Summer is a Good Time to Think About the Cold

Why do we emphasize storing frozen foods at 0 degrees F? Even though other freezer temperatures can stop the growth of microorganisms, quality will continue to be lost even at these cold temperatures. The recommended shelf life listings we have for frozen foods are based on a storage temperature of 0 degrees F. and expected retention of good quality. Warmer temperatures, even though the food may still be frozen, will result in shorter retention times for quality.

Even though blanching for specific time at a given temperature is recommended to inactivate enzymes, oxygen around the food as well as the dryness of the air in a freezer will cause other quality losses. And foods that are not blanched, or are inadequately blanched, will have active enzymes. Enzymatic and oxidative changes in stored food will occur more slowly at freezer temperatures than higher ones, but they still will proceed. One chemical reaction that will proceed, even though slowly, in the freezer is oxidative rancidity of fats (including those contained within meats, poultry, etc.).

Another way to protect quality of frozen foods is to achieve a fast rate of freezing. The faster that the water in foods gets frozen, the more protective for quality. Fast freezing promotes the formation of smaller ice crystals than slow rates of freezing. The smaller the ice crystals, the less damage done to cell walls and the texture of foods.

Fast freezing can be promoted by making sure hot or warm foods are completely cooled before putting them into the freezer, using small package size, and then spreading your packages out within the freezer until the food is frozen. The packages can then be stacked or arranged together if you wish, but while they still becoming frozen, make sure the cold air can surround all sides of the package. It is a good organizational plan to package your foods into suitable serving sizes anyway, but a good rule of thumb to promote fast freezing is to keep each package size fairly small. If you know you will be placing a large quantity of foods into the freezer at once, consider setting the temperature control of your freezer to -10 degrees F. or lower about 24 hours in advance. Usually about 2 to 3 pounds of food per cubic foot of storage space can freeze within 24 hours.

Speaking of freezing foods that are first blanched or cooked, make sure they are completely cooled before even putting them into your freezer containers or bags, also. An important reason is to promote quick freezing once inside the freezer for food quality and energy efficiency; however, another reason is the size of those ice crystals again! Moisture that condenses on a lid or sides of a package from hot steam will lead to quality-damaging large ice crystals inside the package.

Freezing food is an excellent way to preserve the freshness in most foods, as well as the nutrients, colors and tastes. However, there are best practices to make sure these advantages are realized. For more readings on this topic:

Freezing Pointers: http://nchfp.uga.edu/how/freeze/pointers.html

General Shelf Life of Frozen Foods: http://nchfp.uga.edu/how/freeze/freezer_shelf_life.html

How to Freeze Specific Foods: http://nchfp.uga.edu/how/freeze.html

Frozen Shouldn’t Mean Lack of Action

I have a confession to make. No, it’s not that I’ve been silent on this blog site for 11 months. Our followers know that, and I am sorry.  My confession is that despite my teaching others to manage their inventory of frozen foods well, it turns out I am not a good example this month.

IMG_1781For the past few weeks I’ve had to clean out some freezers in our food preservation lab. Some foods were missing labels and dates and others obviously had been poorly packaged (but just a few of them, really!).  I am sure the intent of our workers had been to take care of an immediate need cleaning up after a workshop or late night experiment. But the outcome was that no one had gone back very quickly and corrected the situation.  And that chest freezer, where there was not a great demand on the space, had become quite unorganized and full of really old and some freezer-burned food near the bottom.

Now I want to clean out my home freezer so I can buy a new one. The labeling of packages is in much better situation at home. However, I am finding some that “got lost” and pushed to the back of this upright.  They are older than should still be in there.  So here is my message for beginning of summer.  This article starts a short series on freezing of foods.

Freezing is a great food preservation method, especially for being able to store uncooked, or barely cooked, foods that can be used in many ways when thawed. I am dreaming of the fresh strawberries now in our fields, and the blueberries, blackberries and other fruits to come this summer.  If frozen without sugar and tray-frozen before packaging, I know I can decide later whether to make jam, syrups, cobblers or pies. However the quality of foods in the freezer will deteriorate over time.  Certain practices can better preserve that quality.

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Choose packaging (e.g., bags, wraps, boxes or jars) that will prevent moisture loss from the food. Moisture and oxygen can pass through some packaging material itself and of course through poorly connected lids and seals. Drying of food surfaces (i.e., freezer burn) results in poor quality texture and taste. Best packaging also prevents transmission of odors within the freezer. Most people prefer bags and wraps, although glass jars and rigid plastic freezer containers with tight seals keep food quality very well. Choose plastics and foils that indicate freezer quality and weight (versus just those marked “food storage”). Not all plastics and foils are the same in the way they allow or block transmission of moisture and oxygen.

