Soy Protein
Performance & Recovery
Overview
- Soy protein is a high-quality, plant-derived protein extracted from Glycine max (soybean) seeds.
- It primarily consists of globular proteins (β-conglycinin and glycinin), providing a complete amino acid profile.
- It's a common ingredient in dietary supplements and fortified foods.
- Its purpose is to supply dietary protein and bioactive peptides supporting metabolic, muscular, and cardiovascular health.
Chemistry
- Soy protein is a heterogeneous mixture of globular proteins (β-conglycinin, 7S; glycinin, 11S) with average molecular weights of 150–300 kDa.
- The primary structural motif is a β-sheet-rich globulin stabilized by disulfide bonds (Cys-Cys).
- The empirical formula is approximately (CₓHᵧNₓOₓ) with an average amino-acid composition of ~53 % (by weight) protein, 33 % carbohydrates (including oligosaccharides), and 5 % lipids.
- The isoflavone fraction (genistein, daidzein, glycitein) is a polyphenolic structure: C₁₅H₁₀O₅ (genistein, IUPAC: 5,7-dihydroxy-4′-hydroxy-3-(4-hydroxyphenyl)-2-phenyl-4H-chromen-4-one).
- The protein is soluble at pH 7–9, denatures at >70 °C, and exhibits a net-positive charge at pH < 5 (isoelectric point ≈4.5).
Sources & Quality
- Commercial soy protein is derived from soybeans grown primarily in the United States, Brazil, Argentina, and China.
- Typical manufacturing involves:
- Defatting of de-hulled soybeans using hexane or supercritical CO₂.
- Aqueous extraction at pH 8–9, followed by centrifugation.
- Iso-pH precipitation (pH 4.5) to precipitate protein (soy protein concentrate, SPC) or pH 8.5 for soy protein isolate (SPI).
- High-purity isolates (>90 % protein) undergo spray-drying and may be further filtered (ultrafiltration) to remove residual lipids and anti-nutrients (phytates, trypsin inhibitors).
- Quality considerations include protein purity, isoflavone content, and absence of heavy metals or pesticide residues (verified by GMP and third-party testing).
- Organic, non-GMO, and “fermented” soy proteins are increasingly marketed for enhanced digestibility and lower allergenicity.
Where to Buy Soy Protein
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