Soy Protein Isolate
Completeness scorecard
Deterministic gap audit — no score is composite, no cell is LLM-judged. Each chip is re-derivable by re-running tools/evidence/build-ingredient-scorecard.mjs. review: residuals and missing data are worked autonomously via data/evidence/ingredient-scorecard-review-flags.csv and wiki/completeness-gaps.md.
| Dimension | Status | What’s there (auditable counts) | What’s missing |
|---|---|---|---|
| D1 Analyte coverage (tier: unset) | GAP | 0/10 HMTc analytes, total n=0 | only 0/10 analytes have evidence |
| D2 Regional coverage | below-tier | 1 jurisdictions, top BR 100% | only 1 distinct jurisdiction(s) |
| D3 Anthropogenic evidence | GAP | no upstream/attribution sources | link a supply-chain/ hub page |
| D4 Background mechanism | GAP | section present, 0 drivers, 0 upstream source(s) | drivers[] empty; no upstream source to substantiate |
| D5 Pooling depth | GAP | no priority analytes | — |
| D6 Speciation | OK | iAs, tHg, tAs declared | — |
| D7 Basis declaration | GAP | 0/10 populated cells declare a basis token | 10 populated cell(s) lack a basis token: Pb, Cd, iAs, tHg, Ni, Al, Cr, Sn, tAs, U |
| D8 Provenance integrity | GAP | 8 claims checked, 8 supported; 3 citations, 0 orphan, 3 foreign | 3 foreign citation(s) not naming soy-protein-isolate: burrell2010-aluminium-in-infant-formulas, chuchu2013-aluminium-in-infant-formulas, kazi2009-toxic-elements-in-infant-formulae |
| D9 Mitigation | GAP | 0 cited lever(s), 6 mitigation/ link(s) | section present but no source-cited lever |
| D10 Regulatory coverage | OK | 2 rule link(s), 0 metal(s) covered | — |
| D11 Standards-readiness | NOT-READY | no priority analytes | basis: 10 populated cell(s) lack a basis token: Pb, Cd, iAs, tHg, Ni, Al, Cr, Sn, tAs, U; consumption tier unset (depth bar uncheckable) |
| Principle balance | OK | consumer-protection 0.67, contamination-reduction 0.00, brand-value 0.00, legal-defensibility 0.38, scale 0.00 | — |
This is a structural ingredient node created so product pages can link to a real wiki target. Occurrence values remain pending until a source is promoted for this ingredient.
Heavy metal contamination profile
Per-analyte snapshot derived from the machine-readable contamination_profile in the frontmatter above. data gap indicates the literature has been reviewed for this commodity-analyte combination and no usable occurrence data was found (a finding, not a placeholder). The Key sources column shows the top 2-3 contributing sources by year and sample size, with numbered wikilink aliases.
| Analyte | Coverage | Typical (ppb) | p95 (ppb) | Confidence | Key sources |
|---|---|---|---|---|---|
| Pb | data gap | — | — | — | — |
| Cd | data gap | — | — | — | — |
| iAs | data gap | — | — | — | — |
| tAs | data gap | — | — | — | — |
| tHg | data gap | — | — | — | — |
| Ni | data gap | — | — | — | — |
| Al | data gap | — | — | — | — |
| Cr | data gap | — | — | — | — |
| Sn | data gap | — | — | — | — |
| U | data gap | — | — | — | — |
Routing
This node is linked from infant-formula-concentrated-liquid-soy-based, infant-formula-powder-soy-based, infant-formula-rtf-liquid-soy-based.
Contamination Profile State
The machine-readable contamination profile is pending. Ingredient-level values belong here once parsed; finished-product values belong on the relevant product-category page.
