Why is soy protein the star among plant proteins?

What are the differences between animal and plant protein nutrition?

The reason why proteins contain different amino acids has a lot to do with the source of the protein. Protein mainly comes from animal foods and plant foods. The amino acids contained in animal proteins and plant proteins are different, which means that their nutritional values ​​are also different.
Animal protein mainly comes from meat, eggs and milk of poultry, livestock and fish. Its protein composition is mainly casein (78~85%), which can be better absorbed and utilized by adults. More importantly, animal protein has a complete range of essential amino acids in a reasonable proportion, so it is easier to digest, absorb and utilize than ordinary plant protein, and its nutritional value is relatively high. Generally speaking, the amino acid scores of meat (such as fish, beef) proteins and proteins in milk are between 0.9 and 1.0.

Plant-based protein mainly comes from rice, noodles and beans, but the protein nutritional values of rice, noodles and beans are different. Proteins derived from rice and noodles lack lysine (an essential amino acid), so their amino acid score is low, only 0.3 to 0.5. This type of protein will also be poorly absorbed and utilized by the body. Of course, this deficiency can be improved through scientific methods. For example, adding lysine-rich legumes appropriately to rice noodles can significantly improve the amino acid score of protein.

Why is soy protein the star of protein?

Among the many plant-based proteins, legume protein (also known as soy protein) has the highest nutritional value, and legume foods do not contain cholesterol, which is a feature that animal foods do not have. Unprocessed soy protein has its drawbacks: It contains relatively little methionine, an essential amino acid. Therefore, the amino acid score of whole soybeans is approximately 0.6 to 0.7. However, because soybeans have high protein content and do not contain cholesterol, soybean protein is widely used by people.

The quality of soy protein processed by modern methods has greatly changed, and the fat content in soy protein has also been reduced (the fat content in whole soybeans is about 20%). The protein content of defatted soybean flour can generally reach 50%, and the protein content of soybean protein concentrate can be increased to about 70%, and can be used for infants and young children who are intolerant to milk. After modern processes such as defatting, water extraction, rinsing, and drying The protein content of processed soy protein isolate can be as high as 90%, and the digestibility of processed soy protein isolate has also been improved.

Of course, these processes only increase the protein content, not the amino acid pattern of the protein. However, if methionine, which is relatively lacking in soybean itself (also known as amino acid fortification) or animal protein rich in methionine, is appropriately added to soybean protein, the nutritional value of soybean protein will be significantly improved and the amino acid score of the protein will be improved. For example, when adding With an appropriate amount of whey protein, the amino acid score of soy protein isolate can reach 1.0. Its nutritional value is consistent with that of egg and milk proteins, very close to the standard amino acid pattern, and is easily absorbed and utilized by the body.