Cong Wang

Dairy products have become more common in people's daily diets in recent years, and numerous useful components derived from milk are widely employed in the food industry. Milk fat globule membrane (MFGM) is a kind of film that encases milk fat globules, and has been shown to have a high nutritional value. In this work, the protein, lipid, carbohydrate, and other components of MFGM are discussed, and also common separation, preparation, and analysis technologies, physicochemical properties, and functional features of MFGM are reviewed, to provide some guidance for the development and utilization of MFGM.

The analysis of lactoferrin separation will be an important application in prospect. To develop a new strategy for the detection of lactoferrin, this work adopted the method of uncoated Capillary Electrophoresis (CE), through optimizing the parameters of background electrolyte, pH, surfactant, buffers of the system solution. The optimum lactoferrin separation by CE is 50 mM phosphates buffer added 6M urea. In positive voltage, lactoferrin was separated by CE at pH 4.0. In reverse voltage, lactoferrin can also be separated at pH 10.0 with 50 mM ammonium ace. The auxiliary air pressure was got involved to decrease the absorption by silica capillary through a range of gradient intensity of air pressure. By comparison with 1.2, 1.5 and 1.8 psi, the pressure of 0.5 psi can significantly alleviate the absorption. The best detection conditions of lactoferrin were obtained, which are pH 4.0, 50 mM phosphates with 6M urea, 0.5 psi auxiliary air pressure with the limit of quantification at 0.04 mg/mL and the limit of detection at 0.01 mg/mL. Finally, lactoferrin can be quantitatively detected well and effectively, which the standard curve is y = 117807x + 3018.61374.

Walnut proteins and peptides have been reported to have great zinc‐carrying activity. In this study, the decapeptide EPNGLLLPQY (WP‐10) derived from walnut protein has been prepared to figure out zinc binding mechanisms and structure–activity relationships. The space‐conformation of this peptide has converted after being chelated with Zn(II). As to secondary structure, the β‐sheet structure of the peptide turned into α‐helix and β‐turn structure. According to the atomic absorption spectra analysis, one peptide could bind with one Zn(II) via four different binding sites. The signals of different groups in infrared spectroscopy have shifted before and after chelation, and the major functional groups of this peptide involved in chelation are –NH₂ and –C=O. GLU1, PRO2, ASP3, GLU4, and LEU6, and the molecular docking proved their participation in the chelating with Zn(II).

In the present study, a novel angiotensin I-converting enzyme inhibitory (ACE inhibitory) peptide, EPNGLLLPQY, derived from walnut seed storage protein, fragment residues 80–89, was identified by ultra-high performance liquid chromatography electrospray ionization quadrupole time of flight mass spectrometry (UPLC-ESI-Q-TOF-MS/MS) from walnut protein hydrolysate. The IC₅₀ value of the peptide was 233.178 μM, which was determined by the high performance liquid chromatography method by measuring the amount of hippuric acid (HA) generated from the ACE decomposition substrate (hippuryl-l-histidyl-l-leucine (HHL) to assess the ACE activity. Enzyme inhibitory kinetics of the peptide against ACE were also conducted, by which the inhibitory mechanism of ACE-inhibitory peptide was confirmed. Moreover, molecular docking was simulated by Discovery Studio 2017 R2 software to provide the potential mechanisms underlying the ACE-inhibitory activity of EPNGLLLPQY.