Sources
Auto-generated from source-page frontmatter. The “Used on this page for” column is populated by the orchestrator’s POPULATE-SOURCE-LEGEND action; pending entries appear as *[awaiting synthesis]*.
| # | Citation | Year | Type | Used on this page for |
|---|---|---|---|---|
| 1 | Rebellato et al. 2023. Inorganic Contaminants in Plant-Based Yogurts Commercialized in Brazil, International Journal of Environmental Research and Public Health | 2023 | Peer-reviewed | BR Al, Cr, Co, Ni, tAs, Mo, Cd, Sb, Ba, tHg, Pb occurrence in Forty-three samples of plant-based yogurt (17 different flavors across 5 brands) and 1 sample of cow-milk natural yogurt… (n=44) |
| 2 | Rebellato et al. 2023. Composition and bioaccessibility of inorganic elements in plant-based yogurts, Journal of Food Composition and Analysis | 2023 | Peer-reviewed | BR Al, Cr, Co, Ni, Mo, Ba occurrence in Forty-four plant-based yogurt sample-lots and one cow-milk natural yogurt sample-lot purchased from August to October 2022 in commercial… (n=45) |
Why this commodity accumulates heavy metals
Soy protein isolate is the highly refined protein fraction of soybeans (Glycine max), produced at ≥90% protein content (dry-weight basis). It is the protein base for soy-based infant formula and a major ingredient in plant-based meat alternatives, protein bars, protein powders, and nutritional beverages. Heavy-metal load in soy protein isolate originates dominantly from the source soybean’s inherited Al, Ni, and Cd profile, which the protein-extraction process concentrates on a per-protein-mass basis. Soybeans naturally accumulate Al at concentrations multiples higher than most grains because soy plants have high-affinity Al uptake from acidic soils (a documented agronomic phenomenon — soy yields are Al-stress-sensitive in acidic soils because of root-zone Al toxicity, and the surviving plant tissue carries elevated Al). Cadmium accumulates via the soybean’s high-efficiency Cd transporter (similar to rice’s Cd uptake pathway but operating in upland not flooded conditions); Ni accumulates via the soy plant’s urease-cofactor pathway.
The protein-extraction process (acid-base extraction with isoelectric precipitation, then drying) concentrates the soybean’s metal load on a per-protein-mass basis because the extraction selectively separates protein from carbohydrate, fat, and fiber while retaining the protein-bound metals. The net effect is that soy protein isolate carries the soybean’s Al/Ni/Cd profile at concentrations several-fold higher than the source soybean on a per-mass basis. This is the upstream pathway that feeds into soy-based infant formula and explains why soy-based formula carries elevated Al relative to cow-milk formula per Burrell 2010 and the broader corpus. The HMTc panel concerns for soy protein isolate are Al, Ni, and Cd (dominant), with secondary Pb from minor source-soybean and processing-equipment inheritance.
The data gap status across all ten analytes in the body table reflects that no source in the current routing audit reports soy-protein-isolate-specific values; the synthesis is inferred from the source soy commodity and from soy-based-formula evidence in Burrell 2010, Chuchu 2013, and Kazi 2009.
Ranges by source, region, and variety
Variance within soy protein isolate tracks source-soybean origin region (US Midwest soybean production, Brazilian soybean production, Argentine soybean production, Chinese domestic soybean production, European soybean production — each carrying different Al/Cd profiles reflecting regional soil characteristics), cultivar choice within Glycine max (Al-tolerant cultivars accumulate more Al; commercial cultivar selection drives variance), and protein-isolation process (acid-base extraction vs membrane-based separation; ion-exchange polishing as a post-extraction step). Brazilian and Argentine soy production from acidic Cerrado/Pampean soils carries higher Al than US Midwest production from less-acidic Mollisol soils. Soy-isolate suppliers competing on infant-formula specifications operate to internal Al ceilings; competing suppliers offer different impurity-tier guarantees.
