Can I Can in a Multi-Cooker?

cartoon cookerYou may have seen advertisements for electric multi-cooker appliances now containing “canning” or “steam canning” buttons on their front panels. Before you make a purchase, we want you to be aware that we do not recommend our canning processes for use in electric multi-cookers at this time.  We do not know if proper thermal process development work has been done in order to support the canning advice that is distributed with these multi-cooker appliances. The way the USDA, National Center for Home Food Preservation and University of Georgia process development work has been done would not yield results expected to be transferable to these electric cookers.

Our process directions for low-acid foods, for example, were developed for stovetop pressure canners which hold four or more quart-size jars standing upright. Even if there are referrals to the National Center for HFP in the instructions for canning in the manufacturer’s directions, we do not currently support the use of the USDA canning processes in electric, multi-cooker appliances. If you are canning low-acid foods and the proper amount of heat is not delivered to all parts of the food in the jars during the process, then the risk is botulism food poisoning in under-processed foods.cartoon pressure canner

Some of the major reasons we cannot recommend using electric multi-cookers for canning:

  1. No USDA thermal process work has been done with jars inside an electric pressure cooker of any kind. Thermal process canning work relates the temperatures in the jars to the temperature inside the canner throughout the processing. It is not the temperature or pressure in just the canner that matters, but ultimately the temperature and heat distribution inside the jars is most important for the destruction of microorganism in the food product. The position of jars in the canner and flow of steam around them also impacts the temperature in the jars.  For example, there would be expected differences in jars piled together on their sides from those standing upright.
  2. What matters is temperature, not pressure.  Even if a manufacturer says its cooker reaches the pressure required for canning, that does not prove the food in the jars is heated throughout at the same rate as in the canner used for process development.  What is important is what temperature relates to the pressure reached in that cooker, and what the temperatures are throughout the whole canner environment.  And does the temperature stay at the minimum required the whole process time? If air is mixed in the steam, the temperature is lower than the same pressure of pure steam. (That’s why a proper venting process is so important in pressure canning – to obtain as pure a steam environment inside the canner as possible.) How does the user adjust for altitude changes if the cooker is set to reach only one pressure? If the pressure actually obtained reaches a desired temperature, can the user actually verify the pressure reaches the stated description and stays there throughout the continuous process time? We do not know of ways in which these questions have been answered.  (And unfortunately we do not have a budget to be able to buy and use all of the versions in the marketplace.  We have been able to read some user manuals that do not answer these questions, however.)
  3. In order to ensure the safety of the final product, the temperature in the canner must stay at minimum throughout the process time, so do power surges or drops with an electric canner cause the temperature to drop too low?  How will you know if that happens?
  4. USDA process times rely on food continuing to remain at a high temperature during the time a pressure canner naturally cools down to 0 pounds pressure. If anything is done to shorten the cooling period, including using a very small cooker, then the food could cool down more quickly, and be under-processed.  (That is why we recommend using only pressure cookers that hold four or more quart-size jars.) Bacteria are not killed in the food only during the process time; the time it takes the canner to come up to pressure, the process time, and the cool-down time all matter.

Please note: This statement about electric cookers does NOT include the Ball Automatic Home Canner for acid foods only, which is electric, but (1) is not a “multi-cooker”, but a dedicated canner, (2) comes with its own instructions and pre-set canning options for specific food preparations, and (3) has had thermal process development done specific to that canner to support the recommendations with it.

For more information about canning in pressure cookers, please read “Burning Issue: Canning in Pressure Cookers”: http://nchfp.uga.edu/publications/nchfp/factsheets/pressurecookers.html

Going Nutty Over Advice for Preserving Nutmeats?

Various Nuts

This time of year, you might be eager to find the best way to make your bounty of pecans, almonds, chestnuts, walnuts or peanuts last through the holiday season and beyond. While canning is a go-to for preserving, let’s not forget that some foods don’t fare so well as a canned product. USDA has never had a home canning recommendation for canning a pack of only nut meats, and the NCHFP website only has a recommendation for canning green peanuts from past work at the University of Georgia.

