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Lactic Acid Bacteria - Friend or Foe?

Last Updated: 1/2025

Summary: This article was inspired by questions we regularly get about how to interpret microbial analysis or ETS Scorpion panels. Lactic acid bacteria are easy to ignore as they are omnipresent in wineries; however, they can create off-odors and flavors, even in dry wines. This article covers both positive and negative impacts of lactic acid bacteria as well as risk management strategies. 

Understanding and controlling LAB spoilage

Lactic acid bacteria (LAB) are part of the natural microflora in vineyards and wineries. For that reason, they’re easy to overlook when it comes to microbial analysis and write them off as organisms that are always present and unavoidable. Furthermore, a complicated truth of wine microbiology is that microbial presence does not mean microbial impact.

That being said, LAB are worth paying attention to. LAB can metabolize a wide range of compounds in “dry” wines. LAB may persist in the background, but once an inhibiting factor is removed, or the population reaches a critical mass, spoilage may occur. 

Fortunately, LAB are relatively easy to control. Understanding what LAB species do and what they metabolize can help determine the best approach to prevent potential spoilage issues.

LAB in wine & their impact

LAB’s can utilize a wide variety of substrates in juice and wine. This is why we state that (from a microbiological standpoint) there is no such thing as a “dry” wine. Wine may not have residual fermentable sugars or malic acid, but it does contain many other compounds that if metabolized can lead to spoilage (Bartowsky 2009); either subtle or obvious.

Oenococcus oeni

(Your Best Friend – Until it Isn’t!)

While there are a few species in the Oenococcus genus, Oenococcus oeni is the organism of choice for malolactic fermentation (MLF). Much like yeast, there are many strains of O. oeni, some are commercially produced and well-characterized, while others are ambient and uncharacterized. O. oeni also have a range of positive sensory impacts, but also have the potential to produce off-aromas and flavors (see figure for impacts). 

Our commercial strains are characterized for their positive sensory impact and they lack the genes to produce biogenic amines or vinyl phenols. However, even commercial strains can pose risks if not properly managed after MLF, so it’s essential to monitor and control O. oeni to prevent unintended spoilage.

Lactobacillus spp.

(Never Your Friend, And You Need to Break Up ASAP)

Over twelve species of Lactobacillus can be found in wine. Lactobacillus species are often most problematic during stuck fermentations or in high pH environments.

  • During stuck fermentations: Many Lactobacillus species can utilize glucose and fructose to produce lactic acid and excessive diacetyl, with species such as L. casei and L. rhamnosus being high producers of diacetyl, leading to strong buttery flavors. Additionally, certain, species including L. kunkeei, L. brevis, L. hilgardii, and L. fermentum, can rapidly produce significant amounts of volatile acidity from glucose and fructose.

  • Post-fermentation: High pH levels (above 3.6) create a friendly environment for Lactobacilli. While VA production from sugars is not a concern at this point, Lactobacillus can still metabolize a range of other compounds leading to the development of mousy, bitter (acrolein), and acetic acid (see figure).

Pediococcus spp.

(The One You Ignore But Probably Shouldn’t)

Among the lactic acid bacteria (LAB) in wine, Pediococcus is the least well-understood, though it may play a role in malolactic fermentation in the future (Wade et al. 2018). Common spoilage issues caused by Pediococcus include geranium taint, acrolein bitterness, biogenic amine formation, and excessive diacetyl production (see figure). While “ropiness” due to exo-polysaccharide production is documented, this spoilage is rare but possible. Like other LAB, there is significant strain variation, which means that Pediococcus will continue to be a spoilage concern until we learn more.

Lactiplantibacillus plantarum

(Maybe Your New BFF!)

Until 2020, Lactiplantibacillus was part of the Lactobacillus genus but due to recent taxonomic reclassification, it now has its own category, alongside 16 other species (Zheng et al. 2020). In winemaking, the primary species of interest is Lactiplantibacillus plantarum. L. plantarum opens up a new avenue for malolactic fermentation because of its ability to rapidly degrade malic acid without producing diacetyl or acetic acid production (from hexose sugars).

