Hydrolysis Of Soy Protein Isolate Research Articles

Enhancing the catalytic efficiency of M32 carboxypeptidase by semi-rational design and its applications in food taste improvement.

Carboxypeptidase is an exopeptidase that hydrolyzes amino acids at the C-terminal end of the peptide chain and has a wide range of applications in food. However, in industrial applications, the relatively low catalytic efficiency of carboxypeptidases is one of the main limiting factors for industrialization. The study has enhanced the catalytic efficiency of Bacillus megaterium M32 carboxypeptidase (BmeCPM32) through semi-rational design. Firstly, the specific activity of the optimal mutant, BmeCPM32-M2, obtained through single-site mutagenesis and combinatorial mutagenesis, was 2.2-fold higher than that of the wild type (187.9 versus 417.8 U mg-1), and the catalytic efficiency was 2.9-fold higher (110.14 versus 325.75 s-1 mmol-1). Secondly, compared to the wild type, BmeCPM32-M2 exhibited a 1.8-fold increase in half-life at 60 °C, with no significant changes in its enzymatic properties (optimal pH, optimal temperature). Finally, BmeCPM32-M2 significantly increased the umami intensity of soy protein isolate hydrolysate by 55% and reduced bitterness by 83%, indicating its potential in developing tasty protein components. Our research has revealed that the strategy based on protein sequence evolution and computational residue mutation energy led to an improved catalytic efficiency of BmeCPM32. Molecular dynamics simulations have revealed that a smaller substrate binding pocket and increased enzyme-substrate affinity are the reasons for the enhanced catalytic efficiency. Furthermore the number of hydrogen bonds and solvent and surface area may contribute to the improvement of thermostability. Finally, the de-bittering effect of BmeCPM32-M2 in soy protein isolate hydrolysate suggests its potential in developing palatable protein components. © 2024 Society of Chemical Industry.

Comparison of prediction models for soy protein isolate hydrolysates bitterness built using sensory, spectrofluorometric and chromatographic data from varying enzymes and degree of hydrolysis

The bitterness of soy protein isolate hydrolysates prepared using five proteases at varying degree of hydrolysis (DH) and its relation to physicochemical properties, i.e., surface hydrophobicity (H0), relative hydrophobicity (RH), and molecular weight (MW), were studied and developed for predictive modelling using machine learning. Bitter scores were collected from sensory analysis and assigned as the target, while the physicochemical properties were assigned as the features. The modelling involved data pre-processing with local outlier factor; model development with support vector machine, linear regression, adaptive boosting, and K-nearest neighbors algorithms; and performance evaluation by 10-fold stratified cross-validation. The results indicated that alcalase hydrolysates were the most bitter, followed by protamex, flavorzyme, papain, and bromelain. Distinctive correlation results were found among the physicochemical properties, influenced by the disparity of each protease. Among the features, the combination of RH-MW fitted various classification models and resulted in the best prediction performance.

Including protein hydrolysates during thermal processing mitigates the starch digestion of resulted starch-based binary matrix

Staple foods with starch and protein components are usually consumed after thermal processing. To date, how including protein hydrolysates (with varied hydrolysis degrees) tailors the structure and digestion features of starch-based matrix with thermal processing has not yet been sufficiently understood. Here, corn starch (CS), soy protein isolate (SPI), and soy protein isolate hydrolysates (SPIH) with different hydrolysis time (5–60 min) were used to prepare starch-based binary matrices. With the addition of SPI or SPIH during thermal processing, the resultant binary systems exhibited higher thermal stability (breakdown visibility was increased by 1.9–10.8 times), denser networks, and fewer short-range orders (R995/1022 was decreased by up to 15.3 %). These structural changes allowed an inhibited starch digestion within the binary system, especially with increased SPI or SPIH content. Compared with CS, the content of resistant starch (RS) for CS-SPI binary complex (10:3 w/w) increased from 9.89 % to 16.69 %. Compared to SPI, SPIH inclusion displayed a stronger inhibitory effect on starch digestion since the reduced molecule size of SPIH probably enhanced its interplays with starch or amylase. For instance, the 10:3 w/w starch-SPIH 60 binary matrix possessed the highest RS content (19.07 %).

