•Mung bean protein hydrolysate (MPH) was treated by ultrasound.•MPH contained mainly four bands of 25.6, 12.8, 10.6 and 4.9 kDa.•Ultrasonicated-MPH had more contents of aromatic and hydrophobic amino ...acids.•The α-helix of MPH was significantly destroyed by ultrasonic treatment.•MPH with 546 W ultrasonic power exhibited superior antioxidant activities.
This study aimed to investigate influence of ultrasonic treatment on physicochemical and antioxidant properties of mung bean protein hydrolysate (MPH). Physicochemical properties of MPH were evaluated by Tricine-SDS-PAGE, particle size distribution, fourier transform infrared spectroscopy (FTIR) and fluorescence spectroscopy, among others. Radicals scavenging activities of ABTS, hydroxyl, superoxide anion, Fe2+ chelating ability and reducing power characterized antioxidant activities of MPH. MPH contained four bands of 25.6, 12.8, 10.6 and 4.9 kDa, in which 4.9 kDa was the most abundant. Ultrasonic treatment increased the contents of aromatic and hydrophobic amino acids in MPH. Ultrasonic treatment decreased the content of α-helix of MPH and increased β-sheet and β-turn compared to MPH. MPH-546 W (ultrasonic treatment 546 W, 20 min) had the lowest average particle size (290.13 nm), zeta potential (-36.37 mV) and surface hydrophobicity (367.95 A.U.). Antioxidant activities of ultrasonicated-MPH increased with the ultrasonic power, achieving the lowest IC50 (mg/mL) of 0.1087 (ABTS), 1.796 (hydroxyl), 1.003 (superoxide anion) and 0.185 (Fe2+ chelating ability) in 546 W power. These results indicated ultrasonic treatment would be a promising method to improve the antioxidant properties of MPH, which would broaden the application scope of MPH as bioactive components in the food industry.
•Enzymatic hydrolysis disrupted the α-helices of tree peony seed protein.•Alcalase had the strong hydrolytic ability for tree peony seed protein.•Alcalase hydrolysate had well physicochemical ...properties.•Alcalase hydrolysate exhibited superior antioxidant ability to TPSP.
The physicochemical and antioxidant properties of tree peony seed protein (TPSP) hydrolysates by Alcalase, Neutrase, Papain, Protamex, and Flavourzyme were investigated in this study. The physicochemical properties were characterized by SDS-PAGE, particle size distribution, fourier transform infrared and fluorescence spectroscopy etc. The antioxidant activities were determined by DPPH radical, ABTS radical, Fe2+ chelating, and reducing power. The results showed five proteases produced hydrolysates with a significantly reduced average particle size, α-helices, and surface hydrophobicity compared to TPSP. Alcalase and Neutrase hydrolysis enhanced the nutritional value of the hydrolysates. Alcalase hydrolysates possessed the highest degree of hydrolysis (27.97%) and lowest molecular weight (<13 kDa) with average particle size (231.33 nm). Alcalase hydrolysate displayed the highest radical scavenging (DPPH IC50 = 0.18 mg/mL, ABTS IC50 = 1.57 mg/mL), Fe2+ chelating activity (IC50 = 0.99 mg/mL), and reducing power (0.594). These results provide the fundamentals for TPSP hydrolysates as antioxidants to be employed in food industry or pharmaceutical industry.
•Mung bean protein (MBP) was hydrolyzed by five proteases.•Alcalase had a stronger hydrolytic ability to MBP than other proteases.•Five proteases hydrolysis significantly destroyed the α-helix and ...β-sheet of MBP.•Protamex, papain hydrolysates had stronger functional properties than others.•Alcalase hydrolysate exhibited stronger antioxidant activity than other hydrolysates.
This study aimed to investigate physicochemical, functional and antioxidant properties of mung bean protein (MBP) enzymatic hydrolysates (MBPEHs) by alcalase, neutrase, protamex, flavourzyme and papain. Physicochemical properties were evaluated by SDS-PAGE, particle size distribution, FTIR, ultraviolet visible and fluorescence spectrophotometries. ABTS, hydroxyl scavenging, Fe2+ chelating activity were used to evaluate antioxidant activity. Enzymolysis with five proteases decreased average particle size, α-helix, β-sheet, surface hydrophobicity of hydrolysates. Alcalase hydrolysate had the highest degree of hydrolysis (23.55%), absolute zeta potential (33.73 mV) and the lowest molecular weight (<10 kDa). Protamex and papain hydrolysates had higher foaming capacities, emulsification activity indexes, emulsion stability indexes (235.00%, 123.07 m2/g, 132.54 min; 200.10%, 105.39 m2/g, 190.67 min) than MBP (135.03%, 20.03 m2/g, 30.88 min). Alcalase hydrolysate demonstrated the lowest IC50 (mg/mL) in ABTS (0.12), hydroxyl (2.98), Fe2+ chelating (0.22). These results provide support for application of MBPEHs as foaming agent, emulsifier and antioxidant in food industry.