Note: Inability to produce diacetyl or acetic acid from hexose sugars is strain-specific and does not apply to all L. plantarum.

Controlling Lactic Acid Bacteria (LAB)

The strategies outlined below can each contribute to controlling LAB individually; however, combining multiple control measures creates a synergistic effect. By implementing several methods simultaneously, the barriers to LAB growth and activity are significantly increased, resulting in more effective and longer-lasting control.

Controlling Lactic Acid Bacteria (LAB)

The strategies outlined below can each contribute to controlling LAB individually; however, combining multiple control measures creates a synergistic effect. By implementing several methods simultaneously, the barriers to LAB growth and activity are significantly increased, resulting in more effective and longer-lasting control.

pH MANAGEMENT

LAB tend to thrive at pH levels above 3.6. While lowering pH by adding tartaric acid (pre-fermentation) or lactic acid (post-fermentation) can reduce spoilage risk, this isn’t always ideal for sensory reasons. Citric acid can also be used to adjust pH, but antimicrobial measures are critical as many LAB can metabolize citric acid to produce volatile acidity.

DELVOZYME® (LYSOZYME)

DELVOZYME (Lysozyme) degrades the cell walls of lactic acid bacteria (gram-positive bacteria). It is not active against acetic acid bacteria (gram-negative bacteria) or yeast. It can be used at any stage of winemaking and is particularly helpful in wines with elevated pH (>3.6) or when sulfur dioxide levels need to be kept low.

SULFUR DIOXIDE (SO2)

After fermentation, maintain molecular SO₂ levels above 0.5 ppm to inhibit LAB growth. This can be achieved using potassium metabisulfite, INODOSE tablets, or SULFIVIN K150.

BACTILESS™ (CHITOSAN)

BACTILESS is a natural chitosan-based antimicrobial agent from fungal origin that can reduce lactic and acetic acid bacteria in wine.

GOOD CELLAR PRACTICES

Good cellar practices are also critical to control microbial spoilage. These include regular headspace/oxygen management, racking, temperature control, and filtration.

Note: Acetobacter spp., responsible for ethyl acetate (nail polish remover aroma) and acetic acid (vinegar) production, can also cause spoilage. The same tools used to control LAB—except lysozyme—are effective against Acetobacter.

Recognizing Bacteria Flaws

While it’s helpful to know the technical details, these are the more common sensory descriptors used to identify flaws caused by lactic acid bacteria in wine.

  • Acetaldehyde: Bruised apples, Sherry, nutty

  • Acetic acid: Vinegar

  • Acrolein taint: In the presence of phenolic compounds gives an extreme bitterness

  • Biogenic amines: Dull fruit/varietal expression, metallic, rancid, meaty

  • Diacetyl: Butter, buttery popcorn

  • Ethyl acetate: Nail polish, glue, solvent

  • Geranium taint: Crushed geranium leaves, excessively floral

  • Tourne disease: dull, flat mouthfeel and very high acetic acid

  • Mannitol: Sweet-sour aroma, slimy texture, and irritating finish

  • Mousy taint: Rice crackers, greasy corn-chips, or caged mice

  • Ropiness: Viscous, slimy texture

Citations

Bartowsky, E.J. “Bacterial spoilage of wine and approaches to minimize it.” Letters in Applied Microbiology, vol. 48, no. 2, Feb. 2009, pp. 149–156, https://doi.org/10.1111/j.1472-765x.2008.02505.x.
Wade, M.E., et al. “Role of Pediococcus in winemaking.” Australian Journal of Grape and Wine Research, vol. 25, no. 1, 14 Sept. 2018, pp. 7–24, https://doi.org/10.1111/ ajgw.12366.
Zheng, Jinshui, et al. “A taxonomic note on the genus lactobacillus: Description of 23 novel genera, emended description of the genus lactobacillus beijerinck 1901, and union of Lactobacillaceae and Leuconostocaceae.” International Journal of Systematic and Evolutionary Microbiology, vol. 70, no. 4, 1 Apr. 2020, pp. 2782–2858, https://doi.org/10.1099/ijsem.0.004107

Lactic Acid Bacteria - Friend or Foe?