Whether you choose boxes, bags or wraps, make sure all seals and folds are very tight and prevent air loss or entry. Boxes with snap-on lids and jars with twist-on lids are not all the same, either. Snap-on lids should have a deep and tight overlap of the lid channel for sealing and the top rim of the bottom part.  Twist- or turn-on lids should have some type of gasket to prevent air gaps.

freezerheadspaceThe shape and type of package, as well as type of food, can also influence how much headspace is needed. Headspace is empty space between the food and top of the container (or bag) that allows room for expansion as water in the food freezes to ice.  But, too much air left in the package is not good for food quality.  See guidelines for headspace at our website.  More about packaging  is written here.

After packaging your food, label it with the food type and date. Then, actively manage your inventory. One option is to make a table or chart of foods going in your freezer by date that can be checked off as your remove items. Paper and pencil work as does one on a tablet or computer. (Some of you may be lucky enough to have built-in computer technology on your newer freezer!)  If you are not a person to keep up with lists, at least re-organize your inventory when you add new foods. Put the newest foods toward the bottom or back and bring older foods toward the front or top.  Labels should be easy to read and follow.  Find a system that works for you.  It’s a shame to waste good food, let alone the time and expense of packaging you put into preserving your food.

In my next article, I’ll cover some other tips for successful freezing. You can also read more at the National Center for Home Food Preservation website, under “How Do I…..Freeze.”

Oh, and actually, that lab freezer still will be storing some of that freezer-burned food. I need those example for the next class I’m teaching or photos!  But your own, real food supply, like mine, shouldn’t include those items.

It’s Berry Season!

Some of us are in the middle of it, some have seen strawberries come and go for this year, and some of us are still waiting for blueberries. Berries are a favorite for jams, whether a full flavor using one berry, or in combinations that allow our creative streak to show.  Strawberry-raspberry, blueberry-blackberry, or even 3 or more berries in combination.  Yum! As I write this, I’m past my morning breakfast decisions but now my mind is thinking ahead to what I can stir into my yogurt at lunch.

Another way to preserve our delicate, hand-picked berries is by freezing. Now we can start thinking about future pies, cereal toppings, or a quick, refreshing smoothie.

A dry pack is simply placing clean berries in freezer containers, sealing the container, and freezing. Unless they are tray packed (see below), they might clump together and be difficult to separate into individual berries.  Note:  If you do wash blueberries before freezing, dry blueberries completely after rinsing, or else the moisture on the blueberry skin will cause tougher skins.

A tray pack works well to help maintain the shape of each individual berry and keeps them easy to remove from the container and separate from each other. This method is called a tray pack because after rinsing the berries, you spread them in a single layer on a shallow smaller_Blueberry tray close-uptray (like a cookie sheet), then carefully lift the tray into the freezer without causing berries to touch each other.  As soon as they freeze, seal the berries in an airtight container and place them back into the freezer so they don’t get freezer burn.

A sugar pack is like a dry pack but with one extra step – gently mix ¾ cup sugar per 1 quart (1⅓ pounds) berries before filling into freezer containers, sealing, and placing in the freezer. You can view step-by-step directions and photos for a sugar pack by selecting the PowerPoint presentation under “Strawberries” on the National Center’s ‘Freezing’ page.

A syrup pack surrounds the berries in a sweetened liquid, changing the sweetness and texture of the berries quite noticeably. Based on the natural sweetness of the berries and your own preference, you can decide the proportion of sugar to water from very light syrup (10% sugar) to very heavy syrup (50% sugar).  More tart berries may produce the most desirable flavor from using a 40%-50% syrup.  Exact proportions for the range of syrups are listed on this Syrups chart, along with directions to make the syrup and notes about replacing part of the sugar with corn syrup or honey.

Crushed or puréed is an option for berries like blueberries and huckleberries that you might use an ingredient in other recipes. The berries can be crushed, pressed through a fine sieve or puréed in a blender or food processor.  Mix 1 cup (or 1⅛ cups) sugar with each quart (2 pounds) of crushed or puréed berries.

