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/β-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).

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.

[Methylthioadenosine phosphorylase and p16 as surrogate diagnostic markers for CDKN2A homozygous deletion in brain tumors]

Objective: To examine whether immunohistochemistry of methylthioadenosine phosphorylase (MTAP) and p16 could be used to predict the CDKN2A status in various brain tumors. Methods: A total of 118 cases of IDH-mutant astrocytomas, 16 IDH-wildtype glioblastoma, 17 polymorphic xanthoastrocytoma (PXA) and 20 meningiomas diagnosed at Xuanwu Hospital, Capital Medical University, Beijing, China from November 2017 to October 2023 were collected and analyzed. The CDKN2A status was detected by using fluorescence in situ hybridization or next-generation sequencing. Expression of MTAP and p16 proteins was detected with immunohistochemistry. The association of loss of MTAP/p16 expression with CDKN2A homozygous/heterozygous deletion was examined. Results: Among the 118 cases of IDH-mutant astrocytoma, 13 cases showed homozygous deletion of CDKN2A. All of them had no expression of MTAP while 9 cases had no expression of p16. Among the 16 cases of IDH wild-type glioblastoma, 6 cases showed homozygous deletion of CDKN2A. All 6 cases had no expression of MTAP, while 3 of these cases had no expression of p16 expression. Among the 17 PXA cases, 4 cases showed homozygous deletion of CDKN2A, and the expression of MTAP and p16 was also absent in these 4 cases. Among the 20 cases of meningiomas, 4 cases showed homozygous deletion of CDKN2A. Their expression of MTAP and p16 was also absent. Among the four types of brain tumors, MTAP was significantly correlated with CDKN2A homozygous deletion (P<0.05), with a sensitivity of 100%. However, it was only significantly correlated with the loss of heterozygosity (LOH) of CDKN2A in astrocytomas (P<0.001). P16 was associated with CDKN2A homozygous deletion in IDH-mutant astrocytoma and PXA (P<0.001), but not with the LOH of CDKN2A. Its sensitivity and specificity were lower than that of MTAP. Conclusions: MTAP could serve as a predictive surrogate for CDKN2A homozygous deletion in adult IDH-mutant astrocytoma, PXA, adult IDH-wildtype glioblastoma and meningioma. However, p16 could only be used in the first two tumor types, and its specificity and sensitivity are lower than that of MTAP.

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.

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.

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, β-red, and α-white. Lambs fed SB had larger α-white (p < 0.10) and smaller-diameter β-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.

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.

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.

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.

[Effect of peer education on knowledge, attitude and practices towards schistosomiasis among primary school students in endemic foci of Wuhan City]

OBJECTIVE

To evaluate the effect of peer education on knowledge, attitude and practices towards schistosomiasis control among primary school students in endemic foci of Wuhan City.

METHODS

Yucai Hankou Primary School in Jiang' an District, Wuhan City was selected in 2021, and all students at grades 4 and 5 were sampled using a cluster sampling method to receive peer education about schistosomiasis. The changes of knowledge, attitude and practices towards schistosomiasis control were compared before and after peer education to evaluate the effect of peer education on knowledge, attitude and practices towards schistosomiasis control.

RESULTS

The overall awareness of schistosomiasis control knowledge and the overall proportion of correct attitudes towards schistosomiasis control and correct schistosomiasis-related behaviors increased from 51.50%, 93.70% and 92.99% before peer education to 86.50%, 98.98% and 98.72% after peer education among primary school students, respectively (χ²=149.457, 21.692 and 20.691, all P values < 0.05). The overall awareness of schistosomiasis control knowledge and the overall proportion of correct attitudes towards schistosomiasis control and correct schistosomiasis-related behaviors were 49.19%, 92.20% and 92.72% among Grade 4 primary school students and 53.83%, 95.21% and 93.28% among Grade 5 primary school students prior to peer education (χ² = 1.214, 2.034 and 0.096, all P values > 0.05), and increased to 75.93%, 98.09% and 97.59% among Grade 4 primary school students and 97.16%, 99.87% and 99.87% among Grade 5 primary school students after peer education, respectively (χ² = 40.798, 9.572, 7.207, 133.194, 9.678 and 14.926, all P values < 0.05). The overall awareness of schistosomiasis control knowledge and the overall proportion of correct attitudes towards schistosomiasis control and correct schistosomiasis-related behaviors were 51.25%, 76.92% and 77.97% among male primary school students and 51.80%, 94.42% and 95.70% among female primary school students prior to peer education, the differences in the overall proportion of correct attitudes towards schistosomiasis control and correct schistosomiasis-related behaviors between male primary school students and female primary school students were significant (χ² = 30.462 and 33.416, both P values < 0.05), and increased to 86.23%, 98.25% and 97.79% among male primary school students and 86.83%, 99.85% and 99.85% among female primary school students after peer education (χ² = 0.081, 3.529 and 3.335, all P values > 0.05), respectively.

