Properties Of Heat-induced Gels Research Articles

Synergistic Improvement of Quinoa Protein Heat-Induced Gel Properties Treated by High-Intensity Ultrasonic Combined with Transglutaminase

Synergistic Improvement of Quinoa Protein Heat-Induced Gel Properties Treated by High-Intensity Ultrasonic Combined with Transglutaminase

Effect of high pressure shucking on the gel properties and in vitro digestibility of myofibrillar proteins from red swamp crayfish (Procambarus clarkii)

The effect of high pressure shucking (HPS) on heat-induced gelation properties of myofibrillar proteins from shucked crayfish meat mince was investigated, by comparing with conventionally industrial shucking methods (i.e., freeze-thawing and cooking). The texture, color, water holding capacity, water distribution, microstructure, protein patterns and secondary structure as well as the pepsin digestibility and antioxidant activity of gels were evaluated. Compared to conventional shucking, HPS at 300 MPa resulted in good-quality gels with improved mechanical properties and desirable reddish color. The treatment seemed to be conducive to the maintenance of astaxanthin, although it slightly reduced the water holding capacity and proportion of T22 water. SEM analysis showed that the gels treated by HPS at 300 MPa had a more orderly and uniform microstructure with reduced pore size. Under this scenario, more myosin heavy chains appeared to be involved in the crosslinking as revealed by SDS-PAGE. However, FTIR results suggested that no obvious change was found in the protein secondary structure of gels. Intriguingly, HPS of 300 MPa enhanced the pepsin digestibility and ABTS-radical scavenging activity of the gels during in vitro digestion. These findings underlined the advantages of HPS for creating new gel-type products based on crayfish meat.

Effects of micro-/nano-scaled chicken bones on heat-induced gel properties of low-salt pork batter: Physicochemical characteristics, water distribution, texture, and microstructure

The effect and mechanism of micro-/nano-scaled (MCB/NCB) chicken bones on improved gel properties of low-salt (0.5%) pork batters (LSPB) were investigated. Results showed that the Ca2+ released from MCB/NCB induced protein conformational transition of LSPB from α-helix and β-turn to random coil, which facilitated the orderly protein aggregation, resulting in the formation of denser and more uniform gel network. The better-organized gel network not only improved the textural properties and gel strength, but also contributed to the cooking loss reduction, water release decline, water state transition from free water into more immobilized water, and proton density increase, resulting in better sensory attributes. NCB showed more preferable effects on the property improvement of LSPB gels than MCB, because of its smaller particle size, less redness and yellowness, higher dispersibility, and higher Ca2+ release. This study could help promote the high-value utilization of poultry by-product bones and development of low-salt meat products.

Heat-induced gel properties and gastrointestinal digestive properties of egg white produced by hens fed with selenium-enriched yeast

The aim of this study was to investigate the effect of selenium enrichment on the gel properties and gastrointestinal digestive properties of egg white. Results of texture profile analysis, scanning electron microscopy and differential scanning calorimetry showed that the heat-induced gel of selenium-enriched egg white (EW-2) exhibited higher gel strength, smoother microstructure, and higher thermal denaturation temperature than ordinary egg white (EW-1), which might be due to the change of ovomucin and ovotransferrin content. The gastrointestinal digestive products of the EW-2 protein contained a higher proportion of small peptides and more free amino acids than those of EW-1. Results of oxygen radical absorbance capacity and cellular antioxidant activity assays indicated that digestive products of the EW-2 protein exhibited stronger antioxidant activity than those of the EW-1 protein. In summary, Se enrichment improved heat-induced gel properties of egg white, and promoted the gastrointestinal digestion of egg white protein.

L-Histidine Modifies the Structure and Heat-induced Gel Properties of Whey Protein

L-Histidine Modifies the Structure and Heat-induced Gel Properties of Whey Protein

Thermal stability and rheological properties of heat-induced gels prepared using edible insect proteins in a model system

