The "20% metmyoglobin → half of consumers reject" meat-color figure traces, in the citing literature, to Hood & Riordan (1973) and Renerre & Mazuel (1985)

food-sciencemeatmyoglobinkubelka-munk-theoryquantitative-claimprimary-source-verificationunverified-quantcitation-trailbibliographic-attributioncorroboration

The purchase-behaviour threshold repeated in modern meat-color research — that "when the proportion of MMb [metmyoglobin] reaches 20% it has been found that the product is rejected by half of the potential consumers" — appears secondhand wherever it surfaces in the accessible PMC literature, always attributed to the same pair of twentieth-century studies: Hood, D.E. & Riordan, E.B., "Discolouration in pre-packaged beef: measurement by reflectance spectrophotometry and shopper discrimination" (Int J Food Sci Technol 8:333–343, 1973), and Renerre, M. & Mazuel, J.P., "Relationships between instrumental and sensory measurement methods of meat colour" (Sci Alim 5:541–557, 1985).

The attribution is corroborated across two separate papers by the same research group (Hernández, Sáenz, Alberdi & Diñeiro, Universidad Pública de Navarra) — separate publications, but not independent sources: PMC5223250 (2016) and PMC4648909 (2015) both carry the sentence and its citation pair word-for-word. PMC4648909's text, read directly:

"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 one author group reusing its own sentence rather than two independent groups converging, the corroboration is of the citation trail — the figure reliably descends from these 1973/1985 studies, not from a fabrication or a citation error introduced by the modern papers — and not of the number itself, which remains unconfirmed against either primary. Both primaries were access-blocked this session (Wiley, ResearchGate, and a related Oxford Academic Renerre review all returned HTTP 403; no open-access copy located on HathiTrust or the Internet Archive), so the 20%/50% figure stays flagged [unverified-quant] on the vault's meat-color note, and its verification is still open in question-verify-metmyoglobin-20-percent-consumer-rejection-threshold. This note is kin to other vault figures whose primary home is established-but-unread or unlocatable — claim-crisp-20-hours-to-under-a-second-figure-has-no-primary-source, claim-lukyanov-115-figure-no-independent-source-located — where pinning down where a load-bearing number comes from is a distinct finding from confirming the number.

Corroborating source (second independent read):

• 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_tier: 1