Properties Of Peanut Protein Isolate Research Articles

The structural and functional properties changing of peanut protein isolate (PPI) via different treatments and their application in pork meatballs production

Herein, the effects of pretreatment methods, such as ultrasound, enzymatic hydrolysis, and their cotreatment methods on the changes in structural and functional properties of peanut protein isolate (PPI) were investigated. The cotreatment method decreased the particle size, molecular weight, surface hydrophobicity, and order extent; moreover, the hydrophobic amino acids and secondary structure of PPI also changed during the cotreatment. Simultaneously, the cotreatment method positively affected the functional properties of PPI. Notably, the solubility could be greatly increased to 88% at pH 5 via ultrasound-papain (U–P) treatment, whereas emulsifying activity was improved to 143.97 m2/g via ultrasound-neutrase (U–N) treatment. Moreover, foaming capacity increased to 65% via U–P treatment, showing that the cotreatment method substantially improved the functional properties of PPI. Pork meatball preparation was used to further investigate the practical application of cotreated PPI. The results indicated that pork meatballs with ultrasound-alcalase (U-A) addition (PMU-A) and ultrasound-protamex (U–Pr) addition (PMU-Pr) exhibited better acceptance in terms of color, tissue status, and overall acceptability compared with control meatballs, indicating that the cotreated PPI has great potential in pork meatball production and can serve as a reference for PPI commercialization.

Effects of Different Amounts of Corn Silk Polysaccharide on the Structure and Function of Peanut Protein Isolate Glycosylation Products.

Covalent complexes of peanut protein isolate (PPI) and corn silk polysaccharide (CSP) (PPI-CSP) were prepared using an ultrasonic-assisted moist heat method to improve the functional properties of peanut protein isolate. The properties of the complexes were affected by the level of corn silk polysaccharide. By increasing the polysaccharide addition, the grafting degree first increased, and then tended to be flat (the highest was 38.85%); the foaming, foam stability, and solubility were also significantly improved. In a neutral buffer, the solubility of the sample with a protein/polysaccharide ratio of 2:1 was 73.69%, which was 1.61 times higher than that of PPI. As compared with PPI, the complexes had higher thermal stability and lower surface hydrophobicity. High addition of CSP could made the secondary structure of PPI change from ordered α-helix to disordered β-sheet, β-turn, and random coil structure, and the complex conformation become more flexible and loose. The results of multiple light scattering showed that the composite solution exhibited high stability, which could be beneficial to industrial processing, storage, and transportation. Therefore, the functional properties of peanut protein isolate glycosylation products could be regulated by controlling the amount of polysaccharide added.

Rheological properties of peanut protein isolate aggregation suspension and acid-induced gel

The dynamic rheological properties of peanut protein isolate (PPI) suspension and acid-induced PPI gels were studied. In frequency sweep test, the storage modulus (G′) and the loss modulus (G″) of PPI aggregation suspensions at different concentrations increased with the increase of frequency. The steady state shear flow test showed that PPI aggregation suspension had a thinning behavior of the shear, and the image of steady shear curve fitted the Carreau model. After gel formation, acid-induced PPI gels showed a typical Type I behavior (strain thinning) in strain sweep test, meaning that PPI gel got easily broken down, and there was a very small opportunity for the protein molecules to re-establish the network. Compared with the strain sweep of PPI aggregation suspensions and gels, the range of the storage modulus existed a dramatic difference, which could get about tenfold. As the frequency increased, both elasticity and viscosity increased in frequency sweep test, which indicated that the frequency dependence of the storage modulus increased with the increase of concentration. Keywords: peanut protein isolate (PPI), aggregation suspension, acid-induced PPI gel, dynamic rheological properties DOI: 10.25165/j.ijabe.20211403.6021 Citation: Huang Z G, Wang X Y, Chi S Y, Hua Z, Bi C H. Rheological properties of peanut protein isolate aggregation suspension and acid-induced gel. Int J Agric & Biol Eng, 2021; 14(3): 255–260.

Effect of urea concentration on properties of peanut protein isolate, arachin and conarachin-based adhesives during urea-epichlorohydrin modification.

