Soy protein isolate

Soy protein isolate is the most refined of the soy protein fractions. It starts as dehulled, defatted soybean white flakes, which are extracted with water adjusted to roughly pH 7.5–9.0, clarified, then precipitated near the isoelectric point at about pH 4.5. The curd is washed, neutralised and spray-dried. What survives that sequence is essentially protein: the FAO reference composition for isolated soy protein is 90% protein, 0.5% fat, 4.5% ash and 0.3% carbohydrate on a moisture-free basis. Yield is around 75% of the protein in the starting material — roughly three tonnes of defatted soybean per tonne of isolate — which is why isolate carries a substantially higher cost than flour or concentrate. For formulators the appeal is functional rather than nutritional alone. Soy protein isolate is amphiphilic and behaves well as an emulsifier, a gelling agent and a water-binder, and it forms fibrous structures under high-moisture extrusion, which is why it and wheat gluten dominate meat-analogue production. Nitrogen Solubility Index is typically 75% or higher; solubility bottoms out near pH 4.5 and recovers above pH 7, so acidic beverage systems need a grade selected for that duty. Standard grinds pass 100 mesh; agglomerated grades exist for instantising. Isoflavone content depends on the wash: aqueous-process isolates have been reported at roughly 690–1,096 µg total isoflavones per gram of protein, while alcohol washing removes most of it. If isoflavone level matters to your specification, say so at enquiry — it is a process choice, not a lot-to-lot variable. Two commercial points deserve attention before you buy. First, soy is a declared major allergen under FSSAI labelling rules, US FALCPA and EU Regulation 1169/2011 Annex II, and soy protein isolate is named explicitly in guidance as requiring declaration — it must be carried through to every downstream label. Second, soybean is a widely genetically modified crop, so non-GMO material has to be identity-preserved and documented rather than assumed. Note also that this product does not belong at the tariff line the trade often uses for it; see the classification note.