Soybean Protein Hydrolysates Research Articles

A comparative analysis of anti-lipidemic potential of soybean (Glycine max) protein hydrolysates obtained from different ripening stages: Identification, and molecular interaction mechanisms of novel bioactive peptides

This study aims to investigate the potentials of mature (MSPHs) and young (YSPHs) soybean enzymatic protein hydrolysates for the inhibition of pancreatic lipase (PL) and cholesterol esterase (C-Ease) enzymes. Higher proteins degradation levels were recorded with Bromelain compared to Flavourzyme and Alcalase, and upon hydrolysis, improved PL and C-Ease inhibition performances were displayed compared to unhydrolyzed proteins. Afterwards, six PHs with potent anti-lipidemic activities were selected for sequencing using LC-MS QTOF and molecular binding studies. Peptides FPFPRPPHQ, QCCAFEM, FAPEFLK from MSPHs and SFFFPFELPRE, FMYL, PFLL, FPLL, LPHF from YSPHs were predicted to possess potent inhibitory activities against PL. Furthermore, FPFPRPPHQ, FMYL, MMLM from MSPHs, and SFFFPFELPRE from YSPHs were predicted to be potent inhibitors of C-Ease. FPFPRPPHQ and SFFFPFELPRE derived from MSPHs and YSPHs, respectively, demonstrated effective inhibition potentialities against both PL and C-Ease. Therefore, mature and young soybean-derived protein hydrolysates could be recognized as a potential ingredient in the management of hypercholesterolemia.

Hydrolysis of Soybean Milk Protein by Papain: Antioxidant, Anti-Angiotensin, Antigenic and Digestibility Perspectives.

The objective of the investigation was to understand the biochemical activities of hydrolysate of soybean milk protein (SMP). Hydrolysis was carried out by different concentrations of papain (0.008 g·L−1, 0.016 g·L−1, 0.032 g·L−1 and 0.064 g·L−1). The antioxidant capacity was measured by the ferric-reducing ability of plasma (FRAP) and 2,2-Diphenyl-1-picrylhydrazyl (DPPH) assays. The anti-angiotensin activity of hydrolysate was measured by the recombinant angiotensin converting enzyme and substrate Abz-FRK(Dnp)-P. The contributions of the Kunitz trypsin inhibitor (KTI) and Bowman–Birk inhibitor (BBI) on antigenicity, and the in vitro digestion of papain-hydrolyzed SMP were studied. Rabbit polyclonal anti-KTI and anti-BBI antibodies together with peroxidase-labelled goat anti-Rb IgG secondary antibody were used to identify the antigenicity of KTI and BBI in unhydrolyzed and papain-hydrolyzed SMP. The antioxidant capacity and anti-angiotensin activity of SMP were increased after the papain hydrolysis of SMP. The KTI- and BBI-specific antigenicity were reduced in SMP by increasing the concentration of papain. However, there was interaction between papain-hydrolyzed SMP and trypsin in native gel, while interaction with chymotrypsin was absent. The interaction between trypsin and SMP was reduced due to the hydrolysis of papain in a concentration-dependent manner. According to the in vitro gastrointestinal digestion simulation protocol (Infogest), the digestibility of SMP was not statistically increased.

Structure and activity of bioactive peptides produced from soybean proteins by enzymatic hydrolysis

Peptides are good food stabilizers and thickeners. They also present good bioactivities. The structure characteristics of peptides are related to the health benefits. In this study, immunoregulatory peptides were produced by Alcalase® and neutrase hydrolysis of soybean proteins. UHPLC-MS/MS was applied for structure identification. The immumoregulatory activities and mechanisms were investigated. Eighty five peptides were identified from the hydrolysates and 84 peptides might be immunoregulatory peptides. Most of them were novel immunoregulatory peptides. These peptides had good immunoregulatory activities, including increasing the pinocytotic capacity, and inducing the production and genes expression of NO, IL-6 and TNF-α in a dose-dependent manner. Specific inhibitors of NF-κB and JNK could significantly suppress NO production stimulated by soybean peptides, implying that NF-κB and JNK pathways were involved in their immunoregulatory mechanisms. Our results suggested that the soybean peptides prepared in this study were promising immunomodulatory neutraceuticals.

