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Why Does Bread Mold Need Air to Grow?

Bread mold--the colorful substance that will almost invariably begin to grow on bread once it's been left out for sufficient time--doesn't strictly require "air" to live. What it requires is oxygen, which is of course a major component of Earth's air.

  1. Bread Mold

    • Hundreds of distinct types of bread mold exist, but all of them are varieties of fungi that get their food from the bread. Unlike photosynthetic plants, which convert solar into chemical energy, fungi must get their energy by absorbing nutrients from their environment, which is what the bread mold is doing on the bread.

    Source

    • A piece of bread needs to be in a place with air to develop any kind of mold in the first place because the mold grows out of the rapid reproduction of tiny fungal spores that drift through the air and land on the bread. These spores are in a passive search for a food source--once they happen across the bread, they'll set up shop and begin to grow into a fungus.

    Growth

    • Most molds, like human beings, require oxygen to live, and thus cannot survive in an oxygenless environment. This is why molds require air to grow, and why, even if spores have already landed on a piece of bread, placing it in a completely oxygenless chamber will kill off those spores. However, many molds are able to survive in extremely low-oxygen environments, which is why simply sealing a breadbox is not enough to inhibit mold growth.

    Ideal Conditions

    • Mold grows most readily in dark places (because light dries it out and, because mold isn't photosynthetic, light isn't required for energy), wet places (because mold requires moisture to live and prevents it from drying out) and places of around 80 degrees Fahrenheit (because mold can't regulate its temperature and is reliant on appropriate environmental conditions).

    Prevention

    • Some manufacturers prevent mold growth by selling their products in packaging from which all the oxygen has been removed and replaced with other gases such as carbon dioxide, which is easier and more reliable than trying to create a genuine vacuum in which there simply isn't any air. However, most bread is simply sold in cellophane or plastic bag packaging and is vulnerable to mold growth; this is one reason you don't want to buy a loaf of bread and leave it lying around for a while, even unopened.

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