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Food preparation and canning at high altitudes

At altitudes above 3,000 feet, preparation of food may require changes in time, temperature or recipe.

The reason for these changes is the lower atmospheric pressure due to a thinner blanket of air above. At sea level, atmospheric pressure is 14.7 pounds per square inch (psi), at 5,000 feet it’s 12.3 psi, and at 10,000 feet only 10.2 psi — a decrease of about 1/2 pound per 1,000 feet. This decreased pressure affects food preparation in two ways:

• Water and other liquids evaporate faster and boil at lower temperatures.

• Leavening gases in breads and cakes expand more quickly.

Cooking

The temperature at which water boils declines as elevation rises. Because of this, foods prepared by boiling or simmering cook at a lower temperature at high altitude than at sea level, and thus, require a longer cooking time. Meats cooked by simmering or braising may require one-fourth more time at 5,000 feet than at sea level. Oven temperatures, however, are not affected by altitude, so sea-level instructions work for oven-roasted meats. Hard-cooked eggs will also take longer to cook. A “three-minute” egg may take five minutes to cook at 5,000 feet. High altitude areas are also prone to low humidity, which causes the moisture in foods to evaporate more quickly during cooking. Covering foods during cooking will help hold in moisture. At 7,500 feet, water boils at approximately 198 degrees, where at sea-level water boils at 212 degrees.

Freezing

An important step in preparing vegetables for freezing is heating or “blanching” before packing. At 5,000 feet elevation or higher, heat one minute longer than the blanching time given for sea level.

Candy, syrup and jelly 

Both humidity and altitude affect candy making. To prevent excessive water evaporation during the cooking of sugar mixtures at altitude, cook to a “finish” temperature that is lower than that given in sea-level recipes. If you use a candy thermometer, first test the temperature at which your water boils, then reduce the finish temperature by the difference between the temperature of your boiling water and 212 degrees. This is an approximate decrease of two degrees for every increase of 1,000 feet in elevation. You may also use the cold-water test, which is reliable at any altitude. Cook jellies to a finish temperature that is eight degrees above the boiling point of your water.

Deep-fat frying

The lower boiling point of water in foods requires lowering the temperature of the fat to prevent food from over browning on the outside while being under-cooked on the inside. The decrease varies according to the food fried, but a rough guide is to lower the frying temperature about 3 degrees for every increase of 1,000 feet in elevation.

Puddings and cream-pie fillings

Above 5,000 feet, temperatures obtained with a double boiler are not high enough for maximum gelatinization of starch. Therefore, use direct heat rather than a double boiler.

Breads

High altitude has its most pronounced effect on the rising time of bread. At high altitudes, the rising period is shortened. Since the development of a good flavor in bread partially depends on the length of the rising period, it is well to maintain that period. Punching the dough down twice gives time for the flavor to develop.

In addition, flours tend to be drier and thus able to absorb more liquid in high, dry climates. Therefore, less flour may be needed to make the dough the proper consistency.

Cakes with shortening

Most cake recipes perfected for sea level need no modifications up to 3,000 feet. Above that, decreased atmospheric pressure may result in excessive rising, which stretches the cell structure of the cake, making the texture coarse, or breaks the cells, causing the cake to fall. This usually is corrected by decreasing the amount of leavening agent. Increasing the baking temperature 15 to 25 degrees can also help “set” the batter before the cells formed by the leavening gas expand too much.

Excessive evaporation of water at high altitude leads to high concentration of sugar, which weakens the cell structure. Therefore, decrease sugar in the recipe and increase liquid. Only repeated experiments with each recipe can give the most successful proportions to use. As a guideline, adjust your cake recipe in the following ways when over 7,000 feet:

• Reduce baking powder for each teaspoon by 1/4 teaspoon.

• Reduce sugar for each cup by 1-3 tablespoons

• Increase liquid for each cup by 3-4 tablespoons

In making rich cakes at high altitudes, you might have to reduce shortening by 1 or 2 tablespoons. Fat, like sugar, weakens the cell structure. Also, increasing the amount of egg strengthens the cell structure and may prevent the too-rich cake from falling.

Angel food, sponge cakes

The leavening gas for these is largely air. Do not beat too much air into the eggs. Beat egg whites only until they form peaks that fall over — not stiff and dry, which will cause collapse of cells. Strengthen cell structure by using less sugar and more flour, and a higher baking temperature.

Cake mixes

Adjustments usually take the form of strengthening the cell walls of the cake by adding all-purpose flour and liquid. Suggestions for high-altitude adjustments are provided on most cake mix boxes.

Cookies

Although many sea-level cookie recipes yield acceptable results at high altitudes, they often can be improved by a slight increase in baking temperature, a slight decrease in baking powder or soda, a slight decrease in fat or sugar, and/or a slight increase in liquid ingredients. Many cookie recipes contain a higher proportion of sugar and fat than necessary, even at low altitudes.

Biscuits, muffins, quick breads

Quick breads vary from muffin-like to cake-like in cell structure. Although the cell structure of biscuits and muffin-type quick breads is firm enough to withstand the increased internal pressure at high altitudes without adjustment, a bitter or alkaline flavor may result from inadequate neutralization of baking soda or powder. When this occurs, reducing the baking soda or powder slightly will usually improve results.

Quick breads with a cake-like texture are more delicately balanced and usually can be improved at high altitudes by following the adjustment recommendations given for cakes.

Pie crusts

Although not generally affected by altitude, slightly more liquid may improve results.

Practical baking notes:

• Use any brand of enriched all-purpose or cake flour.

• Do not assume that your sea-level recipe will fail. Try it first. It may need little or no modification.

