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Manufacturing process of soy protein isolate

Soy protein isolate technology
  1. Raw materials

The quality of soybean meal directly affects the extraction rate and functional characteristics of isolated proteins. The raw material used for protein separation production, soybean meal, should be low denatured soybean meal after cleaning, peeling, solvent defatting, and low-temperature or flash evaporation. This soybean meal has low impurities, high protein content, and low degree of protein denaturation, making it suitable for the production of soy protein isolate. The degree of protein denaturation in soybean meal, also known as nitrogen solubility index (NSI), is closely related to the extraction rate of soy protein isolate.

  1. Extraction process

When extracting protein from soybean meal, the amount of water added, pH, temperature, and extraction time have a significant impact on the yield of separated protein.

Soaking: Many companies first dry crush soybean meal and then mix it with water for extraction. Dry crushing is not conducive to improving the extraction rate of proteins, and it is also prone to thermal denaturation of proteins, reducing their NSI value. If defatted soybean meal is soaked in water for a period of time before grinding, it can effectively improve the protein extraction rate. The method of soaking first and then grinding is more in line with the dissolution mechanism of soybean protein than dry crushing and soaking. According to the measurement, the protein extraction rate of soaking and then grinding is 2-4 percentage points higher than that of dry crushing and then soaking.

  1. Separation process

In the process of producing separated protein using alkaline solution acid precipitation method, there are two separation steps. The first step is to extract soy protein with alkaline solution, then centrifuge and separate the protein extraction solution and soybean residue; The second is to separate protein curd and whey by centrifugation after acid precipitation. The separator is a key equipment in the production of soy protein isolate. It is necessary to fully understand the performance of the separator and its adaptability to materials, otherwise it will greatly affect the separation effect, reduce the protein extraction rate and purity., In terms of equipment selection, we have cooperation with the most advanced domestic and foreign centrifuge manufacturers, proficient in the performance, operation methods, and maintenance of various centrifuges. We can maximize your efficiency in the production process. You can also adopt auxiliary facilities based on your own equipment.

  1. Acid precipitation, water washing, neutralization process

The acid precipitation process of soy protein mainly utilizes the principle of minimizing the solubility of soy protein under isoelectric pH conditions to make it coagulate and precipitate. Soy protein cannot agglomerate and precipitate under all acidic conditions. It can only agglomerate and precipitate when the pH is near the isoelectric point of soy globulin. Therefore, only by strictly controlling the pH required for acid precipitation can satisfactory results be achieved. To achieve this, it is necessary to achieve automatic control of process parameters. There are many factors that affect isoelectric precipitation, and the presence of a large amount of phosphorus containing compounds in protein extraction solution is one of the major factors. The speed of adding acid and stirring during the acid precipitation process also affects the precipitation of proteins. Poor control can easily lead to slow protein aggregation and sedimentation, as well as cloudy supernatant. Although the pH value reaches the isoelectric point.

  1. Sterilization, homogenization, and drying processes

The protein slurry that has been neutralized by beating needs to be heat treated. Heat treatment at different temperatures has different effects on the viscosity, gel strength, NSI value and flavor of protein products. High pressure homogenization treatment has a significant impact on the functionality of protein isolate products. The viscosity of protein slurry treated by high-pressure homogenization is significantly reduced. The high shear force can break the cross-linking and condensation of protein molecules, and the sensitivity of protein slurry to heat is weakened. The NSI value of the product increases with the increase of homogenization pressure, but excessive homogenization will damage the gelatinization of protein products. The spray drying method is generally used for the drying of protein isolate. spray drying includes pressure spray, centrifugal spray, two fluid spray and other forms. Pressure spray drying is the best way to produce protein isolate. The protein isolate products produced by pressure spray drying have small particles but high bulk density. The product dried by centrifugal spray has low unit weight. A large number of bubbles are brought into the product after hydration, which will reduce the gelation strength of the protein. The shelf life of the product with low unit weight is also not ideal. When protein solution is dried by spray, poor control of inlet air temperature, exhaust air temperature and spray temperature will affect NSI. If protein powder stays in spray tower for too long, gel property and NSI value will also be reduced.

The above is the production process of soy protein. Through the above process, high-purity soy protein isolate can be obtained, providing important raw materials for food industry production. But what needs to be emphasized is the cleanliness of equipment, hygiene of operations, and quality of raw materials in production to ensure the quality of the final product and food safety.

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