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In the last several years, research has prominently featured several debates about the safety of plastic materials for food storage.
Two of the main components of plastic, polyethylene and polypropylene are often debated.
While both are strong, durable plastics, which is better for food storage?
This is a question that food scientists, food packaging experts, and food manufacturers often pose.
Let’s learn more about the use of polyethylene vs polypropylene in food safe containers.
Food safe material
Why is the discussion about polyethylene and polypropylene materials so important?
These materials comprise the majority of food storage containers, so they must be food safe.
The FDA (Food and Drug Administration) goes to great lengths to ensure that all material used in food storage materials is safe to come into contact with our food.
Material that touches food, as well as material that we come into direct contact with, must be void of harmful chemicals and toxins.
Polyethylene and polypropylene are classified as food contact substances, which are substances that are used in food manufacturing, packaging, packing, transporting, or holding.
If food contact substances are not safe, such hazardous substances can easily leach into our food and consequently into our bodies.
When you think about this chain, it’s easy to see why discussing polyethylene and polypropylene is so important!
Polyethylene vs polypropylene food safe containers
Polyethylene is actually found in a few different forms of plastic.
PET (polyethylene terephthalate)
Let’s start with one of the most common uses of polyethylene, polyethylene terephthalate, or PET.
A common substance used to make food storage plastics, PET is prevalent in soda bottles, salad dressing containers, and peanut butter packages.
You may also find PET in take out containers, too.
Take out containers need to be highly durable since they are often used to reheat food, and the initial contents stored in them may be very hot.
PET is also safe to put in the refrigerator, which is very important for leftover storage.
Some PET containers are durable enough to be microwave safe.
Polyethylene is even strong when recycled.
After thorough study for adverse health effects, recycled PET was found to be biologically inert.
This means that PET resins can be recycled and used for food storage even after they have already been through the manufacturing process.
What properties make PET a good candidate for food storage?
PET is a highly stable resin that resists corrosion and degradation, and it also repels microorganisms.
HDPE (high density polyethylene)
The most common plastic found in consumer goods, HDPE is used to make food storage containers for many common cool and room temperature foods.
For example, HDPE is used to store butter, juices, and some dairy products.
HDPE is also used to make liners for food storage containers.
You’ve probably seen this in action when you pour your morning bowl of cereal.
Anytime you find a liner inside of a food storage container, you are most likely looking at HDPE.
HDPE is a very strong, opaque plastic material.
HDPE does not transmit chemicals to the materials that it touches, and it is highly resistant to moisture absorption.
LDPE (low density polyethylene)
LDPE is very similar to HDPE, but it is softer and more flexible. When you use a soft plastic container, it is most likely LDPE.
LDPE is often found in condiment containers like ketchup, mustard and relish. You most likely use LDPE at your summer cookouts!
Another prominent plastic material, polypropylene (PP) is prevalent in many single use food storage containers.
It’s commonly found in reusable storage containers, but is even more prevalent in single use applications.
For example, polypropylene is probably in your home as you’re reading this article.
Do you have any yogurt containers in the fridge?
Have you eaten cottage cheese or any other single serve foods? If so, you have probably touched polypropylene.
Polypropylene has been used for food storage purposes since it gained FDA approval in 2013.
What makes PP such a great candidate for single use food storage containers?
PP has an incredibly high melting point that is even higher than the melting point of PET.
Due to this characteristic, PP is a great choice for microwavable materials.
Many single use plastic containers hold meals that are meant to be cooked in the microwave, which means that the plastic construction must be durable enough to withstand microwaves and high heat.
With it’s high melting point and durability, PP is a great substance to make such containers.
PP is also incredibly resistant to acids, bases, and other liquids, which is important for food storage.
For example, if food storage containers degraded at the first sign of acids, you would not be able to store tomatoes, some dairy products, or soda.
These are the reasons that PP is used so often in food storage and in single use plastic applications.
Featured image credit: Shutterstock.com Image ID: 1144752497 (NOTE: image does not feature specific products discussed in article)