Last Updated: 1/2025

Summary: This article was inspired by questions we regularly get about how to interpret microbial analysis or ETS Scorpion panels. Lactic acid bacteria are easy to ignore as they are omnipresent in wineries; however, they can create off-odors and flavors, even in dry wines. This article covers both positive and negative impacts of lactic acid bacteria as well as risk management strategies. 

Understanding and controlling LAB spoilage

Lactic acid bacteria (LAB) are part of the natural microflora in vineyards and wineries. For that reason, they’re easy to overlook when it comes to microbial analysis and write them off as organisms that are always present and unavoidable. Furthermore, a complicated truth of wine microbiology is that microbial presence does not mean microbial impact.

That being said, LAB are worth paying attention to. LAB can metabolize a wide range of compounds in “dry” wines. LAB may persist in the background, but once an inhibiting factor is removed, or the population reaches a critical mass, spoilage may occur. 

Fortunately, LAB are relatively easy to control. Understanding what LAB species do and what they metabolize can help determine the best approach to prevent potential spoilage issues.

LAB in wine & their impact

LAB’s can utilize a wide variety of substrates in juice and wine. This is why we state that (from a microbiological standpoint) there is no such thing as a “dry” wine. Wine may not have residual fermentable sugars or malic acid, but it does contain many other compounds that if metabolized can lead to spoilage (Bartowsky 2009); either subtle or obvious.

Oenococcus oeni

(Your Best Friend – Until it Isn’t!)

While there are a few species in the Oenococcus genus, Oenococcus oeni is the organism of choice for malolactic fermentation (MLF). Much like yeast, there are many strains of O. oeni, some are commercially produced and well-characterized, while others are ambient and uncharacterized. O. oeni also have a range of positive sensory impacts, but also have the potential to produce off-aromas and flavors (see figure for impacts). 

Our commercial strains are characterized for their positive sensory impact and they lack the genes to produce biogenic amines or vinyl phenols. However, even commercial strains can pose risks if not properly managed after MLF, so it’s essential to monitor and control O. oeni to prevent unintended spoilage.

Lactobacillus spp.

(Never Your Friend, And You Need to Break Up ASAP)

Over twelve species of Lactobacillus can be found in wine. Lactobacillus species are often most problematic during stuck fermentations or in high pH environments.

  • During stuck fermentations: Many Lactobacillus species can utilize glucose and fructose to produce lactic acid and excessive diacetyl, with species such as L. casei and L. rhamnosus being high producers of diacetyl, leading to strong buttery flavors. Additionally, certain, species including L. kunkeei, L. brevis, L. hilgardii, and L. fermentum, can rapidly produce significant amounts of volatile acidity from glucose and fructose.

  • Post-fermentation: High pH levels (above 3.6) create a friendly environment for Lactobacilli. While VA production from sugars is not a concern at this point, Lactobacillus can still metabolize a range of other compounds leading to the development of mousy, bitter (acrolein), and acetic acid (see figure).

Pediococcus spp.

(The One You Ignore But Probably Shouldn’t)

Among the lactic acid bacteria (LAB) in wine, Pediococcus is the least well-understood, though it may play a role in malolactic fermentation in the future (Wade et al. 2018). Common spoilage issues caused by Pediococcus include geranium taint, acrolein bitterness, biogenic amine formation, and excessive diacetyl production (see figure). While “ropiness” due to exo-polysaccharide production is documented, this spoilage is rare but possible. Like other LAB, there is significant strain variation, which means that Pediococcus will continue to be a spoilage concern until we learn more.

Lactiplantibacillus plantarum

(Maybe Your New BFF!)

Until 2020, Lactiplantibacillus was part of the Lactobacillus genus but due to recent taxonomic reclassification, it now has its own category, alongside 16 other species (Zheng et al. 2020). In winemaking, the primary species of interest is Lactiplantibacillus plantarum. L. plantarum opens up a new avenue for malolactic fermentation because of its ability to rapidly degrade malic acid without producing diacetyl or acetic acid production (from hexose sugars).

