How to read the numbers
Each organism is reported in cells/mL, worked out from how many copies of its DNA are in your sample. Our assays count viable cells whether or not they'll grow on a plate, and exclude dead cells. Three things follow from that:
- Stressed, dormant or viable-but-non-culturable cells that never grow on a plate are still counted. Plating can read zero on a wine qPCR shows is carrying a live population.
- Our numbers usually sit above a plate count on the same sample. That's expected, not a discrepancy.
- A result after SO₂, chitosan or filtration shows what survived the treatment.
| On your report | Meaning |
|---|---|
| Not detected (<10 cells/mL) | Below our detection limit. Not the same as sterile |
| cells/mL | Estimated viable cells per millilitre |
| log cells/mL | The same number on a log scale: 2 = 100, 3 = 1,000, 4 = 10,000 |
| Ct | Cycle threshold, the raw instrument value; lower Ct = more DNA. Shown on request only |
| Flag (Low / Medium / High) | Our indicative risk band for that organism, explained below |
It's a snapshot of the sample you sent. A barrel sampled from the top can read differently from the lees; see sampling.
Indicative levels: Low, Medium, High
These bands are our working guide for a finished or maturing dry wine. They're indicative, not pass/fail: pH, free SO₂, residual sugar, temperature and time to bottling all shift where the real risk sits. Use the band to decide how urgently to act, then the organism guide and the actions below to decide what to do.
| Organism | Low (monitor) | Medium (act soon) | High (act now) | If left |
|---|---|---|---|---|
| Brettanomyces bruxellensis | 10–100 | 100–1,000 | >1,000 | 4-EP/4-EG: barnyard, medicinal, band-aid; loss of fruit |
| Pediococcus spp. | 10–500 | 500–5,000 | >5,000 | Diacetyl, ropiness, acrolein bitterness, biogenic amines |
| Lactobacillus spp. | 10–500 | 500–5,000 | >5,000 | VA rise, mousiness; stuck or sluggish ferment in juice |
| Oenococcus oeni (post-MLF) | 10–1,000 | 1,000–10,000 | >10,000 | Refermentation of leftover malic in bottle, CO₂, haze |
| Acetobacter / Gluconobacter | 10–100 | 100–1,000 | >1,000 | Acetic acid and ethyl acetate (VA) |
| Zygosaccharomyces bailii | 10–50 | 50–500 | >500 | Refermentation of sweet wines, fizz, sediment; very SO₂/sorbate tolerant |
| Saccharomyces cerevisiae (RS >2 g/L) | 10–100 | 100–1,000 | >1,000 | Refermentation in bottle |
All values in cells/mL. During active fermentation or MLF, bacterial counts are naturally far higher and these bands don't apply.
Three things that move a result up a band
- Residual sugar above 2 g/L — any yeast or Zygosaccharomyces result counts one band higher.
- pH above 3.7, or molecular SO₂ below 0.5 mg/L (roughly 39 mg/L free at pH 3.7) — Brett and bacteria count one band higher.
- Bottling within four weeks — anything Medium is treated as High.
Check a wine's conditions before you test.
