Canning sun-dried tomatoes

If I were to oven-dry my tomatoes and pack them in olive oil, would I need to heat-process them? I've asked a couple of local canning experts, including a county extension agent, and no one's had anything more than a shrug of the shoulders to offer. What does the collective wisdom here say? Thank you!



Clipscoupons365 August 20, 2012
I have had great luck with canning slow roasted tomatoes. I simply slice thin, put on a cookie sheet, drizzle with a good balsamic vinegar, and roast at 200' for a few hours. Then I can in small jars, and since they have a decent amount of moisture they don't need extra oil or water. I process them for 20 minutes in a hot water bath and they turn out great. They last a long time and since I use the small jars, I use one jar per recipe, so I don't have them open in the fridge for long. Good luck!
boulangere August 11, 2011
Thank you very much for your thorough explanation, Eugenia!
susan G. August 11, 2011
nomnivorous brings up slow-roasted tomatoes. They are different from sun dried tomatoes. At least in my experience, you might call them semi-dried, since they still have a good bit of moisture in them, maybe a 50% reduction. Delicious, but I have learned from sad experience that frozen is the way to go, unless you eat them up quickly (and that's not hard to do).
Droplet August 11, 2011
Thank you for a knowledgeable input, Mrs Bone.
Eugenia B. August 11, 2011
Preserving in oil is really a bit of a misnomer: oil acts as a shield between your food and the billions of little spores that are floating around in the atmosphere. But if there are any spoilers hiding in the food beneath the oil, then they may bloom at room temperature and spoil your food. If you don't want to take any chances of your food fermenting (you don't have to worry about botulism--tomatoes are generally too acidic for the bacterium to grow although that is not always the case: some cultivars are not acidic enough, and growing and handling conditions can affect the pH of tomatoes), you must refrigerate dried tomatoes packed in oil. (And they will last quite a long time that way.) If your tomatoes are properly dried--they should be leathery and need to be conditioned (packed in a baggie or jar and shaken once in a while for a few days which equalizes the moisture throughout), then they will be shelf stable, as per SKK. It is a good idea to dunk the tomatoes in a citric acid solution prior to drying as well--it helps maintain the color of the tomato and discourage the viability of a range of microorganisms. Sun-dried tomatoes are notoriously tricky: they are exposed to all kinds of microorganisms in the outdoor environment, and those critters can settle onto the tomatoes (even if you use a screen and all that) before the tomatoes have finished drying. Likewise, I find it hard to properly dry tomatoes in the oven. The temperature has to be very low, air needs to circulate, and they can take a hellava long time. Definitely, for drying tomatoes, mushrooms, and fruits, a dehydrator is the way to go. Water bath processing foods that have more than 2 tablespoons of oil per pint is problematic: there are no USDA guidelines for us to follow (unless you are talking about foods that are significantly acidified to compensate for the alkalinity of the oil). Theoretically, it should be doable, but, bummer, the science just hasn't been done yet.
SKK August 7, 2011
I have an Excalibur dehydrator and every year dry about 60 pounds of tomatoes at 105F. Then I simply put them in glass containers and on my shelf. They last forever and do not have to be frozen. My nephew the Chef prefers to prefers to vacuum seal his. And when we do a taste comparison both processes work.
Emily H. August 7, 2011
Aah, be careful about this. Preserving sun dried tomatoes usually just involves freezing. My go-to canning expert, Marisa at FoodInJars, has posted about slow-roasted tomatoes twice and both times only recommends freezing them.
boulangere August 7, 2011
Thank you both! This helps tremendously.
Droplet August 7, 2011
In general olive oil does act as a preservative.The jars would need to be tigthly closed to prevent oxidation, and I would say the tomatoes would need to be on the drier side of semi-dried (whatever that means in percentage terms). If you are drying them in the oven as opposed to sun drying, I would think you would have less potential trouble makers to introduce into the oil, and might be able to do it without a water bath. You could also put a drop (only) of essential oil of rosemary (food grade) in each jar; it is a natural preservative and goes well here as s classic combination.
boulangere August 7, 2011
Thank you so much! That's an abundance of very helpful information. Why? Because here, at least, they're dreadfully expensive to buy, and I'm hoping they'll make beautiful Christmas gifts.
SKK August 7, 2011
This recipe says water bath for 20 minutes. The link won't copy, but I included it and cut and pasted the recipe.


Sun-dried tomatoes
Olive oil to cover
1 Tbs. Capers per jar
1 Tbs. Garlic chopped fine per jar
1 Tbs. Parsley or any other fresh herb (s) minced per jar

Fill sterilized Mason jar with sun-dried tomatoes, capers, garlic and chopped herbs. Cover with Olive Oil. Cover with a sterilized lid and screw band. Set on a counter for two weeks.

Use as an appetizer; add to homemade pizza or garlic bread, or use in any recipe that calls for sun-dried tomatoes.

(Note: recipe makes as many jars as you have sun-dried tomatoes because you simply add 1 Tbs. each of the other ingredients and then cover completely with olive oil.)

NOTE: Unless you are making more than a jar or two, you don’t have to process this. For large batches, I would process these in a water bath canner for 20 minutes.

Now you have me curious as why can sun-dried tomatoes?
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