The anti-inflammatory effect of vasoactive peptides from soybean protein hydrolysates by mediating serum extracellular vesicles-derived miRNA-19b/CYLD/TRAF6 axis in the vascular microenvironment of SHRs

The excessive accumulation of angiotensin II (Ang II) in the vascular microenvironment promotes vascular dysfunction including vascular endothelial inflammation and remodeling. In the present study, a soybean protein hydrolysate enriching with vasoactive peptides was prepared and explored the anti-inflammatory effects on the aorta of spontaneous hypertensive rats (SHRs). The soybean-derived vasoactive peptide (SVP) significantly reduced the blood pressure and attenuated inflammation of the aorta in SHRs. Pathologically, the SVP improved the wall thickening and inflammatory cell infiltration of the aorta. Mechanistically, the SVP not only reduced the expression of miRNA-19b in the aorta but down-regulated the packaging of miRNA-19b in serum EVs. The miRNA-19b targeted the deubiquitinating enzyme cylindromatosis (CYLD) in the aorta and broke the ubiquitination balance of CYLD-TRAF6. These results caused a disorder of the TRAF6-mediated signaling pathway in the aorta, which resulted in upregulation of the expression of IL-6 and TNF-α in the aorta. This pathological process in SHRs was improved by the SVP hydrolysate gavage administration. These results reported a novel anti-inflammatory mechanism of SVP through the serum EVs mediating the miR-19b/CYLD/TRAF6 axis.

Integrated Evaluation of the Multifunctional DPP-IV and ACE Inhibitory Effect of Soybean and Pea Protein Hydrolysates.

Nowadays, notwithstanding their nutritional and technological properties, food bioactive peptides from plant sources garner increasing attention for their ability to impart more than one beneficial effect on human health. Legumes, which stand out thanks to their high protein content, represent valuable sources of bioactive peptides. In this context, this study focused on the characterization of the potential pleotropic activity of two commercially available soybean (SH) and pea (PH) protein hydrolysates, respectively. Since the biological activity of a specific protein hydrolysate is strictly correlated with its chemical composition, the first aim of the study was to identify the compositions of the SH and PH peptides. Peptidomic analysis revealed that most of the identified peptides within both mixtures belong to storage proteins. Interestingly, according to the BIOPEP-UWM database, all the peptides contain more than one active motive with known inhibitory angiotensin converting enzyme (ACE) and dipeptidyl-dipeptidases (DPP)-IV sequences. Indeed, the results indicated that both SH and PH inhibit DPP-IV and ACE activity with a dose-response trend and IC50 values equal to 1.15 ± 0.004 and 1.33 ± 0.004 mg/mL, and 0.33 ± 0.01 and 0.61 ± 0.05 mg/mL, respectively. In addition, both hydrolysates reduced the activity of DPP-IV and ACE enzymes which are expressed on the surface of human intestinal Caco-2 cells. These findings clearly support that notion that SH and PH may represent new ingredients with anti-diabetic and hypotensive effects for the development of innovative multifunctional foods and/or nutraceuticals for the prevention of metabolic syndrome.

Preparation and Antioxidant Properties of Germinated Soybean Protein Hydrolysates.

