The interplay of muscle and pea proteins in low-salt gels: An insight into in situ structure formation in hybrid meat alternatives.

The present study investigated thermal gelation of mixed sarcoplasmic (Sarc), myofibrillar (Myof), and pea proteins corresponding to partial meat replacements (0, 25, and 50%) by pea protein isolate (PPI) at reducing salt levels (0.6 â†’ 0.1 M NaCl) to understand in situ (simulated) structure-forming properties of hybrid meat analogues. The amount of soluble proteins in hybrids generally increased with salt concentrations and PPI substitution. While muscle proteins (mixed Sarc and Myof) had the strongest gelling capacity, hybrid proteins also exhibited moderate aggregation and gelling activity based on the sol→gel rheological transition and gel hardness testing. Sarc and pea 7S/11S globulins collectively compensated for the attenuated gelling capacity of mixed proteins due to diminishing Myof in the hybrids. Immobilized water within hybrid protein gels was tightly bonded (T2 from nuclear magnetic resonance), consistent with the dense and uniform microstructure observed. These findings offer a new knowledge base for developing reduced-salt hybrid meat analogues.

Heat/Cold Stress and Methods to Mitigate Its Detrimental Impact on Pork and Poultry Meat: A Review.

This paper aims to provide an updated review and current understanding of the impact of extreme temperatures-focusing on heat stress (HS)-on the quality of pork and poultry meat, particularly amidst an unprecedented global rise in environmental temperatures. Acute or chronic HS can lead to the development of pale, soft, and exudative (PSE) meat during short transportation or of dark, firm, and dry (DFD) meat associated with long transportation and seasonal changes in pork and poultry meat. While HS is more likely to result in PSE meat, cold stress (CS) is more commonly linked to the development of DFD meat. Methods aimed at mitigating the effects of HS include showering (water sprinkling/misting) during transport, as well as control and adequate ventilation rates in the truck, which not only improve animal welfare but also reduce mortality and the incidence of PSE meat. To mitigate CS, bedding on trailers and closing the tracks' curtains (insulation) are viable strategies. Ongoing efforts to minimize meat quality deterioration due to HS or CS must prioritize the welfare of the livestock and focus on the scaleup of laboratory testing to commercial applications.

The effects of resonance acoustic mixing modulation on the structural and emulsifying properties of pea protein isolate.

The effects of resonant acoustic mixing (RAM) with different treatment times (0, 5, 10, 15, 20 and 30 min) on the structural and emulsifying properties of pea protein isolate (PPI) were investigated for the first time. Increasing the RAM treatment time from 0 to 20 min decreased the α-helix/ß-sheet ratio and particle size of the PPI samples by 37.84 % and 46.44 %, respectively, accompanied by an increase in solubility from 54.79 % to 71.80 % (P < 0.05). Consequently, the emulsifying activity index of PPI (from 10.45 m2/g to 14.2 m2/g) and the physical stability of RAM-PPI emulsions were effectively enhanced, which was confirmed by the small and uniformly distributed oil droplets in the micrographs of the emulsions. However, excessive RAM treatment (30 min) diminished the effectiveness of the aforementioned improvements. Therefore, obviously enhanced solubility and emulsifying properties of PPI can be attained through proper RAM treatment (15-20 min).

Antioxidant properties of bovine liver protein hydrolysates and their practical application in biphasic systems.

