Written by Samantha Kiever, Research Entomologist, Insects Limited, Inc.

There is a growing interest in incorporating insects into our diets due to their nutritional value and sustainability, and in many parts of the world, insects are a common and valuable food source, providing essential nutrients and protein.

However, the thought of consuming food that has been infested with insects may understandably raise concerns about safety and hygiene. At the same time, sifting beetles from flour before use was once a normal part of everyday life.

Nowadays, we often turn to methods such as freezing to kill the infesting insects.

While this is a viable option for killing what is infesting your pantry, to what end?

After the offending insects are dead, you’re now left with food that is no longer infested but has been lived in by hundreds to thousands of critters.

So what’s the scoop? After you kill the bugs infesting the food in your pantry, should you dig in or ditch it?

Insects Allowed in Our Food Supply

First, I’m sure you’re already thinking about it, so let’s talk about the amount of insects and insect fragments allowed in processed foods in the United States. The Food and Drug Administration’s Defect Action Level (DAL) sets the maximum number of insect parts permitted in food products to ensure they pose no known hazard to human health. For example, in a 50-gram sample of flour, up to 75 insect fragments are permitted—a number that sounds high until you’ve faced the actual volume of each side-by-side.

A study performed in India quantified the number of insect fragments a single red flour beetle (Tribolium castaneum) produces over the course of its lifecycle from egg to adult. The study found that a beetle going through its normal life cycle in optimal conditions can produce enough fragments (exuviae, frass, etc.) to cause a 50-gram sample of flour to exceed the DAL in as little as 21 days.

If we extrapolate that out to your average 2.27 kg bag of flour from the grocery store, it would take an infestation of only 50 individuals to cause your flour to exceed the DAL in 21 days.

Given that a single female can lay hundreds of eggs, you are almost certain to have more than 50 individuals in even the first generation of flour beetles.

So, in reality, the infested flour in your pantry is likely to exceed the DAL in less than 21 days, at which point food safety can no longer be guaranteed.

Quality and Nutritional Changes in Infested Food

Extensive research has been conducted on the nutritional and quality changes of foods that have been infested by insects. The type of insect and the product in question determine the amount and types of changes that occur, but there are commonalities across product types. Generally speaking, starch content tends to go down, while sugar content increases. Studies have even shown that this effect can change the glycemic index of foods such as rice, which sees an increase in glycemic index after infestation. There’s also a notable decrease in essential amino acids. This decrease in essential amino acids is particularly concerning because these building blocks are vital for our health—our bodies can't produce them, so we rely on their presence in our food to meet our needs.

The taste can also be negatively impacted by the presence of insects in food. Food that has been infested may taste acrid, musty, or sour. This is due to the increase in uric acid from insects excreting in the food, mold growing, or chemical substances such as quinones being released by insects. The quality of flour is of special concern, as the reduction in gluten, increase in acidity, and other changes also change the way flour behaves during baking. This can result in darker-colored, crumby, less dense breads and cakes with a flavor just as unsavory as it looks.

Breads produced from flour infested with flour beetles of varying degrees. N1 = 500 insect/kg; N2 = 1000insect/kg; N3 = 2000 insects/kg; C = control. (Carvalho, 2023)

Sanitary Concerns and Microbial Growth

There are sanitary concerns associated with insects infesting food in our pantries. Insects are poikilothermic, which means that they experience a wide range of internal temperatures that can vary by region of the body and with ambient temperature.

This fact is often oversimplified to: insects cannot produce their own body heat, which is why their rate of development depends so heavily on temperature. While it is true that insects heavily rely on ambient heat for metabolism, and therefore development, it is also true that insects produce some of their own heat as a result of metabolic processes.

They are also able to produce water from metabolic processes, which they release into the environment during respiration and excretion. This means that the insects can raise the temperature and the humidity of their environments provided there are enough of them in a confined space such as food containers. Add in the fact that most dry food goods are excellent insulators, and you have a recipe for disaster.

When you look at a box of macaroni and cheese in the cupboard, or anything for that matter, you are likely to see the warning, “Store in a cool dry place.” Some packages may even specify the ideal temperature and humidity ranges for storage.