CONCLUSIONS

Peer education is effective to improve the knowledge, attitude and practices towards schistosomiasis control among primary school students in endemic foci of Wuhan City, which may be more effective to improve the awareness of schistosomiasis control knowledge and proportion of correct schistosomiasis-related behaviors among primary school students at high grades.

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.

Muscle protein oxidation and functionality: a global view of a once neglected phenomenon

Muscle is a highly organized apparatus with a hierarchicmicrostructure that offers the protection of cellular components againstreactive oxygen species (ROS). However, fresh meat immediately postmortem andmeat undergoing processing become susceptible to oxidation due to physicaldisruption and the influx of molecular oxygen. Upon the activation byendogenous prooxidants, oxygen species are rapidly produced, and bothmyofibrillar and sarcoplasmic proteins become their primary targets. Direct ROSattack of amino acid sidechains and peptide backbone leads to proteinconformational changes, conversion to carbonyl and thiol derivatives, andsubsequent aggregation and polymerization. Interestingly, mild radical andnonradical oxidation enables orderly protein physicochemical changes, which explainswhy gels formed by ROS-modified myofibrillar protein has improved rheologicalproperties and binding potential in comminuted meat and meat emulsions. Theincorporation of phenolic and other multi-functional compounds promotes gelnetwork formation, fat emulsification, and water immobilization; however,extensive protein modification induced by high levels of ROS impairs proteinfunctionality. Now recognized to be a natural occurrence, once-neglectedprotein oxidation has drawn much interest and is being intensively studiedwithin the international community of meat science. This review describes thehistory and evolution of muscle protein oxidation, the mechanism andfunctionality impact hereof, and innovative oxidant/antioxidant strategies tocontrol and manipulate oxidation in the context of meat processing, storage,and quality. It is hoped that the review will stimulate in-depth discussion of scientificas well as industrial relevance and importance of protein oxidation and inspirerobust international collaboration in addressing this global challenge.&nbsp;

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.

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.

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.

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 β 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.

Synergistic recovery and enhancement of gelling properties of oxidatively damaged myofibrillar protein by l-lysine and transglutaminase

The influence of combined Lysine (Lys) and transglutaminase (TG) on the conformation and gelling properties of oxidatively damaged myofibrillar protein (MP) was investigated. The addition of Lys (5 mM) significantly increased the α-helix content (by 47.8%) and decreased the particle size of oxidatively damaged MP, and improved the cooking yield (by 16.8%) and the breaking strength of MP gels (by 65.5%). The treatment with TG (E:S = 1:500) led to a slightly reduced α-helix content but improved breaking strength (by 41.8%) and cooking loss (by 13.3%) of the gels. Their combination (Lys + TG) showed the greatest and synergistic overall improvement, with the set gel displaying a fine, smooth and compact network structure. Notably, the gelling ability of oxidatively damaged MP upon Lys + TG treatment was significantly stronger than that of non-oxidized MP far exceeding its recovery. Therefore, significantly enhanced gelling properties of oxidatively damaged MP can be attained through the combination Lys and TG.

Myoprotein-phytophenol interaction: Implications for muscle food structure-forming properties

Phenolic compounds are commonly incorporated into muscle foods to inhibit lipid oxidation and modify product flavor. Those that are present in or extracted from plant sources (seeds, leaves, and stems) known as "phytophenols" are of particular importance in the current meat industry due to natural origins, diversity, and safety record. Apart from these primary roles as antioxidants and flavorings, phytophenols are now recognized to be chemically reactive with a variety of food constituents, including proteins. In processed muscle foods, where the structure-forming ability is critical to a product's texture-related quality attributes and palatability, the functional properties of proteins, especially gelation and emulsification, play an essential role. A vast amount of recent studies has been devoted to protein-phenol interactions to investigate the impact on meat product texture and flavor. Considerable efforts have been made to elucidate the specific roles of phytophenol interaction with "myoproteins" (i.e., muscle-derived proteins) probing the structure-forming process in cooked meat products. The present review provides an insight into the actions of phytophenols in modifying and interacting with muscle proteins with an emphasis on the reaction mechanisms, detection methods, protein functionality, and implications for structural characteristics and textural properties of muscle foods.