To lay a theoretical basis for the preparation of peanut protein-based adhesives and promote the sustainable development of the adhesive industry, properties of peanut protein isolate (PPI), arachin and conarachin-based adhesives modified by urea and epichlorohydrin (ECH) were investigated under different urea concentrations. When the urea concentration was 2 mol l−1, the wet shear strength of the PPI-based adhesive was 1.24 MPa with the best water resistance. With the increase of urea concentration from 0 to 4 mol l−1, the apparent viscosity of the PPI-based adhesive increased from 3.87 to 136.80 Pa s and the solid content increased from 18.11% to 31.11%. Compared with conarachin-based adhesive, the properties of arachin-based adhesive were improved more obviously during the combined modification. Scanning electron microscopy images illustrated that when the urea concentration was 2 mol l−1, the surface of the PPI-based adhesive was more compact and smoother, which was beneficial to the improvement of water resistance and related to the structure changes of arachin and conarachin components. Fourier-transform infrared spectroscopy results indicated that different urea concentrations caused the change of ester and ether bonds in the PPI-based adhesive, which was mainly related to arachin component. Thermogravimetry results suggested that when the urea concentration was 2 mol l−1, the decomposition temperature of protein skeleton in the PPI-based adhesive reached a maximum of 314°C exhibiting the highest thermal stability. The improvement of the thermal stability of conarachin was greater than that of arachin during the combined modification.

Rheological properties of peanut protein isolate aggregation suspension and acid-induced gel

The dynamic rheological properties of peanut protein isolate (PPI) suspension and acid-induced PPI gels were studied. In frequency sweep test, the storage modulus (G′) and the loss modulus (G″) of PPI aggregation suspensions at different concentrations increased with the increase of frequency. The steady state shear flow test showed that PPI aggregation suspension had a thinning behavior of the shear, and the image of steady shear curve fitted the Carreau model. After gel formation, acid-induced PPI gels showed a typical Type I behavior (strain thinning) in strain sweep test, meaning that PPI gel got easily broken down, and there was a very small opportunity for the protein molecules to re-establish the network. Compared with the strain sweep of PPI aggregation suspensions and gels, the range of the storage modulus existed a dramatic difference, which could get about tenfold. As the frequency increased, both elasticity and viscosity increased in frequency sweep test, which indicated that the frequency dependence of the storage modulus increased with the increase of concentration. Keywords: peanut protein isolate (PPI), aggregation suspension, acid-induced PPI gel, dynamic rheological properties DOI: 10.25165/j.ijabe.20211403.6021 Citation: Huang Z G, Wang X Y, Chi S Y, Hua Z, Bi C H. Rheological properties of peanut protein isolate aggregation suspension and acid-induced gel. Int J Agric & Biol Eng, 2021; 14(3): 255–260.

Effect of ultrasound-assisted extraction on the structure and emulsifying properties of peanut protein isolate.

With an increasing demand for edible protein, research on new extraction methods is attracting more attention. The effects of such methods on functional properties are important. The present study aimed to evaluate the effect of ultrasound-assisted extraction on the extraction efficiency, structure, and the emulsifying properties of peanut protein isolate (PPI). Ultrasound-assisted extraction significantly improved extraction efficiency and shortened the processing time. The nanostructure, molecular weight distribution, and particle size of PPI were altered by ultrasound-assisted extraction. The emulsifying properties of the PPI from ultrasound-assisted extraction were significantly improved compared with alkaline extraction. Peanut protein isolate had lower molecular weight fractions, higher levels of hydrophobic amino acids, and the highest fluorescence intensity with ultrasound intensity, temperature, and time of 3.17 W cm-3 , 35 °C, and 30 min, respectively. These contributed to the higher emulsifying activity index and emulsifying stability index of the PPI emulsions. The uniform distribution of droplets and smaller particle size of the PPI emulsions was also observed. The results suggested that ultrasound can be used to induce the conformational changes to modify the interfacial association between protein-oil phases, thereby improving the emulsifying properties of peanut protein. © 2020 Society of Chemical Industry.

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.