The anti-digestibility mechanism of soy protein isolate hydrolysate on natural starches with different crystal types

The effects of soy protein isolate hydrolysate (SPIH) on the physicochemical properties and digestive characteristics of three starch types (wheat, potato, and pea) were investigated. Fourier-transform infrared spectroscopy and molecular dynamics simulations showed that hydrogen bonds were the driving force of the interaction between SPIH and starch. Furthermore, the SPIH was predicted to preferentially bind to the terminal region of starch using molecular dynamics simulations. Compared to pure starch, adding 20 % SPIH to wheat starch, potato starch, and pea starch, the content of resistant starch increased by 39.71 %, 125.66 % and 37.83 %, respectively. Both the radial distribution function (RDF) and low field-nuclear magnetic resonance (LF-NMR) showed that SPIH reduced the flow of water molecules in starch, indicating that SPIH competed with starch for water molecules. Multiple characterization experiments and molecular dynamics simulations confirmed that the anti-digestibility mechanism of SPIH on natural starches with different crystal types could be attributed to the interaction between starch and SPIH, which decreased the catalytic efficiency of amylase. This study clarified the anti-digestibility mechanism of SPIH on natural starches, which provides new insights into the production of low-glycemic index foods for the diabetic population.

Characteristics of soy protein hydrolysate nanofibrils and their stabilization mechanism for Pickering emulsion: Interfacial properties, Rheology and stability

Enzymatic hydrolysis is an effective method to improve the physicochemical properties of soy protein isolate (SPI) nanofibrils and expand their application in stabilizing Pickering emulsion. In this work, the effects of enzymatic hydrolysis on the SPI fibrillation and the stabilization mechanisms of SPI hydrolysate nanofibrils for Pickering emulsion were investigated. According to sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) images and Thioflavin T (ThT) fluorescence data, a higher degree of hydrolysis (DH) contributed to releasing more small molecular weight peptides (mainly from α, α′, and β subunits) to improve apparent rate constant and surface hydrophobicity during fibrillation. When DH increased to 8%, SPI hydrolysate could form long and flexible nanofibrils and possessed the highest content of β-sheet (21.40%), when heated for 12 h. Enzymatic hydrolysis played various positive impacts on the interfacial properties of nanofibrils, including faster interfacial adsorption and near-neutral wettability (92.87°). SPI hydrolysate nanofibrils could impart enhanced gel-like structure and exceptional thermal stability to Pickering emulsions, resulting in a decrease in droplet size from 52.06 μm to 32.74 μm. This work will enhance the exploration of the formation mechanism of nanofibrils and broaden their application in the functional emulsion.

Characterization of the structure, antioxidant activity and hypoglycemic activity of soy (Glycine max L.) protein hydrolysates

This study aimed to hydrolyze soy isolate protein (SPI) using five enzymes (alcalase, pepsin, trypsin, papain, and bromelain) in order to obtain five enzymatic hydrolysates and to elucidate the effect of enzymes on structural and biological activities of the resulting hydrolysates. The antioxidant and hypoglycemic activities of the soy protein isolate hydrolysates (SPIEHs) were evaluated through in silico analysis, revealing that the alcalase hydrolysate exhibited the highest potential, followed by the papain and bromelain hydrolysates. Subsequently, the degree of hydrolysis (DH), molecular weight distribution (MWD), amino acid composition, structure, antioxidant activities, and hypoglycemic activity in vitro of SPIEHs were analyzed. After enzymatic treatment, the particle size, polymer dispersity index (PDI), ζ-potentials, β-sheet content and α-helix content of SPIEHs was decreased, and the maximum emission wavelength of all SPIEHs exhibited red-shifted, which all suggesting the structure of SPIEHs was unfolded. More total amino acids (TAAs), aromatic amino acids (AAAs), and hydrophobic amino acids (HAAs) were found in alcalase hydrolysate. For 1,1-Diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, metal ion chelating activity, α-glucosidase inhibitory activity and α-amylase inhibitory activity, alcalase hydrolysate had the lowest IC50; alcalase hydrolysate and papain hydrolysate had the lowest IC50 for hydroxyl radical scavenging activity. Physiological activity of SPIEHs was evaluated thoroughly by 5-Axe cobweb charts, and the results revealed that alcalase hydrolysate exhibited the greatest biological activities.

