After hydrolysis or fermentation, peanut protein forms peptides of different molecular weights. Peanut peptides contain all eight essential amino acids required by the human body, with a high content of sulfur-containing amino acids. The solubility and stability of peanut peptides are superior to those of peanut protein. They can be directly absorbed by the small intestine, rapidly replenishing nutrients, directly participating in the synthesis of amino acids and proteins, promoting the function of protein active groups, and enhancing immunity. In recent years, basic research on peanut peptides has become increasingly active, and understanding of peanut peptides has deepened.
Peanut peptides are prepared using enzymatic hydrolysis. To ensure the activity of proteases and the speed of hydrolysis, it is necessary to add some alkali or acid to adjust the system's pH value. The resulting peptide product contains a certain amount of salt, which affects the product's purity and application range, as well as its functional activity. Therefore, it is necessary to desalt peanut peptide products.
Methods for peptide desalting include ion exchange resin desalting, macroporous resin desalting, and nanofiltration membrane separation desalting. Ion exchange resin desalting and macroporous resin methods are cumbersome, have low peptide recovery rates, and are inconvenient to apply. Nanofiltration membranes have a pore size range of approximately a few nanometers, operate at a working pressure of 0.5-2 MPa, and exhibit high retention efficiency for organic compounds and large anionic groups with a relative molecular weight greater than 200 Da, along with high transmission rates for monovalent ions and solvents. Thus, they can simultaneously desalt and concentrate.
Nanofiltration separation is a separation technology that uses pressure difference as the driving force, the solution as the separation object, and nanofiltration membranes as the separation medium. Nanofiltration membranes have two significant characteristics: first, their molecular weight cutoff is approximately 200~2000, falling between reverse osmosis membranes and ultrafiltration membranes. Second, nanofiltration membranes have a certain retention rate for inorganic salts. The nanofiltration membrane separation process involves no chemical reactions, phase changes, or heating, does not damage the biological activity of peptides, and offers advantages such as simple operation, rapid separation, and high efficiency and energy savings. Protein enzymatic hydrolysates have a complex composition, with low concentrations of target active short peptides but large volumes of feed solution. To obtain active short peptide products with concentrated molecular weights and high purity, membrane technology with good separation performance and continuous processing may be a necessary treatment method.
