Does Vacuum Sealing Prevent Freezer Burn?
Even though frozen raw meat may look brown or grey, freezer burn isn't a “burn” at all. The condition we call freezer burn is tissue damage that can happen in the freezer when meats and other foods are stored improperly or for too long.
What is Freezer Burn?
You may have noticed that if you leave an ice cube tray in a freezer for too long, the ice disappears. Despite all the cold, icy conditions inside a freezer, it's important to remember that it's also a dry environment. Water in a freezer quickly evaporates, without remaining in its liquid state; it goes from ice to vapor without ever becoming moisture.
When we freeze foods, even “dry” foods like bread, they have water molecules deep inside the cells and tissues. Those water molecules freeze into ice in the cold environment of the freezer, as intended.
When those foods are improperly sealed, the ice molecules in the food are subject to movement and evaporation, just like the water in an ice cube tray.
When the ice molecules in the food is allowed to evaporate because the food isn't fully sealed, a few things happen:
All the moisture that helps foods be tender and juicy evaporates into the freezer, leaving the food dry and leathery.
As the ice crystals move within the food, traveling toward colder air and motivated by temperature variations, they can damage the delicate cells and tissues in foods, impairing the texture.
When water molecules leave our food, they leave room for oxygen molecules to move in. Exposure to oxygen alters the chemical composition of the fats in our food, creating carbon molecules that turn foods brown or grey, and giving food an unpleasant flavor.
Freezer burned food is not actually spoiled or harmful to eat, but it usually has lost the taste and texture that we prefer in our food, and has an unpleasant smell and flavor.
How Does Vacuum Sealing Prevent Freezer Burn?
Vacuum sealing does prevent freezer burn. Vacuum sealing stores food in a sealed, air-tight package, which prevents freezer burn in a couple of ways.
In a properly sealed, air-tight package (even if the packaging isn't vacuum sealed), the package is forced to maintain its own internal humidity. The water molecules can't escape into the air of the freezer, so they stay sealed in the food where they originally were. This preserves the moisture and texture of foods.
When food is vacuum sealed, air is removed from the package. This prevents oxygen molecules from interacting with the food, and causing the chemical changes known as “oxidation.” Eliminating air from the packaging prevents food from spoiling.
Vacuum sealing also has other benefits for prolonging the life of food. It helps to prevent the growth of harmful microorganisms, slow the action of decaying enzymes, and helps to keep foods at a consistent temperature.
How to Prevent Freezer Burn
Even if you have a vacuum sealer, there are still some important tips to keep in mind to use your vacuum sealer in the best way to prevent freezer burn.
Use “freezer” plastic
If you don't have a vacuum sealer, and are wrapping foods in plastics prior to freezing them, make sure that you are using plastic that is designed for the freezer. Many plastics, as well as parchment, papers, and foils, may wrap and protect food, but they are permeable to oxygen and gases. Gas-permeable plastics will not prevent freezer burn, so make sure you use the right kind of plastic. Vacuum sealer bags are not gas permeable, and will prevent oxygen from accessing your food.
Pre-chill your food
If you are freezing cooked food to eat later, it's important to thoroughly cool the food, and not put hot food in the freezer (no matter how you are sealing it). Placing hot foods in the freezer can raise the temperature inside your freezer, which is potentially not just unsafe for the food you are adding, but may be unsafe for other foods that are already in the freezer.
Freeze liquids before vacuum sealing
The most efficient way to store liquids like soups, stocks, and stews for a long time is to freeze them into cubes, then vacuum seal the cubes. Vacuum sealing machines don't work well with liquids, so freezing them into cubes first allows the machine to work well and efficiently. This technique can also work for freezing liquids in a conventional freezer bag if you don't have a vacuum sealer.
Vegetables freeze exceptionally well, and stay fresh in the freezer without losing their vibrancy and crispness. However, quickly blanching them before vacuum sealing and freezing halts the enzymatic reaction that ages fruits and vegetables, and helps them to stay fresh and more delicious. The combination of blanching and then vacuum sealing and freezing helps fresh vegetables to last as long as possible.
Wrap bone ends
If you are vacuum sealing large roasts and meats that have exposed bones, it's a good idea to wrap exposed bone ends in parchment paper prior to vacuum sealing. That way the sharp bones don't burst the bag during the pressure of vacuum sealing. It also helps keep them from stabbing other foods in the freezer and makes them easier to stack and store.
You Can't Keep Foods Fresh Forever
Even perfectly sealed foods won't stay fresh in the freezer forever. It's always a good idea to regularly eat your frozen foods, and keep frozen foods rotating into your diet, instead of languishing in the back of the freezer.
The best way to ensure that you are getting the most value from your grocery budget, and from your vacuum sealer, is to write the date of your food on the freezer bag, so that you can keep track of how long you have had food and make sure to eat it while it is still good. Follow these tips to avoid freezer burn, and use your vacuum sealer to get the most value and flavor from your food.