheological Properties of Pork Myofibrillar Protein

The changes in texture and rheological characteristics, water holding capacity, and microstructure of pork myofibrillar protein with high-pressure homogenization-modified (0-150 MPa) soy 11S globulin were studied. The cooking yield, whiteness values, texture properties, shear stress, initial apparent viscosity, storage modulus (G'), and loss modulus (G″) of pork myofibrillar protein with high-pressure homogenization-modified soy 11S globulin were significantly increased (p < 0.05) compared with the sample of 0 MPa, and centrifugal yield was significantly decreased, except for the sample of 150 MPa. Therein, the sample of 100 MPa had the largest values. Meanwhile, the water and proteins bonded more tightly because the initial relaxation times of T_2b, T₂₁ and T₂₂ from pork myofibrillar protein with high-pressure homogenization-modified soy 11S globulin were shorter (p < 0.05). Overall, the water-holding capacity, gel texture and structure, and rheological properties of pork myofibrillar protein could improve when adding soy 11S globulin treated with 100 MPa.

Investigation of the Effect of Rice Bran Content on the Antioxidant Capacity and Related Molecular Conformations of Plant-Based Simulated Meat Based on Raman Spectroscopy

At present, plant-based simulated meat is attracting more and more attention as a meat substitute. This study discusses the possibility of partial substitution of rice bran (RB) for soybean protein isolate (SPI) in preparing plant-based simulated meat. RB was added to SPI at 0%, 5%, 10%, 15%, and 20% to prepare RB-SPI plant-based simulated meat by the high moisture extrusion technique. RB-SPI plant-based simulated meat revealed greater polyphenol content and preferable antioxidant capacity (DPPH radical scavenging capacity, ABTS scavenging ability, and FRAP antioxidant capacity) compared to SPI plant-based simulated meat. The aromatic amino acids (tryptophan and tyrosine) of RB-SPI plant-based simulated meats tend to be masked first, and then the hydrophobic groups are exposed as RB content increases and the polarity of the surrounding environment increases due to the change in the disulfide conformation of RB-SPI plant-based simulated meats from a stable gauche-gauche-gauche conformation to a trans-gauche-trans conformation.

Effect of Oudemansiella raphanipies Powder on Physicochemical and Textural Properties, Water Distribution and Protein Conformation of Lower-Fat Pork Meat Batter

The effects of the addition of different amounts (0%, 1%, 2%, 3% and 4%) of Oudemansiella raphanipies powder (ORP) to lower-fat pork batter on its physicochemical, textural and rheological properties, water distribution and protein conformation were evaluated. The results showed that the addition of ORP from 0% to 4% significantly decreased the pH and L* value of pork batter (p < 0.05); however, it also increased the a* value and enhanced the cooking yield of pork batter from 77% to 92%. Pork batter with 1−2% ORP added had an improved texture profile and a higher storage modulus (G’), but the addition of 3−4% ORP resulted in an inferior texture of pork batter and G’. LF-NMR showed that the addition of ORP significantly increased the peak area ratio of immobile water and reduced the peak area ratio of free water (p < 0.05). ORP significantly affected protein secondary structure of pork batter. The α-helix content of pork batter with 1−2% ORP decreased and β-sheet content increased. Overall, the addition level of 1−2% ORP effectively improved the texture and water holding capacity of lower-fat emulsified sausage and provides a new reference for developing nutritional meat products.

Changes in Gel Structure and Chemical Interactions of Hypophthalmichthys molitrix Surimi Gels: Effect of Setting Process and Different Starch Addition

The modifications of histological properties and chemical forces on heated surimi gels with starch addition (0-12 g/100 g surimi) were investigated. Two types of heating processes (direct heating and two-step heating) were carried out on surimi gels in order to reveal the effect of setting on mixed matrices. The results of transverse relaxation time showed less immobile water and free water converted into bound water in a matrix subjected to the setting process. Scanning electron microscope and light microscopy images revealed inefficient starch-swelling in two-step heated gels. Chemical interactions and forces in direct cooking gels were more vulnerable to starch addition, resulting in significant decreases in hydrophobic interaction and sulfhydryl content (p < 0.05). With the increment of starch, the disulfide stretching vibrations of the gauche-gauche-gauche conformation were reduced in both gel matrices. The structural variations of different components collectively resulted in changes in texture profile analysis and water holding capacity. Overall, the results demonstrated that starch addition had a great and positive effect on the weak gel matrix by direct heating.

