Ropy / Greasy Wine — Bacterial Exopolysaccharide Spoilage

Ropy wine is a bacterial spoilage condition caused primarily by specific strains of Pediococcus damnosus and Pediococcus parvulus, lactic acid bacteria that synthesize viscous β-glucan exopolysaccharides in wine. The French term "graisse" (meaning fatty or greasy) and the alternative name "vins filants" both describe the oily, thread-forming texture produced when these polymers accumulate. The condition was first formally documented as one of four major bacterial wine diseases by Louis Pasteur in his landmark 1866 work "Études sur le Vin." While Leuconostoc mesenteroides is a heterofermentative lactic acid bacterium found in grape must, it is Pediococcus species carrying the ropy gtf gene that are the established primary agents of wine ropiness.

• Primary causative agents: Pediococcus damnosus and Pediococcus parvulus carrying the plasmid-borne gtf gene
• Leuconostoc mesenteroides and some Oenococcus oeni strains can carry gtf but rarely cause clinical ropiness in wine
• The French term "graisse" translates to fatty; "vins filants" describes the thread-forming viscosity
• Ropiness was identified as one of four major bacterial wine diseases by Pasteur in 1866

The ropy phenotype in wine is controlled by a single glucosyltransferase enzyme, Gtf, encoded by the gtf gene. In Pediococcus strains isolated from ropy wines, this gene is carried on a small plasmid (approximately 5.5 kb, designated pF8801 in P. damnosus) and the ropy phenotype disappears when the plasmid is lost. Gtf polymerizes glucosyl residues into a high-molecular-weight β-glucan: a fibrillar polymer with a β-1,3-linked glucosyl backbone and single β-1,2-linked glucopyranosyl branches. Part of this β-glucan accumulates as a capsule around the bacterial cell, while the remainder is released into the wine, creating the characteristic viscous texture. Bacterial strains carrying the functional gtf gene also show enhanced resistance to wine stresses such as low pH, elevated ethanol, and SO2.

• Single glucosyltransferase Gtf controls all ropy β-glucan synthesis; one gene, one enzyme
• gtf is plasmid-borne in Pediococcus wine isolates; curing the plasmid eliminates the ropy phenotype
• β-glucan forms both a cell capsule and soluble polymer released into wine, reaching up to 200 mg/L
• gtf-positive strains show enhanced survival against wine stresses including SO2, low pH, and ethanol

Ropy wine is characterized by a striking increase in viscosity, rendering it unpalatable and commercially unmarketable. The wine pours with an oily, slow consistency and, at advanced stages, strings of mucilaginous material are visible stretching between glass surfaces. Even though β-glucan has no specific taste or known human health impact, the texture alone makes the wine impossible to sell. The condition also elevates risk of secondary spoilage: high viscosity impairs clarification, impedes racking and filtration, and the increased LAB population may also produce volatile acidity and biogenic amines alongside the ropy polymer. If ropiness develops in bottle, the wine is irretrievably lost to the consumer.

• Viscosity increases dramatically due to β-glucan colloidal networks; wine pours slowly and forms threads
• β-glucan itself is tasteless, but the mouthfeel is slimy, oily, and incompatible with wine enjoyment
• Accompanying LAB growth may produce elevated volatile acidity and biogenic amines
• In-bottle ropiness is unrecoverable; cellar-stage detection allows physical and chemical intervention

Prevention centers on controlling Pediococcus populations through effective SO2 management, temperature control, and prompt malolactic culture inoculation with Oenococcus oeni. Research indicates that at least 100 mg/L of total SO2 is required for reliable LAB suppression. Risk escalates markedly at wine pH above 3.5, where Pediococcus and Lactobacillus are more likely to outcompete O. oeni. Grapes with Botrytis infection bring elevated LAB loads and gluconic acid, which promotes heterolactic fermentation. The link between low or zero SO2 additions and ropiness is well established; Peynaud noted as early as 1984 that the condition was most likely in wines destined for distillation that could not be sulfited. The resurgence of minimal-intervention and natural winemaking has renewed interest in ropiness monitoring.

• High-risk conditions: wine pH above 3.5, total SO2 below 100 mg/L, temperatures promoting LAB growth
• At least 100 mg/L total SO2 is the established threshold for effective LAB control in wine
• Oenococcus oeni inoculation for MLF reduces the window for opportunistic Pediococcus growth
• Natural and zero-SO2 winemaking practices increase ropiness risk; the link has been documented since Peynaud's 1984 observations

Once ropiness is detected, physical intervention is the most effective approach. Racking with vigorous aeration can break down the β-glucan network and reduce viscosity at early stages of the condition, and if caught early in the cellar, winemakers can often recover the wine through agitation, SO2 addition, and microbial stabilization. Membrane filtration at 0.45 to 0.22 μm removes both bacterial cells and polymer aggregates but may be hindered by fouling from the viscous EPS. Lysozyme (approved by the OIV in 1997) targets the peptidoglycan cell wall of Gram-positive bacteria, but critically, ropy Pediococcus parvulus strains are resistant to lysozyme alone because the surrounding β-glucan capsule shields them. Research has shown that combining lysozyme with β-glucanase significantly improves efficacy against established ropy strains in both model media and red and white wine.

• Early-stage ropiness: racking, aeration, and SO2 addition can reduce viscosity and arrest bacterial growth
• Membrane filtration (0.45 to 0.22 μm) removes cells and polymer but requires pre-filtration to manage fouling
• Lysozyme alone is ineffective against ropy P. parvulus because the β-glucan capsule confers resistance
• Lysozyme combined with β-glucanase improves treatment efficacy against ropy strains in wine

Ropiness has been recognized as a wine disease for centuries and was given its first scientific characterization by Louis Pasteur, who identified it as one of four major bacterial alterations of wine in his 1866 "Études sur le Vin." Ropy strains isolated from Bordeaux-region red and white wines were initially classified as Pediococcus cerevisiae, later reclassified as Pediococcus damnosus via DNA hybridization, and finally as Pediococcus parvulus based on 16S RNA sequencing. Research by Lonvaud-Funel and colleagues at the University of Bordeaux contributed substantially to characterizing the LAB ecology of wine ropiness from the 1980s onward. The molecular determinant, the plasmid-borne gtf gene, was characterized in the 2000s, enabling PCR-based detection of ropy strains before spoilage becomes visible. The condition is now less common in commercial wine thanks to SO2 protocols and selected MLF cultures, but remains a documented risk in low-intervention and natural winemaking.

• Pasteur identified ropiness as one of four major bacterial wine diseases in 'Études sur le Vin' (1866)
• Ropy wine strains were progressively reclassified from Pediococcus cerevisiae to P. damnosus to P. parvulus as taxonomy evolved
• Bordeaux University researchers including Lonvaud-Funel characterized the LAB ecology of ropiness from the 1980s onward
• PCR detection of the plasmid-borne gtf gene now allows winemakers to screen for ropy strains before visible spoilage occurs