Editing Openai/6939a858-8b8c-8006-b827-ae43c13df6f8


{{DISPLAYTITLE:Philly Sour pellicle growth}}

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== gpt-5-1 ==
=== User: You are an experienced brewmaster. ===
You are an experienced brewmaster. Can Lallemand Philly Sour yeast grow pellicle or is such a batch of beer contaminated?

=== Assistant: Short answer: Philly Sour does not form a pellicle. ===
Short answer: Philly Sour does ''not'' form a pellicle.

Lallemand Philly Sour (Lachancea thermotolerans) is a lactic-acid-producing yeast, but it behaves like a clean yeast in terms of surface growth. It does not create pellicles (no ropey film, bubbles trapped in a skin, or powdery white islands).

If you’re seeing a pellicle, it almost certainly means contamination, most commonly:
* Brettanomyces
* Pediococcus
* Lactobacillus (in mixed culture)
* Wild yeast + oxygen exposure

Key indicators it’s contamination:
* White/tan film with bubbles underneath
* Patchy islands or brain-like texture
* Development after active fermentation slows
* Funk, horsey, barnyard, or intense sour beyond expected Philly profile

Philly Sour alone gives:
* Clean lactic tartness (yogurt/lemon)
* No surface film
* No continued gravity drop months later

Conclusion:
A pellicle ≠ Philly Sour. That batch is contaminated or unintentionally mixed-fermented. Whether it’s dump-worthy depends on aroma, flavor, and your tolerance for funk.

=== User: The aroma and taste are ok. ===
The aroma and taste are ok. The taste has a bit vinegar in it but the level is not terrible. However I am worried about keezer contamination

=== Assistant: You’re safe as long as it’s not Acetobacter + oxygen. ===
You’re safe as long as it’s not Acetobacter + oxygen.

Key points, no fluff:
* Vinegar note → likely low-level Acetobacter.
* Acetobacter is not airborne. It spreads via liquid contact, fruit flies, dirty lines, not by sharing headspace in a keezer.
* Cold + CO₂ pressure halts it.

Keezer risk assessment
* ✅ Same keezer, separate kegs → safe
* ✅ Serving through normal beer lines → safe
* ❌ Shared transfer hoses, racking canes, QDs without cleaning → risk
* ❌ Open fermenter near fruit flies → risk

What to do now
* Keep the keg cold and under pressure
* Do not open it repeatedly
* Clean/sanitize: - Liquid & gas QDs - Lines if this beer touched them
* No need to nuke the keezer or discard other kegs

If it’s carbed and sealed, it won’t contaminate anything else.
Worst case: the beer slowly sharpens over time — not a system-wide infection.

=== User: It would be carbed and kept cold but the co2 lines are connected and shared between various kegs. ===
It would be carbed and kept cold but the co2 lines are connected and shared between various kegs.

=== Assistant: Still not a problem. ===
Still not a problem.

Why:
* CO₂ lines only see dry gas, not beer.
* Contaminants (Acetobacter, Brett, LAB) cannot travel upstream through gas posts under pressure.
* Check valves in regulators/manifolds add another barrier.

When it ''could'' be an issue (edge cases):
* Beer backed up into gas lines (overfilled keg + no check valve)
* Shared spunding line with liquid present
* Wild pressure swings causing liquid carryover

Quick sanity check
* Disconnect gas QD → if it’s dry and doesn’t smell sour, you’re fine.
* If paranoid: spray some starsan into the gas QD, reconnect.

Bottom line
* Shared CO₂ manifold = safe
* No keezer contamination risk
* Drink it sooner rather than later

If you want, describe the pellicle (thin skin vs chunky islands) and I can ID the likely culprit.

=== User: How like do I contaminate the kegs for later? ===
How like do I contaminate the kegs for later? I use sodium percarbonate to sanitize it.

=== Assistant: Low risk — but one correction first. ===
Low risk — but one correction first.

Sodium percarbonate is a cleaner, not a sanitizer.
It removes organics very well, but it does not reliably kill Brett/LAB/Acetobacter on its own.

Actual contamination risk
* Kegs used for that beer: low
* Future beers infected if cleaned properly: very unlikely
* Biggest risk parts: dip tubes, posts, poppets, O-rings

Best-practice reset (fast + effective)
# Percarbonate soak (hot) - Disassemble keg completely - 30–60 min soak
# Rinse thoroughly
# Acid sanitizer (mandatory) - Star San / PAA / iodophor - Reassemble wet with sanitizer
# Optional but solid: - Replace O-rings (cheap insurance)

What ''not'' to worry about
* Stainless steel: non-porous
* CO₂ exposure
* Cold storage

Bottom line
* Percarbonate alone = not enough
* Percarbonate + proper sanitizer = near zero risk
* No need to dedicate kegs unless you intentionally brew mixed ferms

If you want absolute certainty: boil dip tubes for 10 min and replace O-rings once.

== References ==
<references />


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