Can flour go bad and make you sick?

In this brief guide, we will answer the query, “Can flour go bad and make you sick?” and will discuss signs of flour spoilage.

Can flour go bad and make you sick?

Yes, flour can go bad and make you sick. Spoiled flour contains a high number of mycotoxins which are associated with liver diseases and cancer. Although refined flours may have extended shelf lifes, whole flours may deteriorate in a few months, due to the fat oxidation of its components, which include germ and bran (1). 

How long does it take for flour to go bad?

Several elements affect flour’s shelf life, or how long it lasts before it goes bad. Most flours may be stored at room temperature for 3–8 months, which is far beyond their expiry date. When it comes to flour’s shelf life, there are several factors to consider. Temperature, moisture conditions and packaging material are determinants of the shelf life of the flour, as well as its chemical composition (2).

Different types of flour

The degree of processing, which has an impact on the shelf life of flour, is a common way to classify it. There is also an influence on the source component, such as wheat or arrowroot.

White all-purpose flour, for example, tends to keep fresh longer than whole-wheat flour because of the processing methods used to make each of the two.

The bran and germ of the grain are removed, leaving just the starchy endosperm of white flour. Whole-wheat flour, on the other hand, comprises the bran, germ, and endosperm of the grain.

Whole-wheat goods are particularly susceptible to spoiling since the bran and germ contain a lot of oil. Fats degrade when they are exposed to light, moisture, or the air, and this usually results in an unpleasant taste and smell. 

The major ways of lipid degradation are by hydrolytic or oxidative reactions or sometimes combination of both. Hydrolysis of lipids generates free fatty acids, which in turn serve as substrates for further oxidation. Lipases are the enzymes responsible for hydrolytic degradation of lipids. Lipoxygenase and peroxidase are known to initiate the oxidative breakdown of lipids in cereals (1).

Flour millers stamp use-by dates of 3 to 9 months after milling on whole wheat flour packages, while regular wheat flour use-by dates range from 9 to 15 months after milling. Although these dates can be helpful, actual shelf-life could be shorter or longer depending on temperature and humidity during storage and on failure endpoints (i.e., the point at which the flour is deemed unacceptable as determined by the company or the experimenter (2).

Almond and coconut flour, two common gluten-free substitutes, are heavy in oil, making them more likely to become rancid than white flour.

A gluten-free flour blend made from a variety of different nuts or roots may be more susceptible to mold growth because of the higher moisture content.

How to store flour properly?

Storage of flour is influenced by several factors such as moisture content, enzyme activity, packaging material, and storage conditions. Flour’s shelf life depends on how it’s stored. Shelf-stable flour is defined by the United States Department of Agriculture (USDA). So long as you keep it at room temperature, you’re good to go. However, in order to maintain its freshness, it must be stored in an airtight container in a cold, dry location. Its shelf life may be extended by cooling or freezing it.

The freezing of foods slows down, but does not stop, the physicochemical and biochemical reactions that govern the deterioration of foods. During storage, there is a slow progressive change in organoleptic quality, which does not become objectionable for some time. The loss of quality of frozen foods depends primarily on storage temperature, length of storage time, and thawing procedure. Microbial growth is completely stopped below –18°C, and both enzymatic and nonenzymatic changes continue at much slower rates during frozen storage (4).

All-purpose flour, for example, may be stored for six to eight months on the shelf but can be kept refrigerated or frozen for up to a year and a half. To avoid mold, store your flour in the refrigerator away from moisture and water. If possible, use an airtight container like a plastic bag or food storage bin to keep it contained.

Before using flour that has been refrigerated or frozen, make sure it is at room temperature. In order to avoid clumping, this is necessary.

What to look for when determining whether or not flour has gone bad?

Expiration dates, also referred to as “best-by dates,” are placed on the bags of most packaged flours to indicate how long they will remain fresh. Although these labels aren’t required and don’t indicate safety, they’re nevertheless useful. As a result, even if the expiration date on your flour has passed, you may still use it.

The smell is the greatest method to tell whether or not your flour is safe. Bad flour has a stale, musty, or nearly sour scent, while fresh flour has a neutral odor. With an extended shelf life, lipid oxidation can occur in wheat, which can generate undesirable odor components that affect sensory acceptability of wheat flour based products (2).

Additionally, it may seem discolored. When the flour has been exposed to water or moisture, mold may grow in huge clumps on the surface. If this is the case, you should toss the whole bag right away.

When your flour is about to expire or has already expired, think of new methods to utilize it. Additionally, it may be used to make non-food things such as playdough or homemade glue.

Spoiled flour might be a health hazard

Rancid flour alters its molecular structure, which may lead to the production of hazardous substances. Rancid flour hasn’t been linked to any health problems in recent research, though. Foods cooked with it may be unpleasant to eat, but they are unlikely to affect your health if consumed in moderation.

Moldy flour, on the other hand, is both harmful and unpleasant to eat. Mycotoxins are hazardous substances that may be produced by certain molds. Mycotoxin contamination can occur pre-harvest when the crop plant is growing or post-harvest during processing, packaging, distribution, and storage of food products. Generally, all crops and cereals that are improperly stored under feverish temperature and prompting humidity for a prolonged time can be subject to mold growth and mycotoxin contamination. The major fungi causing frequent and problematic contamination of foods and feeds with mycotoxins are members of the fungal genera Aspergillus, Fusarium, and Penicillium (3). Vomiting and diarrhea may occur as a result of taking these substances.

Depending on the quantity consumed and the length of exposure, mycotoxins have been related to various significant ailments such as cancer and liver disease. Among the mycotoxins, aflatoxins are considered the most toxic, with a significant economic burden to agriculture. Aflatoxins have carcinogenic, teratogenic, hepatotoxic, mutagenic, and immunosuppressive effects, with the liver the main organ affected and are also associated with both acute toxicity and chronic carcinogenicity in human and animal populations (3).

Because of this, if your flour has a terrible odor or mold growth, it’s better to toss it away. 

Other FAQs about Flour that you may be interested in.

Is flour vegan?

How long does flour last?

Can you eat coconut flour raw?

How do you store flour for years?


In this brief guide, we answered the query, “Can flour go bad and make you sick?” and discussed signs of flour spoilage.


  1. Deepa, C, Umesh Hebbar, H. Effect of micronization of maize grains on shelf-life of flour. J Food Process Preserv, 2017, 41, e13195. 
  2. Doblado-Maldonado, Andres F., et al. Key issues and challenges in whole wheat flour milling and storage. J cereal sci, 2012, 56, 119-126.
  3. Alshannaq A, Yu J-H. Occurrence, Toxicity, and Analysis of Major Mycotoxins in Food. Int J Environ Res Public Health, 2017, 14, 632. 
  4. Rahman, Mohammad Shafiur, and Jorge F. Velez-Ruiz. Food preservation by freezing. Handbook of food preservation. CRC press, 2007. 653-684.