Line-scan Raman scattering image and multivariate analysis for rapid and noninvasive detection of restructured beef

The mean spectral (MS) features were extracted from Raman scattering images (RSI) of beef samples over the region of interest covering the spectral range of 789-1710cm^-1 and the spatial offset range of 0-5 mm (for two sides of the incident laser). The RSI monitored the main change in the protein, amide bands, lipids, and amino acid residues. The classification model performance based on MS features compared the conventional Raman spectral features and confirmed the usefulness of RSI. Finally, the results showed that RSI technology is a reliable tool for rapid and noninvasive detection of restructured beef.

Enrichment of NaCl-reduced burger with long-chain polyunsaturated fatty acids: Effects on physicochemical, technological, nutritional, and sensory characteristics

This study aimed to determine the effect of NaCl reduction and addition of long-chain polyunsaturated fatty acids (PUFA) on the quality traits of burgers. Fish oil was either directly incorporated or added as encapsulated by freeze-dried microparticles (complex coacervates) composed of soy protein isolate and inulin. Despite the differences in some parameters associated with NaCl reduction (e.g., instrumental hardness), the quality of the burgers was mainly affected by the microparticles. Thus, a decrease in pH and increase in hardness and chewiness were observed, and a higher exposure of fish oil to oxidation was observed thus increasing volatile oxidation compounds and negatively impacting on the sensory profile and overall liking of the burgers. However, the encapsulation of the fish oil helped to retain EPA and DHA after cooking. The results of the NaCl-reduced burger with unencapsulated fish oil suggest the possibility of incorporating PUFAs, but only containing EPA after cooking.

Effect of Fermentation with Two Molds on Characteristics of Chicken Meat

In the present study, we investigated the characteristics of chicken meat fermented with Penicillium nalgiovense and Penicillium chrysogenum. Hardness and springiness gradually decreased, while gumminess gradually increased during fermentation. Fermentation with P. chrysogenum led to higher hardness and lower gumminess than fermentation with P. nalgiovense. Fermentation with two molds resulted in similar microstructure, such as granule formation and fractured myofibril. The highest percentage of secondary structure was ɑ-helix, and tyrosine residues were buried after fermentation. P. nalgiovense-fermented samples contained more bound water, lower relative content of alkanes, and higher relative content of aldehydes than P. chrysogenum-fermented samples.

Effects of Physical and Chemical Factors on the Structure of Gluten, Gliadins and Glutenins as Studied with Spectroscopic Methods

This review presents applications of spectroscopic methods, infrared and Raman spectroscopies in the studies of the structure of gluten network and gluten proteins (gliadins and glutenins). Both methods provide complimentary information on the secondary and tertiary structure of the proteins including analysis of amide I and III bands, conformation of disulphide bridges, behaviour of tyrosine and tryptophan residues, and water populations. Changes in the gluten structure can be studied as an effect of dough mixing in different conditions (e.g., hydration level, temperature), dough freezing and frozen storage as well as addition of different compounds to the dough (e.g., dough improvers, dietary fibre preparations, polysaccharides and polyphenols). Additionally, effect of above mentioned factors can be determined in a common wheat dough, model dough (prepared from reconstituted flour containing only wheat starch and wheat gluten), gluten dough (lack of starch), and in gliadins and glutenins. The samples were studied in the hydrated state, in the form of powder, film or in solution. Analysis of the studies presented in this review indicates that an adequate amount of water is a critical factor affecting gluten structure.

Advancement of food-derived mixed protein systems: Interactions, aggregations, and functional properties

Recently, interests in binary protein systems have been developed considerably ascribed to the sustainability, environment-friendly, rich in nutrition, low cost, and tunable mechanical properties of these systems. However, the molecular coalition is challenged by the complex mechanisms of interaction, aggregation, gelation, and emulsifying of the mixed system in which another protein is introduced. To overcome these fundamental difficulties and better modulate the structural and functional properties of binary systems, efforts have been steered to gain basic information regarding the underlying dynamics, theories, and physicochemical characteristics of mixed systems. Therefore, the present review provides an overview of the current studies on the behaviors of proteins in such systems and highlights shortcomings and future challenges when applied in scientific fields.