A previously (and no longer) recommended canning process for “canning” dry nutmeats found in So Easy to Preserve from the University of Georgia is no longer included in the new edition of the book. It was actually just a way to create a vacuum-sealed jar and there was no documentation for any microbial sterilization that might have been taking place. Questions about the risk (even if a low risk) of some bacterial growth if condensation of moisture occurred inside the jars from canning in boiling water led to re-consideration of this advice for sealing jars. Compared to when this was first published years ago, now there are other ways to vacuum pack dry, shelled nut meats at home without heating in boiling water.

Nuts in a jarNuts tend to store very well by proper drying and storing in air-tight containers in a cool location. Refrigerated (at 32-45°F) nuts will maintain quality for one year and frozen (at 0°F) nuts will maintain quality for 1, 2, or even 3 years depending on the type of nut. See this publication from the University of California for more specific information about harvesting and storing different types of nuts.

While we know of no tested recommendations for canning pecan pie filling, another common request, you can easily make your pecan pies as usual, cool rapidly, and then freeze briefly before packaging for long term freezer storage (pies will be easier to wrap after freezing). Stored at 0°F, frozen pecan pies are expected to last 3-4 months.

Conserves are a delicious way to use up smaller quantities of nuts. By definition, conserves are jam-like products that contain nuts, raisins, and/or coconut. These conserve recipes allow you to choose your preferred nut type: Apple Conserve, Apricot-Orange Conserve, Cranberry Conserve, Damson Plum- Orange Conserve, Grape Conserve, and Plum Conserve.

walnut pieces backgroundAre you wondering why it’s ok to can nuts in conserves but not by themselves? The recommendation we withdrew was just one procedure for canning a jar of all nutmeats in a dry pack. There is nothing wrong with canning foods with nuts in them, if tested that way. Other recommendations (like conserves) were developed with a called for amount of nuts along with other ingredients which influence the characteristics of the final product. ApplesLet’s consider Apple Conserve, for example: Apples are an acid food and the lemon juice is a strong acid; if other ingredient proportions are kept as expected, the final product should remain acid enough for boiling water canning. Furthermore, in this conserve, the pectin and sugar combine with this acid and fruit to make a gel, which reduces the water activity of the final product. These characteristics make a difference in what the process recommendation should be, and were taken into consideration for that recipe when a canning process was determined.

A Particular Pear to Bear in Mind

pears

Anjou, Asian, Bartlett, Bosc, Concorde…all these types of pear and more are typically available across the U.S. from August through early springtime, thanks largely to orchards in Oregon and Washington. As those pomaceous fruits begin ripening in your home kitchen, you might be tempted to preserve some for later. But did you know that not all pears are created equal, and that there’s a particular type of pear to be aware of before canning?

We’re talking about those pears that are sometimes mistaken for apples – those petite, round, crisp Asian pears.

Asian pearAsian pears are generally slightly smaller and rounder than other varieties, and are distinctly crisp in texture. There are more than ten varieties of Asian pear and some are classified as low-acid for canning purposes. So, before boiling water canning, Asian pears must have a strong acid (e.g. lemon juice) added to them in order to increase the acidity enough to prevent the growth of botulism-causing bacteria. The exact amount recommended is 1 Tablespoon bottled lemon juice per pint jar (2 Tablespoons per quart). Complete canning recommendations for Asian Pears, Halved or Sliced also include soaking pears in an ascorbic acid solution to prevent discoloration and preparing a covering liquid of a syrup, juice, or water. (Aside from the addition of bottled lemon juice, the recommendation is very similar to canning Pears, halved.)

pears, halvedYou could also wash, peel, core, and cut into ½-inch slices then dry until pliable, but not sticky. If you fold a piece in half, it should not stick to itself.

Due to the relatively large amount of vinegar in the recipes, it’s fine to use Asian Pears in Pear Pickles and Pear Relish or even this unique recipe for Chayote and Pear Relish. Also, Pear-Apple Jam has enough bottled lemon juice that you could use Asian pears if you are willing to try a jam that may have a bit of a crunch to it.