IMPORTANT! If you add sugar to the berries before freezing (as in the sugar pack, syrup pack, or crushed/puréed), then label the container with exactly how much sugar you add, so that you can include that quantity as part of the amount of sugar called for on the ingredient list of your final product recipe.  If you know you want to use the fruit in jam later, you can also measure the amounts of sugar and fruit now for a specific recipe and freeze those together; then use the total contents when thawed to make the jam.

For all types of pack, remember to leave at least ½-inch headspace (more for some styles of pack; see chart for exact measurements) between the berries and the lid of each container so that the containers don’t break open while expanding in the freezer.

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And most importantly, protect your fragile berries with the right kind of packaging for freezing. You don’t want the air inside the freezer to dry out your packs, or for flavors from one food to mingle with others. Freezer-weight plastic bags with good tight seals are a must if going the bag route. Glass jars with straight sides or wide mouth openings, plastic freezer boxes or re-purposed plastic tubs from frozen whipped toppings work well (as long as the seal between the lid and bottom is still intact and not misshapen from use).

Get Ready Now for the Summer Harvest

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If you are thinking about joining the trend in our communities to preserve food this summer, start planning and preparing now! Start by checking your equipment and supplies. Proper equipment in good condition is required for safe, high quality home canned food, for example.

If you’ve not yet purchased your needed equipment, there are two types of canners to consider: boiling water canners and pressure canners. A boiling water canner is used for canning acid or acidified foods like most fruits, most pickles, jams and jellies. Boiling water canners cost about $30-$100, or can be assembled yourself with a large stock pot, secure lid, and rack to keep jars off the bottom of the pot.

A pressure canner is essential for canning low acid foods such as vegetables, meats, fish, and poultry. Temperatures inside pressure canners reach higher than boiling water canners (for example, 240°F and above as compared to about 212°F). This is necessary to follow the tested processes available to be sure and kill the toxin–producing spores of the bacteria Clostridium botulinum.  If not killed, these spores can grow out and produce a deadly toxin (poison) in room-temperature stored jars of the low-acid foods mentioned.

You have two choices for type pressure canner: a dial gauge canner or a weighted gauge canner. Most steps in managing the pressure canning process are the same, but the two styles have different types of gauges to indicate the pressure inside the canner. Expect to spend $100-$150 or more on a pressure canner.

If you use a dial gauge canner, then it’s important to have the gauge tested for accuracy before each canner season or if you drop or damage your gauge. It isn’t as easy as it used to be to get gauges tested. Try a local hardware store or your local Cooperative Extension agent, even though not all still provide this service. For either type of canner, check that the rubber gasket is flexible and soft, and if it is brittle, sticky, or cracked then replace it with a new gasket. Also check that any openings, like vent ports, are completely clean and open.

You’ll also need jars, lids, and ring bands for canning. When getting started, new jars are a worthwhile investment (versus purchasing used jars from a yard sale or flea market) because very old jars may break under pressure and heat. Mason-type jars of standard sizes (e.g., half-pint, pint, and quart) for the tested processes available from science-based sources such as USDA and your land-grant university are recommended. Make sure those jars are manufactured and sold for canning purposes; not all glass and Mason-style jars are tempered to prevent breakage with the extreme heat and temperature swings during canning. When you actually get to canning your harvest, be sure to follow manufacturers’ advice for preparing your jars and lids. In addition to standard cooking utensils like cutting boards and bowls, a jar funnel, jar lifter, lid wand, headspace tool, and bubble-freer are items that you will want to have handy for canning.

If you are freezing your harvest, be sure to use packaging such as plastic bags or rigid containers that are intended for freezer storage of foods.  Not all plastics are the same, and you want materials that will hold up to freezer temperatures as well as protect your goodies from damaging air and mixtures of odors.

Growing your own? You may be lucky enough to have previously started keeping garden records so you remember the name of that great tomato or pepper variety you have liked this past year. If not, think about planning to keep records this year. A garden journal might include variety, seed source, date planted, date harvested, notes on how it grew and resisted disease, and your personal evaluation of the crop.

A final must is reliable, up-to-date canning and other food preservation instructsetp5ions. Specific kitchen equipment or ingredients could be needed to follow directions as they are written for food preservation. And in the case of canning especially, very significant food safety risks by following unsound recommendations. Reliable, up-to-date canning instructions are available at the NCHFP website, the USDA Complete Guide to Home Canning, So Easy to Preserve, or the county or local area Extension office in your state.

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This entry contains information from Keep A Garden Record Book—Thomas Jefferson Did by Wayne McLaurin.