---
id: "20260820-0216-verify-the-primary-source"
title: "Capture: Verify the primary source for the '20% metmyoglobin → half of consumers reject' fresh-meat threshold"
type: "capture"
status: "promoted"
promoted_to: ["30-notes/claim-metmyoglobin-20-percent-figure-traces-to-hood-riordan-1973-and-renerre-mazuel-1985.md (Claim 1 — the citation-trail corroboration)"]
not_promoted: ["Claim 2 (neither named primary independently read; both access-blocked) — an access-attempt log and epistemic-status about a research gap, not a durable atomic world-claim. Folded into the new note's body and the open question's progress line rather than given its own file. Per the no-network design, access-blocks are not re-logged as claim-notes.","Claim 3 (search-derived 'sales-ratio, not consumer-rejection' framing gap) — rests ONLY on WebSearch synthesis over snippets, inadmissible per sources.md's quote-provenance/fabrication rule ([unverified-quant — needs primary]); no claim above the sourcing floor may rest on it. The doubt is real and preserved where it IS admissible: as a watch_flag on the new claim-note and the sharpened next-step in [[question-verify-metmyoglobin-20-percent-consumer-rejection-threshold]] — not asserted as a fact.","'Central question status', 'Further leads', 'Entity candidates' sections — session-status synthesis and leads, not atomic claims. Leads folded into the question's progress line; entity candidates judged and declined (see journal 2026-08-22)."]
origin: "batch"
writer_model: "claude-sonnet-5"
date_created: "2026-08-20T00:00:00.000Z"
provenance: "this batch run, 2026-08-20"
derived_from: []
tags: ["food-science","meat","myoglobin","kubelka-munk-theory","quantitative-claim","primary-source-verification","unverified-quant","corroboration"]
source_url: "https://pmc.ncbi.nlm.nih.gov/articles/PMC5223250/"
source_sha: "fa2b1d1410ce0a328eade441f514c5a85f25e82c44a96f7146d2b8d7d926d64e"
source_title: "CIELAB color coordinates versus relative proportions of myoglobin redox forms in the description of fresh meat appearance"
source_author: "B. Hernández, C. Sáenz, C. Alberdi, J. M. Diñeiro"
source_date: "2016-12-19T00:00:00.000Z"
source_venue: "Journal of Food Science and Technology 53(12):4159–4167 (PMC5223250)"
source_quote: "As the proportion of metmyoglobin increases meat color turns to brown. This induces a negative response in consumers and when the proportion of MMb reaches 20% it has been found that the product is rejected by half of the potential consumers (Hood and Riordan 1973; Renerre and Mazuel 1985)."
source_tier: 1
seek_code_commit: "17d9798"
---


This capture directly answers the open question raised while promoting
[[claim-kubelka-munk-reflectance-theory-grades-meat-freshness-via-myoglobin]]
(tracked as `question-verify-metmyoglobin-20-percent-consumer-rejection-threshold`
in `50-questions/`). That note carries the figure "when the proportion of MMb
reaches 20% it has been found that the product is rejected by half of the
potential consumers," flagged `[unverified-quant]` because the citing paper
(PMC5223250) attributes the number secondhand ("it has been found that")
rather than reporting its own data. The task here was to trace the citation to
its primary home and read that source directly.

---

## Claim: The figure is consistently traced, in the citing literature, to two named 20th-century studies — Hood & Riordan (1973) and Renerre & Mazuel (1985) — not invented or garbled by the modern paper that repeats it

**Claim type:** historical/bibliographic-attribution claim (what the citation
trail says, not the underlying number itself) — Tier 1–2 required; met at
Tier 1 via direct full-text reads of two independent papers.

PMC5223250 (Hernández, Sáenz, Alberdi & Diñeiro, 2016) attributes the figure
inline to two references: "Hood DE, Riordan EB. Discolouration in
pre-packaged beef: measurement by reflectance spectrophotometry and shopper
discrimination. Int J Food Sci Technol. 1973;8:333–343" and "Renerre M,
Mazuel JP. Relationships between instrumental and sensory measurement
methods of meat color. Sci Alim. 1985;5:541–557." A second, independent
paper by an overlapping author set — Hernández, Sáenz, Alberdi & Diñeiro,
"Comparison between two different methods to obtain the proportions of
myoglobin redox forms on fresh meat from reflectance measurements" (*J Food
Sci Technol* 52(12):8212–8219, 2015; PMC4648909) — carries the **identical**
sentence and the same citation pair, word for word:

> "As the proportion of metmyoglobin increases meat color turns to brown,
> this induces a negative response in consumers and when the proportion of
> MMb reaches 20 % it has been found that the product is rejected by half of
> the potential consumers (Hood and Riordan 1973; Renerre and Mazuel 1985)."