In this study, soybeans during different germination stages were described and compared with regard to morphology, water content, protein, amino acids, and isoflavones. The optimal conditions for the hydrolysis of proteins obtained from germinated soybeans were determined using the response surface methodology. Gel filtration chromatography was used to separate germinated soybean protein hydrolysates after ultrafiltration, whereas 2,2-Diphenyl-1-picrylhydrazyl (DPPH), ABTS•+, and FRAP assays were used to assess the antioxidant activity of different fractions. Findings of this study revealed that protein and isoflavone contents were high in soybean at 24 h following germination (the bud was about 0.5–1 cm). The proteins from germinated soybeans were hydrolyzed and separated into five fractions (G1–G5) and evaluated in terms of their molecular weight and antioxidant activity. Interestingly, the antioxidant activity was found to be higher in germinated soybean protein hydrolysates than in other soybean protein hydrolysates derived from soybean meal protein. This suggests that germination can effectively improve the utilization rate of soybean proteins. The antioxidant activity of G3 was best among G1–G5. The results obtained in this study demonstrate that germination for 24 h when the bud length is about 0.5–1 cm can be applied as a special pretreatment of plant seeds in the development of germinated foods. These findings can be used to identify the structure of the potential antioxidative hydrolysates for their possible exploitation in functional foods.

A Comprehensive Comparison of Different Selenium Supplements: Mitigation of Heat Stress and Exercise Fatigue-Induced Liver Injury.

This study aimed to compare the protective effects of different selenium supplements against heat stress and exercise fatigue-induced liver injury and to investigate the potential mechanisms of action. Selenium-enriched soybean protein (SePro), selenium-enriched soybean peptides (SePPs), and selenomethionine (SeMet) are organic selenium supplements in which selenium replaces the sulfur in their sulfur-containing amino acids. Common peptides (PPs) are obtained by enzymatic hydrolysis of soybean protein which was extracted from common soybean. The SePPs with higher hydrolysis degree and selenium retention were isolated via alkaline solubilization and acid precipitation and the enzymatic hydrolysis of alkaline protease, neutral protease, and papain. The results showed that SePPs could significantly increase the antioxidant levels in rats, inhibit lipid peroxidation, and reduce liver enzyme levels in rat serum, while the histological findings indicated that the inflammatory cell infiltration in the liver tissue was reduced, and new cells appeared after treatment with SePPs. Moreover, SePPs could increase glutathione (GSH) and GSH peroxidase (GSH-Px) in the liver, as well as protect the liver by regulating the NF-κB/IκB pathway, prevent interleukin 1β (IL-1β), interleukin 6 (IL-6), and tumor necrosis factor α (TNF-α) release in the liver. The SePPs displayed higher antioxidant and anti-inflammatory activity in vivo than SePro, SeMet, Sodium selenite (Na2SeO3), and PPs. Therefore, SePPs could be used as a priority selenium resource to develop heatstroke prevention products or nutritional supplements.

A novel process for synthesis of soybean protein hydrolysates and study of its effectiveness as a biostimulant and emulsifier

We study in extensive detail synthesis of protein hydrolysates (PHs) from soybean meal (SBM) using high shear stator-rotor impeller. The effects of alkali concentration, soaking and shearing time, SBM loading and combination of soaking and shearing on the extent of SBM hydrolysis and protein/amino acid concentration are elucidated. Effectiveness of soybean protein hydrolysates (SPHs) as a plant-based biostimulant and as an emulsifier for the synthesis of oil-in water emulsions was investigated. Use of a high shear mixer and alkaline conditions resulted in up to 80% extraction of protein in 30 min at room temperature. Amount of protein extracted increased with NaOH concentration, SBM loading and shear mixing time. However, alkali concentration and application of shear mixer were dominant factors for maximum SBM hydrolysis and protein extraction. SPHs showed excellent biostimulant activity for wheat and fenugreek plants. Wheat and fenugreek plants which received SPHs treatment showed enhanced percent germination, survival and overall growth of the plants (shoot and root length and dry weight). SPHs stabilised oil-in water emulsions showed excellent long-term stability and its emulsifying properties were comparable with the similar emulsions stabilised by soy protein isolates.