Ice Recrystallization Inhibition Activity of Soy Protein Hydrolysates.

Identifying and developing ice recrystallization inhibitors from sustainable food proteins such as soy protein isolate (SPI) can lead to practical applications in both pharmaceutical and food industries. The objective of this study was to investigate the ice recrystallization inhibition (IRI) activity of SPI hydrolysates, and this was achieved by using an IRI activity-guided fractionation approach and relating IRI activity to interfacial molecular activity measured by vibrational sum frequency generation (VSFG). In addition, the impact of molecular weight (MW) and enzyme specificity was analyzed using three different proteases (Alcalase, trypsin, and pancreatin) and varying hydrolysis times. Using preparative chromatography, hydrolysates from each enzyme treatment were fractionated into five different MW fractions (F1-F5), which were then characterized by high-performance liquid chromatography (HPLC). All SPI hydrolysates had IRI activity, resulting in a 57-29% ice crystal diameter reduction when compared to native SPI. The F1 fraction (of 4-14 kDa) was most effective among all tested hydrolysates, while the lower MW peptide fractions lacked activity. One sample (SPI-ALC 20-F1) had a 52% reduction of ice crystal size at a lower concentration of 2% compared to the typical 4% used. SFG showed a difference in H-bonding and hydrophobic interactions of the molecules on the water/air interface, which may be linked to IRI activity. This study demonstrates for the first time the ability of SPI hydrolysates to inhibit ice crystal growth and the potential application of SFG to study molecular interaction at the interface that may help illustrate the mechanism of action.

Ultrasound-assisted limited enzymatic hydrolysis of high concentrated soy protein isolate: Alterations on the functional properties and its relation with hydrophobicity and molecular weight

The effects of power ultrasound (US) pretreatment on the preparation of soy protein isolate hydrolysate (SPIH) prepared at the same degree of hydrolysis (DH) of 12 % were measured. Cylindrical power ultrasound was modified into mono-frequency (20, 28, 35, 40, 50 kHz) ultrasonic cup coupled with an agitator to make it applicable for high density SPI (soy protein isolate) solutions (14 %, w/v). A comparative study of the alterations of the hydrolysates molecular weight, hydrophobics, antioxidants and functional properties change as well as their relation were explored. The results showed that under the same DH, ultrasound pretreatment decelerated the degradation of protein molecular mass and the decrease rate of the degradation lessened with the increase of ultrasonic frequency. Meanwhile, the pretreatments improved the hydrophobics and antioxidants properties of SPIH. Both surface hydrophobicity (H0) and relative hydrophobicity (RH) of the pretreated groups increased with the decrease of ultrasonic frequency. Lowest frequency (20 kHz) ultrasound pretreatment had the most improved emulsifying properties and water holding capacities, although decrease in the viscosity and solubility were found. Most of these alterations were correspondence toward the change in hydrophobics properties and molecular mass. In conclusion, the frequency selection of ultrasound pretreatment is essential for the alteration of SPIH functional qualities prepared at the same DH.

Improvement of the encapsulation capacity and emulsifying properties of soy protein isolate through controlled enzymatic hydrolysis

Self-assembling nanoparticle made from soy protein hydrolysates has proved to be a promising delivery system due to its excellent biocompatibility and synthetic feasibility. In this study, the critical parameters that control the SPI hydrolysate structure and its encapsulation capacity have been assessed. Three different enzymes, including Flavorzyme, Neutrase and Alcalase, were selected to hydrolyze soy protein isolate (SPI), and a solvent evaporation method was used to fabricate β-carotene loaded nanoparticles. Microstructure observation, SDS-PAGE, surface hydrophobicity, and endogenous fluorescence analysis were carried out to examine the key structural factors influencing encapsulation efficiency of SPI hydrolysates nanoparticles (SPIHs). It was found moderate exposure of hydrophobic amino acids inside the 7 S globulin via Flavorzyme controlled hydrolysis can increase the surface hydrophobicity of SPIH, therefore improving its emulsifying properties, while excessive hydrolysis of 7 S by Alcalase would cause weak hydrophobic interactions between the hydrophobic amino acids, which restricted the binding site with β-carotene. Above results provide a foundation for fabricating nanoparticles encapsulating lipophilic compounds with high encapsulation rate from SPI hydrolysates (SPIH).

