The Best Egg Carton Material, According to Food Scientists

When you walk by the egg section of the grocery store, have you ever wondered why your eggs are packaged in styrofoam, plastic, or paper cartons? As a customer, does the egg carton material matter and sway your purchase? We spoke with a food safety expert and a food scientist to weigh in.  

Why the Egg Carton Material Matters

Eggs have a fragile and porous shell, providing compounds and bacteria an environment to move from the package to the eggshell and the inner content, especially if the shell breaks. To ensure safe transport from processing plants to grocery stores and ultimately to the final destination—the kitchen—the materials that make up the carton matter. 

A 2018 study from the "Journal of Food Science and Technology" looked at the different materials of egg carton boxes and found that cardboard boxes provide the best mechanical protection for eggs compared to polystyrene foam containers. The downside of cardboard boxes though, is that once moisture is present in the environment, such as when the cartons are stowed in the refrigerator, the carton material absorbs moisture, weakening the materials and providing less protection. 

Is One Type of Egg Carton Material More Likely to Harbor Bacteria?

While some producers pasteurize eggs before selling them to grocers and consumers, it is also important to note that germs are everywhere, and they can transfer to the egg carton during processing and packaging. For example, salmonella enteritidis is one of the common types of bacteria present in eggs. A 2021 study published in the "Journal of Applied Poultry Research" found that of the 144 egg carton samples made from polystyrene foam, 142 samples made from plastic, and 143 samples made from pulp, six of the eggshells placed in the polystyrene foam, and two samples placed in plastic had salmonella contaminated. No salmonella was found in the eggshells from the cartons made from pulp materials.

The researchers reasoned that the likelihood of salmonella transfer from egg cartons made with pulp, cardboard, and wood crates to eggs was lower than styrofoam and plastic counterparts due to the many micropores present in pulp, cardboard, and wood that could trap the compounds and microorganisms. Still, the chance of bacteria moving from the carton to the eggshell and potentially into the egg persists, particularly in high moisture and humidity conditions.

Are Styrofoam Egg Cartons Harmful to Your Health?

Some online stories have headlines that may leave you wondering whether styrofoam impacts your health, as these stories talk about volatile compounds found in styrofoam, such as aldehydes and styrene monomer, could be transferred from the carton to the egg when the two come in contact. These headlines and stories undoubtedly grab your attention and create curiosity and, perhaps, fear. 

Carol Zweep, Senior Global Regulatory Manager, Food and Sustainability Advisory Solutions at NSF International, debunks this myth. Zweep explains, “Some stories you may have come across were quoting a research study in 1990. There have been styrene production changes [since] that may affect the amounts and types of volatile compounds currently present in styrofoam egg cartons.” 

Before you turn away from buying eggs placed in styrofoam and plastic containers, rest assured that egg cartons, whether made with foam, plastic, or cardboard, are considered as safe packaging materials by FDA standards, according to Brian Chau, food scientist and principal of Chau Time. The FDA requires all shell egg cartons that have not been treated to destroy salmonella to clearly label safe handling instructions for consumers. Pasteurized eggs will state that they have been treated and don’t require safe handling instructions. 

Which Egg Cartons Are Environmentally Friendly? 

How food manufacturers choose one type of egg carton material over the other is based on the material’s price, durability, and the manufacturers’ sustainability practices. Chau says, “Some manufacturers opt for cardboard because it is quite sturdy and can protect eggs well in transit and can be recycled, as long as the inner egg contact stays intact and doesn’t leak to the cardboard carton.”

A recent trend in food packaging is to use more environmentally friendly materials, per Zweep. “Polystyrene is not recyclable. Fiber-based materials are made from renewable resources and can be composted or recycled. Egg cartons are now being made from PET (Polyethylene terephthalate), a recyclable material,” expands Zweep.

The Takeaway

Should you buy eggs sold in cardboard, plastic, or styrofoam? The decision comes down to your personal choice. No matter what the egg carton materials are made from, always follow safe food handling practices to decrease the risk of food poisoning.