A Brief Introduction To Freezing Basics


Freezing is the newest addition to the field of home food preservation. It had to wait for refrigeration to become economical and that meant there needed to be a steady and reliable supply of electricity. And therein lies the greatest weakness of this modern miracle. When the power goes out, it doesn’t matter how high tech your freezer or refrigerator is, time is the enemy and you hope the power will be restored quickly before your food spoils. However, hope isn’t a good survival strategy and the basic tenet of home food preservation is self-sufficiency.

What’s surprising is to read numerous reports that the average household only has between 3 to 7 days’ worth of food on hand. In the event of any disruption in delivery of food supplies or breakdown of the infrastructure, this reality quickly goes from disturbing to catastrophic. The fact you’re reading this means you’re not average! You have a plan and you’re ready to put that plan into action.

Thinking ahead is important, so many home food preservers who live in rural and suburban areas have backup generators. Indeed, many new homes come with the capability of being generator-powered in case of a natural disaster or another emergency. Even if you’re a city dweller, you can still ensure your food supply will see you through.

As with each method of food preservation we’ll discuss, freezing has its pros and cons. “Don’t put all your eggs in one basket” is time-honored advice and it bears repeating and adhering to.

The Science Behind Freezing

There’s some interesting science behind how freezing works to preserve food and this chapter will take a look at how to put that science to work for you. We’ll discuss the equipment and supplies you need to begin freezing foods, and we’ll cover the basic procedures involved.

In 1924, Clarence Birdseye invented a method of quick-freezing foods and ended up revolutionizing the food-preservation industry. He got the idea while fishing in Canada, and as with most ingenious discoveries, he just simply became aware of what was happening around him. It was so cold that the fish froze about as soon as he hauled them out of the water. When thawed months later, he noted that the quality was good. Quick-freezing, he decided, was the way to go.

Up until this time, freezing foods wasn’t an especially quick process, and because of this, large ice crystals formed in the foods. This caused rupturing of the cell membranes of the foods being frozen. This wasn’t good. When the foods were thawed, all the ice melted, water drained from the food, and the flavor and texture suffered.

Birdseye got busy and developed a couple of ways to quick-freeze foods. One method used calcium chloride and the other used ammonia. Ammonia—or, more specifically, evaporating the ammonia to get a temperature of –25°F—allowed fruits and vegetables to be frozen in about 30 minutes and a 2-inch-thick (5cm) package of meat to be frozen in about 90 minutes. The rest, as they say, is history and the frozen food industry we take for granted today owes its existence to an observant fisherman. The Birdseye brand of frozen foods became a supermarket staple and is still a staple today.

How Freezing Works

When you freeze foods, you’re freezing the water content of that food. Water expands as it freezes and creates ice crystals inside the food. These ice crystals can rupture the cell walls of the food being frozen, but freezing the food quickly will result in smaller ice crystals and less damage to the cell walls.

Maintaining a temperature of 0°F or below also keeps ice crystal formation in check, but constant temperature fluctuations will result in larger ice crystal formation and more damage to the texture of the food. Keep opening and closing the freezer door to a minimum to prevent this from happening!

The home food preserver can use a vacuum sealer to come close to this method and we’ll discuss that later on in this chapter.

The Spoilers

Air, microorganisms, chemical changes, and enzymes are the enemies of frozen foods. Proper processing, packaging, and storage are necessary for dealing with these potential food spoilers.

Freezing stops microorganisms from growing, but it’s just temporary. It doesn’t destroy them; they’re just in a state of suspended animation, so when foods begin the thawing process, those microorganisms start to multiply again and can cause food to spoil.

The presence of air can result in oxidation as well as freezer burn. Both adversely affect the texture and flavor of frozen foods. The oxidation process causes fats in frozen meats to go rancid in the presence of air. In freezer burn, air causes moisture loss from the frozen foods—ice crystals evaporate from the product, and when you unwrap it, you’ll see frost on top of whatever you’ve frozen. The surface will look dry and brown or sometimes white. The food is safe to eat, but it will definitely be less than good.

Enzymes control the ripening process in fruits and can cause light-colored fruits to turn brown when their cut surfaces are exposed to air. Freezing slows down the enzyme process but doesn’t stop it. Ascorbic acid or commercial antidiscoloration products can keep these fruits from turning brown (see Chapter 4) and blanching will protect the quality of vegetables. (Blanching is discussed later in this chapter. Specific blanching times for vegetables are covered in Chapter 5.)