We investigated the thermal stability and rheological properties of heat-induced gels prepared using edible insect proteins originating from various edible insect species: Tenebrio molitor L., Protaetia brevitarsis larvae, and Allomyrina dichotoma larvae. The protein solubility and pH of the heat-induced gel prepared from A. dichotoma exhibited the highest value (P < 0.05) among all samples. The redness and yellowness (P < 0.05); water holding capacity (P < 0.05); and springiness, cohesiveness, gumminess, and chewiness (P < 0.05) of the heat-induced gel from P. brevitarsis showed the highest values. The apparent viscosity of the gel from P. brevitarsis was higher than that of the other samples (P < 0.05). The storage modulus (G′) and loss modulus (G″) of the gel from T. molitor were lower than those of the gel from P. brevitarsis and A. dichotoma. Compared to the edible insect proteins obtained from T. molitor, those from P. brevitarsis and A. dichotoma were more heat stable, with a more complex structure, and showed various peak temperatures. P. brevitarsis and T. molitor gels displayed the highest and lowest emulsion capacity, respectively (P < 0.05). Thus, the gels from P. brevitarsis and A. dichotoma proteins exhibited excellent processing functionalities as heat-induced gels.

Impact of phosphates on heat-induced egg white gel properties: Texture, water state, micro-rheology and microstructure

The impact of phosphates (sodium pyrophosphate, sodium tripolyphosphate and sodium hexametaphosphate) on gelling properties of heat-induced egg white gel were investigated in this study. The hardness and springiness of the gels treated with sodium pyrophosphate and sodium tripolyphosphate were significantly improved compared with the control group. The hardness of sodium tripolyphosphate-treated gel was increased to 768.17 g when heated for 30 min and the springiness of sodium pyrophosphate-treated gel increased to 1.09 when heated for 30 min. The water holding capacity (WHC) of the sodium pyrophosphate-treated gel reached 85.57% when heated for 45 min. This improvement was ascribed to the formation of more ordered network structure. At 30 min of heat induction, the disulfide bond content of the gels treated with sodium pyrophosphate and sodium tripolyphosphate were 0.98 and 0.96, respectively. Moreover, decreasing mobility of water in the phosphate-treated gel was obtained with the heat induction time increased. The results of micro-rheological analysis showed that sodium pyrophosphate and sodium tripolyphosphate had better effects on the gel properties than sodium hexametaphosphate. Scanning electron microscopy showed that dense and uniform network structure and small pores appeared in the phosphate-treated gels. These results provided an important basis for phosphates to improve the heat-induced gel properties of egg production, and further expanded the application of phosphate additives in the food processing industry.

Simultaneous application of hydrostatic pressure and microbial transglutaminase as pretreatment to improve the physicochemical properties of heat-induced gels from tilapia surimi paste

Tilapia pastes were subjected to pretreatment using a combination of hydrostatic pressure processing (HPP) (0.1 to 300 MPa/25°C/60 mm) and simultaneous addition of microbial transglutaminase (MTGase) (0.044 unit/g of paste), which was followed by cooking at 90°C for 20 mm, to investigate the changes in the physicochemical properties of heat-induced gels. The pretreatment with MTGase at 300 MPa produced a gel having the strongest breaking force and strain compared with all the other treatments in the study; the gel strength was 3.5 times higher than that of the gel obtained by the 300 MPa treatment without adding MTGase. The combined use of MTGase and HPP for pretreatment could also improve the water-holding capacity of the gel, the value of which ranged from 63.12 to 89.34%. Adding MTGase also could decrease protein solubility under different pressure treatments. Thus, pretreatment of the sample is a better way to improve the gel-forming ability of tilapia surimi.

Synergistic effect of pH shifting and mild heating in improving heat induced gel properties of peanut protein isolate

Peanut protein isolate (PPI) was first subjected to pH shifting treatment at pH 7 or pH 10 with temperatures ranging from 25 °C to 70 °C. Then the structure and heat induced gel properties of PPI were investigated. The breaking force and water holding capacity of PPI10-40 (PPI after pH shifting with pH 10 at 40 °C) gel were 2.2 times and 2.15 times that of PPI7-25. Moreover, they were higher (p = 0.001637, p = 0.000916, p = 0.000021, p = 0.23) than that PPI7-40 or PPI10-25, indicating the synergistic effect of pH shifting and mild heating in improving the gel properties of PPI. These results were probably because the particle size of PPI10-40 decreased was 1.8 times that of PPI7-25 measured from DLS. Moreover, the solubility, free sulfhydryl content and surface hydrophobicity of PPI10-40 were 1.3 times, 1.8 times and 1.6 times that of PPI7-25 respectively, which resulted in enhanced covalent or non-covalent interactions between proteins. Circular dichroism and intrinsic fluorescence spectroscopy suggested that both heating and pH shifting significantly changed the secondary and tertiary structure of PPI. So the combined treatment of pH-shifting and mild heating is an efficient method to improve the gel properties of PPI (PPI10-40) to the maximum extent.