The conditions listed on the package are there to minimize microbial growth in your food goods. Having insects in your food that produce excess heat and moisture can increase the rate of growth of bacteria and fungi, especially mold.

Ironically, the bacteria and mold also have their own metabolic processes that can produce heat and moisture, which also creates conditions favorable to insects. This process can create a feedback loop, similar to what happens in a thermal runaway event in a damaged lithium-ion battery, where increasing heat leads to even more heat, eventually causing a dangerous, uncontrollable situation.

See just how moldy insects can make your food here.

Dealing with Microbes: Is cooking enough?

Microbes are organisms, though. Can’t we just “kill them with fire” and all will be well?

The answer is yes and no. Besides enhancing the taste and texture of our foods, we cook foods to make them safe for human consumption. The process of heating food is crucial in killing microorganisms that may try to infect us and make us sick. The same is true for the microbes in food; however, killing pathogens is the easy part. Even though we can kill microbes fairly easily with heat, it is much harder to destroy the abiotic toxins that are left behind. Think about it, even if you microwave some two-month-old leftovers to an internal temperature that can kill all of the microbes, you’re still likely to get sick. That’s because the toxins are left behind after the heating process.

In the case of dry, stored food products, mycotoxins are of great concern. Mycotoxins, such as aflatoxins and ochratoxins, are toxins produced by molds that can have significant negative impacts on human health such as birth defects, cancer, and even death. They can also have toxic effects on the kidneys and liver, both of which are involved in the processing and excretion of toxins.

Molding of rice caused by an initial infestation of 100 adult rice weevils over 250 days.

Other Health Risks: Allergies, Asthma, and Infested Food

Allergies and asthma are also potential health consequences that should be considered when discussing whether to use a previously infested food product. If you are prone to either of these conditions, the presence of mycotoxins, mold, and even insects themselves can stimulate or exacerbate these conditions.

Making the Right Call: To Treat or to Discard

The prospect of consuming insect-infested food may seem unsettling, but it’s important to recognize that the issue goes beyond just killing the pests. Even after taking steps to eliminate the insects, the residual impact on the food’s safety, quality, and nutritional value remains significant. The presence of insect fragments, changes in nutrient composition, and the risk of microbial contamination all point to the complexities involved in deciding whether to salvage or discard infested goods.

When deciding what to do with that infested canister of oats, simply killing the insects inside may not be the food-saving solution it’s often portrayed as online. However, treatment does have its benefits. Freezing the infested food before disposal can help prevent any remaining insects from escaping and reinfesting other items in your pantry, supporting your sanitation and exclusion efforts.

In the end, while insects may offer nutritional benefits in some contexts, their unintended presence in our pantry staples introduces risks that shouldn’t be ignored. The decision to discard or consume infested food isn’t just about waste reduction; it’s about ensuring that what we eat is truly safe and beneficial for our health.

References

Carvalho, M. A. M. de, Geirinhas, H., Duarte, S., Graça, C., & Sousa, I. (2023). Impact of red flour beetle infestations in wheat flour and their effects on dough and bread physical, chemical, and color properties. https://doi.org/10.1016/j.jspr.2023.102095

Center for Food Safety and Applied Nutrition. (n.d.). Food Defect Levels handbook. U.S. Food and Drug Administration. https://www.fda.gov/food/current-good-manufacturing-practices-cgmps-food-and-dietary-supplements/food-defect-levels-handbook

Negi, A., Pare, A., Loganathan, M., & Rajamani, M. (2021). Effects of defect action level of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) fragments on quality of wheat flour. https://doi.org/10.1002/jsfa.11349

Stathas, I. G., Sakellaridis, A. C., Papadelli, M., Kapolos, J., Papadimitriou, K., & Stathas, G. J. (2023). The Effects of Insect Infestation on Stored Agricultural Products and the Quality of Food. https://doi.org/10.3390/foods12102046

Insects Limited, an Insect Pheromone Company

Insects Limited, Inc. researches, tests, develops, manufactures and distributes pheromones and trapping systems for insects in a global marketplace. The highly qualified staff also can assist with consultation, areas of expert witness, training presentations and grant writing.

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