tannin

Supported tannin assignment

Record which evidence supports tannin identity, what it excludes and what remains ambiguous.

1. Does tannin here denote an identified compound, a characterised mixture or a constituent inferred within a host material? definition
2. Which structural, separation and functional observations support the assignment, and which other phenolics or precipitants remain plausible? boundary

Resolved family profile

Record family assignments, mixture proportions where measurable and uncertainty about constituent structures.

1. Which tannin family or combination of families is supported, and by which analytical evidence? definition
2. What molecular-size, constituent-unit, linkage or substitution information distinguishes this tannin material from another lot bearing the same name? measurement

Tannin source lineage

Preserve the source and batch relationships needed to investigate differences between tannin preparations.

1. Which organism, tissue, parent material and batch supplied this tannin, and which of those identities were verified? provenance
2. Was the tannin isolated directly, purchased as a preparation, blended or chemically modified before receipt? provenance

Recovery and selection

Record extraction conditions, recovered fractions and evidence of losses or compositional selection.

1. Which solvents, pH, temperatures, durations and separation steps produced the measured tannin fraction? provenance
2. What recovery evidence distinguishes low tannin content from incomplete extraction or exclusion of a bound fraction? measurement
3. Which non-tannin constituents remain, and do they require further separation before the proposed test or use? action

Interpretable tannin result

Record the measured fraction and reporting basis. Methyl-cellulose precipitation is an example of an assay developed and validated for particular grape and wine matrices. [Method study](https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1755-0238.2006.tb00042.x).

1. Which tannin fraction does the assay measure, and what evidence supports its use for this family and matrix? measurement
2. Is the result an identified-compound mass, a reference-standard equivalent or a functional response, and what denominator and uncertainty accompany it? measurement
3. Are two reported tannin values directly comparable, or is a method-comparison study required before substitution or dosing? boundary

Condition-specific accessibility

Treat accessibility as condition-dependent. Experiments in water-ethanol systems demonstrate the relevance of solvent conditions to tannin aggregation and precipitation. [Experimental study](https://arxiv.org/abs/0810.1136).

1. At the stated solvent composition, pH, temperature and concentration, what proportion is dissolved, dispersed, precipitated or associated with the matrix? measurement
2. Does a proposed dissolution, filtration or extraction step recover the intended tannin fraction, and how will that recovery be checked? action

Protein response envelope

Record the observed protein response over relevant conditions rather than assigning universal precipitation capacity; experimental results show dependence on pH and protein-to-tannin ratio. [Experimental study](https://academic.oup.com/ijfst/article/47/4/875/7866065).

1. Which protein was tested, and what binding or precipitation was measured at the stated tannin-to-protein ratio, pH and contact time? measurement
2. What controls distinguish tannin-induced precipitation from protein instability, solvent effects or other extract constituents? boundary

Justified tannin operation

Record the intended effect, qualifying test and decision criteria for adding, removing, blending or reacting tannin.

1. What effect is sought, such as collagen interaction, protein removal or a specified complexation reaction, and what target-system evidence supports it? action
2. What dose range, performance limits and linked host-material requirements must be satisfied before this batch may be used? action
3. Which conclusions remain limited to a laboratory assay and cannot yet be transferred to the intended application? boundary

Demonstrated tannin change

Record evidence for hydrolysis, oxidation, condensation, modification or aggregation without identifying a mechanism from colour change alone.

1. What changes in constituent profile, molecular-size distribution, soluble fraction or functional response distinguish the current material from its baseline? measurement
2. Which exposure or processing event preceded the change, and what evidence supports the proposed mechanism? provenance

Continued tannin usability

Assess whether the current tannin still meets the identity, content and interaction criteria of its intended use.

1. What stability observations support the specified container, light exposure, temperature, moisture or solution conditions and retention period? measurement
2. Which observed changes or exposure excursions trigger retesting, requalification or withholding this tannin from the intended use? action

Kinds and varieties

Reported by the breadth pass; each item needs checking against its source before it becomes normative.

• hydrolysable tannins (gallotannins and ellagitannins)
• condensed tannins / proanthocyanidins
• complex / mixed tannins (e.g. acutissimin-type)
• phlorotannins (brown-algal polyphenols)
• tannic acid (commercial hydrolysable tannin mixture)
• vegetable tannins used in leather (mimosa, quebracho, chestnut, tara, valonea)
• synthetic tannins (syntans) used in leather chemistry
• oenological tannins (grape-skin, grape-seed, oak, and exogenous oenotannins)

1. Which of these kinds and varieties hold for the sense of tannin this model covers, and on what evidence? provenance

Identifiers and schemes

Reported by the breadth pass; each item needs checking against its source before it becomes normative.