Enzyme‐catalyzed acylation improves gel properties of rapeseed protein isolate

Although rapeseed protein isolate (RPI) possessed some good functional properties, the use of RPI as an ingredient in the food industry is restricted mainly due to its inferior gelation. The purpose of this study was to improve the heat-induced gel properties of RPI using double processes of acylation and additional transglutaminase catalysis. Scanning electron microscopy showed that the gel formed by native RPI exhibited randomly aggregated particulate network structures whereas transglutaminase (TG)-assisted RPI gels significantly improved gelation properties. More importantly, the combined modifications of RPI using TG-assisted acylation can form a gel with unique percolating and small porous structure. Furthermore, TG-catalyzed 5% acylated RPI gel (100 U g-1 , protein basis) exhibited excellent gel properties in terms of gel strength, thermal stability, surface roughness and apparent viscosity compared to non-treated or single modification of RPI gel as determined by texture analyzer, atomic force microscopy and rheometer. Mechanistically, Fourier-transform infrared spectra and gel dissociation test revealed that TG-catalyzed acylation extensively unfolded the hydrophobic and sulfhydryl residues of RPI, in turn, reinforced re-assembly of protein molecules via hydrophobic interactions and disulfide bonds during gel formation. Combined processes of acylation and additional TG catalysis improved the thermal gelation properties by altering inter- and intra-protein structures. Such sequential processes will provide a promising approach to improve the protein gelation that could be potentially applied in the food industry. © 2020 Society of Chemical Industry.

Characterization of healthier mixed surimi gels obtained through partial substitution of myofibrillar proteins by pea protein isolates

Mixed surimi gels with 8%, 10% and 15% of pea protein isolate (PPI) were made in order to replace part of the myofibrillar proteins with PPI. Phytochemical, mechanical, viscoelastic and structural properties of heat-induced gels were analysed. Resulting gels contained low amounts of galactosides, inositol phosphates, protease inhibitors and phenolic compounds with potential specific health roles. A coupled PPI-myofibrillar matrix was produced on a basis of water binding capacity, electrophoresis profile, reticular flexibility and homogeneous microstructure. Mixed gels were less rigid (lower complex modulus -G*-) and exhibited slightly greater water binding ability than control gel. Addition of 8% and 10% PPI improved conformational flexibility, energy stability and elastic character. In mixed gels with 15% PPI the continuity of the mixed-protein matrix was disrupted and the mechanical and viscoelastic parameters deteriorated. Mixed surimi gels with 8% or 10% were thus more sustainable and healthy for use in meat or seafood analogue processing.

Effect of pH-shifting treatment on structural and heat induced gel properties of peanut protein isolate

Modifying proteins with new methods to improve their functional properties is essential to extend their application in food related field. In this study, the effect of pH-shifting treatment on structural and heat induced gel properties of peanut protein isolate (PPI) were investigated. PPI was subject to different pH conditions (pH 2, pH 4, pH 10, and pH 12) for 1 h, then adjusted back to pH 7 and they were marked as PPI2, PPI4, PPI10, and PPI12, respectively. It was found that the breaking force (BF) and water holding capacity (WHC) of PPI10 gel were significantly improved due to the decreased particle size, increased solubility, free sulfhydryl group content and surface hydrophobicity of PPI10. While PPI2 or PPI12 lost their gel ability due to the formation of large protein aggregates. These results indicated that pH-shifting treatment might be a convenient and economical method to prepare PPI with different gel and structural properties.

Underlying mechanism for the differences in heat-induced gel properties between thick egg whites and thin egg whites: Gel properties, structure and quantitative proteome analysis

