Microbial Control Program

A microbial control program is a food business's coordinated set of practices for keeping harmful bacteria, molds, yeasts and viruses out of food, stopping their growth and destroying them where needed.

  • Food safety
  • Food safety programs

A microbial control program pulls together everything a food business does to manage microorganisms, which federal rules define as yeasts, molds, bacteria, viruses, protozoa and microscopic parasites. It usually combines sanitation of food-contact surfaces, safe water, lethal steps such as baking or pasteurizing, time and temperature control, and product formulation that limits growth through acidity or water activity. Under FDA's preventive controls rule, many of these measures appear as process controls and sanitation controls, supported by monitoring, verification and records. The aim is threefold: prevent contamination, keep any microbes present from multiplying, and destroy those that must be eliminated.

Microbes cause both illness and spoilage, and different controls stop different organisms. Federal good manufacturing practice rules require foods that support rapid microbial growth to be held at temperatures that prevent adulteration, foods relying on pH to be kept at 4.6 or below, and foods relying on water activity to be kept at a safe moisture level. Virginia Cooperative Extension sums up the growth factors as FAT TOM: food, acidity, time, temperature, oxygen and moisture. Controlling one or more of them keeps microbes from reaching dangerous levels.

Key facts

pH limit for acid-controlled foods (21 CFR 117.80)
4.6 or below
Shelf-stable water activity (VT Extension)
0.85 aw or less
Minimum water activity for most spoilage bacteria
About 0.90 aw
Lower water-activity limit for molds and yeasts
About 0.61 aw

In a bakery or commercial kitchen

  • Match controls to each product: a validated bake for raw-flour items, cold holding for perishables, low water activity for shelf-stable goods
  • Clean food-contact surfaces as often as needed and, in wet processing, sanitize them before use and after interruptions
  • Protect batters, sauces, dressings and similar preparations held over time from contamination and microbial growth
  • Use only safe water of adequate sanitary quality for ingredients and for cleaning food-contact surfaces
  • Verify the program works through records review and testing, not just routine monitoring

For home and cottage bakers

  • Think FAT TOM: controlling time, temperature, acidity or moisture keeps germs from reaching dangerous levels
  • Know that dry baked goods with water activity of 0.85 or less, such as many breads and cookies, are generally considered shelf stable
  • Remember that molds tolerate drier conditions than most bacteria, so store even dry baked goods covered

Related entries

Sources

Written by VanillaGoods in our own words from these sources. Last reviewed October 17, 2026.

  1. 21 CFR 117.135: Preventive controls, Electronic Code of Federal Regulations (eCFR)
  2. 21 CFR Part 117 Subpart B: Current Good Manufacturing Practice, Electronic Code of Federal Regulations (eCFR)
  3. 21 CFR Part 117 Subpart A: General Provisions (§ 117.3 Definitions), Electronic Code of Federal Regulations (eCFR)
  4. Food Safety Factors Affecting Microbial Growth (FST-9), Virginia Cooperative Extension
  5. Water Activity of Foods (Food Safety Fact Sheet MF3674), K-State Research and Extension, Kansas State University