Interfacial dilatational and emulsifying properties of ultrasound-treated pea protein

In this study, the structural, interfacial, and emulsifying properties of high-intensity ultrasound (HUS)-treated pea protein isolate (PPI_US) were investigated. HUS at 50% amplitude and 57-60 W·cm^-2 for 5 min markedly improved protein solubility (by 132%), surface hydrophobicity (by 173%), and reduced particle size (by 52%). These physicochemical changes in PPI_US led to more rapid protein adsorption at the oil-water interface, improved emulsifying activity (by 18-27%) and capacity (by 11%), and enhanced emulsion physical stability. The multilayer nature, albeit less elastic, of the interfacial membrane formed by PPI_US when compared to control protein (PPI_C), based on dilatational testing, contributed to the above results. Moreover, PPI_US-stabilized emulsions exhibited a tendency of being less susceptible to lipid oxidation during storage. Thus, structure-modifying HUS may be a valuable processing technology for the manufacture of pea protein-based emulsion foods.

Myofibrillar Protein Cross-Linking and Gelling Behavior Modified by Structurally Relevant Phenolic Compounds

Protein gelation is an important phenomenon in processed meats. The present study investigated the structure-activity relationship of six phenolic compounds, that is, gallic acid (GA), chlorogenic acid (CA), propyl gallate (PG), quercetin (QT), catechin (CC), and (-)-epigallocatechin-3-gallate (EGCG) in a myofibrillar protein (MP) gelling system under controlled oxidative conditions. All phenolics induced unfolding and promoted cross-linking of MP via sulfhydryl or amine groups. At an equal molar concentration, EGCG boosted the elastic MP gel network more than other phenolics except PG. However, all three monophenols (GA, CA, and PG) and the diphenol QT increased the MP gel strength more than CC (diphenol) and EGCG (triphenol). The flavanol structure appeared to interfere with the protein gel structure development. All phenolics retarded lipid oxidation in MP-emulsion composite gels during refrigerated storage with the least polar phenolic compounds, PG and QT, showing the greatest efficacy.

Animal and Plant Protein Oxidation: Chemical and Functional Property Significance

Protein oxidation, a phenomenon that was not well recognized previously but now better understood, is a complex chemical process occurring ubiquitously in food systems and can be induced by processing treatments as well. While early research concentrated on muscle protein oxidation, later investigations included plant, milk, and egg proteins. The process of protein oxidation involves both radicals and nonradicals, and amino acid side chain groups are usually the site of initial oxidant attack which generates protein carbonyls, disulfide, dityrosine, and protein radicals. The ensuing alteration of protein conformational structures and formation of protein polymers and aggregates can result in significant changes in solubility and functionality, such as gelation, emulsification, foaming, and water-holding. Oxidant dose-dependent effects have been widely reported, i.e., mild-to-moderate oxidation may enhance the functionality while strong oxidation leads to insolubilization and functionality losses. Therefore, controlling the extent of protein oxidation in both animal and plant protein foods through oxidative and antioxidative strategies has been of wide interest in model system as well in in situ studies. This review presents a historical perspective of food protein oxidation research and provides an inclusive discussion of the impact of chemical and enzymatic oxidation on functional properties of meat, legume, cereal, dairy, and egg proteins based on the literature reports published in recent decades.

Sensitivity of oat protein solubility to changing ionic strength and pH

Understanding the relationship between ionic strength and protein solubility is essential to the utilization of salt in the formulation design of plant protein-based food and beverage products. In this study, suspensions of oat protein isolate (OPI) were treated with two kinds of common salts (sodium chloride NaCl; sodium phosphate NaP) at different ionic strengths (I). Electrical conductivity, protein solubility, particle size, and protein profile (sodium dodecyl sulfate-polyacrylamide gel electrophoresis) were analyzed. The results showed the highest protein solubility at extremely low I (< 0.005 for NaCl; < 0.012 for NaP) and a minimum solubility at I 0.03 to 0.2 depending on the type of salt. Particle size and electrophoretic patterns supported the solubility profile. The combination effect of ionic strength and pH was also investigated. A characteristic U-shaped solubility curve observed within pH 2.0 to 8.0 at low ionic strengths (I < 0.01) was altered by increasing the salt concentration. The findings demonstrate that ionic strength and ion species play a crucial role in oat protein solubility, and the ionic effect can be modified by changing the pH. Therefore, the application of appropriate salt concentrations is vitally important to the manufacture of oat protein-based food products. PRACTICAL APPLICATION: Sodium chloride and phosphate are two of the most widely utilized salts in food processing. This study highlights the relationship between ionic strength of the two salts and oat protein solubility at different pH levels, providing useful information for selecting proper salt concentrations in the manufacture of oat protein-based food products.

