Tuesday, March 4, 2014

How to Freeze Your Food Without Getting Freezer Burn?

 

Top Freezing Tips and Techniques

Preparing double or even triple recipes and freezing portions for later means you don’t have to cook every night to have a delicious and nutritious meal on the table.

Freezing food can be a convenient way to store excess food or meals that you can prepare at a later date; however, it is important to store each food type in a certain manner to guarantee its freshness and quality. There are also steps you can take to prevent your food from experiencing freezer burn and ensuring it retains its texture. Take the guesswork out of freezing food with our guide that will have you saving time, money and effort in the kitchen.

how-to-freeze-your-food-without-getting-freezer-burn

What Food Can You Freeze?

You can freeze almost any food. Some exceptions are canned food or eggs in shells. However, once the food (such as a ham) is out of the can, you may freeze it.

Being able to freeze food and being pleased with the quality after defrosting are two different things. Some foods simply don't freeze well. Examples are mayonnaise, cream sauce and lettuce. Raw meat and poultry maintain their quality longer than their cooked counterparts because moisture is lost during cooking.

When freezing food, make sure you leave plenty of clear space around each container or package you are freezing to allow the air to flow around the unfrozen food and freeze the food quickly and evenly. After the packages are frozen, stack them more efficiently. Foods frozen in smaller quantities will freeze faster than foods frozen in larger quantities, helping to prevent a buildup of large ice crystals.

Use shallow containers with a wide surface area relative to depth. This will enable food to freeze quickly all the way through. If using plastic freezer bags for meats, vegetables, sauces, or soups, seal them well, then place them flat on a chilled baking sheet until frozen solid. Again, a wide surface area will aid in the formation of tiny ice crystals and will also make for faster thawing. It is important to cool food completely to room temperature before freezing. Placing hot foods in the freezer will raise its temperature, slowing down the freezing time and possibly thawing other foods, and the centers of the foods may not freeze quickly enough to prevent spoilage.

To make sure that foods such as uncooked meatballs, ground meat patties, dumplings, ravioli, cookies, profiteroles, meringues, and individual cakes retain their shapes and remain separate upon freezing, use the open-freeze or dry-freeze method to freeze food quickly on all sides. Place a baking sheet lined with parchment paper or plastic wrap in the freezer and chill for 10 to 20 minutes. Place the food in a single layer on the lined baking sheet, leaving about 1 inch between the pieces, and freeze for about 1 hour or until solid. Then pack in plastic freezer bags, vacuum-sealed bags, or airtight freezer-safe plastic containers and return to the freezer. Be sure to mark the packages or containers with their contents and the date.

Do Not Freeze these Foods

Most individual ingredients can be frozen. However, some foods simply aren't freezer friendly:

1) Raw eggs in the shells will expand and crack.

2) Hard-boiled eggs go rubbery.

3) Vegetables with a high water content, such as lettuce, cucumber, bean sprouts and radishes, go limp and mushy.

4) Soft herbs, like parsley, basil and chives, go brown.

5) Egg-based sauces, such as mayonnaise, will separate and curdle.

6) Plain yogurt, low-fat cream cheese, single cream and cottage cheese go watery.

What Containers to Use?

Choose packaging materials that will protect the food’s flavor, color, moisture content, and nutritional value from the dry climate of the freezer. Containers should:

1) Not become brittle and crack at low temperatures. Look for the freezer symbol, often a snowflake, to indicate that it is freezer safe.

2) Be durable, leak proof, and easy to seal and mark.

3) Be oil, grease, and water resistant (no uncoated paper containers).

4)  Protect against absorption of outside flavors and odors.

A. Glass and Ceramic: If using glass containers, choose dual-purpose types that are designed for freezing and also are heatproof. Pyrex and Simax are brands made from boro silicate glass, which cannot go from freezer to hot oven immediately—the dish must stand at room temperature for at least 30 minutes, as the sudden heat change may cause it to break. Dishes with tempered glass such as Anchor Hocking and Duralex must be completely thawed before placing in a hot oven.

If you’re using glass jars to freeze sauces, soups, or stocks, be sure to leave at least a 3⁄4- to 1-inch space at the top, as the water in the recipe will expand and may cause the glass to break if filled too high. There are also many brands of freezer to-oven-to-table ceramic dishes, such as Corning Ware and GlassLock tempered storage containers. These are especially good for baked pastas and casseroles, as they can be placed in the oven straight from the freezer, and then brought to the table. Be sure they are suitable for freezer use.