Benefits of Freezing Foods

Stacked containers of frozen yellow puree in freezer

All methods of preserving foods have their benefits, but freezing definitely has quite a bit going for it as far as the home food preserver is concerned:

  • Freezing temporarily stops the growth of organisms (such as bacteria, yeast, and molds) that cause spoilage in foods. It doesn’t kill them but essentially puts them in a state of suspended animation.
  • Freezing inactivates enzymes responsible for controlling the ripening process.
  • Properly frozen foods generally keep more of their nutrients, flavor, and texture than foods preserved by other methods.
  • Freezing food saves space. Frozen foods can be stacked in the freezer, whereas glass canning jars can’t be stacked.
  • The Freezer

When it comes to freezing foods, the biggest and most expensive item to consider is, of course, a freezer, but it’s an investment you’ll amortize over time. The other supplies and equipment you’ll need are relatively inexpensive and, like the freezer, most will last for years with proper care.

Freezer capacity is measured in cubic feet, ranging from 5 to 25 cubic feet. You might be tempted to buy the biggest freezer you can find, but before you plunge ahead and purchase a mega-freezer, stop to consider how you’ll use this appliance.

Keeping a smaller freezer full will be more energy-efficient than running a larger freezer that’s less than half full. Modern, smaller freezers have more storage capacity than older, bigger freezers. This is because of improvements in insulation technology that have reduced the need for thicker walls.

Smaller units generally use less electricity than larger ones, but the difference isn’t huge. What is huge is keeping your freezer as full as possible to get the most return on your food-preserving dollar. Freezers are designed to run more efficiently when full, so keeping your freezer at least half (and preferably three-quarters or more) filled is the way to go.

If you have a large or growing family, the larger freezer might make sense. Also, if you’re planning on stocking up for the year, a larger freezer will store that much for you. However, if your family is small or if you’re also planning on preserving foods by other means, such as canning or drying, a smaller unit might make more sense. Many families have two freezers and put them to different uses, such as one for meat and the other for bulk-food purchases. Uncover the details of essential and helpful canning and preserving equipment.

Important Features

There are certain features you’ll want to look for in a freezer. Most of them are standard in newer models. These include the following:

  • A power-on light. This light tells you the freezer is working. Checking this every day can save you a lot of headache and expense if something goes haywire (such as, the power going out or a mouse chewing through the cord or any other weird occurrence). If your freezer is in the garage, just make it a habit to check the light each day as you walk to the car.
  • A locking mechanism with a key. This is an essential item, especially in homes with children. I know a friend’s child who was playing hide-and-seek and hid in the freezer. She couldn’t get out, but fortunately, she was found in time.
  • An adjustable temperature control dial with a “fast freeze” setting. This quickly gets your foods to the optimum temperature. Once the food has frozen, you can then return the freezer to 0°F.
  • An internal light. Especially with chest freezers, peering into the dark abyss can be frustrating. Holding a flashlight in one hand while you’re rummaging with the other is annoying. The second best option is a headlight that makes you look like someone out to explore the Carlsbad Caverns.
  • ENERGY STAR designation. The Environmental Protection Agency (EPA) developed the ENERGY STAR program to promote energy-efficient products.
    A defrost drain. This is found in the bottom for manual defrost units.
  • Automatic or Manual Defrost?

Of the two, automatic defrost is definitely the easier way to go. You don’t have to devote a morning or afternoon to scraping, wiping, draining, and especially moving all your frozen foods into boxes while you clean out their home.

On the other hand, manual defrost units are generally less expensive than automatic defrost units. Also, if you have a tendency to drop items haphazardly into the freezer instead of carefully entering them on an inventory sheet and putting them in their proper place, a semiannual investigation of your freezer’s contents can yield some interesting discoveries. Additionally, it will prompt you to use those items that are nearing the end of their recommended storage times. (See Appendix D.) It can be quite refreshing to perform this chore on an especially hot summer day—just remember to keep your storage containers stacked and covered, and return them to the freezer as quickly as possible.

Situating the Freezer

The main requirements are a dry, level space that’s not subject to extremes in temperature. If your garage is heated or if winters in your area are mild, this might be the best place. The basement is another option, but only if you live in areas where earthquakes don’t occur. A personal story: The Loma Prieta earthquake of October 17, 1989, in the Santa Cruz Mountains of California destroyed more than 500 homes and damaged more than 18,000 others. My home was toast. Unfortunately, the freezer and all the year’s canning were in the basement. The house came to rest on top of all this and all was lost. Bottom line: Know where you live and plan accordingly.

Other Equipment & Supplies

There are several options when it comes to deciding which type of containers you’ll use for freezing foods and new technology has expanded your choices. Whether you choose to be traditional or modern, you’ll easily find just what you want.

