How long is flour good for?

In this brief study, we will answer the question, “How long is flour good for?”. We will also discuss in detail, the shelf life, and storage methods of flour.

How long is flour good for?

“All-purpose flour” lasts six months to a year at ambient temperature, depending on the package and storing conditions. Refrigerated or frozen, it can last for up to two years, as concluded by Lancelot and others in recent research [1].

According to these authors, the flour stored at room temperature exhibit many more changes than the flour stored at -20 °C after 30 months of storage, concluding that storage at low temperature preserved the initial quality of the flour.

As a general rule, flour is a shelf-stable product due to its low water content, but upon inadequate storage conditions, such as high humidity and air exposure, the growth of fungi may be encouraged [1,2].

Furthermore, flour spoilage can be due to chemical alterations, like protein denaturation, starch degradation, fat oxidation; alteration of enzymatic origin; cracks, or breakage which favors the invasion of microorganisms and insects [1].

In contrast to white flour, whole wheat flour has a shorter shelf life, of about 3 months at room temperature, and for a year in the fridge or freezer. 

This happens because whole grains contain a higher fat content than refined flour, making whole wheat easier to oxidize. 

According to Lancelot and others fat oxidation is the main alteration promoting the loss of quality of flour during storage [1]. 

How long are other flours good for? 

The shelf life of different flours will strongly depend on their chemical composition. Let´s see the example of coconut and almond flour.

If correctly stored and handled, the shelf life of coconut flour is 1 year unopened, and 30 days after opening.

Almond flour, in turn, can last for 6-12 months in the pantry or refrigerator, provided it is stored properly. Both almond and coconut flour are high in fat. For instance, 50% of almond flour is fat, and most of it is unsaturated [3]. 

The high-fat content makes these flours prone to fat oxidation (more than all-purpose flour or whole flour) [3]. This rational also applies to other flours high in fat, such as walnut flour.

When making these estimations, keep in mind that the numbers will only apply to the finest quality. That flour that has been stored properly is safe for usage for years to come, although its quality (flavor, odor) may have declined. 

How to keep your flour fresh?

Store your flour, regardless of the type, in a cool, dry area, away from heat, and in an airtight container. Studies have stated that flour is highly hygroscopic and can absorb water from the surroundings [1].

Lancelot and others [1] found that flour stored in paper bags had an increase of 7% in their water contents during three months at room temperature, while in watertight containers this increment was less than 1% within the same period.  

The problem with increasing the moisture content of the flour is that this favors microbes’ growth, as already reported by Abdullah and others [2].

Moreover, remember that fat oxidation is a main factor of flour degradation, so keeping it in an airtight container and sealing it after opening the packaging is generally preferable. 

The best option is an insulated cereal storage container with a flip-top cover.

When only using particular types of flour – such as whole wheat, almond, or coconut – on a fairly seldom basis, keeping the flour in the fridge or freezer is generally the most practical.

If the flour is stored at a low temperature, it will last longer because chilling or freezing reduces the rate of unwanted reactions [4]. 

It is especially important to pay attention to this for gluten-free flour, such as coconut and almond flour because they are higher in fat than all-purpose flour and may undergo oxidation easier. 

For instance, based on fat oxidation markers, Raisi and others [3] found that almond flour stored at ambient temperature (23°C) spoiled faster than that kept under refrigeration (4°C).

That means, if you want to keep using that particular packet of flour for an extended time, you should store it in the fridge.

How do you know if your flour is bad?

To know if your flour has gone bad, you should observe its appearance and feel its smell.

As fat oxidation is the one important spoiling reaction taking place in flour, rancidity can be easily noticed by unpleasant rancid odors and tastes. 

Rancidity will not make you sick, but it is not healthful consuming oxidized fat. Moreover, keep in mind that using oxidized flour can ruin your recipes due to the off-flavors that rancid flour can bring to the product. 

So the wise thing to do is to discard it. 

Mold growth is also a possibility, and can be identified by bluish-green spots on the powder. If any signs of mold are detected, it is recommended to discard the flour as certain mold species can produce toxic compounds. 

If you detect clustering, this indicates that the flour absorbed moisture from the environment. It is not safe to consume flour like this because the higher moisture could have favored microorganisms’ growth [5]. 

You should also look for bugs or flour worms if the item is contaminated. Flours can attract insects, and even though the product is still useful, the appearance of bugs signals that it’s time to throw it out. 

Can you get sick from eating expired flour?

Most of the times, you will not be sick from eating expired flour. They are low moisture and low water activity products [6], where harmful microorganisms will rarely grow if the flour is stored and handled properly during its shelf life.

Therefore, you can use expired flour as long as you are sure that it has been stored properly over its shelf life, and that you do not detect any sign of mold and spoilage, or damaged package, which could indicate insect infestation.  

Particularly, you should not consume flours with clusters or that clearly indicate moisture absorption, as this could have encouraged fungal growth and eventually favor the growth of harmful bacteria [6].

Flours are usually given a best-before date, which means that after the printed date, the quality may start to drop quickly, but it is still safe to consume.

One negative consequence of using expired flour is that baked items simply do not taste or perform well, as confirmed by Lancelot and others [1]. 

Conclusion

In this brief study, we answered the question, “How long is flour good for?”. We also discussed in detail, the shelf life and storage methods of flour.

Citations

1. Lancelot E, Fontaine J, Grua-Priol J, Le-Bail A. Effect of long-term storage conditions on wheat flour and bread baking properties. Food Chem. 2021 Jun 1;346:128902. 

2.  Abdullah N, Nawawi A, Othman I. Fungal spoilage of starch-based foods in relation to its water activity (aw). Journal of Stored Products Research. 2000;36(1):47-54.

3. Raisi M, Ghorbani M, Sadeghi Mahoonak A, Kashaninejad M, Hosseini H. Effect of storage atmosphere and temperature on the oxidative stability of almond kernels during long-term storage. Journal of Stored Products Research. 2015;62:16-21.

4. 7. Fellows PJ. Food Processing Technology Principles and Practice. Fourth ed2017.

5. Jeong S, Marks BP, Ryser ET, Harte JB. The effect of X-ray irradiation on Salmonella inactivation and sensory quality of almonds and walnuts as a function of water activity. Int J Food Microbiol. 2012 15;153(3):365-71.

6.  Leiras MC, Iglesias HA. Water vapour sorption isotherms of two cake mixes and their components. International Journal of Food Science & Technology. 1991;26(1):91-7.