Can peanut butter go bad?

In this brief guide, we are going to answer the question “can peanut butter go bad” with an in-depth analysis of whether or not peanut butter goes bad. Moreover, we are going to discuss the shelf life of peanut butter, ways to spot bad peanut butter, and the tips to store peanut butter properly.

Can peanut butter go bad?

Yes, like all other food items, peanut butter does go bad after a certain time and if it has been contaminated.

During storage, lipid oxidation can lead to a fading out of the desirable peanut butter flavor with time. There are various factors that cause the lipid degradation in peanut butter, such as intrinsic factors, related to the nature of the fats; and the storage conditions, related to the oxidation induced by light and metal ions. 

The oxidation process results in the generation of aliphatic aldehydes, ketones, and alcohols that are associated with unpleasant odors and flavors, and which can compromise the nutritional properties of the peanut butter. In addition, these compounds are possibly toxic (1).

How long does peanut butter last?

Peanut butter lasts from a few months to years, depending on its composition and the storage conditions to which it is submitted. The shelf life of different types of peanut butter will be discussed in the following sections:

Commercially processed peanut butter

When it comes to the unopened commercially processed peanut butter then it has a long shelf life and it lasts for about 6-24 months when kept in a cool, dry and dark corner of your pantry away from direct sunlight and heat (2).

On the other hand, once you open your commercially processed store-bought peanut butter, its shelf life decreases and it lasts for about 2-3 months when stored in a cool, dry, and dark corner of the pantry.

On the other hand, if you are storing the opened peanut butter in the fridge at or below 40 degrees Fahrenheit then it lasts for about 3-6 months past the “best by” date. However, this depends on the composition of the product, which is related to the production process and the peanut cultivar (1).

Powdered peanut butter

Powdered peanut butter lasts for about 12 months if stored properly in a cool, dry, and dark corner of the pantry away from direct sunlight and heat (2).

Homemade peanut butter

While talking about the shelf life of homemade peanut butter, as it does not have any additional preservatives added to it therefore it has a shorter shelf life than the store-bought commercially processed peanut butter. Homemade peanut butter lasts for about 1-3 months when stored in an air-tight container at or below 40 degrees Fahrenheit in the fridge (2).

It is worth mentioning that these are the estimated shelf lives of peanut butter, peanut butter can last even longer than this, provided that it was stored properly.

Other FAQs about Peanut Butter which you may be interested in.

How long is peanut butter good for?

Does peanut butter go bad?

Can you get sick from eating expired peanut butter?

Is peanut butter safe to use after the best-before date?

Yes, it is possible that the peanut butter can be consumed after the expiration date, unless there are visible signs of spoilage. The “best by” or “best before” date that is written on the bottle of peanut butter refers to the quality rather than safety so the peanut butter doesn’t necessarily go bad immediately after the best before date (5). 

Peanut butter produced from different cultivars can have different shelf lives, due to the lipid composition, which determines the oxidation rate of the product and the generation of off-flavors during storage. 

High-oleic cultivars have better oxidation stability and, subsequently, increased shelf life, compared with that of conventional cultivars. 

In a study, when the sensory and oxidation stability of a high-oleic peanut variety (i.e., Granoleico) was compared with that of a normal-oleic peanut variety (i.e., Tegua,), both prepared under the same conditions and stored at 4°C, 23°C, and 40°C, the peanut paste prepared with high-oleic peanuts had four (at 4°C), two (at 23°C), and three (at 40°C) times longer shelf-life than peanut paste prepared with the normal-oleic variety (1).

How to tell if peanut butter has gone bad?

To tell if peanut butter has gone bad, you should be able to identify the possible signs of spoilage. Possible signs of spoilage in the peanut butter are noticed on the texture, the odor and the flavor.

The rancid, oxidized off-odor is an indication of bad peanut butter. The oxidation process of the lipids in the peanut butter results in the generation of off-odors from increasing concentration of oxidation products, such as aliphatic aldehydes, ketones, and alcohols.

