Exogenous Tannin Additions (Oak Tannins, Grape Tannins)

Exogenous tannins are commercial polyphenolic compounds extracted from botanical sources outside the fermenting grape material and added deliberately to must or wine. The OIV International Oenological Codex recognises two major structural classes. Hydrolyzable tannins, primarily gallotannins and ellagitannins, come from oak wood, chestnut wood, gallnuts, and tara; they are esters of gallic or ellagic acid linked to a sugar core. Condensed tannins, also called proanthocyanidins, are polymers of flavan-3-ol units linked by C-C bonds and come mainly from grape seeds and skins, quebracho, mimosa, and acacia. Each botanical origin produces a chemically distinct profile with different sensory and functional properties in wine.

• Hydrolyzable tannins from oak and chestnut include the ellagitannins castalagin and vescalagin, the dominant compounds in oak heartwood
• Condensed tannins from grape seeds are rich in procyanidins with a high galloylation level; skin tannins also contain prodelphinidins
• Quebracho tannins are profisetinidins, chemically similar to grape tannins but from a South American hardwood; they are classified as condensed tannins
• All commercial oenological tannin products must comply with OIV Codex specifications for phenolic content, metal limits, and botanical origin labelling

Oenological tannins function through several simultaneous mechanisms in must and wine. Their affinity for proteins allows them to precipitate excess proteinaceous matter, preventing protein hazes and facilitating clarification. In red wines, condensed tannins react with anthocyanins during and after fermentation to form stable colour-tannin complexes, protecting pigment from degradation over time. Oak ellagitannins such as castalagin and vescalagin act as significant oxygen consumers during ageing, moderating oxidative reactions and contributing to a gradual colour evolution. Tannins added pre-fermentation can interact with yeast enzymes and bind with proteins and oxygen that would otherwise degrade innate grape tannins; post-fermentation additions integrate more slowly and require adequate cellaring time before bottling.

• Protein precipitation: the primary OIV-recognised function, reducing haze risk and improving clarification efficiency
• Colour stabilisation: condensed tannins polymerise with anthocyanins to form more stable pigment complexes that persist through ageing
• Antioxidant and antioxidasic protection: tannins consume dissolved oxygen and inhibit oxidative enzymes such as laccase, protecting aroma and colour
• Pre-fermentation additions bind proteins and oxygen that would otherwise consume native grape tannins; post-fermentation additions build mouthfeel and aging structure

The sensory impact of exogenous tannin additions depends on the botanical source, dosage, and timing. Oak-derived ellagitannins contribute subtle complexity and support colour evolution without adding coarse astringency. Gallotannins from oak galls, such as those in Scott Laboratories' FT Blanc Soft and FT Rouge Soft ranges, are described as contributing a soft, round mouthfeel and a perception of sweetness. Grape-seed condensed tannins provide structural grip and colour-stabilising reactivity with anthocyanins. Near bottling, toasted oak-derived products can contribute aromatic nuances such as vanilla, coconut, and smoke. In all cases, practical supplier guidance and individual bench trials are essential, as over-addition risks reducing total phenolic concentrations and creating coarse, unbalanced mouthfeel.

• Fermentation-phase additions (5 to 30 g/hL): bind proteins and protect colour; grape-seed tannins most reactive with anthocyanins
• Ageing-phase additions (5 to 30 g/hL): build structure, resist oxidation, and improve mouthfeel roundness through polymerisation
• Finishing tannins near bottling (lower doses, 3 to 6 weeks before): can impart subtle vanilla, coconut, or light oak nuance from toasted wood extracts
• Over-addition risk: excess exogenous tannins can reduce total phenolics after fermentation and generate harsh, unresolved astringency

Tannin additions are most commonly employed when endogenous phenolic levels are insufficient for the desired wine structure or stability. In cooler or wetter vintages, grapes may accumulate sugars before full phenolic ripeness is achieved, leaving the resulting wine with thin tannin structure even at acceptable alcohol levels. Winemakers working with low-tannin varietals such as Pinot Noir, Gamay, or lighter expressions of Merlot often use condensed tannins to support colour stability without overriding fruit character. Tannins are also used in oxidative incident recovery, after poor cap management, or when treating musts from botrytis-affected fruit where laccase activity threatens colour and aroma. In white and rosé winemaking, additions protect against premature oxidation and can improve mouthfeel in tank-fermented styles.

• Phenolic underripeness in cool or wet vintages: additions supplement structural deficiency without altering fermentation
• Low-tannin red varieties: soft condensed tannin additions stabilise colour and build mouthfeel while preserving fruit expression
• Botrytis or mould-affected fruit: gallic tannins inhibit laccase activity and protect colour and aroma during fermentation
• White and rosé wines: tannin additions reduce oxidation risk and can improve mouthfeel, especially in tank-fermented or low-SO2 production

The global market offers a wide range of oenological tannin products, with major suppliers including Laffort, Scott Laboratories, Enartis, Martin Vialatte, and Silvateam. Laffort's range includes TANIN VR SUPRA for red wine fermentation, TANIN VR COLOR for colour stabilisation using catechin-rich grape tannins, and QUERTANIN for oak ellagitannin-based ageing. Scott Laboratories offers FT Rouge Soft, derived from quebracho wood and suited to delicate red varieties, and FT Blanc Soft, an oak gallnut product for white and rosé fermentation. Enartis Tan V, extracted from non-fermented grape seeds, is designed for addition at the start of maceration to react rapidly with anthocyanins, while Enartis Tan Skin is extracted from unfermented white grape skins for post-fermentation structural work. Silvateam produces tannins from chestnut, quebracho, tara, gallnut, oak, and grape sources.

• Laffort TANIN VR range: fermentation tannins from grape sources for sacrificial binding, colour stabilisation, and structure
• Laffort QUERTANIN: ellagitannins extracted from oak heartwood for ageing and finishing applications
• Scott Laboratories FT Rouge Soft (quebracho) and FT Blanc Soft (oak gallnut): fermentation-phase additions for reds and whites respectively
• Enartis Tan V (grape seed, pre-fermentation) and Enartis Tan Skin (grape skin, post-fermentation): grape-derived condensed tannin options

Oenological tannin additions are classified as permitted practices under the OIV International Code of Oenological Practices and are authorised in the EU, USA, South Africa, Australia, and New Zealand, though specific use conditions vary by jurisdiction. All commercial tannin products must comply with OIV Codex chemical specifications, including limits on metals such as arsenic, iron, mercury, and lead, and a maximum ash content of 4 percent by weight. Product labelling must indicate botanical origin, extraction solvent, and approximate total phenol content. In organic winemaking, tannins are permitted in both the EU and Australia, with a preference for organically sourced raw material where available. Practical risks of exogenous tannin use include over-addition, which can decrease total phenolics after fermentation and generate coarse, unintegrated astringency, and poorly matched botanical origins for the style of wine being produced.

• OIV authorisation covers additions to both musts and wines; all products must meet Codex chemical purity specifications
• Tannin addition is permitted under EU, US, Australian, New Zealand, and South African winemaking regulations, with jurisdiction-specific conditions
• Organic winemaking: tannins are permitted in EU and Australian certified organic production, preferably sourced from organic raw material
• Key risks: over-addition can reduce phenolic concentration and create harsh mouthfeel; bench trials before full-scale use are essential