So this will be my first blog entry concerning pressure canned foods. Let's get the rules and regs out and dealt with first, then I'll tell you what I did.
First off, if it's a low acid food, it has to be pressure canned. No ifs ands or buts, I really don't want to hear otherwise honestly. My decisions are based on real science, not the canning snobs and canning cops. Simply put if a food doesn't have an acid level of 4.6 or lower or a sugar content of 60%, it's just NOT safe to can it in a water bath due to all kinds of bacteria and molds, namely botulism. Botulism kills. Botulism takes a temperature of 240 degrees Fahrenheit or higher to kill it off (or high acid or high sugar content). Boiling water will NEVER reach more than 212 degrees unless it's under some sort of pressure, and unless you live in the lowest part of the ocean or a few miles under ground you need a pressure canner. I kinda like living so I'll er on the side of caution and stick with canning low acid foods (foods with an acidity level above 4.6, and yes I'm just geeky/nerdy enough to have a PH meter) in a pressure canner.
If there are rules/steps set out by the canning authorities I will try to explain them to you, but honesty, you can research them yourself if you still have questions and I don't explain the issue well enough. A lot of it was common sense to those who canned years ago and this info was just not passed down for some reason or other.
Now..... on to those potatoes...... Not sweet potatoes, regular old russets and reds were what I had.
With our first paycheck in 6 months I paid everything I could and saved out enough to buy a very few groceries. Namely everything I could find on sale that we were out of. Potatoes were on that list so I managed to lay my hands on 25 pounds for a decent price. I saved out 5 pounds for fresh and started working on the rest of them. I've been researching the canning of potatoes for a few weeks, I have my Ball Complete book instructions, I have the National Center of Home Food Preservation instructions, I also have large amounts of blog and other anecdotal 'evidence', enough to make me feel comfortable with my canning of the little beasties.
First off, wash off your potatoes really, really good. I usually take one of those green scrubby pads to mine anyway since I really don't like the taste of dirt. Then you have a decision to make, to peel or not to peel. There's a lot of misinformation out there on the subject. Here's my take on it... since botulism lives in dirt and your potatoes grow in dirt, they are potentially infected and since they are not hermetically sealed while growing, the insides have a chance of having it as well as the skins, plus the act of cutting through the peel to remove it will introduce the nasties to the flesh as well. Simply put the skins do not 'cause' botulism and since everything in those jars will be pressure canned to the point where botulism is supposed to die, I'm leaving my skins on! It's just not aesthetically pleasing to some people to see them on. I like whole foods. If you are still leery, peel yours, no problem. Won't offend me in the slightest!
Now we cut them up and dump into acidulated water, yes I think that's misspelled! Cut them into chunks, dice, whatever. If they are smaller than say 2" in diameter you can leave them whole if you want. The water you are putting them in should be cool and have plenty of lemon juice in it. I typically use 1 cup lemon juice to 1 gallon of water, this helps prevent browning and it will start to pull the excess starch out of the potatoes. I then let them sit there a while while I prepare for canning.
Read your canner's instructions, memorize them if you need to. And yes you really need to use a canner for this, not just a pressure cooker. Sometimes pressure cookers just don't hold pressure as well as a canner will and can give a false sense of having killed off the stuff that causes spoilage. Canners were made to do this! And if you really want to be sure your canner is operating properly, contact your extension office and they can test it for you. If you have a dial gauge you need to see them every year anyway to be on the safe side to make sure your dial is still working properly.
I'll assume you know the procedure for preparing your jars and lids. What we do next is fish the potatoes out of the soaking water and blanch them for 2 minutes in boiling water, then drain and hot pack them in jars. There's a reason why the instructions say to blanch. If you don't, if you decide to raw pack, you will end up with a bit of excess starch in your jar that will congeal as your potatoes wait on you to pull them out and use them. This can be rinsed right off, it's not going to hurt you or anything, it's just icky looking and scares the crap out of people. Either way you decide you now need to fill the jars with boiling water. Use fresh water for this or you get the congealed mass later. 1" head space please!
Clean off the rims, lid up and load up your canner, which has been patiently waiting on you to hurry up with the whole process and heating up your kitchen. Vent the canner 10 minutes (yes, do this, don't skip, helps equalize the pressure within the jars and food more evenly as the canner is heating up so that you don't have spoilage). Process quarts for 40 minutes, pints for 35. Once time has been reached let the canner come back to no pressure naturally, yes another step to not miss because releasing the pressure too fast can cause jars to explode, lids to leak internal liquids, and other mayhem that can lead to spoilage. Once back to no pressure, let it sit there for a couple minutes so that they can drop temp a little. Then unload onto towels for cooling. Use cotton towels here if you can and double them up. These jars are hot enough to melt plastic and harm counter tops! Yeah, I had a poly blend dish towel that was stuck to the bottom of a jar the first time I used the pressure canner last year. Learned that lesson the hard way!
Now for the questions I know are going to come..... why are they bubbling? Well the contents are out gassing, during the pressure treating of the food air finds its way into things it normally can't and once the pressure is released it has to come out plus the food already has some air in it and the vacuum of the jar just sucks it right out. Think of it like the bends for divers, they have to go through depressurization after a deep dive to keep the dissolved air from bubbling back out into their blood. Those jars basically have the bends ;) They'll bubble for about an hour or so while their temps come down.
Why is there less water in there that before? Couple reasons actually. First is the potatoes absorbed some of it to replace all the air that was hidden in them. Then there's the possibility that you filled the jar with too much liquid, happens to the best of us and as long as the jar seals it's fine.
Once the lids seal and the jars are completely cooled move them to the pantry or other storage. If a lid doesn't seal, toss the jar in the fridge and use as soon as possible.
Now as for my potatoes... 20 pounds or so landed me 19 quarts.
I even cut 2 quarts of those into 'fries' (the 2 in front) based on a little tip I found in the comments section of another canning blog. See here: Canning Granny She has really nice step by step directions with pictures for hers if you need some hand holding to do this!
Now if these start looking off to you, toss them. If you crack open a jar and it smells off, toss them. If the lid pops up or off, toss them. Not worth your life or someone else!