Fermentation Off-Flavor & Defect Troubleshooter
Diagnose rotten egg sulfur smells, DMS, stalled fermentations, haze, and harsh fusel alcohols with certified BJCP/WSET resolution steps.
All Defects
Sulfur & Aromas
Oxidation & Contamination
Fermentation Health
Off-Flavors
Clarity & Appearance
Oxidation & Contamination
Cardboard & Papery Wet Paper (Oxidation)
Root Cause
Exposure to atmospheric oxygen post-primary (splashing during racking, dry airlocks, loose bungs).
Step-by-Step Resolution
1. Add Potassium Metabisulfite (Campden) + Ascorbic Acid to scavenge free oxygen.
2. Backsweeten slightly to mask papery staling.
Prevention Tip: Purge carboys with CO2 prior to racking, siphon gently without splashing, and avoid unnecessary racking.
Oxidation & Contamination
Vinegar / Volatile Acidity (Acetic Acid / VA)
Root Cause
Acetobacter bacterial infection in the presence of oxygen, dried out airlocks, or excessive headspace.
Step-by-Step Resolution
1. If VA is low, blend with a clean, low-acid batch.
2. If VA is high, convert into artisan mead/wine vinegar.
Prevention Tip: Minimize headspace during secondary aging and keep airlocks filled with sanitizer solution.
Oxidation & Contamination
Viscous Slime / Ropiness (Pedio / Extracellular Polysaccharides)
Root Cause
Pediococcus or Leuconostoc bacterial contamination producing dextran slime ropes.
Step-by-Step Resolution
1. Sulfite with Campden tablet (50 ppm free SO2).
2. Vigorous racking through a fine screen and long aging allows slime dextrans to break down.
Prevention Tip: Sanitize all equipment thoroughly with Star San or iodophor.