Effect of two-step microwave heating on the gelation properties of golden threadfin bream (Nemipterus virgatus) myosin

The effects of different microwave heating (MH) methods on gelation properties of golden threadfin bream myosin and related mechanism were investigated in this study. Compared with conventional heating and one-step MH methods, myosin gel developed by 100 W coupled with 300 W MH method (MH100 + MH300) had stronger gel strength (p < 0.05) with more immobilized water (p < 0.05). Raman analysis suggested that this two-step method promoted the suitable unfolding of myosin before aggregation formation, and contributed to stabilizing the ordered secondary structure. Confocal laser scanning microscopy images revealed that 100 W microwave followed by 300 W MH produced a compact networked structure with small cavities and a thick cross-linked gel wall. Furthermore, from a perspective of molecular forces, the improvement of gelation properties by the MH100 + MH300 method were mainly involved in the enhancement of regular hydrophobic interaction and stabilization of weak protein-water hydrogenbonds.

The characteristics of gelation of myofibrillar proteins combined with salt soluble Rhodotorula glutinis proteins by enzymatic crosslinking

Some microbial single-cell proteins are capable of producing synergistic crosslinking interactions with edible proteins by rational regulation. Herein, we reported that salt soluble proteins (RGP) extracted from Rhodotorula glutinis in an alkaline and saline system may combine with myofibrillar proteins (MP) by transglutaminase (TG) polymerization to form improvable irreversible thermal co-gels. The combination of MP, RGP, and TG, namely restructured MP gels, led to significantly enhanced water holding capacity (WHC), up to 90.76 ± 1.88% (% of retained water) and textural properties (hardness, springiness, and adhesiveness) as well as decreases of 'gauche-gauche-gauche' SS bonds and α-helix conformations and increases of 'gauche-gauche-trans' SS bonds and β-fold conformations, compared to MP and MP-RGP groups. Differential scanning calorimetry analysis validated that thermostability of myosins and actins from MP was reduced after using RGP, TG, and their combination, and unfolding and denaturation of myosin occurred easily during thermal co-gelation by TG and/or RGP.

Use of l-arginine-assisted ultrasonic treatment to change the molecular and interfacial characteristics of fish myosin and enhance the physical stability of the emulsion

The effects of l-arginine (Arg)-assisted ultrasonic treatment on the molecular and interfacial characteristics of myosin and emulsifying properties of the emulsion were evaluated to ascertain the underlying mechanism in improving the emulsion stability. Ultrasonication induced the exposure of residues of native myosin, which was increased by the addition of Arg (40 mM). Furthermore, in terms of emulsions containing Arg, the higher the ultrasonication intensity was, the greater the increase in adsorbed protein (from 15.43 ± 0.28% to 50.49 ± 1.65%) and π value, and the decrease in droplet sizes (from 4098 nm to 2324 nm) (P < 0.05). Moreover, the increase in the ordered structures of interfacial myosin induced by Arg and ultrasonication favoured the formation of a protein gelation network. In summary, Arg-assisted ultrasonic treatment improved the stability of the emulsion by inducing the exposure of native myosin and facilitating the formation of ordered structures of interfacial myosin.

The effects of sodium chloride on proteins aggregation, conformation and gel properties of pork myofibrillar protein Running Head: Relationship aggregation, conformation and gel properties

The objective of this study was to evaluate relationship with aggregation, secondary structures and gel properties of pork myofibrillar protein with different sodium chloride (1%, 2% and 3%). When the sodium chloride increased from 1 to 3%, the active sulfhydryl, surface hydrophobicity, hardness and cooking yield of myofibrillar protein were increased significantly (p < 0.05), the particle size, total sulfhydryl and Zeta potential were decreased significantly (p < 0.05), these meant the aggregations of pork myofibrillar protein were decreased. The changes of proteins aggregation induced the strongest intensity band of Amide I shifted up from 1660 cm^-1 to 1661 cm^-1, meanwhile, the β-sheet structure content was increased significantly (p < 0.05) with the sodium chloride increased. From the above, the lower proteins aggregation and higher β-sheet structure content could improve the water holding capacity and texture of pork myofibrillar protein gel.