Processing effects
Soy protein isolate manufacturing involves five primary steps: defatting (hexane extraction of soybean oil from flaked soybeans, leaving defatted soy meal), aqueous extraction (alkaline pH ≈8-10 solubilizes protein from carbohydrate and fiber), isoelectric precipitation (pH adjustment to ≈4.5 precipitates protein from solution), neutralization and washing (removal of soluble salts and minor components), and spray-drying (concentration to powder form). The aqueous extraction step partially mobilizes water-soluble metal salts but the subsequent precipitation retains protein-bound metals; ion-exchange polishing as a post-extraction step can substantially reduce Al, Ni, and trace heavy metals. Most commodity-grade soy isolate does not include the ion-exchange polishing step; infant-grade soy isolate from leading suppliers does.
Ingredient-derivative risk
Soy protein isolate routes into three soy-based infant formula product rows (infant-formula-powder-soy-based, infant-formula-rtf-liquid-soy-based, infant-formula-concentrated-liquid-soy-based) plus the broader soy-protein-containing product universe (plant-based meat alternatives, protein bars, protein shakes, nutritional beverages). The per-finished-product metal load is determined by inclusion rate × per-isolate concentration; soy-based infant formula at high inclusion rate carries the most consequential per-product metal exposure. Soy protein concentrate (≥70% protein) and textured vegetable protein (TVP) are related but less refined derivatives with broadly similar per-mass metal profiles.
Mitigation options
Sourcing levers (supply-chain-screening) are the dominant intervention. Soy-isolate supplier specification at infant-grade impurity tier (typically <500 ppb Al, <100 ppb Pb in finished isolate); supplier audit programs verifying ion-exchange polishing practice; soybean-origin specification favoring lower-Al production regions; and contractual specification of Al/Ni/Cd ceiling on incoming isolate.
Agronomic levers (agronomic) operate at the soybean-cultivation stage; see soy for the soil-pH management (lime application to raise pH from acidic to near-neutral reduces Al availability), cultivar-selection (Al-tolerant vs Al-sensitive cultivars accumulate different Al loads), and remediation interventions.
Processing levers (processing) are highly effective. Ion-exchange polishing of the soy isolate during the extraction process removes substantial Al, Ni, and trace heavy metals; this is the dominant per-isolate-supplier differentiator. Selection of soy-isolate suppliers that operate ion-exchange polishing is the practical brand-side lever.
Formulation levers (formulation) include alternative-base-protein substitution where medically appropriate. For infant formula, hydrolyzed cow-milk protein or amino-acid-based formula substitutes for soy isolate. For plant-based meat alternatives and protein products, legume proteins (pea, fava), wheat gluten, and rice protein offer alternative bases with different metal profiles.
Testing and QC levers (testing-and-qc) are mature: lot-level Al, Ni, Cd, Pb testing on incoming soy protein isolate against per-mass-in-finished-formula compliance targets. ICP-MS is the standard analytical platform.
Packaging and storage levers (packaging-and-storage) are minor; the metals are intrinsic to the isolate. Avoidance of aluminum-foil-lined containers for stored isolate is a basic precaution.
Regulatory limits that apply
Soy protein isolate as an ingredient does not have direct regulatory maximum levels; the operative limits apply to the finished products into which it is incorporated:
- eu-2023-915 — EU Reg. 2023/915 sets maximum levels for infant formula (Pb 10 ppb prepared-for-feeding, Cd 5 ppb, iAs 20 ppb, Hg 20 ppb); the soy isolate must be specified to deliver finished-formula concentrations within these limits.
- US FDA Closer to Zero infant-and-young-child food framework: applicable to soy-based infant formula.
- Codex Alimentarius CXS 72-1981 (infant formula) and CXS 156-1987 (follow-up formula) establish composition standards.
- JECFA Al PTWI of 2 mg/kg b.w./week and EFSA TWI of 1 mg/kg b.w./week are the relevant dose-response references for the Al-elevated route specific to soy-based infant feeding.
- California Prop 65 (california-prop65) Pb MADL applies to soy-isolate-based products sold in California.
Page history
The five most recent substantive edits to this page. The full version history lives in git; when DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.
| Commit | Date | Description |
|---|---|---|
| b0f3d38 | 2026-06-12 | batch | corpus rescreen b04 old terminal skips |