Fresh chicken egg whites can be easily categorized into two types, including the colloid-like egg white and the solution-like egg white, which are called thick egg white (TKEW) and thin egg white (TNEW), respectively. In the present study, the heat-induced gel properties of TKEW and TNEW were systematically analyzed and compared. The results showed that TKEW (72.51 °C) had higher temperature of heat denaturation than TNEW (67.01 °C). The texture profile analysis demonstrated that the TKEW gel appeared soft and tough (lower hardness and higher cohesiveness), while the TNEW gel appeared hard and brittle (higher hardness and springiness, but lower cohesiveness). SEM images showed that the TKEW gel exhibited a “mesh structure” with “mountain-like” protrusions and micropores, while the TNEW gel exhibited a “block structure” with a dense section and “rope-head” protrusions. Quantitative proteomic analysis revealed that a higher content of ovotransferrin in TNEW might be the main reason for its lower temperature of thermal denaturation, and a higher content of ovomucin in TKEW might regulate the microstructure of the gel during heating and cause the differences in the gel texture properties. Overall, this study provides insights into the mechanism for the differences of heat-induced gel properties between TKEW and TNEW from the comprehensive “composition-structure-function” perspective, and can give guidance for the regulation of egg white gel properties during its application.

Combined Use of Rheology, LF-NMR, and MRI for Characterizing the Gel Properties of Hairtail Surimi with Potato Starch

The effects of potato starch (4%, 8%, 12%, 16%, and 20%) on the gel properties of hairtail surimi were investigated by rheology, low-field nuclear magnetic resonance (LF-NMR), and magnetic resonance imaging (MRI). The results indicated that the addition of potato starch markedly improved the gel properties, including the maximum texture profiles, gel strength, and water holding capacity. The addition of potato starch significantly increased both the storage modulus and loss modulus after the formation of gel rather than changed the type of two curves. Furthermore, there was a positive correlation between heat-induced gel properties and rheological properties in the surimi-starch system. The LF-NMR results indicated that the addition of potato starch had a positive effect toward the shortening of T2 spin-spin relaxation time of gel and water exchange from free water to bound water. Additionally, more uniform water distribution in surimi gel contained potato starch was observed from the result of MRI. The overall results suggested that interactions of starch-protein promoted the most favorable properties of hairtail surimi at the addition of 16% potato starch.

Phytase treatment of a protein-enriched rice bran fraction improves heat-induced gelation properties at alkaline conditions

The effect of phytase treatment on the technological functionality of a protein-enriched rice bran fraction produced by air classification was studied. Protein solubility and surface hydrophobicity were analysed and heat-induced gels formed at pH 5, 6.7 and 8 were characterised using rheological measurements, confocal laser scanning microscopy (CLSM) and by measuring water retention capacity. Phytase treatment decreased phytic acid content from 22% to 1–3%, depending on the dispersion dry matter content, which led to improved protein solubility at acidic pH 2–4. Similarly, phytase treatment increased protein surface hydrophobicity; however, the difference between phytase-treated and control sample was diminished after heat treatment. During heat-induced gelation the non-phytase-treated fraction formed viscoelastic structures at pH 6.7 and 8 with final Gʹ over 1000 Pa, while only weak gels were obtained at pH 5 (Gʹ ~100 Pa). Phytase treatment improved gelling ability of the fraction at pH 8 reaching significantly higher final Gʹ (11 340 Pa) and water holding capacity (77.8%) compared to the non-phytase-treated gel (1140 Pa and 54.6%, respectively). At pH 5 and 6.7 gel characteristics were not affected by phytase treatment. CLSM revealed a more evenly distributed protein and fibre network for phytase-treated protein-enriched rice bran gels formed at pH 8 compared to the other gels, which consisted of more void areas and densely packed protein aggregates. The results emphasise the advantage of using a phytase-treated protein-fibre ingredient from rice bran in gelled products both for techno-functional and nutritional quality improvement.

Textural Properties of Heat-induced Gels Prepared Using Different Grades of Alaska Pollock Surimi under Ohmic Heating

Textural Properties of Heat-induced Gels Prepared Using Different Grades of Alaska Pollock Surimi under Ohmic Heating

Physicochemical characteristics and gel-forming properties of myofibrillar protein in an oxidative system affected by partial substitution of NaCl with KCl, MgCl2 or CaCl2

Effects of partial substitution of NaCl with KCl, MgCl2 or CaCl2 on oxidative characteristics of myofibrillar protein (MP) in a hydroxyl radical generating system and their heat-induced gel properties were investigated. Results indicated that MP oxidation is dependent upon the different chloride salt types and substitution degree. MP at 0.60 M NaCl was beneficial to protein unfolding and gel quality in the oxidative system. Increased formation of disulfide bonds affected the MP conformation and resulted in a large particle size and an aggregatednetworkofgel at the 50% substitution degree of KCl. The presence of CaCl2 or MgCl2 substitutes contributed to protein polymerization and insolubility. MP aggregation restrained the formation of dense and continuous gel networks during heating, and thus resulted in a low-grade gel. Ca2+ had more serious impact on gel properties than Mg2+, dependent on different cation effects. Substitution of 25% NaCl by KCl gave acceptable gel quality in MP.