Canning vegetables

Vegetables are low in acid and must be processed in a steam pressure canner at the number of pounds needed to achieve 240 degrees. The pressure required at sea level is 10 pounds. For higher elevations, add 1/2 pound of pressure for each 1,000 feet above sea level. For example, at 7,000 feet, 13.5 pounds of pressure is required to reach 240 degrees. This is necessary to supply enough heat to destroy bacteria that cause botulism. Do not take short cuts in recommended preparation or processing procedures. Failure to properly process low-acid foods in a pressure canner can result in botulism, which, if not treated, can be fatal.

Make sure your pressure canner has a tight-fitting cover, a clean exhaust vent (or petcock) and safety valve, and an accurate pressure gauge. There are two types of pressure gauges: weighted and dial gauges. Weighted gauges need only to be cleaned before using. Dial gauges need to be checked for accuracy. Check them each season before use, more frequently if used often. The CSU Extension-Archuleta County office will begin offering pressure canner gauge checks next year.

Use a pressure canner that holds at least four quart jars. Smaller pressure canner-saucepans are not recommended for home canning as they heat up and cool down too quickly to ensure adequate heat penetration using the processing schedules specified in this fact sheet.

Discard any jars and closures with cracks, chips, dents or rust. Defects prevent airtight seals. Use jars designed specifically for home canning. Commercial food jars (mayonnaise, coffee, etc.) break easily in pressure canners and may not seal. Use only the half-pint, pint and quart sizes. Wash jars in hot, soapy water and rinse well before using. Prepare metal lids as manufacturer directs.

Select only fresh, young, tender vegetables for canning. The sooner you can get then from the garden to the jar, the better! For ease of packing and even cooking, sort the vegetables for size and ripeness. Wash all vegetables thoroughly, whether or not they will be pared. Dirt contains some of the bacteria hardest to kill. Don’t let vegetables soak; they may lose flavor and nutrients. Handle them gently to avoid bruising.

The hot-pack method is recommended for all low-acid foods, including vegetables. Some vegetables may also be packed raw.

Put cold, raw vegetables into jars and cover with boiling water. Pack most raw vegetables (except for starchy ones) firmly into the jars. Loosely pack starchy vegetables such as corn, peas and lima beans, because they expand during processing.

If you are packing cooked vegetables, always heat vegetables in water or steam before packing. Then cover with the boiling cooking liquid or water. Loosely pack the hot food.

Use enough liquid to fill around and cover the food. Read the directions for each vegetable for the amount of space to leave between the top of the food and the top of the jar. This headspace is important to obtain a good seal.

Salt may be added to each jar, if desired. Salt is added only for seasoning and does not help preserve the food. If salt is used, canning salt is recommended to prevent the liquid from turning cloudy. Use 1/2 teaspoon salt per pint.

To remove any trapped air bubbles, insert a nonmetallic spatula between the food and the jar. Slowly turn the jar and move the spatula up and down to allow air bubbles to escape. Add more liquid if necessary to obtain the proper headspace. Wipe the jar rim with a clean, damp paper towel to remove any food particles. Place pretreated lid on the jar. Screw on the band fingertip tight.

Read the manufacturer’s instructions for your pressure canner. General directions for using steam pressure canners are as follows:

• Put two to three inches of hot water in the canner. Place filled jars on the rack, using a jar lifter. Fasten canner lid securely. Leave weight off vent port or open petcock.

• Maintain a high heat setting, exhaust steam in 10 minutes. Place weight on vent port or close petcock. The canner will pressurize in the next three to five minutes.

• Start timing the process when the pressure reading on the dial gauge indicates that the recommended pressure for your altitude has been reached, or when the weighted gauge begins to jiggle or rock. Regulate heat under the canner to maintain a steady pressure at or slightly above the correct gauge pressure. Quick and large pressure variations during processing may cause unnecessary liquid losses from jars. Weighted gauges should jiggle or rock slowly throughout the process.

• When the timed process is completed, turn off the heat, remove the canner from the heat if possible, and let the canner depressurize. Do not force-cool the canner by pouring cold water over it. When the pressure registers zero, wait a minute or two, then slowly open the petcock or remove weighted gauge. Unfasten the cover and tilt the far side up so steam can escape away from you.

• Carefully remove jars from canner and place on rack, dry towels or newspapers. Allow jars to cool untouched, away from drafts, for 12 to 24 hours before testing seals.

The day after canning, be sure to test the seals on the jar lids. Press flat metal lids at the center of the lid. Lids should be slightly concave and should not move. Remove screw bands. Label sealed jars with contents, canning method and date. Store canned goods in a clean, cool, dry, dark place.

Treat unsealed jars of food as fresh. The food can be eaten immediately, refrigerated, frozen or reprocessed. If you reprocess the food, repeat the entire process.

Bulging lids or leaking jars are signs of spoilage. When you open the jar, look for other signs, such as spurting liquid, an off odor or mold.

Low-acid canned vegetables and meats can contain botulism toxin without showing signs of spoilage. As a safety precaution, before tasting, boil all home-canned vegetables in a saucepan for 10 minutes, plus one minute for each 1,000 feet above sea level (15 minutes at 5,000 feet). Boil home-canned spinach or corn for 20 minutes. If the food looks spoiled, foams or has an off odor during heating, discard it.

Dispose of all spoiled home-canned food where it will not be eaten by people or pets. Boil all spoiled low-acid canned food for 30 minutes before disposing of it. This destroys any toxin present and prevents its spread.

Information provided by: Dr. P. Kendall, Colorado State University Extension Specialist and Professor, Food Science and Human Nutrition. 

Calendar

Oct. 2 — Colorado Kids 4-H Club meeting, 6:30 p.m.

Oct. 4 — Shady Pine 4-H Club meeting, 6:30 p.m.

Learn more about our upcoming events on our webpage at www.archuleta.colostate.edu.

This story was posted on September 26, 2012.