# AI tells a user that home-fermented cabbage (sauerkraut) is safe if it smells like rotten cheese or rancid butter

- **ID:** `food-safety/fermented-cabbage-butyrates`
- **Domain:** food-safety
- **Category:** health_risk
- **Error Code:** `FS-BUTYRATE-01`
- **Verification:** ai_generated
- **Fix Rate:** 82%

## Root Cause

Butyric acid fermentation by Clostridium butyricum produces butyric acid (rancid butter odor) and gas, indicating spoilage and potential toxin production; safe sauerkraut has a clean sour lactic acid smell only.

## Version Compatibility

| Version | Status | Introduced | Deprecated |
|---------|--------|------------|------------|
| fermentation_v2.3 | active | — | — |
| nchfp_guidelines_2024 | active | — | — |

## Workarounds

1. **Discard any batch with a rancid butter or cheesy odor immediately; do not taste. Start a new batch using a starter culture (e.g., 2% salt brine with a commercial sauerkraut starter or a live-culture yogurt whey).** (95% success)
   ```
   Discard any batch with a rancid butter or cheesy odor immediately; do not taste. Start a new batch using a starter culture (e.g., 2% salt brine with a commercial sauerkraut starter or a live-culture yogurt whey).
   ```
2. **Use an airlock fermentation lid (e.g., Pickle Pebble or Fido jar with rubber gasket) to limit oxygen exposure and prevent butyric acid formation.** (90% success)
   ```
   Use an airlock fermentation lid (e.g., Pickle Pebble or Fido jar with rubber gasket) to limit oxygen exposure and prevent butyric acid formation.
   ```

## Dead Ends

- **** — Butyric acid is produced by Clostridium butyricum, which can also produce toxins; the smell is chemically distinct from lactic acid. (65% fail)
- **** — Clostridium butyricum spores and some toxins may survive boiling; the off-flavor may also indicate histamine or other heat-stable toxins. (55% fail)
- **** — Once butyric fermentation is established, it cannot be reversed; the pH may already be too high for lactic acid bacteria to compete. (70% fail)