Soybean Polysaccharide: Does It Contain Soy Protein? (2025)

Soybean polysaccharide is an industrial by-product obtained from the production of soybean protein isolate, tofu, and soy milk. Soy protein isolate is widely known for its diverse functionalities and health benefits, and is commonly used in the food industry. Soybean polysaccharide has been found to have an influence on the properties of soy protein isolate gels. However, it is unclear whether soybean polysaccharide contains soy protein.

Soybean polysaccharide is an industrial by-product of soy protein isolate production

Soybean polysaccharide has been studied for its influence on the properties of soy protein isolate gels. It has been found to increase the β-sheet content and decrease the random coil and α-helix contents in both cooked SPI and SPI gel. The addition of soybean polysaccharide to SPI gel changes the main interactions from non-covalent to electrostatic. It has also been found to improve the hardness, water-holding capacity, and rigidity of CaSO4-induced soybean protein gels.

Soy protein concentrate is made by washing soy protein with water to remove soluble polysaccharides

Soybean polysaccharide is an industrial by-product obtained from the production of soybean protein isolate, tofu, and soy milk. Soy protein concentrate is made by washing soy protein with water to remove soluble polysaccharides, such as the carbohydrates stachyose and raffinose. This process is known as aqueous alcohol extraction or acid leaching. The resulting soy protein concentrate contains at least 65% protein by weight and is easily digestible, with a strong amino acid profile. It is often used as a substitute for animal proteins, such as fishmeal and milk proteins, and in meat products like patties, sausages, and pizza toppings.

Soy protein concentrate is produced from de-fatted flakes or soy flour by removing most of the water-soluble, low-molecular-weight components, mainly sugars. The objective is to immobilise the protein while leaching away the solubles. This can be achieved through three basic procedures: acid leaching, aqueous ethanol extraction, and moist heat-water leaching. In all of these treatments, proteins become insolubilized, while a portion of the carbohydrates remain soluble, allowing for their separation by centrifugation.

Soy protein isolate (SPI) is widely known for its diverse functionalities and health benefits and is commonly used in the food industry. The influence of polysaccharide on the properties of SPI gels has attracted extensive attention. For example, the addition of soybean soluble polysaccharide (SSPS) to SPI gel has been shown to increase the β-sheet content and decrease the contents of random coil and α-helix.

Soy protein isolate (SPI) is widely used in the food industry for its health benefits

Soy protein isolate is obtained by removing soybean oil and water-soluble non-protein parts from dehulled soybeans. It has a high protein purity, with a digestibility of 93% to 97%. It is also a good source of fibre, which is beneficial for gastrointestinal health.

Soy protein isolate has been found to have a positive impact on cholesterol levels, lowering low-density lipoproteins (LDL or "bad" cholesterol) and triglycerides. It can also help to improve cardiovascular health, and may reduce the risk of heart disease.

In addition, soy protein isolate may help to manage hormone balance, and it can help the body to create new tissues to replace damaged ones. It can also prevent urinary calcium loss, promote bone health, and reduce the risk of osteoporosis.

SPI gels are influenced by polysaccharide

Soybean polysaccharide does not contain soy protein. It is an industrial by-product obtained from the production of soybean protein isolate, tofu and soymilk.

Soybean protein isolate (SPI) gels are influenced by polysaccharide. The effect of soybean soluble polysaccharide (SSPS) on the formation of glucono-δ-lactone (GDL)-induced SPI gel has been investigated. It was found that SSPS did not change the electrophoretic behaviour of SPI during gel formation. However, infrared analysis indicated that the β-sheet content increased, and the contents of random coil and α-helix decreased in both cooked SPI and SPI gel. The SSPS and SPI might conjugate via the Maillard reaction. The main interactions during SPI gel formation changed from non-covalent to electrostatic interaction after adding SSPS.

The influence of polysaccharide on the properties of SPI gels has attracted extensive attention. During the gelation of protein aqueous solutions containing polysaccharides, interactions between proteins and polysaccharides, such as electrostatic attraction, disulfide bond, hydrogen bond, and hydrophobic interaction between peptide chains and reducing polysaccharides, play an important role in the emerging of physicochemical properties of protein gelation. SSPS can affect the protein aggregation by steric effects because of the highly-branched chain of SSPS and aggregative interactions between the positively charged proteins (pH < pI) and negatively charged polysaccharide at the final pH, which might lead to the degradation of the characteristics of tofu gelation.

The water-holding capacity and gel strength of SPI gel decreased as the SSPS concentration increased. Larger aggregate holes were observed in the microstructure of SPI gel at higher SSPS concentration. Thus, SSPS could covalently conjugate with SPI and influence the formation of hydrogen bonds, disulfide bonds, and electrostatic interaction among SPI molecules to eventually form a loose gel network.

SPI and soybean polysaccharide might conjugate via the Maillard reaction

Soybean polysaccharide is an industrial by-product obtained from the production of soybean protein isolate, tofu, and soy milk. Soy protein isolate (SPI) is widely known for its diverse functionalities and health benefits and is commonly used in the food industry.

The effect of soybean polysaccharide on the formation of SPI gels has attracted extensive attention. The addition of soybean polysaccharide to SPI gels has been shown to increase the β-sheet content and decrease the contents of random coil and α-helix in both cooked SPI and SPI gel. This results in a structure of looser and increased porosity in SPI gels. Furthermore, the addition of soybean polysaccharide reduced the content of the sulfhydryl group of cooked SPI suspension and changed the main intermolecular forces of the gel network from non-covalent bonds to electrostatic interactions.

The possible mechanism for the effect of soybean polysaccharide on SPI gelation involves the conjugation of soybean polysaccharide and SPI via the Maillard reaction. This hypothesis is supported by the results of grafting degree, color change, and infrared analyses. However, further study is needed to fully understand the effect of glycosylation products between soybean polysaccharide and proteins on the formation of SPI gels.

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