Improved physicochemical properties of peanut protein isolate glycated by atmospheric pressure cold plasma (ACP) treatment

This study investigated the effects of the atmospheric pressure cold plasma (ACP) treatment on the glycation of peanut protein isolate (PPI) and dextran (Dex). The results showed a rapid conjugation between PPI and dextran with a degree of grafting (DG) of 21.62% after 1.5 min of treatment. The solubility and emulsion stability of PPI-Dex conjugates increased remarkably. SDS-PAGE analysis confirmed the coupling of PPI with dextran to form conjugates. After ACP treatment, the amino acid content analysis revealed a decrease in the content of lysine and phenylalanine. FTIR spectroscopy showed an increase in the absorption of the characteristic hydroxyl peaks at 3500-3000 cm−1 and 1260-1000 cm−1 of the PPI-Dex conjugates, a decrease in the content of α-helix and β-sheets, and an increase in the content of β-turns. These alterations were due to the ACP treatment that changed the structure of PPI from compact and hydrophobic to loose and hydrophilic.

Effects of freeze-thaw cycles on the structure and emulsifying properties of peanut protein isolates

This study investigated changes of the structure and emulsifying properties of peanut protein isolate (PPI) during multiple freeze-thaw (F-T) cycles. According to the Fourier transform infrared spectrum, the F-T treatment to PPI reduced the content of protein ordered structure significantly. The result of fluorescence spectrum revealed that the polarity of PPI surroundings first increased and then decreased. Similarly, the free sulfhydryl content and surface hydrophobicity of PPI increased firstly and decreased. However, the carbonyl content and particle size of PPI increased continuously after F-T treatment. The emulsification performance of PPI after F-T treatment was significantly improved. The emulsion prepared by PPI after 3 F-T cycles had the smallest mean particle size, the highest absolute value of zeta-potential and the most uniform microstructure distribution, showed the best performance of emulsifying ability. Therefore, it can be known that F-T cycles treatment could effectively change protein structure and improve protein emulsifying properties.

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.

Influence of heat treatment on structure, interfacial rheology and emulsifying properties of peanut protein isolate

The influence of heat treatment on the protein size, zeta potential, surface hydrophobicity, secondary structure, interfacial rheology and creaming stability of peanut protein isolate (PPI) was studied. Heat treatment of PPI increased the protein size, surface hydrophobicity and interface diffusion rate, and decreased the protein zeta potential, particularly heat treatment at 80°C for 30 min (PPI-80), which increased the surface hydrophobicity from 117.33 ± 2.77 to 253.24 ± 2.47. Interfacial rheology results demonstrated that the heat treatment promoted the absorption of PPI at the oil-water interface, which might be due to the increase of surface hydrophobicity. In contrast, the heat treatment at 90°C resulted in slightly lower surface hydrophobicity and K<sub>diff</sub> compared with PPI-80 due to the hydrolysis of partial protein aggregates during high temperature. Moreover, heat-treated PPI showed better emulsifying properties than unheated PPI. These results would be useful to expand the utilization of PPI products in the food processing industry.

The Molecular Properties of Peanut Protein: Impact of Temperature, Relative Humidity and Vacuum Packaging during Storage.

This study aimed to investigate the variation of molecular functional properties of peanut protein isolate (PPI) over the storage process and reveal the correlation between the PPI secondary structure and properties in the storage procedure. After storage, the molecular properties of PPI changed significantly (p < 0.05). Extending storage time resulted in a decrease in free sulfhydryl content, fluorescence intensity, surface hydrophobicity and emulsifying properties, which was accompanied by an increase in protein particle size. The results of infrared spectroscopy suggested the content decline of α-helix and β-sheet, and the content rise of β-turn and random coil. Based on bivariate correlation analysis, it was revealed that surface hydrophobicity and emulsifying activity of PPI was significantly affected by α-helix and by β-turn (p < 0.05), respectively. This research supplied more information for the relationship between the peanut protein’s secondary structure and functional properties over the stored process.