Freezer Containers & Freezer Bags

Freezer containers are made of rigid plastic with tight-fitting lids, and they’re moisture- and vapor-resistant to prevent freezer burn. Some are designed to allow you to raise one corner of the lid after packing and burp out the extra air. You won’t eliminate all of it, but every little bit helps. Pint and quart sizes are the most versatile. These containers stack nicely and take up less space in your freezer than glass canning jars. Like glass jars, they’re reusable and reasonably priced.

Yes, you read that correctly. You can use glass canning jars for freezing. We’ll cover all aspects of these jars in Part 3 of this book.

There are different types of freezer bags: envelopes with slides that help lock the bag, envelopes without slides but with tracks that fit together to create a tight seal, and soft bags that can be secured with a twisty tie.

You might find it easier to expel air from the softer bags because they conform more easily to the shape of the food in them. With the stiffer bags, you might be able to fold them over, starting at the bottom and pushing out the air as you go up to the seal. These have a greater tendency to cause freezer burn because it can be difficult to expel enough air. If your food product will permit it, first wrap it tightly in plastic food wrap before putting it in the freezer bag.

Vacuum Sealer Packaging Machines

Vacuum packaging machines or vacuum sealers are handy appliances designed to remove air from packages of food and thereby increase their storage life. Different kinds of systems are available and prices vary widely. They work well when used for their specified purpose, but they’re not intended to take the place of the freezer. They’re simply another form of packaging to get food ready for the freezer. Make them the last step before schlepping your foods to the freezer.

But the air is gone, you think. Why can’t I store the packages in the pantry, you ask. Most bacteria that cause food spoilage thrive in the presence of oxygen. When food is going bad because of these microorganisms, there’s a better than good chance you’ll find out about it. The food will smell bad, it might get slimy, and the color will definitely look “off.” You’ll notice all this and should dispose of the food so no one gets sick.

It would seem logical, then, that removing this oxygen from the food’s environment would solve the problem—and it does for those bacteria that love oxygen.

The problem is there’s another genus of bacteria, Clostridium, that thrives in the absence of oxygen and this anaerobic bacteria is potentially lethal. It’s responsible for tetanus, gas gangrene, and botulism. Food that’s contaminated with Clostridium might not smell bad, look bad, or taste bad, but it can kill you.

If you’re using a vacuum-sealing system, you must be aware of proper food storage for low-acid, perishable foods, such as vegetables, meats, poultry, and seafood. Vacuum packaging isn’t a replacement for proper pressure canning of low-acid foods nor is it a replacement for proper refrigeration and freezing of foods that would otherwise require refrigeration and freezing. You must also be aware that perishable food always carries the potential for contamination with pathogens, such as bacteria. Previously frozen foods that are thawed will spoil more quickly than their fresh counterparts. After thawing, keep them refrigerated until ready for use.

If the food won’t keep at room temperature without spoiling, it must be refrigerated or frozen after being vacuum-sealed. Nonperishable food items (such as dried nuts, crackers, lentils, or other dried foods) are good candidates for vacuum sealing because they have very little moisture content. However, these items store very well in regular storage containers with tight-fitting lids and you can remove the product as needed and replace the lid. Once you open the vacuum-sealed package, you must go through the resealing process again. Feel free to learn more about boiling water bath canning.

Freeze & Cook Bags

Packed freezer with bags of vegetables and fruits

These are nifty for doing just what the name says. You can freeze foods in them and then transfer them directly from the freezer to a pot. They’re designed to handle from below 0°F to above boiling. They’re pricey but convenient. Plus, you can save on cleanup.

You can buy these bags in 1½ pint or quart size and they also come in a roll so you can cut whatever size you need. This is handy for odd-shaped items that won’t fit in standard freezer containers. You’ll need a heat sealer if you go the roll route. These are sold separately and are available at most larger department or chain stores.

General Supplies

You’ve decided which freezer will serve your needs, you’ve stocked up on freezer containers and other necessary items for prep work and storage, and you’re ready to preserve food. But there are still some other supplies you also need:

  • Cutting boards in various sizes (especially ones with rims)
  • Good knives (meaning sharp)
  • Pots and pans
  • A colander or sieve
  • Utensils (slotted spoon and regular spoons, vegetable peeler, spatulas, ladle)
  • Measuring cups and spoons
    Clean dishcloths and towels
  • Potholders and/or mitts
  • Sugar (if you’re freezing fruits in a sugar or liquid pack)
  • A timer
  • Scales
  • Plastic wrap, freezer wrap, and aluminum foil
  • Freezer tape, permanent marker, and Freezer Inventory Sheet
  • General Procedures for Freezing

Examine all your containers and jars. Discard any plastic containers with cracks or chips. Examine your glass freezing and canning jars, and discard any with chips or cracks. Run a finger around the rim to detect any small nicks and dispose of any jars that don’t pass muster into the recycling bin.

