Final answer:
The statement that bacteria are likely to grow quickly in PHF with a water activity of 0.85 or higher is true because bacteria require high aw to grow, and this level of moisture availability supports their rapid proliferation in such conditions.
Step-by-step explanation:
Bacteria growth is dependent on several factors, including water activity (aw) and pH levels. Water activity is a measure of the available moisture in a substance and is important for microbial growth. A water activity of 0.85 or higher is indeed conducive to the rapid growth of bacteria in potentially hazardous foods (PHF), making them more susceptible to spoilage and foodborne illnesses. This is because bacteria, especially pathogens, generally require high aw (around 0.97-0.99) to thrive.
In contrast, methods such as drying, freeze-drying, or increasing osmotic pressure with salts or sugars (as seen in brined foods and jams) can effectively decrease the aw, inhibiting bacterial growth. This aligns with the commonly used food preservation techniques that aim to lower aw to prevent spoilage and extend shelf life.
Maintaining food safety involves understanding these concepts as bacteria are most likely to grow quickly in PHF with a water activity of 0.85 or higher. Hence, the statement is true.