Drying Tomatoes

Dried tomatoes are very expensive to buy in stores.

They are very easy to make at home, and if you make them in season when the markets are paying people to take tomatoes away, very inexpensive as well.

See also: Canning tomatoes

Yields and Equivalents

20 lbs tomatoes (9 kg) = 18 oz dried tomato slices (510 g)

Directions

Here we compare directions from three different sources.

Note that two sources say peel first; a third source gives peeling as optional. This is not a safety question, but rather one of preference: when rehydrated, pieces of tomato peel may detach off and float around in whatever dish you are making.

(Note that tomato peel can be dried on its own to be ground into tomato powder, so there is no waste.)

Also note that none of the sources have you seeding the tomatoes.

Ball Blue Book

Preparation:  “Wash, dip in boiling water, 30 to 60 seconds, transfer to cold water. Core, and peel. Cut into slices ¼ inch (½ cm) thick.”

Blanching: None

Temperature: 145 F / 62 C

Time: Until crisp.

Notes: “Choose paste-type varieties.”

Water content: 94%. (Used if doing a Dehydration Weight Test.)

Reference: Ball Blue Book, 37th edition, 2014. Page 167.

Note: In the Ball All New, they suggest slicing or dicing. The suggested drying temperature is 125 F / 52 C.

Excalibur

Preparation:  “Wash tomatoes, dip in boiling water, then in cold water, then slip the skins off. Cut into ¼ inch (½ cm) slices; cut cherry tomatoes in half.”

Blanching: None.

Temperature: 155 F / 68 C

Time: “Until leathery or brittle.” Time estimate is 5 to 9 hours, depending on humidity in your area.

Notes: “High acid, full-flavoured tomatoes like San Marzano and Royal Chico are best for drying; low acid ones will turn black when dehydrated. Use only dark red tomatoes with meaty walls.”

“Low-acid tomatoes: puree them, adding 1 tablespoon lemon juice or vinegar to each quart / litre of pulp. Line trays with parchment, spread out on trays and dry as a leather. This can be powdered and used to make tomato paste or sauce.”

Quality: Good

Reference: Excalibur. Preserve it naturally. 4th edition, 2012. Page 26 and 59.

So Easy To Preserve

Preparation:

As slices: “Wash, trim our core and cut cross-wise into ¼ to ⅜ inch (½ to ¾ cm) slices. No peeling or blanching is necessary. Slices may be lightly sprinkled with crumbled dry oregano or other dry herb of your choice prior to drying.”

As chunks for stewing: “Steam or dip in boiling water to loosen skins. Chill in cold water, peel. Cut into sections ¾ inch (2 cm) wide, or slice. Cut small pear or plum tomatoes in half.”

Blanching: None for slices. For stewing chunks: steam blanch 3 minutes or water blanch 1 minute.

Temperature: 140 F / 60 C

Drying time: 6 to 12 hours for slices. 10 to 18 hours for stewing chunks.

Quality: Fair to good.

Reference: So Easy To Preserve. 6th Edition. 2014. Page 348 & 351.

Black colour

There are at least two possible causes of dried tomatoes turning black.

1. Excalibur says, “…low acid ones will turn black when dehydrated”;
2. So Easy to Preserve says, “Black color can develop because of oxidization.” (SETP, 2014, page 348) (air getting at them while in storage).

Oregon State Extension says,

To prevent tomatoes from darkening or turning black, heat the fresh slices before drying. The enzymatic reaction that causes the blackening will be reduced by steaming, blanching or heating in a microwave oven until the slices are heated throughout, but not cooked.” ^[1]Herring, Peg. Dry your home grown tomatoes. Oregon State University Extension. July 2006.

Storage

Let the dehydrated product cool completely to room temperature before packing it into storage containers.

Watch the sealed containers for the first few days for any sign of condensation. If condensation occurs, dehydrate a bit more.

Label jar with name of product and date. Store away from heat and direct light.

So Easy to Preserve says, “Dried tomatoes re-absorb moisture readily which causes undesirable color and flavor changes, and shortens shelf life. Package tightly.” (SETP, 2014, page 348)

The University of California Extension Service says, “The color, flavor, aroma and nutritive value of dried tomatoes will deteriorate after about a year. Well-wrapped tomatoes can be stored in the freezer for longer periods.” ^[2]Tracy L. Parnell et al. Tomatoes: Safe Methods to Store, Preserve, and Enjoy. University of California ANR. Pub. 8116. March 2004.