Anticholesterol Bioactive Peptides from Bromelain Hydrolysates of Mangrove Sonneratia alba Protein

Cholesterol with high levels in blood vessels can cause atherosclerosis, stroke, and sudden heart attack. Isolates soy protein have bioactive peptides that have the potential as anticholesterol. This research aims to determine the optimum conditions of hydrolysis and characterize bioactive peptides from soy protein isolate hydrolysates by the bromelain enzyme. Hydrolysis optimization conducted using the enzyme bromelain with levels of 0,2%; and 0,5% (w/v) and variation in incubation time 0, 1, 2, 3, 4, 5 to 6 hours at 45, 50 and 55°C. Protein hydrolysates analyzed the degree of hydrolysis (% DH) and tested anticholesterol activity test through HMG-CoA reductase inhibition test with pravastatin as a positive control. The results showed the optimum conditions hydrolysis of isolate soy protein were obtained at 2 hours, temperature 45 °C with enzyme concentration 0,5% that is by DH value of 40,22%. The highest anticholesterol activity was obtained from the hydrolysate with percent inhibition value of 82,80% (7.371 ppm). SDS-PAGE analysis results show the appearance of bands under 10 KDa and the results of fractionation of bioactive peptide fragments has a molecular weight of 2779 and 2609 Da.

Structural characterization, interfacial and emulsifying properties of soy protein hydrolysate-tannic acid complexes

With increasing awareness of health and sustainable dietary pattern, plant-based proteins have shown a growing interest as substitutes for animal proteins. Meanwhile, the non-covalent interaction of protein with natural phenolic compounds can be used to develop functional ingredients. In this work, Alcalase hydrolysates of soy protein isolate (HSPI) were used to fabricate complexes with tannic acid (TA), and their physicochemical properties were investigated and compared with soy protein isolate (SPI) and sodium caseinate (SC) to get insights into the advantage of polyphenol modification. The complex solution showed reduced particle size, higher turbidity, and higher surface charge with increasing TA concentration. The interaction mainly occurred through hydrogen bond and hydrophobic interaction, leading to the unfolding of protein molecular structure. The complexes displayed lower interfacial adsorption activity and reduced interfacial viscoelastic modulus upon increasing TA concentration possibly because of the interference of TA on the diffusion and molecule interaction of protein hydrolysates to form elastic films. Nonetheless, the complex-based emulsion showed enhanced emulsifying stability with small droplet size, superior oxidation stability, high physical stability against heat and freeze-thaw treatment due to the higher surface charge and formation of particle-stabilized interfacial membrane. These findings provide insights for developing plant-based protein with excellent emulsifying properties, which show great potential for application as SC substitute in dairy-free emulsified products.

Effects of soy protein hydrolysates on antioxidant activity and inhibition of muscle loss

Peptides show biological activity, and are more easily digested than complex proteins. In the present work, we evaluated the effects of soy hydrolysate on skeletal muscle. Soy protein isolate (SPI) was hydrolysed using 2% Alcalase (SPHA) and Flavourzyme (SPHF) at pH 8 for 3 h at 60°C, and at pH 7 for 3 h at 55°C, respectively. Antioxidant properties (total phenolic content and DPPH activity) and inhibition of muscle loss (myogenin, myosin heavy chain [MyHC], creatine kinase, and myostatin) by the SPI hydrolysates in C2C12 cells were compared with those of SPI. Alcalase produced more hydrolysed soy oligopeptides than Flavourzyme. Enzymatic hydrolysis increased the levels of essential amino acids, particularly in SPHF (2,466.85 mg/L) as compared to SPI (56.08 mg/L). The total phenolic contents of hydrolysates increased from 12.02 mg GAE/g in SPI to 22.87 and 18.67 mg GAE/g in SPHA and SPHF, respectively. The IC50 value of DPPH activity decreased four times after hydrolysis (SPI: 124.38, SPHA: 32.18, and SPHF: 30.21 mg/mL). SPHA and SPHF treatments increased the expression levels of both MyHC1 and MyHC3, as well as creatine kinase activity. A significant increase in MyHC3 expression was observed in SPHF at 10 µg/mL. Soy hydrolysates (SPHA: 93.5% and SPHF: 61%) induced a greater decrease in the expression of myostatin, a muscle reduction marker, than SPI (30.4%). In conclusion, soy hydrolysates may inhibit muscle loss, showing particularly better effects when Alcalase is used for hydrolysis.