Molecular forces and gelling properties of heat-induced gel from egg white protein glycated with isomalto-oligosaccharide

Glycation with fructo-oligosaccharide (FO) and isomalto-oligosaccharide (IMO) was employed to improve the heat-induced egg white protein (EWP) gels. Results showed that EWP glycated with IMO exhibited a greater degree of glycation (DG) and better gelling properties than those of FO-EWP conjugates. The electrophoresis and liquid chromatography mass spectrometry (LC-MS) indicated that IMO was successfully covalently cross-linked with EWP. Fourier transform infrared spectroscopy (FTIR) showed that the glycation increased the percentages of intramolecular and intermolecular β-sheets of EWP and lowered the contents of 310-helical structure. The rheological test indicated that the gel-forming temperature of EWP was brought forward with the increase of glycation time. Furthermore, the glycation could induce the formation of EWP gel characterized by the higher strength of hydrogen bonds and hydrophobic interactions and lower strength of disulfide bonds. The changes of intermolecular forces resulted in a fine network structure of EWP gel, which significantly enhanced the fracture strength, bound water relaxation proportion and water-holding capacity (WHC) of the gel. A positive correlation existed in the WHC and gel fracture strength. This study proved that glycation with IMO efficiently improved the gelling properties of EWP.

Development of functional egg-free flan using whey proteins and evaluation of heat-induced gel properties

Traditional flan is a pudding composed of egg, milk and sugar. In the present study, egg was substituted by colostrum or whey protein concentrate (WPC) as a source of whey proteins in order to develop a new functional dairy dessert. These formulations were compared with those of traditional or imitation flan (starch and hydrocolloids as a substitute for egg). Texture, viscosity, water holding capacity (WHC), sensory properties and antioxidant activity of flans were evaluated. The results showed that imitation flan had the highest hardness, gumminess and chewiness, while traditional flan was the highest in cohesiveness and springiness. However, colostrum flan behaved almost similar textural properties with those of traditional and WPC flans. The values of apparent viscosity and WHC were in the same range for colostrum, WPC and traditional flans. However, the viscosity and WHC of imitation flan were higher than those of other flans. Colostrum or WPC-flan possessed the highest antioxidant activity. Sensory characteristics of flan improved by addition of colostrum or WPC compared with imitation flan. Also, addition of colostrum or WPC did not significantly affect consumers acceptability compared to traditional flan. Flan containing colostrum or WPC provide a new recipe and could therefore be an effective functional dairy dessert with high antioxidative activity.

Gel properties of potato protein and the isolated fractions of patatins and protease inhibitors – Impact of drying method, protein concentration, pH and ionic strength

The use of plant protein in food products is increasing. Potato protein gelation is scarcely documented, therefore potato protein gel properties were tested for two whole protein isolates (freeze dried or spray dried) and the purified sub-fractions, protease inhibitors and patatins. The effects of protein concentrations, 8 or 15% (w/w), pH-range of 3.0–7.5, and 2 different levels of ionic strength; low (15 mM NaCl) or high (200 mM NaCl) on heat induced gel properties was studied by oscillatory rheology and by uniaxial compression. Spray drying did not impair gel properties of the whole protein isolates, with the spray dried isolate actually showing higher gel strength at most conditions.For whole protein isolates, gel strength expressed as the storage modulus (G′) had a minimum at pH 4.7 at both high and low salt. The isolated patatin fraction showed a similar trend at low salt, but at high salt the gel strength was very low at pH 3, with progressively higher values at pH 5 and pH 7.5. The protease inhibitor fraction gelled best at low salt and pH values below pH 3.3, while higher pH resulted in very weak gels with a 10-fold decrease in G’. Gel appearance was affected by protein sample, pH, and ionic strength. Both whole protein isolates and the protease inhibitor fraction formed translucent gels at pH 3.0 and ionic strength 15 mM, while patatin formed translucent gels at both pH 3.0 and pH 7.5 at low salt concentration. All other conditions resulted in opaque gels.