Effect of Water Activity on the Microbiological Stability of Mobility- Enhancing Ration Components

摘要

The effect of water activity and pH on the anaerobic growth of Staphylococcus aureus in six mobility-enhancing ration components (MERC), including a beef stick (snack) and five meat sandwiches was determined. These are ready-to-eat rations mat can be consumed on me move, eaten without utensils and require no preparation. The MERCs, adjusted to various target water activities and pH, were challenged with a three-strain S. aureus cocktail. Samples were packaged in a clear, permeable, Scotchpack material, overwrapped and sealed in a flexible, high-barrier Meal, Ready-to-Eat pouch containing an oxygen scavenging sachet. Only beef snacks were sealed under 20 mm Hg to simulate commercial practice. All samples were held at 35 degrees centigrade for six months and tested periodically for growth or inhibition of S. aureus, aerobic plate counts, and yeast and molds. S. aureus growth was inhibited in four of the six MERC products tested at a combination of 0.89 water activity and pH 4.8 to 5.4.