However, Asian pears are NOT recommended for use in Pear Preserves. In addition to the potential for a safety concern due to pH, the crisper fruits might not produce the textural quality you are going for in typical preserves. So stick with one of the thousands of other varieties of pear out there for preserves!

Preserving Potatoes

potatoes

Not known for their fragility, potatoes are a robust, starchy tuber in the nightshade family (along with fellow Solanaceae family members tomatoes, eggplants, and peppers). Potatoes pack a nutritional punch, weighing in with substantial amounts of potassium, fiber, protein, vitamin C, Vitamin B-6, Magnesium, and a lesser but still notable amount of Iron.

It’s easy enough to store fresh white potatoes for up to 2 months in a cupboard kept at 50-70°F (sweet potatoes last only 2-3 weeks). But what if you want them to last even longer?

potato masherInterestingly, storing white potatoes in a refrigerator is likely to diminish their quality and they are expected to last only 1-2 weeks there. Alternatively, you could cook and mash them, stuff them, or scallop them for freezer storage, but again, they will retain best quality only for a few weeks in the freezer.

Drying is an option for making potatoes last longer. Wash, peel, then cut potatoes into 1/4-inch thick shoestring strips, or cut into 1/8-inch thick slices. Steam blanch the prepared pieces for 6-8 minutes or water blanch them for 5-6 minutes. Plan for a drying time of 8-12 hours in a dehydrator and up to twice as long in an oven, depending on circulation. If you dry sweet potatoes and want to rehydrate them for a recipe, combine each cup of dried pieces with 1-1/2 cups water and let them soak for 30 minutes.

As for canning potatoes, our recommendation is to peel potatoes before canning. That style of preparation is how the research was carried out to determine the recommended processing, and in order to know that the peeling does or does not make a difference, research would need to be done with unpeeled potatoes. Different assumptions might be needed in assessing just how many spores of C. botulinum or other bacteria might be present at the start of the process and what amount of heat might be needed to meet standards for the risk of possible survivors. We do not know of research of canning potatoes with peels left on, so we recommend the preparation steps provided with the process recommendation, especially because there is a possibility that the deviation could result in a less safe situation. Also due to safety concerns, it is important to use potatoes that are only 1 to 2 inches in diameter if you are canning them whole.  These are sometimes described as “new” potatoes; the idea is to use less mature, smaller potatoes which tend to be less starchy than older, “grown-up” potatoes.

White potatoes for canning should be the “waxy” or “boiling” kind.  Different types of potatoes have different amounts and types of starches and they react to heating differently.  You want a potato that keeps its shape and texture well after a lot of heating, and not one that falls apart, becomes “fluffy” after cooking, and is better for mashing. Most red-skin potatoes are of lower starch than baking potatoes  and work well for canning. Many white round potatoes with thin skins fall into this category with red-skin potatoes too. Russets are not good for canning but are  good for baking (they have a high starch content).  Yukon Gold may not be the best potatoes for canning.  While they seem good for boiling, they do tend to fall apart when overcooked.  From what we have read, there is a wide variety in the types and amounts of starches in blue potatoes, so not all blues are the same, just like not all white potatoes are the same in these characteristics.

Sweet potatoes can be slightly larger, but medium-sized potatoes should be cut to fit in the jar in uniform-sized pieces. Note that the sweet potato pressure canning process time is significantly longer than for white potatoes.

Sweet potatoes can have a sugar syrup for canning, if you like that style. But otherwise, all potatoes — white or sweet — should have fresh, boiling water prepared to pour over the preheated potatoes.  Do not use the cooking liquid.  That cooking water contains a lot of starch that comes out of the potatoes and the process time was determined using fresh boiling water to cover.  The added starch can create  a safety problem by slowing down heating of the potatoes in the canner, and it also creates a very unappealing pack with possible masses of gelled or congealed starches around the potatoes.  If you have spoilage, this makes it very hard to see the signs of some spoilage.

 

potato cartoon