BACKGROUND: The influence of protein hydrolysate produced from bovine liver protein hydrolysate (LPH) by enzymatic hydrolysis, using Alcalase/Protamex (1:1), on lipid dispersions was investigated. LPH production was optimized to maximize the antioxidant activity (at 45, 50, and 55 °C for 12, 18, and 24 h). Different concentrations of LPHs (1, 3, and 5 mg/g) were added to emulsions and to liposomes. Lipid oxidation level and particle size of the lipid dispersions were monitored for 14 days of storage at 25 °C. RESULTS: Radical scavenging activity and reducing power were the highest at 45 °C after 24 h of hydrolysis. Electrophoresis pattern showed that the antioxidant activity was arising from the peptides with molecular weight around 10 kDa. Lipid oxidation occurred more rapidly in samples without LPH during storage. In emulsions, lower thiobarbituric acid-reactive substance and conjugated diene values were measured with increasing concentrations of LPH at day 14. Accordingly, particle size of the samples containing 5 mg/g of LPH was smaller than those of other groups. Phase separation was observed only in lecithin emulsion without LPH at day 14. The use of LPH in liposome limited the lipid oxidation and maintained the size of the particles independently from the concentration. CONCLUSION: This study highlights the potential applications of animal by-products as natural antioxidants in complex food systems. The results demonstrate that LPH, particularly when hydrolyzed at optimized conditions, can effectively inhibit lipid oxidation. The findings suggest that biphasic systems incorporating LPH have promising prospects for enhancing the stability and quality of food products. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Structural modification of oat protein by thermosonication combined with high pressure for O/W emulsion and model salad dressing production.

Oat protein is becoming an important ingredient in beverages and formulated foods owing to its high nutritive value and bland flavor; yet, its functionality remains largely unexplored. This study sought to enhance the surface activity of oat protein isolate (OPI) through high-intensity ultrasound (HIU; at 20 or 60 °C) combined with high pressure homogenization (HP; 30 MPa) treatments. Sonication disturbed the protein conformation and significantly improved surface hydrophobicity (19.7%) and ζ-potential (15.7%), which were further augmented by subsequent HP (P < 0.05). Confocal microscopy revealed a uniform oil droplet distribution in emulsions prepared with HIU+HP combination treated OPI, and the oil droplet size decreased up to 35.6% when compared to that of non-treated OPI emulsion (d = 1718 nm). Emulsifying activity was greater for HIU+HP than for HIU, and the viscosity followed a similar trend. Moreover, while emulsions prepared with HIU or HP treated OPI were more stable than control, the 60 °C HIU+HP combination treatment yielded the maximum stability. In corroboration, a model salad dressing prepared from HIU+HP treated OPI displayed a homogenous oil droplet distribution and an improved viscosity. Therefore, thermosonication combined with high pressure homogenization may be suitable for salad dressings and other oil-imbedded food products.

Non-covalent binding of chlorogenic acid to myofibrillar protein improved its bio-functionality properties and metabolic fate.

As natural antioxidants added to meat products, polyphenols can interact with proteins, and the acid-base environment influenced the extent of non-covalent and covalent interactions between them. This study compared the bio-functional characteristics and metabolic outcomes of the myofibrillar protein-chlorogenic acid (MP-CGA) complexes binding in different environments (pH 6.0 and 8.5). The results showed that CGA bound with MP significantly enhanced its antioxidant activity and inhibitory effect on metabolism enzymes. CGA bound deeply into the MP structure hydrophobic cavity at pH 6.0, which reduced its degradation by digestive enzymes, thus increasing its bio-accessibility from 59.5% to 71.6%. The digestion products of the two complexes exhibited significant differences, with the non-covalent MP-CGA complexes formed at pH 6.0 showing significantly higher concentrations of rhetsinine and piplartine, two well-known compounds to modulate diabetes. This study demonstrated that non-covalent binding between protein and polyphenol in the acidic environment held greater promising prospects for improving health.

Concentration-dependent effect of eugenol on porcine myofibrillar protein gel formation.

The effects of different concentrations of eugenol (EG = 0, 5, 10, 20, 50, and 100 mg/g protein) on the structural properties and gelling behavior of myofibrillar proteins (MPs) were investigated. The interaction of EG and MPs decreased free thiol and amine content, and reduced tryptophan fluorescence intensity and thermal stability, but enhanced surface hydrophobicity and aggregation of MPs. Compared with the control (EG free), the MPs' gels treated with 5 and 10 mg/g of EG had a higher storage modulus, compressive strength, and less cooking loss. A high microscopic density was observed in these EG-treated gels. However, EG at 100 mg/g was detrimental to the gelling properties of the MPs. The results indicate that an EG concentration of 20 mg/g is a turning point, i.e., below 20 mg/g, EG promoted MPs gelation, but above 20 mg/g, it impeded gelation by interfering with protein network formation. The EG modification of MPs could provide a novel ingredient strategy to improve the texture of comminuted meat products.