Effects of soy protein isolate hydrolysate on physicochemical properties and in vitro digestibility of corn starch with various amylose contents

To explore the interaction regarding protein and corn starch with various amylose contents, high amylose corn starch (HACS), normal corn starch (NCS), and waxy corn starch (WCS) were co-heated with soy protein isolate hydrolysate (SPIH), and the physicochemical properties and in vitro digestibility of each of the three combined materials was analyzed. The SPIH inhibited the in vitro digestion of HACS and NCS, but promoted the in vitro digestion of WCS. SPIH restricted the hydration and expansion of NCS and WCS and increased their gelatinization temperatures; however, SPIH had no significant effect on HACS. It was found that the microstructure of the three types of corn starch were significantly different after freeze-drying because of the different distribution of water molecules in the samples with various amylose contents during gel formation. The setback (SB) and peak viscosity (PV) values of these three types of corn starch reduced with the increase of SPIH mainly because SPIH inhibits the interaction of starch chains. This research lead to a novel idea of using corn starch with various amylose contents in food.

Complex coacervation of soy protein isolate-limited enzymatic hydrolysates and sodium alginate: Formation mechanism and its application.

The complex coacervation of soybean protein isolate and polysaccharide has been widely applied for preparing biopolymer materials like microcapsule. In this study, hydrolytic soy protein isolate (HSPI) was prepared by mild hydrolysis of soy protein isolate (SPI) with fungal protease 400 (F400). The degree of hydrolysis (DH) for the enzymatic products was controlled at 1%-5%. Emulsification, oxidation resistance, and thermal stability were used to evaluate the performances of HSPI with different DH. The results showed that the HSPI with the hydrolysis degree of 2% had the optimal property. Subsequently, the complex polymer of HSPI/SA was prepared by the coalescence reaction of HSPI and sodium alginate (SA). The turbidity curves manifested the optimal complex coacervation occurred at the ratio of 7:1 (HSPI:SA). Fourier transform infrared spectroscopy (FTIR) presented that the reaction involved electrostatic interactions between -NH3 + in HSPI and -COO- in SA. Isothermal titration calorimetry experiments indicated that the complex coacervation reactions of HSPI and SA arose spontaneously. The microencapsulation by complex coacervation of HSPI and SA was further produced for embedding sweet orange oil. The thermogravimetric analysis (TGA) result revealed that the microencapsulation system of HSPI/SA had a better heat resistance than that using the SPI/SA complex polymer.

Investigation of enzymatic hydrolysis kinetics of soy protein isolate: laboratory and semi-industrial scale

Using parameters of optimal conditions from laboratory experiments often results in the loss of significant time and resources when trying to scale up the process. In this study, the comparison of results of laboratory and semi-industrial experiments of enzymatic hydrolysis of soy protein isolate is considered. The kinetics of peptides accumulation was investigated by colorimetric method in both microtube (volume reaction is 0.7 ml, 7.14 mg/ml of substrate, incubation in solid state thermostat) and industrial homogenizer (volume reaction is 4,000 ml, 100 mg/ml of substrate, rotor–stator type mixer). The enzyme preparation Protosubtilin G3x (main component is subtilisin) was used as an analogue of the Alcalase preparation, which is already widely used in the food industry. It was found that the pH and the number of proteolytic units in the reaction mixture of both scales had slightly different results of the kinetics, while the temperature showed significantly one. The laboratory scale of the reaction had a wide range of optimal temperature (40–60 ^{circ }C, 30 ^{circ }C showed slowest rate of kinetics reaction), whereas the semi-industrial scale had 50 ^{circ }C of optimal temperature (30, 40, 60 ^{circ }C had the same kinetics). It also was found that maintaining the pH value of the reaction mixture was not mandatory. The obtained results indicate the need to refine the process conditions using semi-industrial experiments before attracting industrial-scale resources. In the case of selection of conditions for the hydrolysis of soy protein isolate in production, it is necessary first of all to take into account the reaction temperature as the most irreproducible parameter when scaling.Graphical