Multi-Dimensional Analysis of Heat-Induced Soybean Protein Hydrolysate Gels Subjected to Ultrasound-Assisted pH Pretreatment

Multi-Dimensional Analysis of Heat-Induced Soybean Protein Hydrolysate Gels Subjected to Ultrasound-Assisted pH Pretreatment

Improvement in Freeze‐Thaw Stability of Rice Starch by Soybean Protein Hydrolysates‐Xanthan Gum Blends and its Mechanism

AbstractTo improve the freeze‐thaw stability of rice starch (RS), the soybean protein hydrolysates (SPHs), xanthan gum (XG), and the blends of SPHs with XG (SPHs‐XG) are added. The syneresis, thermal, texture, rheological properties, and morphological features of samples during seven freeze‐thaw cycles (FTCs) are investigated by syneresis measurement, differential scanning calorimetry (DSC), textural properties analysis (TPA), dynamic rheological, NMR, and SEM. As a result, SPHs‐XG is more effective for improving the freeze‐thaw stability and showed improved structure manifestations with the lower retrogradation rate (22.78%), hardness (153.29 g), gumminess (54.57), and solid‐like structure (p < 0.05). Moreover, the water‐holding capacity is increased and the microstructure is effectively stabilized. All these results suggested that SPHs‐XG could be a potential ingredient to improve the quality of rice starch‐based frozen foods.

Immunomodulatory effects of selenium-enriched peptides from soybean in cyclophosphamide-induced immunosuppressed mice.

In this study, selenium‐enriched soybean peptides (<3 kDa, named Se‐SPep) was isolated and purified from the selenium‐enriched soybean protein (Se‐SPro) hydrolysate by ultrafiltration. The in‐vivo immunomodulatory effects of Se‐SPep were investigated in cyclophosphamide‐induced immunosuppressed mice. Se‐SPep treatment could alleviate the atrophy of immune organs and weight loss observed in immunosuppressive mice. Besides, Se‐SPep administration could dramatically improve total protein, albumin, white blood cell, immunoglobulin (Ig) M, IgG, and IgA levels in blood. Moreover, Se‐SPep strongly stimulated interleukin‐2 (IL‐2), interferon‐gamma (IFN‐γ), nitric oxide (NO), and cyclic guanosine monophosphate productions by up‐regulating mRNA expressions of IL‐2, IFN‐γ, and inducible NO synthase in spleen tissue. Furthermore, Se‐SPep exhibits more effective immunomodulatory activity compared to Se‐SPro and SPep. In conclusion, Se‐SPep could effectively enhance the immune capacity of immunosuppressive mice. These findings confirm Se‐SPep is an effective immunomodulator with potential application in functional foods or dietary supplements.

Identification of monoamine oxidases inhibitory peptides from soybean protein hydrolysate through ultrafiltration purification and in silico studies

Monoamine oxidases (MAOs, including MAO-A and MAO-B) are essential deamination enzymes for neurotransmitters and other amines; thus, they are potential targets for treatment of mental disorders like depression and anxiety, and neurodegenerative disorders like Alzheimer's disease and Parkinson's disease. This study aimed at identifying MAOs inhibitory peptides from soybean protein hydrolysate through ultrafiltration purification and in silico prediction. Ultrafiltration fraction (0–3 kDa, SP-III) from soybean protein hydrolysate showed the highest inhibition activity with IC50 of 3.211 ± 0.125 mg/ml and 1.622 ± 0.025 mg/ml for MAO-A and MAO-B, respectively. Component 3 from SP-III gel filtration fraction exhibited the highest inhibitory activity with IC50 of 1.623 ± 0.150 mg/ml and 1.174 ± 0.111 mg/ml for MAO-A and MAO-B, respectively. Further affinity purified samples were sequenced by liquid chromatography tandem mass spectrometry and screened by HPEPDOCK. Eight peptides were selected for synthesis and evaluation. YSPYPQ displayed the highest MAO-A inhibitory activity with IC50 of 0.663 ± 0.091 mM, while PLYSN possessed the strongest MAO-B inhibition effect as IC50 of 0.204 ± 0.042 mM. Molecular docking revealed that their binding with MAOs might obstruct admission of substrate to the active sites. Current research confirmed that ultrafiltration purification and in silico prediction are effective to screen MAOs inhibitory peptides from soybean protein hydrolysate. The inhibitor peptides screened out here, especially PLYSN could be applied as potential functional nutraceuticals as MAOs inhibitor to treat neurodegenerative and mental disorders. Their application might suggest value of soybean as a routine and cheap source of neuromodulatory bioactive peptides.

