Summary of Soy Protein Isolate Extraction Methods
1. Extraction of acid and alkali. Small Safe,Smart Safe,Electronic Safe,Portable Safe Box Hebei Yingbo Safe Boxes Co.,Ltd , https://www.yingbosafebox.com
This is a traditional separation extraction method. The method utilizes the characteristic that most proteins in soybean are precipitated at the isoelectric point (pH 415), and is separated from other components, and the precipitated protein is dissolved after adjusting the pH, so it is called acid sinking. The defects of acid sinking are: acid consumption, large amount of alkali consumption, high waste water treatment cost, and low product yield. This separation extraction method needs to be improved. But it is still the basic method of industrial production.
2. Membrane separation method.
According to the molecular weight size and shape of the soybean protein and the adaptability of the membrane to the soybean protein, the membrane material and the membrane with different molecular weight cut-off are selected, and the soybean protein extract is ultrafiltered and separated, ultrafiltration purified, and the non-retained components are eliminated to meet the standard. The soy protein solution is separated, and then the purified soybean protein extract is ultrafiltered to a desired concentration, discharged, and spray-dried into a powdery soy protein isolate.
3. Reverse micelle extraction separation method.
The reverse micelle is an aggregate formed by a surfactant in an organic solvent, wherein the non-polar tail of the surfactant is outside, in contact with the organic solvent, and the polar head forms a polar core, and the core has an aqueous solution. And the ability to solubilize the protein, so that the protein can be extracted from the aqueous phase using this organic solvent containing reverse micelles. Extracting soy protein from whole-fat soy flour using reverse micelle technology can extract about 50% at a time. The soy protein extraction process is very fast and is reasonably explained by a non-diffusion model.
The main instruments required for this method are: automatic moisture analyzer, gas bath constant temperature oscillator, centrifuge, Kjeldahl analyzer, analytical balance, thermostatic magnetic stirrer and micro-injection rod.
The main factors affecting the reverse micelle extraction process are the type and concentration of the surfactant, the pH of the aqueous phase, the ionic strength, and the temperature.
The advantages of reverse micelle extraction technology are: high selectivity, easy operation, easy amplification, and the extractant (reverse micelle) phase can be recycled, separated and concentrated simultaneously. The disadvantage is that the stability of the protein in the existing reverse micelle system is not high, resulting in a large loss of protein activity before and after extraction, thus restricting its industrial application.
4. Reversed phase high performance liquid chromatography
This is a method for the rapid separation of 7 S and 11 S globulins in soy protein. The separation of the corresponding globulin was completed in 9 min under the conditions of separation at 40 °C and a flow rate of 1 mL/min. The specific method is:
(1) Reagents and samples. Acetonitrile (CAN) (HPLC grade), trifluoroacetic acid (TFA) (HPLC grade), HPLC grade water for mobile phase preparation. Tris (trimethylaminomethane buffer) and 2-mercaptoethanol (analytical grade) were used to separate soy protein. Soy protein isolate samples can be organized protein, soy flour, soy milk, fortified infant soybeans, and their protein content is determined before use. The sample was dissolved in water and then filtered through a sterile-treated polyphenol filter paper at 0122 μm prior to injection. All samples and standards were stored at 3 °C or under freezing conditions. The sample solution was prepared on the day of analysis and stored on ice for later use.
11 S and 7 S glycinin in 0130% mol/L Tris-HCl buffer and containing 0101 mol/L 22 mercaptoethanol at high speed centrifugation (10000 r/min) at their respective isoelectric points (pH 614 and pH 418) precipitated.
(2) High performance liquid chromatography. Hewlett - Packard 1090 Type II with a diode multiplier and HP 9153C data detection system for 20 μL per injection. Separation was carried out in a PLRP-S column (150 mm × 416 mm ID) filled with polystyrene-divinylbenzene particles (300 ! , 8 μm), column retention time (117 min) through non-adsorbed urine For pyrimidine determination, the protein was determined by UV absorbance at 254 nm. The slow mobile phase A is an aqueous solution of 011% trifluoroacetic acid (TFA); the fast mobile phase B is an 011% TFA acetonitrile solution. The mobile phase was filtered through a 0145 μm nylon filter and vented with a small amount of nitrogen.
The method is characterized by its inability to distinguish between 7 S and 11 S soy protein and is only suitable for rapid qualitative testing of soy protein products.