•The protein 60kDa of tree peony seed protein had two subunits of 38 and 23kDa.•Two subunits with pI 3.6 and 9.0 contained all three types.•Tree peony seed protein had a favourable amino acid ...profile.•Tree peony seed protein had a predominantly β-sheet structure and was heat stable.•TPSP was a pseudoplastic fluid with desirable functional properties.
The physicochemical and functional properties of tree peony seed protein were investigated. Tree peony seed protein with a favourable amino acid profile was composed of a 60kDa protein with two subunits of 38 and 23kDa. The isoelectric points of the two subunits were 3.6 and 9.0. Moreover, acid-Schiff staining indicated both of them were glycoproteins. Diagonal and 2-D electrophoresis data indicated the 38kDa subunit included three types, which two types had inter-disulphide bonds and one type had no-disulphide bonds. So did the 23kDa subunit. Circular dichroism spectra indicated the tree peony seed protein had predominantly a β-sheet structure. Differential scanning calorimetry analysis indicated the denaturation temperatures of the tree peony seed protein at pH 5.0, 7.0 and 9.0 were 92.0, 97.1 and 95.2°C, respectively. Tree peony seed protein could be a food ingredient in the food industry due to its desirable physicochemical and functional properties.
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•Mung bean protein (MBP) contained mainly six bands 64, 62, 48, 32, 25, 23 kDa.•Abundant hydrophobic amino acids of MBP contributed to high thermostability at pH 7.0.•MBP had a looser ...structure in alkaline environment than acid environment.•More than 130 mg/mL MBP formed self-supporting gels at pH 7.0 and 9.0.•MBP had good physicochemical and functional properties in alkaline environment.
This study aimed to investigate the structural characteristics and physicochemical properties of mung bean protein (MBP) at different pH levels. Structures and physicochemical properties were evaluated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, circular dichroism, ultraviolet visible and fluorescence spectrophotometry, differential scanning calorimetry, etc. MBP contained six bands of 64, 62, 48, 32, 25 and 23 kDa, among which the 64, 48 and 32 kDa bands consisted of glycoproteins. The β-sheets and random coils of MBP had structures close to double α-helices and β-turns at pH 3.0, 7.0 and 9.0. MBP in an alkaline environment had higher solubility and free sulfhydryl contents, smaller particle sizes, and lower surface hydrophobicity. Rheological analysis showed that MBP at pH 3.0, 5.0, 7.0 and 9.0 exhibited shear-thinning pseudoplastic fluids. A higher shear stress was needed to initiate flow at pH 5.0 than at pH 3.0, 7.0 or 9.0. MBP (130 mg/mL) formed self-supporting gels at pH 7.0 and 9.0. MBP had good foaming capacity (125.00 %), emulsion activity index (117.05 m2/g) and emulsion stability index (20.86 min) in alkaline environment. These results provide fundamental information about MBP for use in neutral and alkaline environments as a functional food ingredient.
The aim of this study was to investigate the antibacterial characteristics and antibacterial mechanisms of ɛ-poly-lysine against Escherichia coli and Staphylococcus aureus. The diameters of ...inhibition zones of E. coli (10 ± 0.5 mm) and S. aureus (12 ± 0.1 mm) treated by 200 μg/ml ɛ-poly-lysine were much larger than control (5 ± 0.3 mm) (p < 0.05). Minimum inhibition concentration of ɛ-poly-lysine against E. coli and S. aureus was 12.5 μg/ml. Scanning electron microscopy showed that ɛ-poly-lysine damaged the morphology of tested bacterial cells. The increase in electric conductivity of bacterial cells suspension indicated that the cytoplasmic membranes were broken by ɛ-poly-lysine, which caused leakage of ions in cells. SDS-PAGE of bacterial proteins demonstrated that ɛ-poly-lysine could damage bacterial cells through the destruction of cellular proteins. These results indicated that ɛ-poly-lysine has good potential to be as a natural food preservative.
•ɛ-Poly-lysine (ɛ-PL) exhibited antibacterial activity against E. coli and S. aureus.•Scanning electron microscopy revealed ɛ-PL could destroy bacterial cells.•ɛ-PL resulted in bacterial cellular leakage by determining electric conductivity.•ɛ-PL might interfere bacterial cell protein synthesis or induced its aggregation.
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