A comparative study on the functional properties of mealworm (Tenebrio molitor) larvae and soybean protein isolates and hydrolysates

The present work aimed to compare the functional and antioxidant properties of mealworm larvae and soybean proteins at different processing steps. The mealworm larvae protein isolate (MPI) was hydrolysed with 2% alcalase at pH 8 and 60°C for 3 h to produce mealworm protein hydrolysate (MPH). The content of amino acids were higher in MPI than in soybean protein isolates (SPI), except for those of threonine, arginine, glutamic acid, and serine. MPI contained a higher amount of hydrophobic amino acids (941.4 µmol/L) than hydrophilic amino acids (697.1 µmol/L). The emulsifying activity, stability, and fat absorption capacity of MPI were higher than those of SPI, whereas their water absorption and holding capacities were similar. Alcalase hydrolysis increased MPI solubility. MPI showed lower solubility at pH 3 - 9 than that of SPI, whereas MPH had higher solubility than that of soy protein hydrolysate (SPH). The foam expansion capacity and foam stability of MPI were lower than those of SPI, but hydrolysis improved those of MPI. MPI formed a gel at pH 5, 7, and 9 at 15% concentration or at pH 7 and 9 at 10% concentration. However, MPH showed no gel formation under any conditions. The total phenolic content and antioxidant capacity of MPI were higher than those of SPI. The DPPH activity of MPH (70%) was higher than that of MPI (18%), SPI (12%), or SPH (34%). MPI can be used as an alternative to SPI. Alcalase hydrolysis can increase the antioxidant effect, digestibility, and functionality of MPI as a sustainable ingredient in high value-added products.

Combining Alcalase hydrolysis and transglutaminase-cross-linking improved bitterness and techno-functional properties of hypoallergenic soybean protein hydrolysates through structural modifications

Alcalase hydrolysis of soybean proteins was shown effective in degrading epitopes, but with a significant loss of tastes and functional properties. In this study, the combined use of controlled Alcalase hydrolysis and transglutaminase (TGase)-cross-linking was used to produce hypoallergenic soybean protein hydrolysates (SPHs) with improved flavor and techno-functional properties. Through establishing the kinetic model of heterogeneous enzymatic processes, SPHs with different degrees of hydrolysis (2.5–10.0%) were obtained and polymerized by TGase to yield products with various peptide components. Results showed that post-hydrolysis cross-linking rearranged the (poly)peptides in SPHs via glutaminyl modifications. Following TGase-treatments, due to the masking of bitter-active peptides and free amino acids, the bitterness of SPHs was significantly reduced with a slight improvement in the overall flavor. Furthermore, TGase–cross-linking rescued multiple techno-functionalities of SPHs, particularly their emulsifying and foaming properties. Using sera from soybean-allergic individuals, it was evidenced that TGase-addition did not generate neoallergens and the residual allergenicity of SPHs was not distinctly affected. The final products maintained 44–71% reduction in the IgE-binding levels in comparison to the unhydrolyzed protein. Combining limited Alcalase hydrolysis with TGase–cross-linking provides a feasible way to produce hypoallergenic soybean ingredients with desired flavor and functional attributes.

