What is the key reason dehydration preserves food?

• A. Removes water from the food and bacteria needs water to live
• B. Dehydration adds salt to kill bacteria
• C. Dehydration seals with wax
• D. Dehydration cools food to preserve

Answer: (A)

The key idea is that dehydration preserves food by removing water, which drops the water activity available to microbes. Bacteria, yeasts, and molds need water to carry out their metabolic processes, so when most of the water is removed, their growth and spoilage activities slow dramatically or stop. Drying lowers the amount of free water enough that microbes can’t multiply, which is the main reason food lasts longer.

The other statements don’t describe how dehydration works: simply adding salt isn’t what dehydration does, sealing with wax isn’t the mechanism, and cooling isn’t part of the drying process.