Rheological, textural, and water-immobilizing properties of mung bean starch and flaxseed protein composite gels as potential dysphagia food: The effect of Astragalus polysaccharide.

The effects of Astragalus polysaccharide (APS) on rheological, textural, water-holding, and microstructural properties of mung bean starch (MBS)/flaxseed protein (FP) composite gels were investigated. Results showed that the storage modulus (G') of gels with APS were significantly lower than that of the control gel, while different concentrations of APS possessed diverse effects on the hardness, gumminess and cohesiveness of the gels. Adding APS significantly improved the water retention capacity by trapping more immobilized and free water in the gel network. Microstructurally, the MBS/FP/APS composite gels displayed a complex network with reduced pore size compared with that of the control gel (MBS/FP). International dysphagia diet standardization initiative (IDDSI) tests suggested that gels with APS contents below 0.09 % could be classified into level 6, while gel with 0.12 % APS could be categorized as level 7. Mechanistically, APS could influence the interactions between starch and protein within the tri-polymeric composite systems by affecting starch gelatinization and hydrogen bonding, further contributing to the formation of strengthened gel network and the change of gel properties. These results suggest that the macromolecular APS can improve the structural and textural properties of the starch-protein composite systems, and impart various functional properties to the FP-based gel foods.

Influence of Dietary Protein Source and Level on Histological Properties of Muscle and Adipose Tissue of Lambs.

The muscle and adipose tissue histological properties in wether and ewe lambs of Gentile di Puglia breed, fed diets including two protein sources [soybean meal (SB) and SB plus distillers dried grain with solubles (DD)] and three protein levels (12.5, 15.7, and 18.9%) were evaluated. Muscle samples were collected from the longissimus/rump, cut, and stained (reciprocal aerobic and anaerobic stains) for muscle fiber typing and fat cell characterization. Fibers were classified as α-red, ß-red, and α-white. Lambs fed SB had larger α-white (p < 0.10) and smaller-diameter ß-red and α-red fibers (p < 0.05). Among dietary protein levels, lambs fed 12.5% protein exhibited the highest percentage of α-red and the greatest diameter of α-white fibers, whereas wethers had a higher percentage of α-red (p < 0.05), and ewes had a higher percentage of α-white fibers (p < 0.05). Intramuscular fat cells were larger (p < 0.10) in ewes than in wethers. Lambs in the group fed 12.5% protein had larger subcutaneous fat cells at the sacral vertebrae location. Overall, both sources and levels of dietary protein had significant effects on lamb muscle and fat histological features, suggesting the potential of modulating muscle or fiber types through dietary protein strategies.

Textural characterization of calcium salts-induced mung bean starch-flaxseed protein composite gels as dysphagia food.

Effects of calcium gluconate (CG), calcium lactate (CL) and calcium dihydrogen phosphate (CDP) on the structural and functional properties of mung bean starch (MBS)-flaxseed protein (FP) composite gels were investigated to explore the feasibility of developing dysphagia food. The water-immobilizing, rheological and structural properties of MBS-FP composite gels adding different calcium salts (10, 30, and 50 mmol/L) were analyzed by low-field nuclear magnetic resonance measurement, rheological and textural analyses, fourier transform infrared spectroscopy, scanning electron microscopy and confocal laser scanning microscopy. Results showed that calcium salts imparted various soft gel properties to the composite gels by influencing the interactions between MBS and FP. Calcium salts could affect the conformation of amylose chains, accelerate the aggregation of FP molecules, and increase the cross-linking between starch and protein aggregates, resulting in the formation of large aggregates and a weak gel network. Consequently, calcium salts-induced composite gels showed lower viscoelastic moduli and gel strength than the control gel. In particular, different calcium salts had various impacts on the gel properties due to their diverse ability forming hydrogen bonds. Compared with CL and CDP, the gels containing CG presented the higher viscoelastic moduli and hardness, and possessed an irregular cellular network with the increased pore number and the decreased wall thickness. The gel containing 50 mmol/L CL had the highest water-holding capacity, in all the gels tested, by retaining more immobilized and mobile water in the compact gel network with larger cavities. The gels adding CDP presented lower hardness and gumminess due to the obvious lamellar structure within the network. International dysphagia diet standardization initiative (IDDSI) tests indicated that the gels adding CG and CL could be categorized into level 6 (soft and bite-sized) dysphagia diet, while the samples adding CDP could be classified into level 5 (minced and moist). These findings provide insights for the development of the novel soft gel-type dysphagia food.

pH-shifting alters textural, thermal, and microstructural properties of mung bean starch-flaxseed protein composite gels.

