Water or Moisture:

All bacteria need moisture, or water, in a "useable" or "available" form to grow and reproduce. Bacteria use the water to take in food and to remove unwanted waste products. Water activity (aw) is one measure of the available water in a food. The water activity scale runs from 0 to 1.0. The lower the water activity, the less water is available in a form that can be used by bacteria. The water activity of pure water is 1.0 - thus the water activity of all foods falls below this number. However, many food products, particularly meat, poultry, seafood and dairy products, have a water activity of 0.95-0.99. Unfortunately, this is the optimum range for many of the spoilage and disease-causing bacteria. Most fresh seafood products have a water activity above 0.98 - perfect for bacterial growth!!! Pathogenic bacteria do not grow well or produce toxin below 0.85 and most require 0.92 or above. Freezing, drying, or salting are ways to reduce available water to bacteria, and slow down their growth.

What bacteria need to grow and multiply

1. Food (nutrients)
2. Water (moisture)
3. Proper temperature
4. Time
5. Air, no air, minimal air
6. Proper acidity (pH)
7. Salt levels