Effects of Limited Hydrolysis and High-Pressure Homogenization on Functional Properties of Oyster Protein Isolates

Innovative insights into the enzymatic hydrolysis of salmon milt: Structural and functional analysis influenced by protease type and enzymolysis time

In this study, hydrolysates were obtained from salmon milts using four proteases (neutrase, papain, trypsin and novozym 11028). The effects of protease type and enzymolysis time (30, 60, 90, and 120 min) on the structural characteristics and functional properties of the hydrolysates were assessed. The fluorescence intensity of all hydrolysates increased as the extension of enzymolysis time, accompanied by an increase in solubility, emulsifying and foaming ability. Trypsin-hydrolysates showed the highest protein recovery and degree of hydrolysis (DH). The electrophoresis indicated that papain-hydrolysates contained more aggregates (>60 kDa), which was confirmed by larger particle size and lower DH. Neutrase-hydrolysate exhibited the smallest particle size and the highest emulsifying and foaming ability, while the highest emulsifying stability appeared in papain-hydrolysates. Neutrase-hydrolysate displayed the strongest antioxidant potential while papain-hydrolysate possessed the weakest. Results demonstrated that the salmon milt protein hydrolysates can be utilized as nutraceutical and functional food ingredients.

Effect of enzymatic hydrolysis with Alcalase or Protamex on technological and antioxidant properties of whey protein hydrolysates

The aim of this study was to evaluate the effect of the enzymatic hydrolysis, performed using Alcalase and Protamex enzymes, on the technological functionalities and the antioxidant capacity of whey protein hydrolysates (WPHs) to identify the conditions allowing to obtain target functionality/ies. Samples were characterized for hydrolysis degree (DH), molecular weight distribution, structural properties, and food-related functionalities. Free sulfhydryl groups and surface hydrophobicity significantly decreased with the increase in DH, regardless of the used enzyme. The foaming and antioxidant properties of Alcalase WPHs were higher as compared to those of WPI, reaching the maximum value at DH = 18-20 %, while higher DH resulted in impaired functionality. Gelling properties were guaranteed when WPI was hydrolysed by Protamex at DH < 15 % while foaming and antioxidant abilities were fostered at 15 < DH < 21 %. These results were well correlated with MW distribution and were rationalized into a road map which represents a useful tool in the selection of proper hydrolysis conditions (time, DH, enzyme type) to obtain WPHs with tailored functionalities. Research outcomes highlighted the possibility to drive protein hydrolysis to optimize the desired functionality/ies.

Micronization using combined alkaline protease hydrolysis and high-speed shearing homogenization for improving the functional properties of soy protein isolates

The present study aimed to investigate the functional properties of soybean protein isolate (SPI) treated with alkaline protease and high-speed shearing homogenization. Alkaline protease-hydrolyzed SPIs that were characterized by varying degrees of hydrolysis between 0 and 6% were treated with high-speed shearing homogenization to obtain different micro-particulate proteins. The results showed that this combined treatment could significantly reduce the particle size of SPI by markedly degrading the structure of both the 7S and 11S subunits, thereby resulting in a significantly reduced content of β-sheet and β-turn structures. The surface hydrophobicity increased considerably for samples with hydrolysis below the threshold of 2% and then declined gradually above this threshold. Furthermore, the combination of hydrolysis and homogenization significantly improved the emulsion stability of SPI hydrolysates. It also significantly improved the foaming properties of SPI. These results demonstrated that alkaline protease hydrolysis combined with high-speed shearing homogenization represents a promising approach for improving the functional and structural properties of SPI.

Physicochemical and functional properties of Alcalase-extracted protein hydrolysate from oil palm leaves

BACKGROUND

The oil palm tree produces 90% of wastes and the limited usage of these wastes causes a major disposal problem in the mills. Nevertheless, these by-products have a large amount of nutritional components. Thus, the present study aimed to determine the physicochemical and functional properties of protein hydrolysates (PH) from oil palm leaves (OPL) extracted using different concentrations of Alcalase (0-10%) at 2 h of hydrolysis time.

RESULTS

Fourier transform infrared spectral analyses showed that the enzymatic hydrolysis altered functional groups of OPL where a secondary amine was present in the PH. Changes were also observed in the thermal stability where the enthalpy heat obtained for PH (933.93-1142.57 J g^-1 ) was much lower than OPL (7854.11 J g^-1 ). The results showed that the PH extracted by 8% Alcalase exhibited absolute zeta potential, as well as a high emulsifying activity index (70.64 m²  g^-1 of protein) and emulsion stability index (60.58 min). Furthermore, this PH showed higher solubility (96.32%) and emulsifying properties compared to other PHs. It is also comparable with commercial plant proteins, indicating that 8% Alcalase is an optimum concentration for hydrolysis.

CONCLUSION

In summary, the physicochemical and functional properties of PH extracted from OPL showed good functional properties, suggesting that it can be used as an alternative plant protein in food industries. © 2021 Society of Chemical Industry.

Effects of High Pressure Modification on Conformation and Digestibility Properties of Oyster Protein

To expand the utilization of oyster protein (OP), the effects of high pressure (100 to 500 MPa) on chemical forces, structure, microstructure, and digestibility properties were investigated. High pressure (HP) treatment enhanced the electrostatic repulsion (from -13.3Control to -27.8HP200 mV) between protein molecules and avoided or retarded the formation of protein aggregates. In addition, the HP treated samples showed uniform distribution and small particle size. The changes in electrostatic interaction and particle size contributed to the improvement of solubility (from 10.53%Control to 19.92%HP500 at pH 7). The stretching and unfolding of protein were modified by HP treatment, and some internal hydrophobic groups and -SH groups were exposed. HP treatment modified the secondary structure of OP. The treated samples contained less α-helix and β-sheet structures, whereas the proportions of β-sheet and random coil structures were increased. The treated samples have high digestibility in the stomach (from 26.3%Control to 39.5%HP500) and in the total digestive process (from 62.1%Control to 83.7%HP500). In addition, the total digestive production showed higher percentages of small peptides (<1 kDa) after HP treatment. The protein solubility and digestibility were increased after HP treatment, and high solubility and high digestibility might increase the chance that OP become a kind of protein supplement.