B. Plastic: Make sure the containers close tightly and securely and are made of plastic that will not become brittle at a low temperature; look for the snowflake symbol on brands such as Sistema, Klip It, or Lock & Lock. All three have a clipping system for closing the top. Plastic containers are good for foods that have been frozen with the open-freeze or dry-freeze method, as they protect more fragile items, such as meringues, profiteroles, and pastries, from being damaged or crumbled by other bags and containers of food. They also allow you to take out and use as much food as required, resealing the remainder in the plastic container for another day.

C. Plastic Freezer Bags: Be sure to use only plastic bags that are labeled for freezer use. Once the bag is filled, try to squeeze out as much air as possible in order to prevent ice crystals from forming around the food in the bag. Once the air is squeezed out, tightly close the bag, either by sealing with the attached zipper lock, or by twisting the top of the bag and fastening tightly with a freezer clip or plastic-coated wire twist-tie. Bags are best used for small to medium quantities; it’s faster to thaw two smaller bags than it is one large one.

When using freezer bags, ideally freeze flat until solid, then store upright or stack with other frozen foods. Food that is frozen flat will thaw much more quickly than food that is frozen in one big lump.

D. Vacuum-Sealed Bags: These excellent bags work by sucking the air out of the filled bag and heat sealing it at the same time, thus completely eliminating the possibility of freezer burn and flavor deterioration.

What is Freezer Burn? Freezer burn is a condition that occurs when frozen food has been damaged by dehydration and oxidation, due to air reaching the food. It is generally induced by substandard (non-airtight) packaging. The condition is primarily caused by sublimation. Water evaporates at all temperatures, even from the surface of solid ice. If air adjacent to ice is cold enough (so the ice won't melt) and the air is dry enough, water molecules go directly from solid phase (ice) to gaseous phase (vapor) without going through a liquid phase. When the constantly vibrating water molecules in foods stored in a freezer migrate to the surface, crystals of ice outside of the solid food are formed, and some water molecules escape into the air (by sublimation). The meat parts now deprived of moisture become dry and shriveled and look burnt. In meats, air can cause fats to oxidize.

Meats and vegetables stored in a manual-defrost freezer will last longer than those stored in automatic-defrost freezers. That is because the temperature of a manual defrost freezer remains closer to 0 °F/-18 °C while the temperature of automatic defrost freezers fluctuates, and because automatic-defrost freezers have drier air, thus the rate of sublimation increases.

Using sealed bags method is optimal, you will have to buy the vacuum-sealing machine and the special bags. Items such as burgers, meatballs, and fishcakes must be frozen solid first (by the open-freeze or dry-freeze method) or they will become misshapen when the bag is sealed.

Keep the temperature in your freezer below 0 degrees F (-18 degrees C). Freezer burn only happens when temperatures fluctuate above 0 degrees F. Use a freezer thermometer to make sure the freezer is cold enough.

Package food tightly. When the surface of food is exposed to air, the water molecules have a chance to sublimate and migrate. When you're getting food ready for the freezer, try to make sure as little of the surface is exposed as possible.

Freezer burn does not make food unsafe, merely dry in spots. It appears as grayish-brown leathery spots and is caused by air coming in contact with the surface of the food. Cut freezer-burned portions away either before or after cooking the food. Heavily freezer-burned foods may have to be discarded for quality reasons.

Meat stews need to be completely cold with their juices well jelled together; otherwise the moisture will be drawn out and clog the machine, as well as prevent a successful seal to the bag. The vacuum seal is also good for sealing cuts of raw meat,  chicken, and fish. The drawback to this system is that once the bag is opened, you either must thaw all the food inside or reseal the portion you are not using immediately.


Discover the art of vacuum-packing at... How To Vacuum Pack Meat, Poultry and Sea Food Properly?


E. Plastic Wraps and Aluminum Foil: Good materials for wrapping meats and other large or irregularly shaped foods include freezer-coated paper, plastic wrap, and heavy-duty aluminum foil. You’ll notice that freezer paper is shiny on one side; place food directly on the shiny side.

Waxed paper can be used to keep food separate in freezer safe containers. Freezer-safe plastic wrap allows for a super-tight wrap. For extra safekeeping, after being wrapped in plastic freezer wrap, food should then additionally be wrapped in either heavy-duty foil or placed in a plastic freezer bag.

