Is there a way to safely can pesto sauce?

I've never seen canned pesto, nor do I know if there is a way to do it safely. I will propose an alternate solution. Have you thought about freezing it? I've had pesto given to me as a gift before, but it was made as normal then frozen in a canning jar. It worked great.

Did some more digging and eventually came across this, from the National Center for Home Food Preservation. In summary, the oil and herb mixture is too low of an acid to prevent development of nasty bacteria.

See similar questions regarding storing/canning stuff in oil for more about why it might be dangerous: - Garlic Infused Oil - Peppers and Oil

I've never canned pesto, but I always make a big batch and freeze it when the threat of the first frost comes:

1. Make pesto, but leave out any cheese
2. Freeze ice cube trays or other small containers**, with a sheet of waxed paper pressed on top (to prevent signficant oxidation)
3. After 2-3 days, release from the container, and put into a zip-top bag, squeeze out the air, and keep in your freezer.

When it comes time to use, take a portion out, and either defrost in the microwave, or toss it in the hot pan after draining the pasta, then stir in the hot pasta to melt it (turn heat to low if you've still got major frozen bits), and stir in your cheese.

** Beware of plastic ice cube trays, as you can easily stain them and leave a lingering garlic flavor. I keep two trays that I use for freezing pesto & stocks, but when I do large batches at the end of the season, I use muffin pans.

As an alternative ... you might be able to can basil oil, where you blanch the basil, then simmer it in olive oil, and strain it before putting up. (I keep mine in the fridge; I've never tried canning it). You can then use it in various dishes, including pesto (using flt leaf parsley for the green, which you can get more easily in the winter). Don't try to make a garlic-basil oil, or you'll have those same botulism risks.

I think it is mainly the bacteria Clostridium botulinum that you need to watch out for, since it can come from many vegetables and can develop toxins in an anaerobic environment (e.g. in olive oil). It is also not visible and does not alter the taste of the food, and the toxin is one of the most potent natural toxins, so not a bacteria to do any trial and error with. Look for ways of inactivating the spores or lowering pH or adding salt to hinder the growth. I guess that's what the food industry does with their canned pesto. UHT treatment or anything like that.

I can see several ways to can pesto depending on your comfort level.

1) Can it in balsamic vinegar in a water bath as a thick paste pesto base (there are tiny 1/4 pint jars or use 1/2 pints). Then attach a small bottle of gourmet olive oil and a wedge of parmesan with instructions to mix their own.

2) I personally think that parmesan is dry enough to be pressure canned along with the basil mix because I've done it in homemade pasta sauce, but canning dairy is not recommended by the "experts." Then your gift would be shelf stable.

3) I would also trust adding the parmesan to the vinegar mix with the basil in a water bath because botulism can't survive pure vinegar. Then attach that to the oil bottle (maybe put some in a shot bottle with a fancy label, tie it up with ribbon & instructions).

4) Pre-made pesto -- Some preppers have successfully canned oils and butter (again against advice) and managed it, so a full pre-made pesto is conceivably possible. (Search the Prepper websites)

...BUT in my experience anything I've canned that has a high fat or oil content, like meats, has a certain percentage of seal-integrity risk if the oil was to get under the seal and loosen it. Because that type of seal breach would not be caused by microbial growth inside the product, I do it anyways, but keep the product upstairs to supervise so if a seal loosens I can use it - not tried and true like you'd want to give guests.

... A late reply to the question, but worth exploring. Good luck all! :)

I've long wondered this, too, and your question prompted me to do some digging. This article at eHow seems to indicate that you CAN indeed pressure-can pesto if you leave out the olive oil in the recipe, and then add the oil in when you cook with it:

http://www.ehow.com/how_8323914_can-pesto-sauce.html

I also ran across a random comment in another thread by someone who claims to have been using a regular pressure-canning process for his pesto (including the olive oil) "for years" now with no issues. I think the eHow article and process is interesting. I'm not sure why leaving out the olive oil would be critical, but it's an interesting note.

I use walnuts in my pesto, usually in combination with some pine nuts or cashews, mainly because of the cost of pine nuts ($20 per pound in my neck of the woods) b but I do like the rich taste of the walnuts and cashews combined. Having said this, I have successful canned pesto in a pressure canner with no ill effects -- except garlic breath. This could possibly be due to the acidity of the walnuts. Whenever I'm in doubt when canning, I add about a 1/4 tsp of lemon juice per pint of what ever I'm putting up at the time i.e. applesauce, pesto, bean soup, etc. Works for me. :0)

I would also like to can some pesto - thinking maybe blend basil with a little water, then pressure can and add oil, cheese, and nuts when you open the jar?

I think that commercial producers must dehydrate the basil first. By eliminating the water before you mix it with oil you would eliminate the risk of mold growth. Then they can use the oil as a preservative. No oxygen permeates the oil to reach the basil after pressure canning it. Once you open it of course you would expose it to air and it would have to be refrigerated. I make herbal infused oil and this it the rule of thumb I follow: dry herbs for oils, fresh for alcohol. There is no spoilage ever. I think I will freeze some and dehydrate the rest to make it the same way I would make an infusion.. with garlic, pine nuts, and Parmesan!