Note: Inability to produce diacetyl or acetic acid from hexose sugars is strain-specific and does not apply to all L. plantarum.

Controlling Lactic Acid Bacteria (LAB)

The strategies outlined below can each contribute to controlling LAB individually; however, combining multiple control measures creates a synergistic effect. By implementing several methods simultaneously, the barriers to LAB growth and activity are significantly increased, resulting in more effective and longer-lasting control.

Controlling Lactic Acid Bacteria (LAB)

The strategies outlined below can each contribute to controlling LAB individually; however, combining multiple control measures creates a synergistic effect. By implementing several methods simultaneously, the barriers to LAB growth and activity are significantly increased, resulting in more effective and longer-lasting control.

pH MANAGEMENT

LAB tend to thrive at pH levels above 3.6. While lowering pH by adding tartaric acid (pre-fermentation) or lactic acid (post-fermentation) can reduce spoilage risk, this isn’t always ideal for sensory reasons. Citric acid can also be used to adjust pH, but antimicrobial measures are critical as many LAB can metabolize citric acid to produce volatile acidity.

DELVOZYME® (LYSOZYME)

DELVOZYME (Lysozyme) degrades the cell walls of lactic acid bacteria (gram-positive bacteria). It is not active against acetic acid bacteria (gram-negative bacteria) or yeast. It can be used at any stage of winemaking and is particularly helpful in wines with elevated pH (>3.6) or when sulfur dioxide levels need to be kept low.

SULFUR DIOXIDE (SO2)

After fermentation, maintain molecular SO₂ levels above 0.5 ppm to inhibit LAB growth. This can be achieved using potassium metabisulfite, INODOSE tablets, or SULFIVIN K150.

BACTILESS™ (CHITOSAN)

BACTILESS is a natural chitosan-based antimicrobial agent from fungal origin that can reduce lactic and acetic acid bacteria in wine.

GOOD CELLAR PRACTICES

Good cellar practices are also critical to control microbial spoilage. These include regular headspace/oxygen management, racking, temperature control, and filtration.

Note: Acetobacter spp., responsible for ethyl acetate (nail polish remover aroma) and acetic acid (vinegar) production, can also cause spoilage. The same tools used to control LAB—except lysozyme—are effective against Acetobacter.

Recognizing Bacteria Flaws

While it’s helpful to know the technical details, these are the more common sensory descriptors used to identify flaws caused by lactic acid bacteria in wine.

  • Acetaldehyde: Bruised apples, Sherry, nutty

  • Acetic acid: Vinegar

  • Acrolein taint: In the presence of phenolic compounds gives an extreme bitterness

  • Biogenic amines: Dull fruit/varietal expression, metallic, rancid, meaty

  • Diacetyl: Butter, buttery popcorn

  • Ethyl acetate: Nail polish, glue, solvent

  • Geranium taint: Crushed geranium leaves, excessively floral

  • Tourne disease: dull, flat mouthfeel and very high acetic acid

  • Mannitol: Sweet-sour aroma, slimy texture, and irritating finish

  • Mousy taint: Rice crackers, greasy corn-chips, or caged mice

  • Ropiness: Viscous, slimy texture

Citations

Bartowsky, E.J. “Bacterial spoilage of wine and approaches to minimize it.” Letters in Applied Microbiology, vol. 48, no. 2, Feb. 2009, pp. 149–156, https://doi.org/10.1111/j.1472-765x.2008.02505.x.
Wade, M.E., et al. “Role of Pediococcus in winemaking.” Australian Journal of Grape and Wine Research, vol. 25, no. 1, 14 Sept. 2018, pp. 7–24, https://doi.org/10.1111/ ajgw.12366.
Zheng, Jinshui, et al. “A taxonomic note on the genus lactobacillus: Description of 23 novel genera, emended description of the genus lactobacillus beijerinck 1901, and union of Lactobacillaceae and Leuconostocaceae.” International Journal of Systematic and Evolutionary Microbiology, vol. 70, no. 4, 1 Apr. 2020, pp. 2782–2858, https://doi.org/10.1099/ijsem.0.004107