The loss or aroma intensity indicates a really old peanut butter. The oxidation of the lipid component of peanut butter is the chief cause of loss of flavor in peanut butter. Fading of essential volatile compounds, such as pyrazines, alkylpyrazines and compounds of peanut flavor, actually decrease in intensity.

Moreover, if you taste the peanut butter and notice that its taste has changed (sour or bitter) it is evidence that the peanut butter is oxidized. The oxidation of the lipids in the peanut butter generates oxidation flavors, such as the painty and cardboard flavors, due to compounds such as hexanal, octanal, and 2-octanone compounds, increases. 

The exact process of flavor changing during storage of peanut butter is not exactly understood by scientists. It still remains unclear whether or not the desirable peanut flavor compounds undergo a chemical reaction with the off-flavor compounds during storage time, resulting in new products with undesirable off-flavors (1).

How to store peanut butter properly?

To properly store peanut butter, you should:

• Peanut butter should be stored in a cool, dry, and dark place away from direct sunlight and heat. Therefore you can safely store peanut butter in a cool and dry corner of your pantry away from direct sunlight and heat (3).
• Moreover, you can also refrigerate open peanut butter bottles to preserve their freshness and quality for a long time as the cold temperature of the fridge lowers the rate of lipid oxidation. Peanut butter is a product stable in terms of water activity, which promotes product resistance towards microbial contamination (3), unless it is contaminated. Microbial contaminations specifically by Salmonella spp have been reported (4).
• In the case of homemade peanut butter, it is recommended to store the peanut butter in an air-tight container in the fridge at or below 40°F. However, in a study, peanut butter was stable for 12 weeks at 10°C (50°F).
• You should not store your peanut butter in a humid environment.
• Moreover, close the lid of the peanut butter jar as soon as you scoop out the peanut butter that you need to minimize the air (oxygen) exposure of the peanut butter.
• Do not use a wet spoon to scoop out peanut butter from the container.

What are the risks of eating spoiled peanut butter?

If you eat spoiled peanut butter, you can experience negative effects to your health, as peanut butter is susceptible to be contaminated with Salmonella or other photogenic microorganisms, as well as to contain mycotoxins (6,7). 

Salmonella bacteria are the most frequently reported cause of foodborne illness and can cause diarrhea (can be bloody), fever, stomach cramps, vomiting. 

Mycotoxins are toxigenic secondary metabolites of filamentous fungi and have a cumulative effect with a risk of causing damage in the liver and kidney.

Furthermore, the consumption of spoiled peanut butter can have negative consequences to health in the long term. The regular consumption of rancid oils present in the peanut butter can induce the development of  inflammatory diseases and potentially increase the risk of developing cancer. 

When oxidized fats are ingested, they generate oxidative processes in the body. Products of oxidation are potentially toxic to proteins, phospholipids, and nucleic acids (9).

Conclusion

In this brief guide, we answered the question “can peanut butter go bad” with an in-depth analysis of whether or not peanut butter goes bad. Moreover, we discussed the shelf life of peanut butter, ways to spot bad peanut butter, and the tips to store peanut butter properly.

Citations

1. Sithole, Tapiwa Reward, et al. Influence of Peanut Varieties on the Sensory Quality of Peanut Butter. Foods, 2022, 11, 3499. 
2. FSIS’ FoodKeeper. US Department of Agriculture. 
3. Mohd Rozalli, N. H., et al. Quality changes of stabilizer-free natural peanut butter during storage. J food sci technol, 2016, 53, 694-702.
4. Sithole, Tapiwa Reward, et al. Peanut Butter Food Safety Concerns—Prevalence, Mitigation and Control of Salmonella spp., and Aflatoxins in Peanut Butter. Foods, 2022, 11, 1874.
5. Food product dating. United States Department of Agriculture.
6. Sithole, Tapiwa Reward, et al. Peanut Butter Food Safety Concerns—Prevalence, Mitigation and Control of Salmonella spp., and Aflatoxins in Peanut Butter. Foods, 2022, 11, 1874
7. Vieira, Samantha A., Guodong Zhang, and Eric A. Decker. Biological implications of lipid oxidation products. J. Am. Oil Chem.’ Soc., 2017, 94, 339-351.