• Wikidata - Q187760 - Item for the chemical class 'tannin'.
• CAS Registry Number - 1401-55-4 - Tannic acid, the commercial hydrolysable-tannin mixture most often used as a named product; not a unique identifier for all tannins.
• EC / EINECS - 215-753-2 - Tannic acid (EC inventory).
• ChEBI - CHEBI:26848 - Ontology class 'tannin'.
• IUPAC Gold Book - term 'tannin' - Definitional chemical-terminology entry rather than a numeric code.
• INS / food-additive number - INS 181 (tannins) - Codex food-additive listing for tannins; regional E-number practice varies and is often restricted to tannic acid or not assigned.

1. Which of these identifiers and schemes hold for the sense of tannin this model covers, and on what evidence? provenance

Standards and regulation

Reported by the breadth pass; each item needs checking against its source before it becomes normative.

• IUPAC Gold Book - chemical definition of tannin (International Union of Pure and Applied Chemistry).
• OIV International Oenological Codex - identity, purity and conditions of use for oenological tannins (International Organisation of Vine and Wine).
• Codex Alimentarius GSFA - INS 181 tannins as a food additive / processing aid, with commodity-specific provisions (FAO/WHO Codex Alimentarius Commission).
• JECFA monographs on tannic acid / tannins - identity and safety evaluation for food use (FAO/WHO Joint Expert Committee on Food Additives).
• EU food-additive / processing-aid law (Regulation (EC) No 1333/2008 and related purity criteria) - tannic acid / tannins authorised only in specified food categories and functions; not a general-purpose additive.
• US FDA 21 CFR - tannic acid listed among substances with specified food uses and limitations (e.g. flavouring, processing), not as an unrestricted additive.
• IULTCS / ISO leather chemical test methods (e.g. hide-powder / filter methods for vegetable-tannin analysis) - analytical standards for tannin content of vegetable tanning materials (International Union of Leather Technologists and Chemists Societies; ISO).
• REACH (EU) - tannic acid and some vegetable-tannin extracts are registered substances with classification and exposure scenarios for industrial use.

1. Which of these standards and regulation hold for the sense of tannin this model covers, and on what evidence? provenance

Real-world use

Reported by the breadth pass; each item needs checking against its source before it becomes normative.

• Vegetable tanning of hides and skins to leather (mimosa/wattle, quebracho, chestnut, tara, oak, valonea extracts).
• Wine and cider: extraction from grape skins/seeds and oak, plus addition of oenological tannins for colour stability, mouthfeel, protein fining, and oxidation control.
• Tea, coffee, cocoa, persimmon, sorghum and many fruits: astringency and haze/precipitation with salivary and beverage proteins.
• Pharmaceutical and veterinary astringents (historical and some current topical/oral uses of tannic acid; also as an alkaloid precipitant in analysis).
• Ink manufacture (iron-gall ink: tannin + iron(II) salts) and wood staining.
• Adhesives and wood binders from condensed tannins (especially mimosa and pine bark) as phenol-formaldehyde extenders or bio-based resins.
• Water and beverage treatment: protein precipitation, haze control, and (historically) some flocculation uses.
• Laboratory protein assay and histochemistry (e.g. tannic acid as a mordant/fixative adjunct; hide-powder assay of tannin content).

1. Which of these real-world use hold for the sense of tannin this model covers, and on what evidence? provenance

Typical measurements

Reported by the breadth pass; each item needs checking against its source before it becomes normative.

• protein-precipitation capacity (hide-powder or BSA precipitation) - operational; often reported as 10-70% 'tannin' of a vegetable extract on dry matter, depending on source and method - % (m/m) tannin, method-defined
• total phenolics (Folin-Ciocalteu), as gallic-acid equivalents - widely method-dependent; tea infusions often ~0.5-3 g GAE L⁻¹; grape seeds and quebracho extracts much higher on a solids basis - g GAE L⁻¹ or g GAE kg⁻¹
• Stiasny number (aldehyde-condensable polyphenols, condensed-tannin industry) - typically ~70-105 for commercial mimosa/pine extracts used in adhesives - %
• degree of polymerisation (condensed tannins / proanthocyanidins) - mean DP often ~2-10 in foods and wines; industrial extracts and bark tannins commonly mean DP 4-12, with tails much higher - dimensionless (mean DP)
• molecular mass (oligomer window commonly discussed) - roughly 500-3000 for many characterised oligomers; commercial tannic acid centred near ~1701 for a decagalloyl-glucose idealisation - g mol⁻¹ (Da)
• astringency / sensory threshold in beverages - often perceptible from tens to a few hundred mg L⁻¹ depending on matrix, pH, and polymer size - mg L⁻¹
• pH of aqueous tannin solutions / tanning liquors - typically acidic, about pH 3-5 for vegetable tanning liquors and wine; tannic acid solutions are strongly acidic - pH

1. Which of these typical measurements hold for the sense of tannin this model covers, and on what evidence? provenance

Failure modes and hazards

Reported by the breadth pass; each item needs checking against its source before it becomes normative.