Dynamic rheological properties of peanut protein isolate and aggregation suspension and acid-induced gel

The dynamic rheological properties of peanut protein isolate (PPI) aggregation suspension and acid-induced PPI gels were studied. The strain sweep, frequency sweep, steady state shear flow test, and the time sweep were carried out on PPI aggregation suspension (23%–27%) and acid-induced PPI gel (14%–22%) separately. The frequency sweep curve fits the Power Law model very well, and the G′ of PPI aggregation suspensions and PPI gel were shown a greatly frequency dependence within the frequency range of 0.1Hz to 10Hz. The steady-state shear curve indicated well matched with the Carreau and Power Law model, which figured a shear-thinning behavior of the concentrations, and the constants estimated empirically showed shear rate dependence. The acid-induced PPI gel showed a Type I behavior (thinning of the strain), which the chains of acid-induced PPI consisted of a protein entanglement in the linear viscoelastic region (LVR), where the modulus is constant. With the strain rising, the protein chains disentangle and then correspond with the flow region. It was easily broken down and protein gel molecules have small opportunity to re-establish the entanglement.

Effect of flaxseed gum on the rheological properties of peanut protein isolate dispersions and gels

The effect of addition of flaxseed gum (FG) on the rheological and thermal gelation properties of peanut protein isolate (PPI) was studied. Small quantity (1–5 g/kg) of FG was added to PPI solution (140 g/kg) and the resultant rheological properties were studied using steady shear and small amplitude oscillatory measurements. The apparent viscosity of all samples increased with the increase from 1 to 5 g/kg in the concentration of FG and was fitted well by the Herschel-Bulkley model (R2 > 0.99). The addition of FG reduced the gelling time almost from 1000 to 500 s and increased the strength of FG-PPI mixed gels from 2000 to more than 3000 Pa. These FG-PPI gels showed the behavior of physical gels since their storage modulus (G′) was much higher than the loss modulus (G″) and G′ was only slightly frequency dependent.

Emulsifying properties and structure changes of spray and freeze-dried peanut protein isolate

The emulsifying properties of peanut protein isolate (PPI) prepared by spray- and freeze-drying methods were investigated together with the change in protein structure due to drying. Oil binding, water holding capacities and solubility of freeze-dried PPI were significantly higher (p ＜ 0.05) than those of the spray-dried one. The spray-dried PPI had higher emulsifying activity index (EAI), whereas the freeze-dried PPI had higher emulsion stability index (ESI).The freeze-dried PPI had significantly higher surface hydrophobicity, disulfide bonds and β-sheets than the spray-dried one (p < 0.05). While the latter contained more hydrogen bonds than the former (p < 0.05), as shown by the Fourier transform infrared spectroscopy, which suggested that the spray-dried PPI had relatively higher unfolded or flexible structure than the freeze-dried PPI.Folded and wrinkled morphology of spray-dried PPI but plate-shaped structure in the freeze-dried PPI suggested that droplet shrinkage and solute concentration led to the distinct morphology, respectively. These two different drying processes greatly brought about different structure and properties thereof. Thus, the freeze-dried PPI produced more stable emulsions (higher ESI), while the spray-dried PPI occupied the oil water interface faster (higher EAI).

Influence of ultrasonic treatment on the structure and emulsifying properties of peanut protein isolate

Effects of ultrasonic treatment on emulsifying properties and structure of peanut protein isolate (PPI) were evaluated by analysis of particle size distribution, protein surface hydrophobicity, SDS-PAGE, circular dichroism spectra and environmental scanning electron microscopy. The emulsifying properties of the PPI were found to be improved by ultrasonic treatment. The mean particle size decreased from 474.7nm to 255.8nm while the molecular weight remained unaffected. The results of intrinsic fluorescence spectroscopy and surface hydrophobicity indicated that ultrasonic treatment induced tertiary structural changes of the proteins in PPI. Emulsifying activity index and emulsion stability index were found to be correlated fairly well with surface hydrophobicity (H0) (r=0.712 and r=0.668, respectively).

