Based on pulse dry fractionation data from protein-mill.com and peer-reviewed dry-fractionation studies, ash concentrates into the fine protein fraction during air classification because minerals and phytic acid are mainly stored within protein bodies. Ash values are reported on a dry-matter basis.
Yellow pea air-classified protein concentrate (most common)
- Typical range: 2.7–4.0 % ash (dry basis) for standard dry-fractionated pea protein fines (48–58% crude protein)
- When pushing to higher protein grades (>58–60% protein), ash often rises to 3.5–5.0 %, as more mineral-rich protein bodies are captured in fines
Chickpea air-classified protein concentrate
- Typical range: 3.0–4.5 % ash (dry basis). Chickpea raw seed has inherently higher native mineral content than yellow pea, so ash in chickpea protein fines is generally slightly higher than pea.
Other pulses for reference
- Fava bean dry-fractionated protein fines: ~3.5–5.2 %
- Red lentil dry-fractionated protein fines: ~3.2–5.2 %
Key influencing factors
- Raw seed mineral profile: Cultivar, growing soil, harvest conditions strongly affect baseline ash.
- Dehulling completeness: Incomplete dehulling adds hull-associated minerals and raises ash.
- Protein enrichment target: Higher protein purity in fines usually correlates with higher ash, because phytic acid and cations co-concentrate with protein bodies.
- Process cut-point: Aggressive classification to pull more fine particles pulls more mineral-rich micro-fines.
Comparison with wet-extracted protein
Wet-extracted pea protein isolate normally has lower ash (~2.0–3.0 %), because soluble minerals and phytic acid are washed away during aqueous solubilisation and precipitation. Dry fractionation cannot remove these minerals, which is why ash is inherently higher for air-classified concentrates.
Ash is mostly bound phosphorus, calcium, magnesium and potassium (largely as phytate-mineral complexes). This higher ash does not represent added salts; it is native mineral from the pulse cotyledon. If low ash is required, hybrid dry + mild wet polishing is needed.
