Does peanut butter go bad?

In this brief guide, we will be answering the question, “Does peanut butter go bad.” as well as other questions, like how long can peanut butter last and what are the uses and ideal storage practices to prolong the shelf life of your peanut butter.

Does peanut butter go bad?

Yes, peanut butter can go bad. Peanut butter can spoil, especially if it has been contaminated and due to oxidation of lipids and oil separation. 

Store bought peanut butter can be used for months as it contains some additives and preservatives that aids in having a bit longer shelf life than a homemade one (2).

Peanut butter has low moisture content and high levels of fat give it extremely long shelf life. The shelf life and oxidation of lipids as well as the formation of off-flavors is directly dependent on the moisture content of the product and the storage conditions (1). The shelf life of peanut butter depends on the way it is stored.

How to tell if your peanut butter has gone bad?

To tell if your peanut butter has gone bad, you should be able to identify the signs that indicate the degradation of peanut butter. In addition to microbial contamination, the most important reason for the spoilage of peanut butter is the oxidation of lipids.

Due to their high lipid content, which includes a significant amount of polyunsaturated fatty acids, and the possibility of undergoing thermal stress during roasting, these products are highly susceptible to lipid oxidation. 

This process leads to the formation of hydroperoxides that eventually break down into secondary oxidation products like aldehydes, ketones, and other molecules. The release of these compounds into the surrounding atmosphere alters the product’s odor, leading to a rancid smell (7).

Changes in the texture of the product, such as oil separation, leads to a faster lipid peroxidation of peanut butter which develops the off-flavor and results in rancidity. Oil separation may also affect textural quality of peanut butter in terms of spreadability (3).

In addition, associated with peanut butter, microbial contaminations specifically by Salmonella spp., and biological toxins in the form of aflatoxin are the main peanut butter food safety concerns that have consistently been reported over the past years (4). 

Microbial spoilage can be a threat, since Salmonella spp. can survive in low-moisture (<0.83 aw), high-protein, and high-fat foods for several years; furthermore, it is capable of surviving for longer periods at low-temperature storage (4). 

What determines the shelf life of peanut butter?

The shelf life of peanut butter depends on the storage conditions as well as on its ingredients.

Commercial peanut butter products are usually added with hydrogenated vegetable oil such as mixtures of hydrogenated rapeseed, cottonseed oil and soy bean oil, which act as stabilizers to prevent lipid oxidation and extend the shelf life of the products (3). 

Natural peanut butter is susceptible to oil separation which leads to a fast oxidation, due to absence of stabilizers in its composition. 

In addition, the storage conditions are crucial to reduce the rate of oxidation. Exposing the peanut butter to heat, light and oxygen may lead to an accelerated oxidation of lipids and a shorter shelf life.

What is the shelf life of peanut butter?

The shelf life of an unopened peanut butter is, approximately and according to the storage conditions (2):

• 6 to 24 months unopened at room temperature
• 2 to 3 months opened at room temperature
• 6 months opened in the refrigerator in a closed container

How to store peanut butter?

 As a shelf stable product, it should be stored in a cool, dark place, free from moisture, in a closed container (8). The shelf life of peanut butter depends on the way it is processed and stored. 

Peanut butter is shelf stable and can be stored at room temperature but once opened, it is recommended to store at low temperature in the refrigerator after sealing it tightly to keep out the moisture and other contaminants to enhance its shelf life by preventing oxidative degradation of compounds.

You can store peanut butter by following these simple instructions:

●        The peanut butter should be stored away from light, in a dark and dry area. Storing the unopened peanut butter next to a heat source can shorten its shelf life as e the exposure to heat leads to accelerated lipid oxidation. Lipid oxidation is initiated by compounds known as sensitizers which include heat, light and metal ions (5).

●        In order to ensure maximum shelf-life, make sure your peanut butter is isolated in an airtight container. In the presence of oxygen, oxidative reactions are usually of the greatest importance and hence, the storage life is then limited by the development of oxidative rancidity of fat in the food product (5).

●        Avoid the contamination by using clean utensils every time to scoop peanut butter.  Do not leave peanut butter out after using, place it in the fridge immediately after using the required or needed amount. Post-processing and food handling contaminations can be a great issue for the safety of peanut butter (4).

Storing it in the refrigerator is an ideal storage condition when optimal results are desired. A study showed that when stored at 10°C, the shelf life of opened peanut butter could be extended, when compared to higher temperatures of storage (2).

Can you freeze peanut butter?

Yes, you can also freeze the peanut butter. However, it may result in a loss of the texture after the freeze-thawing process. 

There is a clear effect of temperature on storage life, with lower temperatures resulting in extended storage. Freezing can have a significant effect on product appearance and quality of food (6).

What happens if you eat 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. 

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

In addition, consuming rancid peanut butter can have a negative impact on long-term health due to the presence of rancid oils in nut butter, which can induce inflammation and potentially cause cancer. 

When oxidized fats are ingested, they can create lipid oxidation aldehydes, which are highly reactive and potentially toxic to proteins, phospholipids, and nucleic acids. These aldehydes can be transported into cells and tissues, potentially leading to gut inflammation and alteration of the microbiome, which may have health implications (9).

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

How long is peanut butter good for?

What Brand of Peanut Butter is Best for Keto?

Can diabetics eat peanut butter and jelly sandwiches?

Conclusion

In this brief guide, we have answered the question, “Does peanut butter go bad.” as well as other questions, like how long can peanut butter last and what are the uses and ideal storage practices to prolong the shelf life of your peanut butter.

References

1. Gorrepati, Kalyani, S. Balasubramanian, and Pitam Chandra. Plant based butters. J food sci technol, 2015, 52, 3965-3976.
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. Cevoli, Chiara, et al. Storage time of nut spreads using flash gas chromatography E-nose combined with multivariate data analysis. LWT, 2022, 159, 113217.
6. Evans, Judith A., ed. Frozen food science and technology. John Wiley & Sons, 2009.
7. Shakerardekani, Ahmad, et al. Textural, rheological and sensory properties and oxidative stability of nut spreads—a review. Int j mol sci, 2013, 14, 4223-4241.
8. Shelf stable food safety. United States Department of Agriculture.
9. Vieira, Samantha A., Guodong Zhang, and Eric A. Decker. Biological implications of lipid oxidation products. J. Am. Oil Chem.’ Soc., 2017, 94, 339-351.