After 2 days (at standard room temperature and humidity) bread starts to get toxic. The molds that appear in it (Aspergillus, particularly Aspergillus flavus) produce dangerous mycotoxins called aflatoxins. Aflatoxins are carcinogenic, i.e. regular consumption of food that contains aflatoxins can cause cancer (usually after years of usage).

How does the bread mold look like?

In the erliest stage you will see nothing, later some white points will develop on the surface very similar to flour. Taste of such bread is unchanged, aflatoxins are tasteless, odorless and colorless yet very powerful toxins.

Based on the mold type, an old fungus can have variety of colors from white to dark green and contains various amounts of mycotoxins (an experiment has shown that the largest amount of aflatoxins was found in a 7 day old bread stored in a plastic bag at a room temperature).

Why does bread mold?

Molds can be part of the ingredients used to produce the bread (storage of the wheat grains or flour in dry places is probably the most important factor) and can survive the baking process.

And molds also are part of the environment (there are millions od spores flying around you right now, are you scared?) and get into bread after its production.

There are specific conditions that help molds develop and grow - molds will grow better in wet, warm and dark environment.

Mold-proof storage of bread?

It won´t help if you put the bread in your refrigerator (8 degrees C isn´t low enough), in contrary, if the bread gets wet it will spoil even faster.

Also you won´t help yourself if you make toasts of your 4-days old bread as neither 100 Celsius degrees neutralize the toxins that already developed.

So how to avoid molding of bread?

Buy as much bread as you can eat in 2 days. Store it in a breadbox (wooden, plastic, stainless steel). If you happened to buy too much bread, freeze it in a freezer (at -18 Celsius degrees) wrapped in a plastic bag.

Defrosting of such frozen bread is best done if you unwrap it from the plastic bag and place it a clean tissue (fabric, towel… whatever).

Bread older than 2 days should not be used (neither for toasts and crumbs).