The objective of this study was to investigate the effect of pH-shifting on the textural and microstructural properties of mung bean starch (MBS)-flaxseed protein (FP) composite gels. Results showed that different pH-shifting treatments caused changes in hydrogen bond interactions and secondary structures in composite gels, leading to the formation of loose or compact gel networks. The pH 2-shifting modified protein and starch molecules with shorter chains tended to form smaller intermolecular aggregates, resulting in the formation of a looser gel network. For pH 12-shifting treatment, conformational change of FP caused the unfolding of protein and the exposure of more hydrophobic groups, which enhanced the hydrogen bond and hydrophobic interactions between polymers, contributing to the formation of a compact gel network. Furthermore, pH 12-shifting improved the water-holding capacity (WHC), storage modulus, and strength of gels, while pH 2-treated gels exhibited lower WHC, hardness, and gumminess due to the degradation of MBS and denaturation of FP caused by extreme acid condition. These findings suggest that pH-shifting can alter the gel properties of bi-polymeric starch-protein composite systems by affecting the secondary structures of proteins and the hydrogen bonding between the polymers, and provide a promising way for a wide application of FP in soft gel-type food production.

Disulfide cleavage to improve interfacial behavior and emulsification properties of oat protein.

Disulfide bonds play an essential structural role but may hinder the molecular flexibility and functionality of proteins. The present study investigated the effect of disulfide cleavage on emulsifying activity of oat protein isolate (OPI). Four reducing agents tested (dithiothreitol, ascorbic acid, cysteine, and sodium bisulfite) except ascorbic acid disrupted inter-subunit SS bonds of OPI (up to 90 %) in a dose-dependent manner. Emulsification properties were measured specifically on cysteine-modified OPI, and the results showed increased emulsifying activity up to 37 % after subunit dissociation, which exposed hydrophobic groups and loosened the structure. In particular, emulsions formed by cysteine-treated OPI (1.7 to 6.7 mM/mg protein) displayed a superior interfacial protein coverage (0.170 m2/mg compared to 0.092 m2/mg for control) and reduced emulsion particle size (from 4722 to 2238 nm). The application of cysteine as a structure-modifying food additive can broaden the utilization of oat protein in emulsion-based food products.

Comparative structural and emulsifying properties of ultrasound-treated pea (Pisum sativum L.) protein isolate and the legumin and vicilin fractions.

The structural properties, interfacial behavior, and emulsifying ability of ultrasound-treated pea protein isolate (PPI) and the legumin (11S) and vicilin (7S) globulin fractions prepared with a salt-solubilization procedure were investigated. Of the three protein groups, PPI was strongly responsive to ultrasound perturbation (20 kHz, 57-60 W·cm-2) showing the greatest solubility increase, particle size reduction, structure destabilization, and conformational change. Similar but less remarkable effects were observed on 11S globulins; 7S proteins, already highly soluble (>99%), were generally less sensitive to ultrasound. The ultrasound treatment significantly improved emulsifying activity, which resulted in greater emulsifying capacity and stronger interfacial adsorption for all protein samples. PPI exhibited the higher activity increase (70.8%) compared to approximately 30% for 11S and 7S. For both control and ultrasound treated proteins, the emulsifying capacity was in the order of 7S > 11S > PPI, inversely related to the trend of protein loading at the interface, indicating efficiency differences. The latter was attributed to emulsion clusters formed through protein-protein interaction in PPI and 11S emulsions which were visibly absent in 7S emulsions.