Bioactive anti-aging agents and the identification of new anti-oxidant soybean peptides

Degenerative diseases associated with aging could be attributed primarily to the deleterious effects of free radicals on cell constituents and connective tissues. The aim of this study was to compare the anti-aging effects of soybean (PHS), oyster (PHO), and sea cucumber (PHH) protein hydrolysates and then isolate and characterize the responsible anti-aging peptides of the most effective hydrolysate that could allow for the further development of anti-aging bioactive ingredients. Protein hydrolysates were prepared from the three natural products using Alcalase for the enzymatic hydrolysis. D-galactose-induced specific pathogen-free (SPF) Kunming mice were used to explore the anti-aging effects of the three hydrolysates. The results showed that the three protein hydrolysates all had a significant impact on reversing D-galactose-induced aging-associated learning and memory impairments and oxidative stress in the order PHS > PHO > PHH. Consistent with the activity in vivo, PHS also showed the strongest DPPH scavenging activity among the three hydrolysates. Consequently, PHS was further purified using DEAE-52 ion exchange resin into three fractions (Fa, Fb and Fc), of which Fa showed the highest antioxidative activity. Fa was subsequently purified using G-15 gel filtration chromatography. Using LC-MS/MS, two peptides, Trp-Pro-Lys (WPK) and Ala-Tyr-Leu-His (AYLH), were identified as the active components of the purified fraction. In vitro antioxidant analysis showed that the peptides strongly alleviated H2O2-induced oxidative damage in PC12 cells. The results suggested that PHS and its constituent peptides could be potentially effective antioxidant agents in functional foods or nutraceuticals for aging-related learning and memory impairments and oxidative stress.

Debittering effect of partially purified proteases from soybean seedlings on soybean protein isolate hydrolysate produced by alcalase

To explore the potential application of proteases from soybean seedlings in the debittering of soybean protein hydrolysates, soybean seeds were germinated from 1 to 10 days. It was found that the sixth day seedlings exhibited highest proteases activity (130 U/g). After partial purification, the activity of proteases (PSP) from the sixth day seedlings further increased to 2675 U/g. In addition, PSP exhibited maximum activity at 50 ℃ and pH 5.5, and mainly comprised of two proteins with the molecular weight of 64.57 and 25.12 kDa respectively. PSP could decrease the bitterness score of the soybean protein isolate hydrolysate (SPIH) produced by Alcalase 2.4L from 3.45 to 0 in 3 h. Meanwhile, the degree of hydrolysis of SPIH slightly increased from 11.87% to 15.61% without reducing the antioxidant activity. This study may provide a solution to the contradiction between removing the bitterness of soybean protein hydrolysates and maintaining the bioactivity.

Structure identification of soybean peptides and their immunomodulatory activity

Soybean peptides are functional food with good health benefits. The health benefits presented are highly dependent on the peptide structure. In this work, soybean peptides were prepared by alkaline protease hydrolysis of soybean proteins. The peptide structure was identified by UPLC-MS/MS. The full peptide composition was revealed. The sequences of 51 peptides were identified and 46 peptides were assigned as immunomodulatory peptides. By evaluating the immumonodulatory activity and mechanism, soybean peptides could facilitate the proliferation of macrophages. The pinocytotic activity and NO level were increased. Induction of iNOS mRNA expression by soybean peptides was responsible for the increased NO production. The release of cytokines IL-6 and TNF-α was elevated and their levels were equal to positive control. The mRNA expression levels of IL-6 and TNF-α were also improved by soybean peptides, but much lower than positive control. The results were helpful for application of soybean peptides in functional foods.