Because this is the same author group reusing the same sentence and
citations across their own two papers (not two independent research groups
converging on the figure), it corroborates the *citation trail* — the figure
reliably traces to these two 1973/1985 studies and not to some other or
invented source — without corroborating the *number itself*. Both quotes
were confirmed present verbatim in the archived primary texts
(`mcp__seek__quote_check`, both `grounded: true`).

**Provenance:**
- source_url: https://pmc.ncbi.nlm.nih.gov/articles/PMC4648909/
- source_sha: baf432631dd9684527ec56a3c4e413b24d490469159f8ec239d77d7ac41a230d
- source_title: "Comparison between two different methods to obtain the proportions of myoglobin redox forms on fresh meat from reflectance measurements"
- source_author: "B. Hernández, C. Sáenz, C. Alberdi, J. M. Diñeiro"
- source_date: 2015-06-19
- source_venue: "Journal of Food Science and Technology 52(12):8212–8219 (PMC4648909)"
- source_quote: "this induces a negative response in consumers and when the proportion of MMb reaches 20 % it has been found that the product is rejected by half of the potential consumers (Hood and Riordan 1973; Renerre and Mazuel 1985)"
- source_tier: 1

---

## Claim: Neither named primary source has been independently read this session — both are access-blocked, so the number itself is still not confirmed in the original authors' own words

**Claim type:** epistemic-status/access claim about a research gap — Tier
3–4 acceptable for reporting the gap itself; reported plainly.

Multiple routes to Hood & Riordan (1973) were attempted and blocked:
- Wiley Online Library, the DOI's home (10.1111/j.1365-2621.1973.tb01721.x) — HTTP 403.
- ResearchGate's listing for the paper — HTTP 403 (`archive_page` fallback also 403'd).
- No open-access copy located via web search on HathiTrust, Internet Archive, or CORE for either the 1973 *Journal of Food Technology* / *International Journal of Food Science and Technology* volume or the paper itself.

Renerre & Mazuel (1985, *Sciences des Aliments*) was not located online at
all this session (no DOI or open host surfaced). A related, more accessible
Renerre solo review — "Factors involved in the discoloration of beef meat,"
*Int J Food Sci Technol* 25:613–630 (1990), Oxford Academic — was tried as a
possible secondary route to a fuller quotation of the 1973/1985 finding, but
also returned HTTP 403 (`archive_page`).

Because of the fabrication-risk rule on quote provenance (search-result
summaries are not sourced material, however specific), none of the
paraphrases of Hood & Riordan's finding that surfaced in search snippets are
recorded here as claims — see the next claim for why that distinction
matters.

**Provenance:** access attempts only; no admissible quote obtained.
- https://onlinelibrary.wiley.com/doi/10.1111/j.1365-2621.1973.tb01721.x — HTTP 403
- https://www.researchgate.net/publication/229872005_Discoloration_in_pre-packaged_beef_measurement_by_reflectance_spectrophotometry_and_shopper_discrimination — HTTP 403
- https://academic.oup.com/ijfst/article/25/6/613/7867407 — HTTP 403

---

## Claim: search-derived characterizations (not independently confirmed) describe Hood & Riordan's actual 1973 result as a *sales-ratio* finding, not literally "half of consumers reject" — a framing gap that remains open

**Claim type:** quantitative/mechanism nuance — Tier 1–2 required, **not
met**. Recorded as `[unverified-quant — needs primary]` per the fabrication
rule: this characterization comes only from WebSearch's own synthesized
answer text over search snippets, not a direct fetch of the paper, so it is
not admissible as a sourced claim — it is recorded here as the shape of the
open question, not as a fact.

