How Long Does It Keep?Canned vegetables and meat: 1 year under proper storage conditions
*Welcome to our series of Wisline programs on home food preservation. Today we will talk about the basics of canning vegetables safely. Canning vegetables is not only fun to do, but what could be more delicious than winter-time meals prepared with vegetables preserved from your summer garden. Add home-canned meat to those vegetables, and you have a hearty stew prepared from items on your pantry shelf.
Before we get started, lets see who is joining us today. (Roll call)
Thanks to everyone for joining us today. Lets get started.
*Many of the points in todays discussion come from our UWEX publication:B1159 Canning Vegetables Safely
Another good resource is B2593 Using and Caring for a Pressure Canner. Both of these resources are available online: http://cecommerce.uwex.edu/
*It wont be long before gardeners will be harvesting a bounty of green peas, carrots and corn. And fresh green peas are already a part of many family dinners.
Canning low-acid foods like meat, wild game, fish, poultry and vegetables requires special care. Low-acid foods can support the production of the deadly botulism toxin if these foods are not properly processed in a pressure canner. A pressure canner heats food to high temperatures, 240 to 250F or higher, and destroys the spores that produce botulism toxin. A boiling water canner such as might be used for canning pickles or fruit heats food only to 212F, not high enough to ensure safety while maintaining quality.
*The spores of the bacterium Clostridium botulinum are naturally present in the environment, and notably in soil. These spores are very heat resistant and will survive boiling in water for hours. Under conditions of low acid, no air, and warm temperatures, the spores of C. botulinum can germinate (sort of like seeds growing), and as they germinate they produce the deadly botulism toxin. This toxin is one of the most deadly poisons known; even a small amount can kill a human. So, when we can low acid foods like vegetables and meats, we must destroy botulinum spores so that they do not germinate in the jar and produce the poison.
*Remember back to FAT TOM and the relationship between time and temperature? In water bath canning, jars are heated in boiling water at 212F and held in the boiling water for enough time to ensure a seal and destroy some microorganisms. But the spores of Clostridium botulinum are very heat resistant and would not be destroyed unless food was boiled for a long period of time. So, we use high pressure to create higher temperatures. With higher temperatures we can heat process for a relatively short period of time and still destroy the deadly botulinum spores. The result is a product that is safe, but still of high quality.
In pressure canning, water is heated in the canner and turns to steam at 212. In a closed vessel like a sealed canner, the steam will eventually create pressure. This increased pressure forces water to boil at a higher temperature, i.e. 240F - 250F, and destroys heat-tolerant microbes.
PV=nRT*Let me take a minute to ask is there are any questions that you have at this point.*It is very important that you carefully follow instructions for pressure canning. At least once each season check dial gauges for calibration; at each canning session take a moment to check vest ports and gaskets. Use standard home canning jars that are free of chips and cracks. Do not use mayonnaise jars or other commercial jars for pressure canning; these jars may be acceptable for water bath canning if they will accept a standard 2-piece lid.Preheat jars and pre-treat lids. Jars can be filled by the Hot Pack or the Raw Pack method. Regardless, jars need to be preheated to avoid thermal stress on the jars as they are filled with hot liquid.Follow research-tested recipes exactly for jar size, type of pack (hot or raw), whether jars are to be loosely or tightly filled, etc. Failure to follow directions exactly may result in canning an unsafe product. *Jars can be hot-packed or raw-packed, depending on what the recipe calls for; sometimes there is a choice. For instance, green beans can be hot or raw packed. The differences in the 2 recipes are highlighted.Here are some things to note:Raw Pack means that the food is placed in the jars without prior cooking, but the liquid added to the jars still must be hot/boiling. When researchers establish safe canning processes, the heat of the food/liquid in the jar is part of the thermal process. Hot Pack means that the food is heated in liquid prior to being packed into jars. The advantage of the hot pack method is that you can pack more food into a given jar since some of the air is expelled from the product on heating. When canning meat, the quality if often superior with hot pack. In this case, the processing time is the same for hot and raw pack. In each case, leave the appropriate head space. Head space is the space between the top of the jar rim and the level of liquid/food in the jar. Removing air bubbles, along with wiping jar rims, helps to ensure a good seal. The flat lids must be pre-treated according to the manufacturers instructions. Adjust lids so that they are FINGER TIGHT. Do not fully tighten the lids, as the air in the jars needs to escape during process so that a vacuum can form.Both time and pressure are specified for each process.
*When you are ready to process vegetables or meat in a pressure canner, start by placing 2-3 inches of simmering water in the bottom of the canner. Make sure the canner has a rack in the bottom so that jars can rest above the bottom of the canner. A very few recipes call for more than 2-3 inches of water in the canner, so be sure to follow recipe instructions exactly.
Set filled jars on a rack in the canner so steam can flow freely around each jar.
Fill the canner with the appropriate size jar (most often pints and quarts). A double layer of jars may be used as long as there is a rack placed between the layers; rest the upper layer of jars on the rims of the bottom layer, not on the lids. You can mix pints and quarts if the processing time is the same. If the time is not the same, then the contents of the jars with the shorter processing time will be over-processed, but safe to consume.
Fasten the canner lid in place and heat over high heat. The canner MUST be vented for 10 minutes to drive air from the canner. This is often a problem for novice canners- they are frustrated because it takes for ever for their canner to pressurize but this is because they have forgotten to vent the canner. Be sure to select the appropriate canning pressure based on the elevation where you live. Water will boil at different temperatures based on elevation above sea level. At higher elevations, the atmospheric pressure is lower and the temperature at which water boils is lower; so here pressure must be higher to produce the needed high temperatures for canning. Start timing the venting process once a steady stream of steam is seen exiting from the vent port. After steam flows for 10 minutes, close the petcock or place the pressure regulator on the vent pipe and let the pressure r