Microbial risk checkOrganism guide
| Organism | What it does | Where it comes from | Favoured by | Main control levers |
|---|---|---|---|---|
| Brettanomyces bruxellensis | Converts hydroxycinnamic acids to 4-ethylphenol and 4-ethylguaiacol. Grows slowly on trace sugars and cellobiose from new oak; faults show months after infection | Older barrels, cellar surfaces, infected lots, drains and hoses | pH >3.6, low molecular SO₂, cellar >15 °C, RS >0.5 g/L, long maturation, dirty barrels | Molecular SO₂ ≥0.6 mg/L, cool cellar, barrel sanitation (steam/ozone), filtration to 0.45 µm, chitosan, DMDC at bottling |
| Pediococcus spp. | Diacetyl (butter), ropy polysaccharide, acrolein with glycerol (bitterness), biogenic amines | Grape surfaces, cellar equipment, winery MLF populations | pH >3.5, low SO₂, post-MLF wines left unsulphured, high malic | Sulphur promptly after MLF, lysozyme, filtration, pH management |
| Lactobacillus spp. | Heterofermentative strains make acetic acid and mousiness. In high-sugar juice, L. kunkeei and relatives cause stuck or sluggish ferments | Fruit (especially damaged or botrytised), harvest bins, picking gear | High pH, warm must, delayed ferment start, low SO₂ at crush | Prompt inoculation, SO₂ and lysozyme at crush, cool must |
| Oenococcus oeni | The MLF bacterium you want. A problem only if still viable after MLF with malic or sugar left | Winery flora or inoculated culture | Unsulphured post-MLF wines, incomplete MLF (malic >0.3 g/L) | Confirm malic is finished, then SO₂ to ≥0.5 mg/L molecular; filter before bottling |
| Acetobacter / Gluconobacter | Oxidise ethanol to acetic acid and ethyl acetate; film in ullaged vessels | Fruit flies, damaged fruit, air-exposed wine, ullaged barrels | Oxygen, ullage, warm storage, low SO₂ | Top barrels, inert gas, SO₂, exclude fruit flies, sanitation |
| Zygosaccharomyces bailii | Very tolerant of SO₂, sorbate and ethanol. Referments sweet wines in bottle | Concentrate, juice stored for sweetening, sugar-handling areas | Residual sugar, sweetened or back-blended wines | Sterile filtration (0.45 µm) right before bottling, DMDC, test concentrate before use |
| Saccharomyces cerevisiae | Normal ferment yeast. A risk only when the wine still carries fermentable sugar and is headed for bottle | Carryover from ferment, cross-contamination from active lots | RS >2 g/L, inadequate filtration, warm storage | Sterile filtration, DMDC, sorbate (if no MLF risk), verify filter integrity |
Decision trees: what to do at each level
Find your organism, apply the adjustments above first (sugar, pH/SO₂, bottling date), then read down the column for your band. Doses are typical starting points; confirm against the product sheet and your wine's analysis.
Brettanomyces
The phenol result decides whether the wine is worth treating. SO₂ and chitosan stop growth; filtration removes cells. None of them removes 4-EP already formed.
Low · 10–100/mL
- Check molecular SO₂Target ≥0.6 mg/L molecular. Adjust free SO₂ for your pH
- Hold cellar below 15 °CKeep barrels topped, no ullage
- Retest in 3 monthsRising count: treat as Medium
Medium · 100–1,000/mL
- Measure 4-EP / 4-EG<200 µg/L: fruit still intact. >400 µg/L: fault already set
- Raise SO₂ or add chitosan0.8 mg/L molecular, or chitosan 4 g/hL, rack after
- Isolate from clean lotsOwn hoses, pump, barrels
- Retest in 2–3 weeksCounts survivors only
High · >1,000/mL
- Measure 4-EP / 4-EG nowDecide treat, blend or declass
- Treat todaySO₂ 0.8 mg/L mol. + chitosan, or filter to 0.45 µm
- Quarantine the lotSeparate hoses, pump, barrels
- Steam or retire the barrelNever refill untreated
- Bottle with DMDCRetest 2 weeks after treatment
Pediococcus, Lactobacillus and Oenococcus after MLF
Check malic first. Bacteria at Medium or High in a wine still finishing MLF are usually Oenococcus doing its job. For Oenococcus read the same columns at 10× the count. Lysozyme does nothing to Brett and isn't used where MLF is still wanted.
Malic acid <0.3 g/L?