Effect of degree of milling on the cadmium in vitro bioaccessibility in cooked rice

Cadmium (Cd) contamination in rice grain is common worldwide. This study investigated the effect of degree of milling (DM) on the reduction of Cd in cooked rice grain and porridge (rice-to-water ratios 1:1.6 and 1:10, respectively) and Cd in vitro bioaccessibility. Cd-contaminated rice grains with DMs of 20%, 15%, and 0% were cooked and then subjected to successive digestion in a gastrointestinal environment model. Simulated-digestion juices, including saliva, gastric juice, duodenal juice, and bile juice, were used. The degree of gelatinization of cooked rice was measured and the morphological characteristics of the grain were also examined. The results showed that the Cd in vitro bioaccessibility, although less than 50% in all samples, was gradually increased with an increase of DM. The detected Cd bioaccessibility was higher at half meals (reduced grain content) when compared with full meals (full grain content). As DM increased, the surface of cooked rice grain and porridge became smoother, and the amount of fiber, fat droplets, and starch granules were gradually decreased, whereas degree of gelatinization increased. The results indicate that DM affects the Cd in vitro bioaccessibility in cooked rice by altering the gelatinization of starch. PRACTICAL APPLICATION: Degree of milling (DM) significantly influenced the in vitro bioaccessibility of cadmium (Cd) in cooked rice. This work may offer a potential solution to the rice grain with high Cd content because a limited DM will allow a low bioaccessibility of Cd.

Effect of the wheat starch/wheat protein ratio in a batter on fat absorption and quality attributes of fried battered and breaded fish nuggets

Battered and breaded fish nuggets (BBFNs) were prepared by treating fish with a batter composed of wheat starch (WS) and wheat protein (WP) blends (at the ratios of 15:1, 13:1, 11:1, 9:1, and 7:1, w/w), frying at 170 °C (40 s) followed by 190 °C (30 s). Fried BBFNs were evaluated for moisture and fat contents, color, shrinkage, acrylamide content, and fat distribution. Results showed that moisture content and brightness (L^* value from colorimetry) increased with a decrease of WS/WP ratio to 11:1 w/w, then decreased as WS/WP ratio further decreased, while fat content, fat distribution level, and shrinkage of fried BBFNs presented opposite results. However, there was a slight influence of WS/WP ratio on yellowness (b^* value), redness (a^* value), and acrylamide content of fried BBFNs. Among WS/WP ratios, fried BBFNs with 11:1 w/w have the highest moisture content (16.43%) and the lowest fat content (23.39%), fat distribution level, shrinkage (10.72%), and acrylamide content (57 mg/kg), while a crust with golden-yellow color was observed. This study demonstrates that moisture evaporation and fat absorption were significantly influenced by WS/WP ratio in the batter (P < 0.05), with the most effective results in quality attributes improvement of fried BBFNs. PRACTICAL APPLICATION: This study clearly showed that the fat content and quality attributes of fried BBFNs were significantly affected by WS/WP ratio in the batter (P < 0.05). The inhibition of fat absorption and improvement of shrinkage and color in fried BBFNs was the most effective for a 11:1 w/w WS/WP ratio.

Thermosonication-induced structural changes and solution properties of mung bean protein

Mung bean protein is considered a highly nutritive food ingredient, but its solution properties are not well defined. In this study, suspensions of mung bean protein isolate (MPI, 10%, w/v) were subjected to high intensity ultrasound (20 kHz, 30% amplitude) at varied durations (5, 10, 20, and 30 min) with controlled temperatures (30, 50, and 70 °C) to determine the effects of thermosonication treatment on physical properties of the protein solution. Results showed that thermosonication treatment significantly reduced the particle size and free sulfhydryl content of MPI in a time-dependent manner. Ultrasound increased surface hydrophobicity, and the exposure of nonpolar groups led to the formation of soluble aggregates. Changes in secondary structure of MPI were minimal at 30 and 50 °C but were significant at 70 °C. The dissociation of native components followed by reaggregation into soluble particles following ultrasound treatment at 70 °C resulted in remarkable improvements of protein solubility (>2 fold), clarity, and stability of the MPI suspensions. The findings indicated that thermosonication could be a promising technology for the processing of mung bean protein beverage.

