Editing Openai/6939a858-8b8c-8006-b827-ae43c13df6f8 (section)

=== 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.