• Protein precipitation and haze in beer, wine, and tea when tannins meet haze-active proteins.
• Astringency and reduced palatability; in livestock, high condensed-tannin forages can reduce protein digestibility and intake (though moderate levels can also reduce bloat and GI parasites).
• Iron-tannin complexation: nutritional iron binding; also corrosion/staining of iron and formation of blue-black iron-gall complexes that degrade paper in historic inks.
• Oxidation and colour shift (browning, pinking, or blackening) in foods, wines, and leathers.
• Leather defects from unbalanced vegetable tannage (case-hardening, cracks, poor hydrothermal stability if mineral retannage is absent).
• Acute gastrointestinal irritation from concentrated tannic acid; historical high-dose medical use associated with hepatotoxicity; not a general food toxin at dietary levels.
• Allergenic / sensitising potential of some tanning extracts and syntans in occupational leather processing (more often the process chemicals than 'tannin' as eaten).
• Interference in protein assays, PCR, and plant DNA extraction (tannins bind proteins and nucleic acids).
• Incompatibility with gelatin, alkaloids, heavy-metal salts, and many proteins in formulation (precipitation).

1. Which of these failure modes and hazards hold for the sense of tannin this model covers, and on what evidence? provenance

Regional variation

Reported by the breadth pass; each item needs checking against its source before it becomes normative.

• Leather: South American quebracho and African/Australian mimosa (wattle) dominate condensed-tannin trade; Mediterranean chestnut, valonea and Turkish/Peruvian tara dominate hydrolysable-tannin trade.
• Wine: 'tannin' in Bordeaux/Napa usage is largely grape condensed tannin plus oak ellagitannins; Italian and Spanish practice also emphasises exogenous oenological tannins; OIV vs national wine law differs on what may be added.
• Tea: 'tannin' in older British/Indian trade language often meant total tea polyphenols, not chemically defined tannins; modern tea chemistry prefers catechins/theaflavins over 'tannin'.
• Food-additive numbering: INS 181 is used internationally; the EU does not treat 'tannins' as a general E-number colour in the way older lists sometimes implied.
• Forage anti-nutrition: condensed-tannin management is a live agronomic issue in the Andes, New Zealand, Australia and parts of Africa (lotus, sulla, acacia, sorghum), less so in temperate dairy systems built on low-tannin ryegrass/clover.
• Phlorotannins are a North-Atlantic and East-Asian algal product class, not a terrestrial tannin in the leather/wine sense.

1. Which of these regional variation hold for the sense of tannin this model covers, and on what evidence? provenance

Neighbouring kinds and how to tell them apart

Reported by the breadth pass; each item needs checking against its source before it becomes normative.

• lignin - Lignin is an insoluble phenylpropanoid cell-wall polymer that does not dissolve and precipitate proteins the way tannins do; distinguished by insolubility, Klason/acid-insoluble fibre behaviour, and absence of protein-precipitation in aqueous extract.
• simple phenolic acids and flavonoids (gallic acid, catechin monomers) - Monomers may be biosynthetic precursors or subunits but generally do not precipitate proteins at typical concentrations; protein-precipitation assays (hide-powder, BSA, MCP) and polymer-selective methods (butanol-HCl for proanthocyanidins) separate them from tannins.
• humic and fulvic substances - Environmental polydisperse acids from soil/water organic matter; distinguished by origin, elemental ratios, and lack of the discrete galloyl-glucose / flavan-3-ol oligomer signatures of plant tannins (NMR, pyrolysis-GC-MS).
• syntans (synthetic tanning agents) - Naphthalenesulfonic, phenolic-condensate or other industrial tanning chemicals that tan hide but are not plant polyphenols; distinguished by sulfur content, industrial origin, and IULTCS/ISO leather-chemical identification.
• melanins and enzymatic browning products - Indole/catechol oxidation polymers in tissue; not extractable as classic tannins and do not match gallotannin/ellagitannin/proanthocyanidin chemistries.
• saponins - Amphiphilic glycosides that foam and haemolyse rather than precipitate proteins as tannins do; distinguished by foam tests, haemolysis, and glycoside chromatography.
• tannic acid vs 'tannin' - Tannic acid is a commercial hydrolysable-tannin mixture (mainly polygalloyl glucoses), CAS 1401-55-4; 'tannin' is the broader class including condensed tannins that do not hydrolyse to gallic/ellagic acid. Acid hydrolysis yielding gallic/ellagic acid vs oxidative depolymerisation to anthocyanidins (butanol-HCl) separates the two.

1. Which of these neighbouring kinds and how to tell them apart hold for the sense of tannin this model covers, and on what evidence? provenance