Genipin-Aided Protein Cross-linking to Modify Structural and Rheological Properties of Emulsion-Filled Hempseed Protein Hydrogels

Genipin, a natural electrophilic cross-linker, was applied (5, 10, 20, and 30 mM) to modify hempseed protein isolate (HPI). Genipin treatments resulted in general losses of total sulfhydryls (up to 2.9 nmol/mg) and free amines (up to 77.3 nmol/mg). Surface hydrophobicity decreased by nearly 90% with 30 mM genipin, corresponding to similar tryptophan fluorescence quenching. The genipin treatment converted HPI into highly cross-linked polymers. Hydrogels formed with such polymers when also incorporated with hemp oil emulsions exhibited substantially enhanced gelling ability: up to 3.3- and 2.6-fold increases, respectively, in gel strength and gel elasticity over genipin-untreated protein. The genipin-modified composite gels also exhibited superior water-holding capacity. Microstructural analysis revealed a compact gel network filled with protein-coated oil globules that interacted intimately with the protein matrix when treated with genipin. Such gels remained readily digestible. Hence, genipin-treated hemp protein hydrogels show promise as functional food components.

Ultrasound-mediated interfacial protein adsorption and fat crystallization in cholesterol-reduced lard emulsion

Lard with a substantially reduced cholesterol content through aqueous enzyme extraction is an attractive source of lipid in healthy and nutritious emulsion food product development. The objective of this study was to elucidate the crystallization behavior (4-20 °C) of emulsions prepared from low-cholesterol lard in relation to protein emulsifier (2 and 4% whey protein isolate, WPI) and ultrasound (475 w, 5 min) treatments. The physicochemical properties and fat crystallization pattern of the emulsions were investigated. Emulsions with 4% WPI were superior to those with 2% WPI on interfacial adsorption and crystal size reduction. Ultrasonic treatment of prepared emulsions further decreased fat crystal size, promoted small and uniform crystal distribution, and slightly destabilized emulsions. Protein concentration and ultrasonic treatment had no obvious effect on crystal transition from β' to the more stable β-form based on X-ray diffraction. The melting properties determined by differential scanning calorimetry indicated that emulsified lard had a lower onset melting temperature than bulk lard, and with ultrasound treatment, the melting enthalpy increased remarkably. The ultrasound-induced change in fat crystalline structure and emulsion meta-stability may be valuable to the manufacture of healthy, emulsion-incorporated food products.

Textural and sensorial quality protection in frozen dumplings through the inhibition of lipid and protein oxidation with clove and rosemary extracts

BACKGROUND

Oxidation is a major reason for nutritional and quality loss of dumplings during frozen storage. The addition of spice extracts in frozen dumplings may limit and inhibit oxidative impairments. In this study, the antioxidant effects of clove extract (CE) and rosemary extract (RE) and their influence on sensory and quality attributes of the meat-based filler in frozen pork dumplings stored at -18 °C were investigated.

RESULTS

CE and RE significantly suppressed lipid and protein oxidation in terms of thiobarbituric acid-reactive substances and protein carbonyls (P < 0.05) formation. During frozen storage up to 180 days, the dumpling samples with antioxidants had a significantly higher breaking strength and lower cooking loss (P < 0.05) compared with the control, and the effect of RE was stronger than that of CE. Sodium dodecylsulfate polyacrylamide gel electrophoresis showed that samples with antioxidants had reduced protein crosslinking, hence less aggregation. Differential scanning calorimetry analysis proved that the dumplings with antioxidants during storage had a higher thermal stability than those of the control. Based on dynamic rheological testing, the addition of RE to dumpling fillers was more effective in enhancing the gelling capacity of myofibrillar protein compared to the control. Sensory panel results confirmed significant positive effects of both spice extracts on oxidative stability (reduced rancidity) and palatability (texture and juiciness) of dumplings.

CONCLUSION

The addition of phenolic-rich CE and RE in dumpling processing is an excellent approach for the inhibition of sensory and quality deterioration associated with oxidation during frozen storage. © 2019 Society of Chemical Industry.

