White flour takes a lot longer to spoil than whole wheat flour. Whole wheat flour retains essential oils not found in white flour, which can cause it to turn rancid over time. This makes identifying spoiled whole wheat flour easier than spoiled white flour. Spoiled whole wheat flour will produce has a rancid smell and should be discarded immediately.

The shelf life of flour, or the amount of time it takes for flour to spoil, depends on a number of factors including the type of flour and the way it is stored. White flour has a shelf life of 6 to 12 months if stored properly outside of the refrigerator. Stored in the refrigerator at 40 degrees Fahrenheit, white flour lasts for up to 2 years and can be kept indefinitely if stored in the freezer. Whole wheat flour, on the other hand, will only last 1 to 3 months outside of the refrigerator, 6 months in the refrigerator and up to 12 months in the freezer, assuming it is properly stored.

Flour, whether white or whole wheat, must be properly stored to prevent premature spoilage. Always use an air tight container properly sized for the amount of flour you want to store. You may need to convert pounds to cups when purchasing a container. A pound of flour is equal to 4 cups of flour. Keep the container in a cool, dark place such as a cupboard or pantry. To store flour in the freezer, use airtight bags. Remember to return flour to room temperature before using it.

Flour is susceptible to a number of pests that feed on it or use it as a nursery. According to to the University of Nebraska Lancaster County Cooperative Extension, pests commonly found in flour include Indian meal moth, dermestid beetles, flour beetles and weevils. These pests can chew into unopened flour packaging, which is another reason why you should store flour in airtight containers. An infestation is indicated by the presence of tiny beetles, moths, worms or larvae.