desertmarcy -

Now your talking in an area of keenest interest to me - solar energy. Would like to know how in the world did you create a solar powered canner?

I've done a bit of playing with solar - like one of those boxes - with opened sides covered with foil to reflect sun's rays back into the box - very simple affair - but good mostly for camping or short term use.

My desert experiences have been limited, however, as we only use our trailer for winter vacations, so cooking solar was a lark at best.

But now in town, nearer the coast - with much foggy weather now - the solar idea is on the back burner (so to speak), but on sunny days have used it for such simple quick things as herbs, garlic, green onions, but it's biggest test will be when tomato drying time comes. It may take awhile, but I think it will work.

I made a simple frame out of 2 window screens, tied together at the back, then a stainless steel (from a fridge) rack placed between them to hold the screens apart so as to insert a tray of veggies or herbs. The whole apparatus is mounted just outside my kitchen window for easy removal. I ordered a clip-on fan to ward off any bugs.

So - am curious about your cooker - would you mind sharing?

Also - about tomatoes - most of us aren't too keen about bottled lemon juice - but the canning books do recommend it as botulism prevention. We've certainly had a lot of comments about it - but you probably need to decide - citric acid - fresh lemon, bottled lemon - I will cede to the experts here.

I would like to think that cooking spaghetti sauce down - would help concentrate acidity, but perhaps not - ??

Just my 2 c's.

Bejay

Bejay, I think more people could use solar cookers if they just knew more about them. There are 2 basic types, box cookers and parabolic cookers. The box cookers don't get as hot and more gently cook food over a longer time, whereas the parabolic types concentrate the sun's rays on a focused point and can get very hot. The box cookers can be easy and inexpensive or more elaborate, limited only by your imagination. I saw one made from an old suitcase. Mine is a box cooker and is not meant to be portable. I have it set up on a stand in the yard. It is a custom design because I used a lot of recycled materials I had laying around. The website www.solarcooking.org has tons of information, including designs, recipes, etc. Check it out! With water boiling at 212 degrees F, if your cooker gets above that, which is easy enough with a box cooker between 10 am and 2 pm, you can see how it can replace your boiling water bath for canning high acid foods. Except you don't need the bath of water--just put your jars in the cooker.

Sadly, here in the PNW, solar cookers are out. I'd definitely be willing to give it a shot. Hmmn, baking bread. Sun jams.

OK, other questions. No, frozen or fresh lemon juice can't be substituted. Bottled lemon juice is a standardized product twice as strong as vinegar. With fresh or frozen the acidity varies depending upon the variety, growing conditions and ripeness when picked.

What you're looking for are citric acid crystals. Of course they can be ordered online, but if you have one of those big multi-purpose grocery/clothing/auto parts/gardening stores near you, you can probably find it in the Health Foods section or maybe the pharmacy. If not, a pharmacy can always order it for you. Just be sure what you get is pure citric acid without any fillers. Even in my small town I was able to find a jar; it just took a bit of searching.

Carol

maybe I'm misunderstanding, but are putting the jars into the solar cooker without being in a waterbath? e.i. it is the equivalent of being in a 230 degree oven? That's not safe. If you can get water to boil in the solar cooker than it is a great idea. I wish solar cookers would get that hot here.

yes, the jars go in without a waterbath. I'm not sure if that makes it the equivalent of a 230 degree oven or not, but the juices in the jar are bubbling. Yes, water will boil in a solar cooker. See this page--it explains the method used http://solarcooking.org/canning1.htm
Basically the jars are placed in the cooker until the juices boil over. You may be surprised how hot a solar cooker will get in NC. As long as you have a cloudless day, your ambient temperature does not have to be high. We can solar cook here in the winter, so surely you can in the summer.

It's not a matter of how hot it gets. Dry heat and moist heat work differently and canning in dry heat is not safe. If water will boil in your solar cooker than put a pot of water in there and can the tomatoes in that.
I don't want to offend, but this really is dangerous.

"Oven-canning is extremely hazardous. When you can food it is important to know and control temperature. With oven-canning the temperature will vary according to accuracy of the oven regulator and how heat circulates. The dry heat penetrates food jars very slowly. Oven-canning can be dangerous regardless of brand of oven, jar, cap or lid you use. Jars may explode, wrecking the oven and seriously cutting or burning someone. Most important, the temperature of the food in the jars during oven-canning is not high enough to destroy dangerous bacteria.

Solar Canning The heat generated from captured sunlight is not a reliable method to process acid foods and should never be used to can low-acid foods. Picture of solar canner"

"Oven Canning Oven-canning is extremely hazardous. The oven canning method involves placing jars in an oven and heating. In oven canning, product temperatures never exceed the boiling point because the jars are not covered. It is, therefore, not safe to use for low-acid products (e.g. meats, most vegetables) which require temperatures higher than 212 F. "

I totally agree, the solar cooking would be the same as oven canning and not considered safe to do.

