How Bread Goes Bad

• Most bread is made from wheat or another grain source and yeast, a living organism. Mold, microscopic fungi, grows on organic material, such as vegetation, to aid in the process of decomposition. When the compounds in bread begin to decompose, mold spores set up residence. While some types of mold are not harmful, others can produce allergic or respiratory symptoms, and some are potentially carcinogenic. Because mold spores are tiny, you may not be able to see mold growing on bread until it has been deeply embedded with invasive roots. Poisonous toxins often grow in the root threads.

Sell By, Use By, Best By, Oh My!

• Because of the rate of decomposition of specific ingredients, manufacturers and bakers often label bread and other baked goods with a "best before" or "sell by" date. While these dates may appear to indicate when a food spoils, they are more accurately an indicator of when the food begins to lose its freshness or peak flavor. While freshly baked bread begins to decompose after about 48 hours, commercial manufacturers add preservatives to prolong shelf life. Packaged bread from the grocery store can safely be eaten for five to seven days after the best by date as long as it does not show evidence of mold. Bread from the supermarket's bakery usually only lasts about two to three days past the best by date.

How's Your Loaf Life?

• Because humidity and heat encourage mold growth, storing bread in an airtight container in a cool, dry location can extend the life of your loaf. The refrigerator is an ideal location for bread you plan to eat within a few days, especially if you live in an area with high humidity. To maximize freshness, keep the inside of the refrigerator clean, especially if mold spores have been detected. To preserve bread longer, store it in the freezer. Frozen bread can be safely eaten for up to six months past the best before date.

Play Keep-Away

• Steer clear of bread with visible signs of mold, which may begin as white, black or green dots. If one slice shows signs of mold, the spores have infiltrated the rest of the bread and the entire loaf should be discarded. Bread that is simply hard or dried out but does not show signs of mold can still be safely eaten.