Do not use regular plastic wrap, which is porous and can lose its clinging qualities under sustained cold temperatures, possibly allowing foreign odors to penetrate the food. Also refrain from using regular-weight foil, as it becomes brittle at low temperatures. Avoid parchment and greaseproof paper, which becomes soggy on freezing.

How to Organize Your Freezer?

Freezers should be kept at 0°F/18°C. If your freezer or fridge-freezer does not show the exact temperature digitally, consider keeping a refrigerator/freezer thermometer in the freezer. If the temperature rises above 0°F/18°C, turn down the dial in the refrigerator/ freezer to lower the temperature. Look for stars on the freezer compartments. The stars indicate the temperature of the compartment and how long food may safely be stored there.

1) One star (21°F/6°C) is fine for making ice cubes and is sufficiently cold to keep food for three or four days.

2) Two stars (10°F/12°C) stores food for fifteen to twenty days.

3) Three stars (0°F/18°C) will keep food safe for up to three months.

4) Four stars (below 0°F/18°C) means that the compartment provides the ideal conditions for freezing fresh and precooked foods. Learn about food freezer storage-life at... Food Storage Shelf Life Chart.

Once food is placed in appropriate freezer storage containers, try to avoid throwing it in the freezer at random. It is well worth making the time to package, date, and label food and to place it so that you can see right through to the back or bottom of the freezer. If the freezer is deep, keep a list on the door that itemizes the contents. Use a nonmetal rack to create shelves, so that everything is not simply piled up on top of everything else and so that you can access items more easily. For maximum efficiency, keep your freezer at least 75 percent full; otherwise you’ll lose the cold air each time the freezer is opened.

Is Frozen Food Safe?

Food stored constantly at 0°F will always be safe. Only the quality suffers with lengthy freezer storage. Freezing keeps food safe by slowing the movement of molecules, causing microbes to enter a dormant stage. Freezing preserves food for extended periods because it prevents the growth of microorganisms that cause both food spoilage and food borne illness.

How to Freeze Vegetables?

Freezing is the best way of preserving a season's bounty to enjoy later. When properly frozen, vegetables retain all their flavour and nutrients. The best method of freezing is the same for peas, runner, French, dwarf and broad beans, asparagus and broccoli.

1) Freeze vegetables for between 3 and 6 months. Vegetables will retain their flavor and appearance if frozen and thawed within this time period.

2) Blanch certain vegetables before freezing. This method will prevent the enzymes present in vegetables from causing the vegetables to lose their flavor and color.

3) Determine the amount of time each vegetable type needs to boil. Asparagus, broccoli, beans, and cabbage will take up to 3 minutes; whereas Brussels sprouts, large carrots, and slices of eggplant will take up to 5 minutes.

3) Bring a pan of water to boiling, then place small portions of vegetables into the boiling water.

4) Let the vegetables boil for the proper amount of time, then transfer the vegetables immediately to a bowl of cold ice water.

5) Dry your vegetables with a paper towel, then store them in bags or containers in the freezer.

How to Freeze Meats?

1) Trim the fat and bones from all meat. This will release excess fluids and gases that are present in the meat and help retain its freshness and quality during freezing.

2) Store meats in the freezer for the appropriate length of time. Each meat type requires different lengths of freezing time depending on the amount of fluids present in the meat.

3) Keep sliced and shaved meat and hotdogs in the freezer for up to 2 weeks.

4) Store cured ham and bacon in the freezer for up to 1 month, cooked meats for up to 2 months, and ground meat in the freezer for up to 3 months.

5) Store meats from large cuts, such as steaks, in the freezer for up to 12 months.

6) When thawing, ensure that stuffed (seasoned), poultry or rolled meat has thawed right to the center before cooking.

How to Freeze Seafood?

1) Cut large or whole fish into small portions. This will retain the overall freshness of the fish and give you the ability to clean and gut whole fish before freezing.

2) Create a protective icy coating for the fish. An additional coating of ice on your fish will help guarantee its freshness and eliminate odors that the fish may emit during freezing.

3) Remove your fish from the freezer after it has frozen completely, then dip it into water before refreezing. This will allow a new layer of ice to form and cover the fish.

4) Freeze your fish for up to 3 months. If you are freezing oysters, you can store them in the freezer for up to 6 months.

5) When thawing, ensure that that seafood has thawed right to the center before cooking.




How to Thaw Frozen Foods?

