Production Process Of Soy Protein

2.1 Acid precipitation and alkali extraction

This is a traditional separation and extraction method. This method uses the characteristic of precipitation of most proteins in soybeans at the isoelectric point (pH 4~5) to separate them from other components. The precipitated protein is dissolved after adjusting the pH, so it is called acid precipitation and alkali extraction. The process flow is shown in Figure 1. The disadvantages of acid precipitation and alkali extraction are: acid consumption, large alkali consumption, high waste water treatment cost, and low product yield. The separation and extraction method needs to be improved. But it is still the basic method of industrial production.

2.2 Membrane separation method

According to the molecular weight and shape of the soybean protein and the adaptability of the membrane to the soybean protein, the membrane materials and membranes with different molecular weight cut-offs are selected to ultrafiltration separation and ultrafiltration purification of the soybean protein extract, so that non-retained components are eliminated to meet the standard Separate the soy protein liquid, then ultrafiltration and concentrate the purified soy protein extract to the required concentration, then discharge, spray-dry into powdery soy protein isolate.

2.3 Reverse micelle extraction and separation method

Reverse micelles are an aggregate formed by surfactants in organic solvents, in which the non-polar tail of the surfactant is outside, contacts with the organic solvent, and the polar head is inside to form a polar nucleus, which has an aqueous solution. And the ability to solubilize proteins, so this organic solvent containing reverse micelles can be used to extract proteins from the aqueous phase.

The main factors affecting the reverse micelle extraction process are the type and concentration of surfactants, the pH value of the aqueous phase, ionic strength, and temperature. The advantages of reverse micelle extraction technology are: high selectivity, convenient operation, easy amplification, extractant (reverse micelle) phase can be recycled, separation and concentration can be performed simultaneously. The disadvantage is that the protein is not stable in the existing reverse micellar system, resulting in a large loss of protein activity before and after extraction, thus restricting its industrial application.

2.4 Reversed-phase high performance liquid chromatography

This is a method for rapid separation of 7S and 11S globulins in soy protein. Under the conditions of a separation condition of 40°C and a flow rate of 1 mL/min, the separation of the corresponding globulins can be completed in 9 minutes.