Improvement of functional properties of peanut protein isolate by conjugation with dextran through Maillard reaction

Reaction mixtures containing peanut protein isolate (PPI) and dextran (1:1 weight ratio) were dry-heated at 60 °C and 79% relative humidity for 7 days. SDS–PAGE analysis indicated that PPI had become complexed with dextran to form conjugates of higher molecular weight. Arachin, accounting for 50% of peanut proteins, was hard to glycosylate with dextran, which might limit the extent of glycosylation of PPI. The thermal stability of PPI was remarkably improved by mixture/conjugation with dextran. Proteins in mixtures/conjugates might have a more compacted tertiary conformation than PPI. The protein solubility of conjugates at pH 4.5–6.0 was remarkably increased compared with the PPI/mixture. Mixture with dextran could significantly improve the emulsifying and foaming properties of PPI ( p < 0.05). Conjugation with dextran could further enhance emulsifying and foaming properties of PPI.

Effect of denaturation during extraction on the conformational and functional properties of peanut protein isolate

Abstract Peanut protein isolate (PPI) was extracted by alkali dissolution and acid precipitation from defatted peanut flour. The effects of extraction conditions on the denaturation and functional properties of PPI were investigated. In comparison with native peanut protein (NPP) which was extracted by ammonium sulfate, the PPI extracted by alkali dissolution and acid precipitation had a higher extent of denaturation. Arachin was affected more easily by the extraction process than conarachin and led to a noticeable decrease of thermal stability of PPI. PPI contained much lower sulfhydryl and disulfide bond contents than NPP. The analyses of intrinsic fluorescence spectra indicated a more compacted tertiary conformation of NPP than PPI. Extraction process influenced the functional properties of PPI, such as protein solubility, emulsifying activity index and foaming capacity. The relatively poor functional properties of PPI might be associated with protein denaturation/unfolding and subsequent protein aggregation. Industrial relevance Peanut is an important oilseed crop and a well-accepted food. After oil production through thermal treatment, the defatted peanut flour is the main byproduct, which possesses a large amount of proteins. However, due to the low extraction yield and poor functional properties of these proteins, they are not well utilised in industry till now. In this work, peanut proteins were extracted by two techniques. The results indicated that extraction technique could significantly modify the functional properties of peanut proteins. Therefore, this work is helpful for industrial utilisation of peanut proteins.

Enzymatic hydrolysis and their effects on conformational and functional properties of peanut protein isolate

The effects of limited enzymatic hydrolysis by Alcalase on the conformational and functional properties of peanut ( Arachis hypogaea L.) protein isolate (PPI) were investigated. Acid subunits of arachin were most susceptible to Alcalase hydrolysis, followed by conarachin and the basic subunits of arachin. Enzymatic hydrolysis increased the thermal stability of arachin and led to a sharp increase in the number of disulphide bonds with a decrease of the sulphydryl group in PPI hydrolysates in comparison with PPI. The analysis of intrinsic fluorescence spectra indicated a more moveable tertiary conformation of PPI hydrolysates than PPI. The limited emzymatic hydrolysis improved the functional properties of PPI, such as protein solubility and gel-forming ability, but impaired the emulsifying activity index.

Emulsifying properties of the transglutaminase-treated crosslinked product between peanut protein and fish (Decapterus maruadsi) protein hydrolysates

Defatted peanut meal, a protein-rich by-product from the oil extraction industry, is underutilised owing to its inferior functional properties. In this study, transglutaminase (TGase) crosslinking and proteolysis were used to improve the emulsifying properties of peanut protein isolate (PPI) extracted from the meal. PPI and PPI hydrolysate (PPIH) were conjugated separately with fish (Decapterus maruadsi) protein hydrolysate (DPH), catalysed by TGase to obtain improvements in the emulsifying properties. Analyses by electrophoresis and high-performance liquid chromatography indicated that polymers were formed in all TGase-treated samples. In emulsions of PPIH, PPI-DPH and PPIH-DPH the volume/surface average particle diameter (d(32) ), creaming and instability phenomenon were decreased and the zeta-potential was increased after TGase treatment, showing improved emulsifying activity and emulsion stability. In the case of PPI, TGase treatment had no effect on the emulsifying activity, but the emulsion stability of TGase-treated PPI was improved. The study showed that TGase crosslinking and proteolysis could improve the emulsifying properties of PPI, while proteolysis followed by TGase crosslinking proved more efficient. The emulsifying properties of the heterologous protein systems of PPI-DPH and PPIH-DPH were also improved by TGase treatment.