Upregulation of antioxidant enzymes by organic mineral co-factors to improve oxidative stability and quality attributes of muscle from laying hens

This study investigated the impact of organic trace minerals (OTM: Fe, Cu, Mn, and Zn proteinates premix) and Se-yeast (0.25 mg/kg) as a feed supplement versus inorganic forms of the same minerals (sulfated) on the enzymatic (GPX, CAT, SOD), oxidative, and physicochemical properties of fresh breast muscle from 68-week old hens during storage (4 °C) for 0, 2, 4 and 6 days. OTM with Se-yeast was more effective than sulfated minerals or selenite for enriching meat with Zn, Se and vitamin E (P < .05). At only one-third of the full inorganic mineral supplementation level, OTM with Se-yeast still induced higher GPX activity and greater inhibition of lipid (58% less TBARS) and protein (24% less sulfhydryl loss) oxidation. The organic mineral treatments significantly decreased drip loss and improved color stability of meat when compared with inorganic mineral supplements. Enhanced muscle cellular antioxidant enzymatic activity by the mineral co-factors was plausibly implicated in the protection.

Fabrication and Physicochemical Characterization of Pseudosciaena crocea Roe Protein-Stabilized Emulsions as a Nutrient Delivery System

The aim of this study was to develop a protein emulsifier that can be used to construct a nutrient delivery system. Pseudosciaena crocea roe protein isolate (PRPI) was prepared and tested for its emulsifying properties. Benzyl isothiocyanate (BITC) was used as a model delivery nutrient in the constructed emulsions. The average particle size, zeta potential, and BITC retention rate of the emulsions were used as the main evaluation indexes, and confocal laser scanning microscopy was used to test the storage stability of the emulsions (composition: 5 mg/mL protein, 5% oil, 0 to 5 mg/mL BITC, pH 8). After storing at 20 °C for 7 days, the largest particle size of the emulsion at pH 8 increased from 274.27 to 280.82 nm. Storing at higher temperatures had a negative impact on the particle size and BITC retention rate. On the seventh day, the average particle size at 20 and 4 °C was 289.63 nm and 275.67 nm, respectively, and the BITC retention rate at 20 °C (83.30%) was found to be 15.50% lower than that at 4 °C (98.58%). These results demonstrate that the PRPI-based emulsion system is effective in protecting nutrients and has excellent stability at 4 °C. PRACTICAL APPLICATION: This study provides some useful information for the food industry to develop a nutrient delivery system emulsified with fish roe protein isolate. The properties of the isolated protein and its protective effect on nutrients are discussed.

Physiochemical Properties and Functional Characteristics of Protein Isolates from the Scallop (Patinopecten yessoensis) Gonad

Protein isolates were recovered from scallop (Patinopecten yessoensis) gonads to develop a novel functional matrix by investigating their physiochemical and functional properties. Scallop gonad protein isolates (SGPIs) were prepared from degreased scallop gonads (DSGs) by an alkali extraction and isoelectric solubilization/precipitation (ISP) process. The protein compositions of the SGPIs were mainly vitellogenin and beta-actin with molecular weights of 266 and 42 kDa, respectively, as determined using Nano-liquid chromatography-mass/mass (Nano-LC-MS/MS). After the ISP process, the protein solubility of the SGPIs was significantly improved, and the surface hydrophobicity of SGPIs intensely increased by 1.1-fold, which were attributed to the exposure of aromatic residues such as phenylalanine, tyrosine, and tryptophan. However, the content of total/reactive sulfhydryl in SGPIs was decreased compared with that of DSGs. Meanwhile, the ISP process caused partial protein unfolding, as indicated by circular dichroism analysis, which exhibited a remarkable rise in the β-sheet content with a parallel decline in the α-helix and random coil contents (P < 0.05). SGPIs exhibited a better oil absorption capacity and foaming property than both DSGs and soybean protein isolates (SPIs). Moreover, the emulsifying capacity of SGPIs was greatly enhanced by the ISP process, which was superior to the effect of commercial SPIs and was ascribed to its favorable solubility as well as surface characteristics. PRACTICAL APPLICATION: During the processing of scallop (Patinopecten yessoensis) adductors, scallop gonad, a high-protein part, is usually discarded as processing by-products despite its edibility. In recent years, scallop gonads are regarded as good sources to develop protein matrices due to their high protein content and numerous nutrients. In this study, scallop gonad protein isolates (SGPIs) were isolated by isoelectric solubilization/precipitation (ISP) process. The preferable solubility, foaming property coupled with high emulsifying property of SGPIs indicated that the SGPIs could be potentially utilized as a good protein emulsifier and additives in production of kamaboko gels, hamburger patties, sausages, and pet foods.