1) Microwaves are handy for thawing. Check your user manual for specific instructions. Here are some handy tips for thawing different foods at room temperature and in the fridge.

2) Foods with a low moisture content (such as cakes, muffins and biscuits) can be thawed at room temperature.

3) Remove and discard the plastic wrap or other packaging before thawing - otherwise the ice crystals that form on the surface during freezing will form a pool of liquid as they melt, which can cause cakes and muffins to become soggy.

4) Foods with a medium moisture content (such as fresh pasta, sliced bread, frozen meals and frozen veggies) can be reheated immediately after being taken out of the freezer.

5) Foods with a high moisture content (such as meat, chicken, fish, fruit and cooked liquid-based dishes) need to be thawed in the fridge to prevent bacteria growing.

6) Place meat on a plate or in a container to catch any juices. Thaw in the fridge for 24-48 hours. This allows the ice crystals to break down slowly and helps retain the texture of the meat.

7) Be as gentle as possible when thawing frozen fruit. Fruit has high water content, so place, in a single layer, on a baking tray lined with paper towel to absorb excess liquid as it thaws.

Does Freezing Destroy Bacteria & Parasites?

Freezing to 0°F inactivates any microbes— bacteria, yeasts and molds — present in food. Once thawed, however, these microbes can again become active, multiplying under the right conditions to levels that can lead to food borne illness. Since they will then grow at about the same rate as microorganisms on fresh food, you must handle thawed items as you would any perishable food.

Trichina and other parasites can be destroyed by sub-zero freezing temperatures. However, very strict government-supervised conditions must be met. Home freezing cannot be relied upon to destroy trichina. Thorough cooking, however, will destroy all parasites.

Freshness & Quality

Freshness and quality at the time of freezing affect the condition of frozen foods. If frozen at peak quality, thawed foods emerge tasting better than foods frozen near the end of their useful life. So freeze items you won't use quickly sooner rather than later. Store all foods at 0° F or lower to retain vitamin content, color, flavor and texture.

Nutrient Retention in Frozen Food

The freezing process itself does not destroy nutrients. In meat and poultry products, there is little change in nutrient value during freezer storage.

Effect of Food Enzymes

Enzyme activity can lead to the deterioration of food quality. Enzymes present in animals, vegetables, and fruit promote chemical reactions before and after harvest, such as ripening. Freezing only slows the enzyme activity that takes place in foods. It does not halt them.

Enzyme activity does not harm frozen meats or fish and is neutralized by the acids in frozen fruits. But most vegetables that freeze well are low acid and require brief, partial cooking to prevent deterioration. This is called "blanching." For successful freezing, blanch or partially cook vegetables in boiling water or in a microwave oven. Then rapidly chill the vegetables prior to freezing and storage. Consult a cookbook for timing.



References:


Erickson,  Marilyn and Yen-Con Hung. 1997. Quality in Frozen Food. Springer; 1997 edition. ISBN-10: 0412070413

Gould, G. W. 2012.New Methods of Food Preservation. Springer; Softcover reprint of the original 1st ed. ISBN-10: 1461358760

James, S J, and C. B. James MA DM FRCS FRCOphth.2002. Meat Refrigeration (Woodhead Publishing Series in Food Science, Technology and Nutrition) Woodhead Publishing; 1 edition. ISBN-10: 1855734427

Mallett, C.P. 1992.Frozen Food Technology. Springer; Softcover reprint of the original 1st ed. ISBN-10: 1461365767

Neville,  Kat and Lindsay Tkacsik. 2010. Fix, Freeze, Feast: The Delicious, Money-Saving Way to Feed Your Family. Storey Publishing, LLC. ISBN-10: 1603427260

Roberts, Dawn and, Matt Stapleton. 2009. Got Garden?: A Practical Guide for Preserving Your Food. CreateSpace Independent Publishing Platform. ISBN-10: 1448680670

Smith, Durward S. , Jerry N. Cash , Wai-Kit Nip and Y. H. Hui 1997. Processing Vegetables: Science and Technology. CRC Press; 1 edition. ISBN-10: 1566765072

Sun, Da-Wen. 2011.Handbook of Frozen Food Processing and Packaging, Second Edition (Contemporary Food Engineering). CRC Press; 2 edition. ISBN-10: 1439836043

Van Arsdel, Wallace B. 1969. Quality and Stability of Frozen Foods. John Wiley & Sons Inc. ISBN-10: 0471897906

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