Impact of combined ultrasound-microwave treatment on structural and functional properties of golden threadfin bream (Nemipterus virgatus) myofibrillar proteins and hydrolysates

The effects of microwave, ultrasound and combined ultrasound-microwave (UM) treatment with different intensities on structural and hydrolysis properties of myofibrillar protein (MP) were investigated. Freeradical scavenging ability, angiotensin-I-converting enzyme (ACE) inhibitory activity, and cellular antioxidant and anti-inflammatory abilities of the related bioactive peptides were also evaluated. Raman spectroscopic analysis indicated that MP molecule tended to unfold and stretch with increasing in β-turn and random coil content under mild microwave (100 W), ultrasound (100-200 W) and combined UM treatments. Meanwhile, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) revealed these treatments could also improve the thermal stability against heat-induced denaturation and degeneration. The 200 W ultrasound treatment clearly increased MP solubility by disrupting the highly-ordered aggregates into smaller filament and fragment structures. The 300 W ultrasound coupled with 100 W microwave treatment further enhanced these effects. The resulting partially denatured structure induced by suitable ultrasound and combined UM treatments increased the susceptibility of MP to exogenous enzymes, thereby accelerating hydrolytic process and yielding a high peptide concentration in MP hydrolysates. MP peptides could effectively inhibit free radical and ACE activity, which also improved the ability of antioxidant defence system, and suppressed the production of proinflammatory cytokines in RAW 264.7 cells stimulated by H₂O₂. The combination of 100 W microwave and 300 W ultrasound treatment was optimal method for generating bioactive MP peptides with the strongest multi-activity effects against H₂O₂-induced cell damage.

Potential of a Sunflower Seed By-Product as Animal Fat Replacer in Healthier Frankfurters

Upcycled defatted sunflower seed flour (SUN), a by-product obtained from sunflower oil extraction, was used as an animal fat replacer to develop healthier frankfurters. For that end, animal fat was replaced (~50%) with water and 2% or 4% of SUN. Nutritional composition, technological, structural and sensorial properties were evaluated. SUN incorporation led to a significant increase in protein, minerals (magnesium, potassium, copper and manganese) and a decrease in fat content (~37% less than control with all animal fat). The incorporation of SUN in frankfurters promoted the presence of phenolic compounds. Increasing SUN addition lead to an increasingly (p < 0.05) darker frankfurter colour. Samples with SUN at 4% were firmer than the control according to TPA and sensory analysis results and showed the highest lipid disorder attributed to more lipid interactions in the meat matrix. SUN addition as an animal fat replacer in frankfurters is a feasible strategy to valorise sunflower oil by-products and obtain healthier frankfurters.

A Study of Structural Change During In Vitro Digestion of Heated Soy Protein Isolates

Use of soy protein isolate (SPI) as the encapsulating material in emulsions is uncommon due to its low solubility and emulsification potential. The aim of this study was to improve these properties of SPI via heat treatment-induced modifications. We modified SPI under various heating conditions and demonstrated the relationship between structure and in vitro digestibility in simulated gastric fluid by means of Sodium Dodecyl Sulphide-Polyacrylamide Gel Electrophoresis (SDS-PAGE) and Raman spectroscopy. It was found that the degree of hydrolysis (DH) of SPI increased and then decreased upon increasing exposure to heat. Different subunits of conglycinin were digested and degraded by pepsin. Heat treatment improved digestion characteristics that would reduce e the unnecessary loss of protein, offering potential for the efficient delivery of nutrients in nanoemulsions. These results could have significant relevance for research groups that are interested in the biological interactions and activity of functional SPI.

Double-edged effects of aluminium ions on amyloid fibrillation of hen egg-white lysozyme

Elucidating the effects of Al(III) ions on amyloid fibrillation is important to understand the association between metal ions and Alzheimer's disease. Here, Raman spectroscopy was applied to investigate amyloid fibrillation of hen egg-white lysozymes during thermal incubation with Al(III) ions or acids, combined with atomic force microscopy and thioflavin T fluorescence assays. Kinetics of conformational changes in lysozymes were assessed by monitoring six characteristic Raman spectral markers. The peak of Phe residues at 1003 cm^-1 and two bands of Trp residues at 759 cm^-1 and 1340-1360 cm^-1 corresponded to the lysozyme tertiary structure, whereas two NC_αC stretching vibrations at 899 cm^-1 and 935 cm^-1 and an amide I band were associated with the lysozyme skeleton. There may be a four-stage transformation mechanism underlying the kinetics of amyloid fibrillation of lysozymes with the thermal/Al(III) treatment. Comparison of kinetics under thermal/Al(III) and thermal/acid conditions revealed double-edged roles of Al(III) ions in amyloid fibrillation of lysozymes. Specifically, in addition to postponing α-helix degradation, Al(III) ions accelerated conformational transformations from α-helices to organized β-sheets. The present investigation sheds light on the controversial effects of Al(III) ions on amyloid fibrillation of lysozymes.