Functional Properties of Soy Protein

Soybean protein products are more and more widely used in various fields of food processing. On the one hand, it is due to the high nutritional value of soybean protein, abundant resources, and low cost of raw materials, Processability and other related functional characteristics. And with the deepening of research, the latter reason (processability, or functional characteristics) is becoming more and more important. The so-called functional properties refer to the special functions played by soybean protein in the process of food processing and storage, such as emulsification, oil absorption, water absorption and water retention, gelling, etc., which are the inherent physical and chemical properties of soybean protein itself (composition , amino acid sequence, morphological structure), and their performance is affected by certain food components (water, salt, protein, sugar, fat, etc.) Therefore, the functional properties of proteins are determined by many factors.

1. Water retention
The water retention of soybean protein plays an important role in the production of meat products, especially the ability to absorb, combine and bind water during the processing of minced meat products, which can not only retain the juice of raw meat, but also increase the taste and flavor of products , but also increase the yield of the product.
The water retention of protein is also affected by many factors, such as viscosity, pH value, ionization strength and temperature. Scientist studied the effect of the addition of soybean protein isolate on heat-induced gelation of salt-soluble muscle protein. The strength of the protein gel, but the water holding capacity of the gel is improved.

2. Emulsification
The hydrophilicity and lipophilicity of soybean protein determine its emulsification and stability. Soybean protein is a kind of surfactant, which can not only reduce the surface tension of water and oil, but also reduce the surface tension of water and air, so it is easy to form a more stable emulsion. The emulsified oil droplets are stabilized by proteins that accumulate on the surface of the oil droplets, forming a protective layer. This protective layer can prevent the aggregation of oil droplets and the destruction of the emulsified state, thereby stabilizing the emulsifying performance. In the production of baked food, frozen food and soup food, there have been a large number of research reports on adding soybean protein isolate as emulsifier to stabilize the product state.

3. Adhesion
The protein has a large molecular weight, and its strong solubility and adsorption capacity make it cohesive. Suitable for adjusting the physical properties of food. When the protein is heated to 80°C, the protein dissociates or dissociates, the molecular specific volume increases, and the viscosity increases, and the viscosity above 90°C decreases instead. When the pH is between 6 and 8, the protein structure is the most stable and the viscosity is the largest; when the pH exceeds 11, the viscosity decreases sharply because the protein association is destroyed.

4. Gel property
Meat products containing soybean protein will form a gel structure when heated. This feature can improve the hardness, elasticity, flakes and texture of meat products, and has a significant effect on the water retention and chewiness of the product. The formation of gel Affected by many factors, including heating time, temperature and concentration of soybean protein liquid, etc.


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