Cleanliness is the order of the day. Wash all containers and jars in hot, soapy water, rinse, and invert them on a clean towel.

Now you can focus on what you’ll be freezing. Wash fruits and vegetables in cool water. Cut the items according to how you plan to use them (cubes, slices, etc.). Packaging instructions for various types of foods are discussed in the following chapters.


Frozen cookie dough pieces in clear plastic bags

Most vegetables will need to be blanched in order to stop enzyme action from causing the food to deteriorate during storage. Blanching doesn’t destroy these enzymes, but it does inactivate them. Blanching means to put vegetables in boiling water or to steam them for a specified period of time and then plunge them into ice-cold water for rapid cooling. Different vegetables require different blanching times. (See Chapter 5.)

Blanching in the microwave is possible if you’re working with small quantities of vegetables. It doesn’t save any time, but it does require electricity, so you’re not saving energy. Also, most charts only give blanching times for boiling water, so unless you’ve kept the instructions for your microwave, you’ll end up guessing and might produce less than satisfactory results. After blanching and cooling, vegetables need to be drained to remove as much water as possible before being packed for the freezer.


Water expands when it freezes, so you must allow enough room for that expansion when you’re packing foods for the freezer. The room between the food and the lid is called headspace. Headspace requirements vary according to the type of food being frozen and whether it contains syrup or liquid. Proper amounts of headspace for freezing fruits and vegetables are discussed in the following chapters.

Preventing Discoloration

Light-colored fruit oxidizes in the presence of oxygen. This means it turns brown. Apples and peaches are especially vulnerable. You can prevent this by using ascorbic acid or a commercial antidiscoloration product. (See Chapter 4.)

Storing Frozen Foods

During the initial freezing process, packages or jars should come in direct contact with the freezing unit. This will hasten freezing. Leave some air space between packages or jars of food being frozen. This keeps the cold air on the move and more able to do its job. Once everything is frozen, you can stack, cram, and arrange to your heart’s content.

Thawing Procedures

For every safe way of doing something, someone will come up with a creative but totally unsafe way of accomplishing the same task. The US Department of Agriculture (USDA) warns against defrosting foods in any of the following ways:

  • In the basement
  • In your car
  • In plastic garbage bags
  • In the dishwasher
  • Outdoors
  • On the porch
  • In a pan of hot water
  • On the kitchen counter

You probably wouldn’t dream of trying any of these methods, except perhaps for the last one. So what’s wrong with setting a package of meat out on the counter to defrost? Could be plenty. As food thaws, the bacteria that are present (and that were inactive while the food was frozen) begin to get frisky. They multiply when any part of the meat gets to 40°F or above. So while the interior section of the meat is still frozen, the outer layers have passed into the danger zone, which begins at 40°F and extends to 140°F.

Thawing in the Refrigerator

Well-organized chest freezer with various frozen foods

Planning ahead is best. If you know what you’ll want for dinner, take the package out of the freezer the night before and put it in the refrigerator to thaw. Temperatures vary throughout the refrigerator, so take advantage of the warmer portions when you want something to thaw. Generally, the lower shelves are best for thawing if your freezer unit is on top.

Put the package of frozen food on a plate or inside a bowl to contain any liquid that leaches through the wrappings. This is especially important for meat or poultry juices that shouldn’t come in contact with other foods stored in the refrigerator. Plan on using thawed ground meats within a day or two. The same goes for poultry. Solid cuts of beef, such as roasts or steaks, should keep up to 5 days. If your plans change, you can refreeze foods that have thawed, although the quality won’t be as good.

Thawing in Cold Water

This works more quickly than the refrigerator method, but it does require you be on hand to keep changing the water to be sure it stays cold. It can also be messy, especially if the freezer bag is leaking. Not only can bacteria enter through the opening, but water can turn your food product into a soggy mess. If in doubt, put the package in another freezer bag (double-bag it) just to be sure. Change the water about every half hour. You can expect a 1-pound package to thaw in about 1 hour. Once the food has thawed, it must be cooked right away. If you change your mind about using the product right away, it should still be cooked before refreezing.

Thawing in the Microwave

Microwaves are probably used more for reheating coffee and defrosting foods than for any other purpose. However, you’ll need to keep a close eye on the defrosting process when you use the microwave because outer portions of the food can begin cooking while the interior is still hard as a rock.

Once food has thawed by this means, it should be cooked right away to prevent bacteria from growing. If you decide to refreeze the food, it should still be cooked before you return it to the freezer. Again, there will be some loss of quality in a refrozen product.

Now that you’ve got the basics under your belt, let’s get started freezing foods.

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