The Effect of Batter Characteristics on Protein-Aided Control of Fat Absorption in Deep-Fried Breaded Fish Nuggets.

Soy protein (SP), egg white protein (EP), and whey protein (WP) at 6% w/w were individually incorporated into the batter of a wheat starch (WS) and wheat gluten (WG) blend (11:1 w/w ratio). Moisture adsorption isotherms of WS and proteins and the viscosity, rheological behavior, and calorimetric properties of the batters were measured. Batter-breaded fish nuggets (BBFNs) were fried at 170 °C for 40 s followed by 190 °C for 30 s, and pick-up of BBFNs, thermogravimetric properties of crust, and fat absorption were determined. The moisture absorption capacity was the greatest for WS, followed by WG, SP, EP, and WP. The addition of SP significantly increased the viscosity and shear moduli (G″, G') of batter and pick-up of BBFNs, while EP and WP exerted the opposite effect (p < 0.05). SP, EP, and WP raised WS gelatinization and protein denaturation temperatures and crust thermogravimetry temperature, but decreased enthalpy change (ΔH) and oily characteristics of fried BBFNs. These results indicate that hydrophilicity and hydration activity of the added proteins and their interactions with batter matrix starch and gluten reinforced the batter and the thermal stability of crust, thereby inhibiting fat absorption of the BBFNs during deep-fat frying.

Multifaceted functionality of L-arginine in modulating the emulsifying properties of pea protein isolate and the oxidation stability of its emulsions.

The effects of L-arginine (Arg) at different concentrations (0%, 0.05%, 0.1%, 0.2%, 0.5% and 1.0%) on the antioxidant activity, structure and emulsifying properties of pea protein isolate (PPI) were explored. The intrinsic mechanisms of the reactions at different concentrations were specifically examined. With an increase in Arg concentration, the scavenging activities of ABTS+˙ and ˙OH and the Fe2+ chelating activity of PPI increased significantly (P < 0.05). The addition of Arg (0%-0.2%) significantly modified the PPI structure, causing an increase in protein solubility (from 66.2% to 79.0%) and a decrease in protein particle size (from 682 nm to 361 nm) (P < 0.05). In addition, treatment with Arg (0%-0.2%) effectively improved the emulsifying activity of PPI (by 28%), decreased the droplet size and viscosity of the emulsion, and enhanced the physical and oxidation stabilities of the emulsion. The increase in interfacial protein content and the absolute value of ζ-potential, and the microscopy images also showed that 0%-0.2% Arg treatment helped in forming a uniform and stable microemulsion. In contrast, a high concentration (0.5%-1.0%) of Arg diminished its positive effect on the emulsifying properties of PPI. Therefore, treatment with an appropriate concentration of Arg can significantly improve the emulsifying activity of PPI and enhance the stability of the emulsions.

Control of wheat starch rheological properties and gel structure through modulating granule structure change by reconstituted gluten fractions.

Reconstituted gluten fractions (RGF) varying in glutenin/gliadin (glu/gli) ratios was applied to change the property of wheat starch. The addition of RGF, irrespective of glu/gli ratio, significantly decreased the gelatinization enthalpy, viscosity, storage modulus (G'), and gel strength of starch. Starch particle size and leached amylose decreased by 4.5% and 22.2%, respectively, as the ratio of glu/gli changed from 1:0 to 0:1, indicating that the increase in gliadin ratio could inhibit swelling and rupturing of starch granules to a larger extent. Confocal laser scanning micrographs showed that gliadin could surround starch granules more effectively, thereby stabilizing the granule structure better than glutenin. With the increasing of gliadin ratio, the storage modulus (G') and loss modulus (G″) of the starch paste declined, accompanied by more loose gel structure and weaker gel strength. By varying the ratios of glu/gli in RGF, the change of wheat starch granule structure could be modulated, and therefore the rheological properties and gel structure could be regulated.

Electrical conductivity: A simple and sensitive method to determine emulsifying capacity of proteins.