Effects of ultrasound-assisted sodium bisulfite pretreatment on the preparation of cholesterol-lowering peptide precursors from soybean protein

In order to take full advantage of the gastrointestinal digestive function, the effects of S-type ultrasound-assisted sodium bisulfite (UASB) pretreatment on the preparation of cholesterol-lowering peptide precursors derived from soybean protein were investigated and the structural characterizations of pretreated proteins were explored. UASB pretreatment with the operational mode of mono-frequency ultrasound at 28 kHz, ultrasonic power density of 200 W/L and ultrasonic time of 50 min exhibited the highest cholesterol-lowering activity (56.90%) of soybean protein hydrolysates (SPH) after simulated gastrointestinal digestion, which increased by 87.17% compared to the control. Under these conditions, the peptide content of SPH after simulated gastrointestinal digestion was not significantly different (p > 0.05) compared to the control. Further FTIR analysis showed that UASB pretreatment increased β-turn and β-sheet content and decreased α-helix and random coil content. The changes in the surface hydrophobicity and microstructures of soybean protein indicated that UASB pretreatment loosened soybean protein structure and exposed more hydrophobic groups. SDS-PAGE indicated that the restriction sites changed after UASB pretreatment. In conclusion, UASB pretreatment is an efficient method for the preparation of cholesterol-lowering peptide precursors.

Contributions of ethanol fractionation on the properties of vegetable protein hydrolysates and differences in the characteristics of metal (Ca, Zn, Fe)-chelating peptides

Defatted soybean meal, walnut meal, cottonseed meal and wheat gluten flour were hydrolyzed with Alcalase to prepare vegetable protein hydrolysates (VPHs), respectively. Through ethanol fractionation, peptides with lower molecular weight and higher hydrophobicity were enriched in ethanol-soluble VPHs (VPHs-Es), and metal-binding content of VPHs-Es was significantly increased. Zinc and iron were much easier to combine with lower molecular weight peptides (MW < 1 kDa) than calcium. Comparably, ethanol-soluble soybean protein hydrolysates (SPH-Es) had a better metal-binding capacity. The Fourier transform infrared spectra and amino acid composition analysis revealed that the carboxyl oxygen and amino nitrogen were the main binding sites for chelating, and divalent metals had different chelating preferences. The molecular weight distribution, particle size and scanning electron microscope analysis demonstrated significant microstructural differences among the metal (Ca, Zn, Fe) chelates. In particular, obvious aggregation occurred in Ca-SPH-Es, which was induced by hydrogen bonding and electrostatic interaction. Moreover, the gastrointestinal stability of metal chelates was 71.48%, 90.70% and 85.60% for Ca-SPH-Es, Zn-SPH-Es and Fe-SPH-Es, respectively, thus providing a guidance for the exploration of organometallic supplements.

Production of enzymatically hydrolyzed soybean protein isolate by a novel neutral protease from Enterobacter sp. NRCM1 to be used as a base precursor of thermal process flavours

A novel neutral protease from a newly isolated and identified bacteria Enterobacter sp. NRCM1 was used to produce the enzymatic hydrolyzed soybean protein isolate (E-SPM1). The protease was purified and biochemically characterized. The effect of hydrolysis time on degree of protein hydrolysis and released free amino acids was investigated. The enzymatic hydrolysates (E-SPM124, E-SPM148 and E-SPM172) produced after 24, 48 and 72 h, respectively were used as main precursors of beef-like flavours. The generated volatiles were determined by solid phase microextraction combined with gas chromatography- mass spectrophotometer (SPME- GC-MS). The results revealed that the optimum pH and temperature of protease activity were 7.0 and 50oC, respectively. Sample E-SPM172 showed the highest degree of hydrolysis (43.71%) and content of free amino acids (5.78 g/mL). The headspace volatiles of the model mixture based on E-SPMI72 comprised the highest content of the most important compounds for meat aroma. The results of odour sensory analysis confirmed those of GC-MS for all investigated samples. The highest score of beefy note of sample E-SPMI72was mainly correlated to the significant increase of 2-methyl-3-furanthiol, the most potent aroma compound in beef flavour. The gradual increase of savoury note was consistent with that of the disulfide compounds, which possess savoury aromatic note.