Analysis of water-soluble bioactive compounds in commonly consumed soymilk in China

• We developed methods to measure water-soluble bioactive compounds in soymilk.
• We measured the concentrations of bioactive compounds in five types of soymilk.
• Homemade non-genetically modified soymilk showed highest bioactive compound levels.
• Homemade genetically modified soymilk had the highest saponin content (36.7 mg/mL).
• Stachyose in commercial soymilk ranged from 7.28 to 7.85 mg/100 mL.

Soybean, an important source of many bioactive compounds, is of interest because of the health benefits it confers. We compared the contents of different bioactive components, such as peptides, amino acids, isoflavones, saponins, and oligosaccharides, in five commonly used soymilk types in China, using an amino acid analyzer, high-performance liquid chromatography, and an ultraviolet spectrophotometer. The concentrations of almost all bioactive compounds, except for stachyose and raffinose, were significantly higher in homemade soymilk (HSM) samples than in ready-made soymilk (RSM) samples. HSM created using non-genetically modified soybeans contained the most amino acids (21.7%), water-soluble proteins (25.6%), peptides (11.90%), and water-soluble isoflavones (1175 μg/mL). HSM made using genetically modified soybeans contained the most saponin (36.7 mg/mL). RSM samples contained the most stachyose and raffinose. These findings provide basic information for evaluating the function of soymilk with regard to its bioactive ingredients.