No
- MLF still runningOenococcus is the MLF. Low SO₂, hold ~18 °C. Retest when malic <0.3
- Pedio or Lacto highLysozyme 250–500 mg/L. Finish MLF, then SO₂
Yes
Low · 10–500/mL
- Sulphur now0.5 mg/L molecular, within days of MLF end
- Retest pre-bottle4 weeks before the run
Medium · 500–5,000/mL
- Sulphur + lysozyme0.6 mg/L molecular. Lysozyme 250 mg/L
- Test VA, diacetylPedio: check ropiness. Lacto: VA, mousiness
- Retest in 3 weeksCounts survivors only
High · >5,000/mL
- Sulphur and filter0.6 mg/L molecular. Filter to 0.45 µm
- Test the damageVA, diacetyl, amines. Keep, blend or declass
- 0.45 µm at bottlingRetest 2 weeks after SO₂
Zygosaccharomyces and Saccharomyces before bottling
Any Zygosaccharomyces detection in a sweet wine is treated as High, because it shrugs off SO₂ and sorbate. DMDC (Velcorin) must be dosed at the filler by a licensed operator; the maximum permitted dose in New Zealand is 200 mg/L.
Residual sugar above 2 g/L?
No
- Dry wine: low riskNo sugar to referment. Standard filtration. Retest only if fizz
Yes
Zygo · any ≥10/mL
- Filter + DMDC0.45 µm at the line. DMDC 200 mg/L
- Find the sourceTest concentrate, juice. Sanitise sugar area
- Post-bottle check3 bottles across the run
Sacch · 10–100/mL
- Sterile filter0.45 µm membrane. Integrity-test the filter
- Retest post-bottleOnly if RS >5 g/L
Sacch · >100/mL
- Filter + DMDC0.45 µm, DMDC 200 mg/L. Integrity-test the filter
- Check the lineFiller, hoses, filter. Resample after CIP
- Post-bottle check3 bottles across the run
What the number can't tell you
- A High Brett count doesn't mean the wine already tastes faulty. Run 4-EP/4-EG to measure actual phenols; many wines at 1,000 cells/mL are still clean and recoverable.
- A Low count in a wine that already smells of barnyard usually means the population has been knocked back by SO₂ but the phenols remain. That damage is chemical and won't reverse.
- High bacteria in a wine still finishing MLF are usually Oenococcus doing its job. Check malic before acting.
When to test
| Stage | Suggested test | Why |
|---|---|---|
| Harvest intake / cold soak | Lactobacillus, Acetobacter | Catch sluggish-ferment and VA risk before yeast goes in |
| End of MLF | Oenococcus with malic; Pediococcus, Lactobacillus | Confirm MLF is done and decide when to sulphur |
| Barrel maturation, every 3 months | Brettanomyces | Spoilage develops slowly; quarterly screening catches it while it's still Low |
| Pre-blending | Full panel on each component | Don't contaminate a clean blend with one infected lot |
| 2–4 weeks before bottling | Full panel, plus Zygosaccharomyces and Saccharomyces if RS >2 g/L | Time to filter or treat before the line is booked |
| Post-bottling (optional) | Full panel on 3 bottles from start, middle and end of run | Verify filtration and line sanitation |
Turn this into a dated plan for your wine.
Sampling plannerSampling, retesting and when to call
Taking the sample
- Use the sterile 50 mL tubes we supply; fill to the line and cap straight away. Don't rinse the tube with wine.
- Sanitise the valve or bung area and run off the first 200 mL before sampling a tank. For barrels, sample mid-depth with a sanitised thief; for a suspected problem, take a second sample from the lees.
- Pooled samples: up to 5 barrels of the same lot can go in one tube for screening. If the pool comes back Medium or High, resample each barrel.
- Keep samples chilled (2–8 °C), not frozen, and get them to us within 48 hours. Label with lot, vessel, date and any recent treatment (SO₂, filtration, fining).
Retesting
- After any treatment (SO₂, filtration, chitosan, DMDC), allow 1–2 weeks before retesting so the surviving population has settled. Dead cells aren't counted, so the retest shows what the treatment left behind.
- A Medium result with no treatment: retest in 4–6 weeks to see whether the population is growing, stable or declining. Direction matters more than one number.
Call us when
- A result doesn't match what you taste or smell.
- You have a High result and need help choosing between SO₂, filtration and chitosan for that wine.
- You want 4-EP/4-EG, malic, free/molecular SO₂ or VA run on the same sample to complete the picture.
FermLabs guide · indicative bands; your wine's full analysis and context come first.