There are many types of soy protein commonly used in the field of food processing, such as soy protein isolate, soy protein concentrate, and soy textured protein. Among them, soybean protein isolate (soybean protein isolate, SPI) is a kind of complete protein produced under low temperature conditions with defatted soybean meal as raw material. The protein content is as high as more than 90%. , containing a variety of amino acids required by the human body, it can be used as an animal protein substitute in the food industry, and has great potential for development.
The production process and technology of soybean protein isolate in foreign countries have developed rapidly. From the extraction method to the modification method, a multi-series formulation technology has been formed. According to the application field and product performance of the product, the extraction method and modification method are different. The resulting products are widely suitable for different needs in the fields of meat, dairy products, light chemical industry, etc., and truly reflect the high nutrition and high value-added characteristics of soybean protein.
However, natural SPI is difficult to meet the requirements of the food industry. SPI is easily denatured under certain extreme conditions, and the denatured protein will further form water-insoluble aggregates or even precipitate, resulting in poor solubility.
SPI can form a mixed gel with myofibrillar protein (MP) in meat at a certain temperature. Studies have shown that mixing natural SPI with meat products will reduce the gelatinity of the finished product. In the production of products, the central temperature is around 70 ℃, 7S and 11S proteins are the two most important proteins in SPI, and they have not been denatured at this temperature, and at this time MP has reached the denaturation temperature, and the gel begins to form, and the gel formation process The need to continuously absorb water in the medium leads to not only a loose structure but also poor elasticity of the composite gel, which limits the ability of SPI to improve the texture-related properties of MP gels. Modification of SPI can improve its functional properties and expand its application range in meat production and processing.
Modified SPI is used in meat products, which can increase the flavor, prevent the separation of gravy, improve the quality of meat products and extend the shelf life, etc.
1. Meat products
Block meat products usually refer to large or whole pieces of meat products, but their integrity is easily damaged during processing. By adding modified SPI, syneresis can be reduced, tissue characteristics can be improved, and product quality can be improved. The use of modified SPI can not only maintain the appearance and moisture of meat products due to its excellent water holding capacity and gelatinity, but also use its natural anti-oxidation property as a coating material to delay the oxidation of meat products and extend the shelf life of food While maintaining the organoleptic quality of meat products.
2. Minced meat products
Meat patties, meatballs, and surimi products are all minced meat products. The combination of lean meat and fat meat to form minced meat with stable properties is the key to determine its production quality. Because of its good water and oil absorption, SPI can combine lean meat and fat meat to improve nutritional value and product yield. Zhou Yang et al. added egg white powder and soybean protein isolate powder during the production of fish balls. SPI can significantly enhance the gel strength of fish balls and improve the quality of fish balls. The color, emulsification stability and rheological properties of pork mince were changed after soy protein isolate was subjected to high pressure treatment. The results showed that SPI after high pressure treatment could improve the emulsification properties of pork mince.
3. Emulsified meat products
Emulsified meat products mainly refer to sausage, ham, etc. SPI can form a stable emulsified system with salt-soluble protein in meat, especially myofibrillar protein. The excellent emulsifying properties of SPI can prevent oil leakage caused by fat accumulation in minced meat, improve the oil retention of meat products, and endow emulsified sausage and other products with high-quality taste and flavor. The frankfurter sausage was prepared with ultrasonically modified SPI, carrageenan and inulin, and the results showed that the modified SPI could reduce the intake of animal fat and improve the taste of the product.
4. Imitation meat products
SPI is often used as a raw material to replace animal protein because of its good emulsifying and gelling properties. Through extrusion and other processes, under the comprehensive action of multiple factors, complex changes will occur in protein, fat and carbohydrates, so that the taste and flavor of natural meat can be imitated. Because of its high nutritional value and unique flavor, it is very popular among vegetarians. Using molecular recombination technology to structure soybean protein, the results show that the protein can have a lean meat-like fibrous tissue structure, and the imitation meat food made has a good taste and a shelf life of more than 6 months.