Yingtai: Key Control Points for Moist Heat Sterilization Parameters

Yingtai: Key Control Points for Moist Heat Sterilization Parameters

The effectiveness of moist heat sterilization relies on precise control of several critical parameters. Below are the core control points and their scientific rationale:

1. Temperature Control

   - Setpoint and Fluctuation Range

     Typical Temperature: 121°C (saturated steam pressure 103.4 kPa), suitable for most sterilization scenarios.

     Fluctuation Tolerance: Temperature fluctuations during sterilization should be ≤ ±1°C to prevent microbial "sub-lethal injury" leading to revival.

   - Temperature Uniformity Verification

     Heat Distribution Testing: Use multi-point temperature sensors (e.g., wireless validation instruments) to detect temperature distribution within the sterilization chamber, ensuring no "cold spots" (areas with insufficient temperature).

     Hotspot Control: High-temperature areas must avoid material degradation (e.g., carbon source coking in culture media).

2. Time Control

   - Sterilization Hold Time

     Baseline Parameter: 15-30 minutes at 121°C (adjusted based on material properties). For example, batch sterilization of culture media typically requires 20-30 minutes, while continuous sterilization takes 5-7 minutes.

     Equivalent Sterilization Time (F₀ Value): Calculated based on microbial D-value and Z-value, requiring F₀ ≥ 12-15 minutes (ensuring SAL ≤ 10⁻⁶).

   - Heat Penetration Time

     The time required for the center of the material to reach sterilization temperature (e.g., additional time is needed for large-volume liquids).

3. Pressure and Steam Quality

   - Saturated Steam Pressure

     Pressure must strictly correspond to temperature (e.g., 121°C corresponds to 103.4 kPa) to avoid air inclusion or unsaturated steam, which reduces heat transfer efficiency.

   - Steam Dryness

     Steam moisture content should be ≤ 3%. Excessive moisture lowers sterilization efficiency and increases the risk of condensate residue.

4. Loading Configuration and Heat Transfer

   - Loading Specifications

     Items should be arranged to allow steam channels (e.g., instrument basket loading ≤ 80% capacity), avoiding overstacking that hinders steam penetration.

     Porous items (e.g., fabrics) should be placed vertically to facilitate condensate drainage.

   - Packaging Material Selection

     Use breathable packaging (e.g., medical non-woven fabric) to ensure steam penetration while maintaining bacterial barrier properties.

5. Process Monitoring and Validation

   - Biological Indicators (BI)

     Use Geobacillus stearothermophilus (D₁₂₁ = 1.5-2.0 minutes) to verify sterilization effectiveness, requiring a survival probability ≤ 10⁻⁶.

   - Chemical Indicators

     Color-changing indicator strips (e.g., 121°C responsive) provide quick confirmation of reaching sterilization temperature.

   - Data Recording and Traceability

     Use electronic recorders to log temperature-time curves throughout the process, ensuring data integrity.

6. Cooling Phase Control

   - Pressure Reduction Rate

     Liquids should undergo slow depressurization (e.g., 0.5 kPa/min) post-sterilization to prevent boiling or container rupture.

     Solid items can be depressurized quickly but must avoid condensate backflow contamination.