Effect of enzymatic hydrolysis conditions on structure of soy protein isolate/gum arabic complex and stability of oil-in-water emulsion.

The emulsifying, antioxidant and foaming properties of soy protein isolate hydrolysates (SPH) can be improved by the addition of gum arabic (GA). We investigated the effects of different hydrolysis conditions on the complexation of SPH and GA, and the effects of the complex on the properties of emulsions. Fluorescence spectroscopy showed that the addition of GA had a stronger effect on bromelain and pepsin hydrolysates than trypsin hydrolysate, and therefore had a higher binding constant (KA ) and a larger number of binding sites (n). The addition of GA could also improve protein solubility and emulsifying ability. The emulsions prepared with complexes, especially the complex of GA and SPH obtained by pepsin hydrolysis for 3h, had a high absolute charge value, uniform particle size distribution, stable morphology, and good storage stability. After storage, the emulsification index (CI) of the emulsion only increased to 23.08%; its 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging activity was 24.37 ± 1.22% and its 2,2'-Azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS+ ) free radical scavenging activity was largely retained. During long-term storage, pepsin-treated protein (especially protein treated for 3h) and GA can form a stable emulsion with antioxidant properties. This work provides new ideas for the development of natural and safe emulsifiers that have antioxidant properties and can be stored long-term and used in the food industry. © 2022 Society of Chemical Industry.

Effect of high-pressure processing enzymatic hydrolysates of soy protein isolate on the quality characteristics and oxidation stability of emulsion sausage

PurposeThis study aims to investigate the influence of soy protein isolate hydrolysates (SPIH) obtained using 4 h hydrolysis under 200 MPa on proximate composition, cooking loss, textural properties, color, water distribution, microstructure, thiobarbituric acid reactive substance (TBARS) value and carbonyl and sulfhydryl contents of emulsion sausages.Design/methodology/approachSausages with SPIHs at four concentrations (0, 1.0, 2.0 and 3.0%) were prepared, and the sausage with 0.01% butylated hydroxyanisole (BHA) was used as a positive control. Some sausages were selected for the analyses of quality characteristics and microcosmic properties. Other sausages were stored under 4 °C for 0, 7, 14, 21 and 28 days to investigate the oxidative stability.FindingsThe addition of SPIHs at various levels (0–3.0%) or 0.01% BHA did not affect the proximate composition (protein, fat and ash) of emulsion sausages. The addition of 2.0% SPIH decreased cooking loss and increased moisture content, hardness, springiness, chewiness, resilience and L* value, compared to the sausages without SPIH and with 0.01% BHA (p < 0.05). Furthermore, low-field nuclear magnetic resonance results suggested that sausages with 2.0% SPIH had the shortest T2 relaxation time. In addition, 2.0% SPIH and 0.01% BHA could inhibit the oxidation of emulsion sausages when compared with the sample without SPIH (p < 0.05). Moreover, there were no differences between sausages with 2.0% SPIH and 0.01% BHA (p > 0.05).Originality/valueThese findings confirmed that the 2.0% SPIH obtained under 200 MPa can be used as a natural additive to improve quality properties and antioxidant potential of emulsion sausages during storage.