Add me to the warning. I misunderstood the original comment. I thought you were heating water to boiling over the immersed jars, not just heating the jar contents.

Carol

I did some research after reading the comments about solar canning of acid foods being unsafe. In this era of much-needed energy conservation, I believe the naysayers do the readers of this forum a disservice. The safe use of solar cookers to can acid foods comes from Dr. Bob Metcalf, one of the original founders of Solar Cookers International (SCI), a professor in microbiology at California State University at Sacramento. You can check out his info at http://solarcooking.org/media/broadcast/default.htm?metcalf In addition, Eleanor Shimeall has included a chapter on this subject in her book, Eleanor's Solar Cookbook. Learn more about her at http://www.she-inc.org/art.php?id=50

I don't particularly care for the connotation of "naysayer" as it generally describes someone who habitually takes a negative position regardless of merit.

I think many of us appreciate the importance of energy conservation; the fact that some here may disagree about a particular method or are philosophically different in their approach to food safety hardly makes them mindless "nabobs of negativity."

I do understand the visual test of watching for boiling juice to exude under the seal, though that does weaken the seal itself. A jar may be sealed under those conditions but not with a vacuum of the same strength.

Now with peaches I don't suppose it matters a whole lot. The worst that might happen with a high-acid fruit is perhaps mold or oxidation due to a weaker seal. The same would be true of jams and jellies. Europeans don't even water bath their preserves and they're surviving just fine because the product is inherently low-risk.

Where I differ is with tomatoes, which are not invariably high-acid. There I think the risk is greater. The conditions would have to be just right (or maybe we should say "just wrong") but it can and has happened that people have been sickened. So in that case I prefer to rely upon a water bath or pressure canner.

Carol

I feel insulted by the term "nayslayer", too. I have studied long and hard for my certification in food preservation safety. I understand what I have been taught and why I feel as I do about the safety of it, and it is my opinion it is unsafe. I am entitled to my opinion, just as everyone is.
If you disagree and wish to use that method, then it is your choice. It just seems really unkind to label people with that term just because someone disagrees with you.
We all have to decide what amount of risk we are willing to take.
It is good to have the information available on each side so everyone can make the decison for themselves.

I apologize for the negative terminology. I did not intend to insult, only to point out that the solar method of canning is endorsed by qualified individuals. Happy canning, regardless of your method!

Perhaps I should just let this thread die, but I always concerned about how people assess the information they find on the internet.

desertmarcy, I am curious as to why you believe that Dr. Metcalf is a "qualified" individual? Because he is a professor of microbiology? I can assure you, that is NOT sufficient qualification. And the reason I can assure you of that is that I am also a professor of microbiology and I certainly do NOT know as much about food safety as many of the contributors to this forum, including Linda Lou and Carol. There are many areas of microbiology, food safety is a very specialized field.

I was curious, so I went to the Cal State Sacramento web page and looked up Dr. Metcalf. His page describes his research with solar cooking. Wondering where he received his degree and what his previous research has been, I attempted to view his curriculum vitae - it was an inactive link. I then did a literature search to see if he has published his findings. He has only one peer reviewed publication on solar water purification and that was from 1999 - considered quite a long time ago in scientific research.

On his web page, he states that most of the world believes that water must be boiled for 20 minutes to be safe, but that it can be pasteurized by heating to 65C (149°F). There is an important point here and that is the word pasteurization. It is very different than sterilization. Pasteurization only removes some of the microbes that are present, those that are thought to be most likely to cause illness. It certainly will not remove all microbes.

His research appears to be mostly directed toward finding ways that people in developing countries can make their food safer. It is probably a powerful tool in those situations, people don't have money or resources to cook and prepare food the way we do here. Being able to pasteurize water is a huge accomplishment in those situations.

However, appying those principles in countries that do have the ability to prepare food with more care seems unwise in my opinion. It is a proven fact that water must be boiled for 20 minutes to inactivate bacterial endospores, including those of Clostridium botulinum which causes botulism. The USDA has carried out extensive studies to determine safe methods for home canning of foods. While they may err on the side of excessive safety (I'm not saying they do, only that they may), they have used scientific experiments to support their findings. I understand the concern for diminishing energy resources, but compromising the safety of one's food seems a very high risk to take in order to conserve.

This is, of course, only my opinion and, as stated above everyone has to decide what level of risk is acceptable. I did however wish to point out that one must evaluate information from the internet very carefully and know what the qualifications are of the person providing the information. Perhaps you know more about Dr. Metcalf than I could find.

Sorry this is so long.

Wow, prairie_love. I didn't get nearly that far. I quit when I read:

>>Screw lids onto the jars as tightly as you can

How many of us have made that mistake? It sounds like a little thing, but it tells me that the person who wrote those instructions didn't know anything about canning.

I would definitely be interested in solar cookers for other uses. Or for heating my BWB canner. If the sun can keep that sucker boiling, then I don't have to heat up my kitchen!

Julie