Emulsifying capacity (EC) of proteins is a benchmark standard widely used to evaluate the quality of protein ingredients in emulsion foods. EC (mL of oil emulsified per g of protein) is usually measured by a sudden drop in electrical resistance (phase transition) with the continuous addition of oil to a specific protein solution. However, little is known about electrochemical mechanisms behind this process because resistance, measured with an ohmmeter, is not sensitive enough to monitor changes in the concentration of protein electrolytes. Here, pea (PPI), myofibrillar (MPI), and whey (WPI) protein isolates were vigorously homogenized with oil at a series of oil/protein ratios to prepare emulsions with different final protein concentrations. The conductivity was closely monitored using a conductivity meter. A linear relationship was discovered between conductivity and the final protein concentrations. At higher oil fractions, the migration of proteins from the aqueous phase to the oil-water interface limited protein mobility, leading to a conductivity drop. EC was calculated from the regression lines; when the starting protein concentration was raised from 0.5% to 2.0%, the EC of PPI, MPI, and WPI decreased from 717, 782, 1339 to 219, 303, and 540 mL oil/g protein, respectively. The dependence of EC on the initial protein concentration and the sensitivity of conductivity to the depleting protein electrolytes suggest that protein concentration is an important factor to consider when determining EC for a given protein or comparing EC among different proteins. PRACTICAL APPLICATION: The simple and sensitive electrical conductivity test described in this paper allows for the accurate determination of emulsifying capacity of proteins. It may be adopted by the food industry to compare the emulsifying properties of different protein ingredients.

Protein Oxidation in Foods: Mechanisms, Consequences, and Antioxidant Solutions.

Protein oxidation in foods remains a topic of the utmost scientific interest [...].

Physicochemical and Microstructural Characterization of Whey Protein Films Formed with Oxidized Ferulic/Tannic Acids.

Protein-based biodegradable packaging films are of environmental significance. The effect of oxidized ferulic acid (OFA)/tannic acid (OTA) on the crosslinking and film-forming properties of whey protein isolate (WPI) was investigated. Both of the oxidized acids induced protein oxidation and promoted WPI crosslinking through the actions of quinone carbonyl and protein sulfhydryl, and amino groups. OTA enhanced the tensile strength (from 4.5 MPa to max 6.7 MPa) and stiffness (from 215 MPa to max 376 MPa) of the WPI film, whereas OFA significantly increased the elongation at break. The water absorption capability and heat resistance of the films were greatly improved by the addition of OTA. Due to the original color of OTA, the incorporation of OTA significantly reduced light transmittance of the WPI film (λ 200-600 nm) as well as the transparency, whereas no significant changes were induced by the OFA treatment. Higher concentrations of OTA reduced the in vitro digestibility of the WPI film, while the addition of OFA had no significant effect. Overall, these two oxidized polyphenols promoted the crosslinking of WPI and modified the film properties, with OTA showing an overall stronger efficacy than OFA due to more functional groups available.

Partial Removal of Phenolics Coupled with Alkaline pH Shift Improves Canola Protein Interfacial Properties and Emulsion in In Vitro Digestibility.

The effect of polyphenol removal ("dephenol") combined with an alkaline pH shift treatment on the O/W interfacial and emulsifying properties of canola seed protein isolate (CPI) was investigated. Canola seed flour was subjected to solvent extraction to remove phenolic compounds, from which prepared CPI was exposed to a pH12 shift to modify the protein structure. Dephenoled CPI had a light color when compared with an intense dark color for the control CPI. Up to 53% of phenolics were removed from the CPI after the extraction with 70% ethanol. Dephenoled CPI showed a partially unfolded structure and increased surface hydrophobicity and solubility. The particle size increased slightly, indicating that soluble protein aggregates formed after the phenol removal. The pH12 shift induced further unfolding and decreased protein particle size. Dephenoled CPI had a reduced ß subunit content but an enrichment of disulfide-linked oligopeptides. Dephenol improved the interfacial rheology and emulsifying properties of CPI. Although phenol removal did not promote peptic digestion and lipolysis, it facilitated tryptic disruption of the emulsion particles due to enhanced proteolysis. In summary, dephenol accentuated the effect of the pH shift to improve the overall emulsifying properties of CPI and emulsion in in vitro digestion.