Cut apples absorb odors in the fridge because their exposed flesh is porous and readily absorbs volatile organic compounds (VOCs) from the surrounding environment. These VOCs are responsible for the smells we perceive.
When an apple is cut, its cells are damaged, releasing enzymes that cause browning (oxidation). This process also creates a larger surface area that is exposed to the air. The flesh of the apple is porous, meaning it has tiny holes and spaces. These spaces act like a sponge, readily absorbing substances from the surrounding environment.
The fridge is often filled with various foods, each emitting its own unique set of volatile organic compounds (VOCs). VOCs are molecules that easily evaporate at room temperature and are responsible for the smells we associate with different foods. Because the cut apple's flesh is exposed and porous, it readily absorbs these VOCs from the air inside the fridge. This absorption leads to the apple taking on the odors of nearby foods, such as onions, garlic, or cheese.
The process is similar to how baking soda works to deodorize a fridge. Baking soda is alkaline and can neutralize acidic odors. In the case of the apple, it's simply absorbing the odors rather than neutralizing them.
To prevent cut apples from absorbing odors, store them in an airtight container or wrap them tightly in plastic wrap. This creates a barrier that prevents the VOCs from reaching the apple's flesh. You can also sprinkle a little lemon juice on the cut surfaces to slow down oxidation and potentially reduce odor absorption.