Search summaries (not independently verified against primary text)
repeatedly described Hood & Riordan's actual finding as: a linear
relationship between surface metmyoglobin (5–33% MMb) and the proportion of
total beef sales that were discoloured, such that a 1:2 ratio of
discoloured-to-bright-red beef sales was reached when surface MMb was about
20%. A *sales ratio observed in a shop* is not the same claim as "half of
potential consumers reject the product" — the former is a market-level
outcome (roughly a third of realized sales going to the discoloured
category, if bright-red keeps outselling 2:1), the latter is framed as an
individual consumer-acceptance threshold. Whether the "half of consumers
reject" phrasing is a faithful restatement of Hood & Riordan's own framing,
a conflation with the separate Renerre & Mazuel (1985) citation paired
alongside it, or a drift introduced somewhere in the citation chain between
1973 and the 2015/2016 PMC papers, **cannot be determined without reading
the 1973 paper's own text** — which remains blocked (previous claim).

> [!note] Seek's commentary:
> This is the actually interesting finding of this session: not a number,
> but a seam. Two Tier-1 papers by the same careful author group cite the
> figure identically and correctly as secondhand ("it has been found that"),
> which is honest of them — but the moment you go looking for what the 1973
> study actually measured, the shape of the claim changes from an individual
> psychological threshold to an aggregate retail statistic. That's exactly
> the kind of drift a load-bearing number should not be allowed to acquire
> silently, which is why this stays flagged rather than folded into the
> vault's existing note as confirmed. — Seek

**Provenance:** none admissible — WebSearch synthesis only, `[unverified-quant — needs primary]`.

---

## Central question status

**Is the primary source for "20% metmyoglobin → half of consumers reject" verified?**
`[unverified — could not confirm or deny after search]`. The *citation
trail* is now solidly established and doubly corroborated: two independent
Tier-1 papers from the same research group both name Hood & Riordan (1973)
and Renerre & Mazuel (1985) as the sources, using identical wording, which
rules out the figure being a fabrication or citation error introduced by
either PMC paper. But the primary documents themselves remain unread after
genuine effort (Wiley, ResearchGate, and a related Oxford Academic review
all returned HTTP 403; no open-access copy found on HathiTrust or Internet
Archive), so the number's exact wording, sample, and methodology in the
authors' own words is still unconfirmed — and search-derived hints suggest
the commonly repeated "half of consumers reject" framing may not exactly
match what the 1973 study itself measured (a sales ratio, per unverified
secondary characterization). The existing vault note's `[unverified-quant]`
flag on this figure should **remain in place**, now with a more specific
next step: get inside Hood & Riordan (1973) itself, not just another paper
that cites it.

---

## Further leads

- Renerre, M. (1990). "Factors involved in the discoloration of beef meat." *Int J Food Sci Technol* 25:613–630 — Oxford Academic hosts it; 403'd this session but is the most promising secondary review to quote Hood & Riordan more fully if access can be obtained by another route.
- Faustman, C. (1990). "The Biochemical Basis for Discoloration in Fresh Meat: A Review." *Journal of Muscle Foods* — another candidate review from the same era, untried this session.
- Mancini, R.A. & Hunt, M.C. (2005). "Current research in meat color." *Meat Science* 71:100–121 — read in full this session (open PDF at meatscience.org, the American Meat Science Association's own site); notably does **not** cite Hood & Riordan or the 20%/50% figure anywhere in its text or reference list, despite being the field's standard five-year review — a negative data point on how load-bearing this specific figure actually is in current meat-color research.
- HathiTrust holds a catalog record for the journal "Food technology" (https://catalog.hathitrust.org/Record/001116099) — untried this session for a scanned 1973 volume.

---

## Entity candidates

- D. E. Hood — person — co-author of Hood & Riordan (1973), the older, foundational study the whole "20%/half-rejected" figure traces back to; not yet independently read.
- E. B. Riordan — person — co-author of the same 1973 foundational study.
- M. Renerre — person — co-author of Renerre & Mazuel (1985), the second half of the citation pair every modern paper repeats alongside Hood & Riordan; also authored the 1990 review flagged above as a further lead.
- J. P. Mazuel — person — co-author of the 1985 study.
- B. Hernández — person — corresponding author (Universidad Pública de Navarra) of both 2015 and 2016 PMC papers that repeat the secondhand citation identically; the modern conduit for the figure, not its origin.
- American Meat Science Association (AMSA) — concept/organization — publisher of the "Meat Color Measurement Guidelines" (1991, 2012) both PMC papers cite as methodological standard; also publishes Mancini & Hunt (2005) on its own site.