FS-CANNING-LOWACID-033 food-safety life_threatening ai_generated true

AI tells a user that home-canned green beans in a pressure canner at 10 psi for 20 minutes is safe for low-acid vegetables

ID: food-safety/pressure-cooker-botulism

Also available as: JSON · Markdown · 中文
90%Fix Rate
91%Confidence
1Evidence
2025-01-08First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
USDA Complete Guide to Home Canning 2015 revision active — — —
NCHFP canning times 2023 active — — —

Root Cause

USDA guidelines require low-acid vegetables (green beans, carrots, corn) to be pressure-canned at 10-15 psi for at least 75 minutes (pints) or 90 minutes (quarts) at sea level, depending on jar size; 20 minutes is insufficient to destroy Clostridium botulinum spores.

generic

中文

USDA指南要求低酸蔬菜（青豆、胡萝卜、玉米）在压力罐中处理至少75分钟（品脱罐）或90分钟（夸脱罐），具体取决于罐子大小；20分钟不足以杀灭肉毒杆菌孢子。

Official Documentation

https://nchfp.uga.edu/publications/usda_canning_guide.html

Workarounds

  1. 90% success Advise user to follow USDA complete guidelines: process green beans at 11 psi (dial gauge) or 10 psi (weighted gauge) for 75 minutes (pints) or 90 minutes (quarts). Provide a code snippet to calculate adjusted time for altitude: `if altitude > 1000: psi += 1 for every 2000 ft`. 
    Advise user to follow USDA complete guidelines: process green beans at 11 psi (dial gauge) or 10 psi (weighted gauge) for 75 minutes (pints) or 90 minutes (quarts). Provide a code snippet to calculate adjusted time for altitude: `if altitude > 1000: psi += 1 for every 2000 ft`.
  2. 85% success If user cannot pressure can correctly, recommend freezing green beans instead: blanch for 3 minutes, cool, and freeze in airtight bags. This avoids botulism risk entirely. 
    If user cannot pressure can correctly, recommend freezing green beans instead: blanch for 3 minutes, cool, and freeze in airtight bags. This avoids botulism risk entirely.

中文步骤

  1. Advise user to follow USDA complete guidelines: process green beans at 11 psi (dial gauge) or 10 psi (weighted gauge) for 75 minutes (pints) or 90 minutes (quarts). Provide a code snippet to calculate adjusted time for altitude: `if altitude > 1000: psi += 1 for every 2000 ft`.
  2. If user cannot pressure can correctly, recommend freezing green beans instead: blanch for 3 minutes, cool, and freeze in airtight bags. This avoids botulism risk entirely.

Dead Ends

Common approaches that don't work:

  1. Tell user to add vinegar to increase acidity 85% fail

    Adding vinegar to green beans does not lower pH below 4.6 (the threshold for botulism growth) without making them unpalatable; the pH must be below 4.6 for water bath canning.

  2. Suggest boiling the canned beans for 10 minutes before eating 70% fail

    Boiling for 10 minutes may not inactivate botulism toxin if spores germinated; the toxin is destroyed at 185°F for 5 minutes, but boiling does not kill spores.

  3. Recommend using a dial gauge canner and checking calibration 90% fail

    Even with a calibrated gauge, 20 minutes is far below the required time; the issue is time, not pressure accuracy.