Food containers have a deceptively simple job.
Put food inside. Put a lid on it. Try not to wear lunch on the drive back to the office.
Simple enough.
Except anyone who has ever opened a takeout bag and discovered a container that has gone soft, warped, leaked or turned crispy french fries into something resembling warm shoelaces knows there is more science involved than it appears.
At Schneider Paper Products in Baton Rouge, Louisiana, food-service packaging comes in a wide range of materials because different foods create different challenges. Heat matters. Cold matters. Moisture matters. Grease matters. Even Louisiana humidity occasionally decides to participate.
Choosing a food container starts with understanding what is going inside it.
Paperboard: More Complicated Than a Piece of Paper
Paperboard containers are everywhere.
Takeout boxes, trays, cartons and specialty food containers can all be made from paperboard.
The material provides structure without adding much weight, but plain paper and a bowl of hot gumbo aren’t exactly natural partners.
Water and paper have a long and complicated history.
That is why many paperboard food containers use coatings or barriers designed to resist moisture and grease.
Those barriers become particularly important with foods containing sauces, oils or significant moisture.
Hot foods also produce steam, which can gradually soften paper-based materials. The container needs to be designed for the food and the amount of time that food is expected to remain inside.
A cookie and crawfish étouffée may technically both qualify as food.
Their packaging requirements are another matter entirely.
Plastic Isn’t Just Plastic
The word plastic gets thrown around as though every plastic container is made from the same material.
It isn’t.
Different plastic resins behave differently at different temperatures.
Polypropylene is commonly used in containers intended for hot-food applications because certain polypropylene products can tolerate elevated temperatures.
PET is frequently seen in clear containers used for salads, fruit, sandwiches, bakery items and other cold foods.
The difference matters.
Put hot food into a plastic container that wasn’t designed for that temperature and things can get interesting quickly.
And by interesting, I mean the container may decide it no longer wishes to be shaped like a container.
Cold temperatures create another issue. Certain plastics can become more rigid or brittle as temperatures decrease.
The lesson is pretty straightforward: check what the container was actually designed to handle.
Aluminum Likes Heat
Aluminum has been part of food service for generations.
There is a reason.
Aluminum handles heat differently from paper and plastic. It conducts heat efficiently and can tolerate temperatures that would cause problems for many other disposable container materials.
That makes aluminum pans common for baked dishes, hot entrées, catering and reheating applications.
Of course, aluminum’s ability to conduct heat comes with an obvious side effect.
The pan gets hot too.
Physics refuses to negotiate.
Aluminum can also be used for refrigerated and frozen foods, depending on the application.
One consideration involves highly acidic or salty foods. Extended contact with certain foods can interact with uncoated aluminum, so the intended use of the particular container still matters.
Foam Is Basically a Tiny Insulated Building
Foam containers work because the material contains countless small pockets of air.
Air isn’t particularly good at transferring heat, which is useful when attempting to keep hot food hot or cold food cold.
That is why foam has traditionally been used for everything from takeout meals to cold drinks.
It is lightweight, provides insulation and handles moisture reasonably well in many applications.
But foam isn’t indestructible.
Extremely hot foods and direct heating can exceed the limits of certain products. Microwave use depends on the particular container and manufacturer instructions.
Local regulations can also affect whether certain foam products are used in particular areas.
Molded Fiber Has Joined the Party
Molded-fiber containers have become increasingly common in restaurants and takeout operations.
These containers can be made from recycled paper fibers, bagasse and other plant-based materials.
They can work with many hot and cold foods, but moisture and grease remain important considerations.
Some molded-fiber products include treatments or barriers designed to improve resistance to liquids and oils.
Without appropriate resistance, a very wet meal can eventually start working its way into the fibers.
The food may have been ordered to go.
The sauce shouldn’t be allowed to leave independently.
Steam Is the Sneaky Problem
Temperature gets most of the attention when discussing food packaging, but steam deserves its own section.
Put hot food into a container and close the lid.
The food continues releasing moisture.
That moisture becomes steam.
The steam hits the lid, condenses and eventually finds its way back toward the food.
This is how crispy food can become considerably less crispy.
French fries are probably the most famous victims.
Fresh fries go into the container crispy and proud.
Twenty minutes later, they emerge questioning every decision that led to that moment.
Vented containers can help release steam in applications where maintaining texture matters.
Cold Food Has Its Own Moisture Problem
Cold food doesn’t create steam, but it can create condensation.
Take a refrigerated container into warm, humid Baton Rouge air and water can begin collecting on surfaces.
Louisiana humidity doesn’t need an invitation.
Condensation can affect paper products and labels and may make packaging slippery or damp.
That is why moisture resistance matters for cold-food packaging too.
Grease Changes Everything
Then there is grease.
- Pizza.
- Fried chicken.
- Burgers.
- Barbecue.
Certain foods can put packaging through an endurance test.
Grease can penetrate untreated paper materials and weaken some containers over time. Coatings and grease-resistant materials help address those conditions.
Food weight matters as well.
A container holding a side salad doesn’t face the same structural demands as one carrying several pounds of barbecue.
Match the Container to the Food
There is no single container material that makes sense for every application.
- Paperboard has strengths.
- Plastic has strengths.
- Aluminum has strengths.
- Foam has strengths.
- Molded fiber has strengths.
The question isn’t simply whether food is hot or cold.
The better questions involve temperature, moisture, grease, acidity, weight, transportation and how long the food will remain inside.
Food packaging is essentially matchmaking.
Pair the right container with the right meal and nobody thinks twice about it.
Get the combination wrong and suddenly everyone notices the container.
Usually because lunch is leaking through the bottom of the bag.
Mark F. Schneider
President
Schneider Paper Products
Baton Rouge, Louisiana