Effect of modified soy protein isolate on dough rheological properties and noodle qualities

Soy protein isolate, soy protein hydrolysate (SPH), and texturized soy protein (TSP) were used to fortify flour nutrition, and the rheological properties of dough and qualities of noodles were determined. Soy proteins increased the peak viscosity of flour paste. Dough fortified with TSP also exhibited more solid-like behavior with the highest storage modulus, while dough fortified with SPH showed the lowest storage modulus. Soy proteins increased the cooking loss of noodles. The protein loss of SPH-W noodles was up to 32.0%, much higher than wheat noodles, 13.3%, while the protein loss of TSP-W noodles was only 14.3%. Three types of soy proteins weakened the gluten network on different levels. The larger protein molecules in TSP linked with glutenin and formed the higher molecular polymers, counterbalancing the weakening effects deriving from the interfering with the glutenin–glutenin linkages. Therefore, TSP is more suitable to utilize in noodles. Practical applications Wheat flour noodles are widely consumed in most countries, so the protein quality in noodles is critical to consumer health. The essential amino acid, lysine, is relatively deficient in wheat proteins. Soy protein is rich in lysine and could be used to fortify the nutrition of flour products. However, some negative effects of soy protein on the qualities of flour products have been observed. Therefore, we modified Soy protein isolate (SPI), hoping to increase the interaction between soy protein and wheat protein, and reduce the negative impacts of soy protein on qualities of noodles. Results showed texturized soy protein exhibited fewer negative effects on noodle qualities than SPI and soy protein hydrolysate. The results presented in this study provided us with some useful information about how to select soy proteins to fortify noodle nutrition.

Inhibition of ice crystal growth by protein hydrolysates from different plant- and animal-based proteins

Due to the quality deterioration and the corresponding waste of frozen foods, there is a constant need for an effective, consumer and environmentally friendly, and sustainable anti-freezing ingredient. Hence, in this study, enzymatic hydrolysis and food grade chemical modification (succinylation) were evaluated to produce ice recrystallization inhibition (IRI) active peptide-based ingredients. Six different types of plant- and animal-based proteins were evaluated. Soy protein isolate (SPI), after 15- and 60- min alcalase hydrolysis, demonstrated a significant IRI activity compared to polyethylene glycol (PEG; as negative control) resulting in a two-third reduction of ice crystal size annealed at −8 ºC. Annealing temperature and peptide concentration also affected the IRI activity of SPI hydrolysate where decreased temperature and increased concentration resulted in a higher IRI activity. Increased hydrolysis time decreased the IRI activity of SPI hydrolysates but increased the IRI activity of sodium caseinate (SC) and pea protein isolate (PPI) hydrolysates. SPI-60 was less temperature resistant compared to SPI-15 which inhibited the growth of ice crystals (smaller than 23 µm). Moreover, chemical modification via succinylation reaction with OSA enhanced the IRI activity of the PPI and SPI hydrolysates leading to a 55.3% and 60.6% reduction in the size of ice crystals, respectively. Overall, this study demonstrates a great potential in the utilization of common food proteins for the production of value-added natural anti-freezing ingredients which could benefit the food industry by enhancing frozen foods’ shelf-life and reducing waste.

Influence of ultrasound-assisted ionic liquid pretreatments on the functional properties of soy protein hydrolysates

In this work, the effect of dual-frequency ultrasound-assisted ionic liquids (ILs) pretreatment on the functional properties of soy protein isolate (SPI) hydrolysates was investigated. The degree of hydrolysis (DH) of SPI pretreated by ultrasound and [BMIM][PF6] increased by 12.53% as compared to control (P < 0.05). More peptides with low molecular weight were obtained, providing support for the changes in DH. The trichloroacetic acid-nitrogen soluble index presented an increase, suggesting a better protein hydrolysate property. The increase in the calcium-binding activity showed the ultrasound-assisted ILs pretreatment could potentially improve bone health. The foaming capacity and stability of SPI hydrolysates pretreated by ultrasound-assisted [BMIM][PF6] always increased remarkably as compared to ultrasound-assisted [BDMIM][Cl] pretreatment. However, the synergistic effect of ultrasound-assisted [BMIM][PF6] on the emulsifying activity and antioxidant activities (DPPH and hydroxyl radical scavenging activity) was not as ideal as ultrasound-assisted [BDMIM][Cl] pretreatment, which may be affected by the structure of peptide. In conclusion, these results indicated the combination of dual-frequency ultrasound and ionic liquids would be a promising method to improve the functional properties of SPI hydrolysates and broaden the application scope of compound modification in proteolysis industry.