Usage notes

Use in soups and sauces, or combine with other vegetables for flavour. Can be powdered and used to make tomato sauces, paste or ketchup. Soak a bit in a salad dressing such as Italian dressing or simple vinaigrette then purée them into the dressing to make a tomato-flavoured dressing.

To rehydrate dried tomatoes

The University of California Extension Service says,

You can rehydrate dried tomatoes in a variety of ways. You can add them directly to soups and stews or soak them in water, wine, bouillon, or vegetable juice. They usually rehydrate within 1 to 2 hours. If you soak them for more than 2 hours or overnight, you should refrigerate them. Use boiling liquid if you want to shorten the soaking time. The liquid used to rehydrate the tomatoes contains vitamins from the fruit and may be used in cooking.” ^[3]Tracy L. Parnell et al. Tomatoes: Safe Methods to Store, Preserve, and Enjoy. University of California ANR. Pub. 8116. March 2004.

The Master Food Preservers Group of Orange County, California, says:

Tomatoes rehydrate quickly so they can be used dry as they soften up with the moisture from other ingredients and leave a little pockets of “tomatoey” taste in your dish.  However, if you do need them soft you can rehydrate by soaking in either warm water or good quality oil (olive oil is most common) for about 10 minutes…. Rehydrate the tomatoes by marinating in a bit of salad dressing then enjoy tomatoes in your salad in the winter or on a sandwich.” ^[4]How to Use Dehydrated Tomatoes. UUCCE Master Food Preservers of Orange County. Accessed Dec. 2017 at https://ucanr.edu/sites/MFPOC/Food_Preservation/Tomatoes/How_to_Use_Dehydrated_Tomatoes/

Cooks Illustrated says,

Place ½ cup [dried] tomatoes in heatproof bowl, cover with 1 cup broth (250 ml / 8 oz) or ½ teaspoon salt dissolved in 1 cup (250 ml / 8 oz) warm water, then cover with plate and microwave for 2 minutes. Let sit until skin side of tomato can be pierced easily with fork, 5 to 10 minutes. Drain and blot well with paper towels.” ^[5]Cooks Illustrated. The Best Way to Rehydrate Sun-Dried Tomatoes. January 2016. Accessed January 2018 at https://www.cooksillustrated.com/how_tos/9820-the-best-way-to-rehydrate-sun-dried-tomatoes

Storing home-dried tomatoes in oil

Healthy Canning suggests short-term only

At the present time, until further clear solid recommendations come from the National Center for Home Food Preservation on this, we are not storing our home-dried tomatoes in olive oil long term, either in or out of the refrigerator. We do what many University Extension Services recommend.

From your store of dried tomatoes, take as many as you think you currently need for what you are making. Dipping in lemon juice may speed up the softening process, but that is optional. Let soak in oil — 10 to 15 minutes should do it. Use as required by your recipe. Store any unused covered in the refrigerator, and use within 4 days or discard.

Note that when refrigerated, the oil may solidify or go cloudy, but it will quickly return to normal state when removed from the fridge and let stand at room temperature for a few minutes.

What are the uses for dried tomatoes soaked in oil

Oregon State Extension suggests,

Dried tomatoes in oil can be used on pizza, pasta salads, appetizers, and Italian dishes. The oil can be used in vinaigrette dressing, or in a marinade sauce. It can also be used as a dip for French bread.” ^[6]Raab, Carolyn and Margy Woodburn. Herbs and Vegetables in Oil. Oregon State University Extension Service. SP 50-701. Revised Feb 2015. Page 2. https://extension.oregonstate.edu/fch/sites/default/files/documents/sp_50_701_herbsandvegetablesinoil.pdf

The full story

Here’s a brief survey of the literature that we’ve found on the topic.

In 2009, 2011, and 2015, one University Extension Service publication (Oregon, SP 50-701) has repeated in each revision the following advice:

Because of their acidity, unseasoned (i.e., no vegetables or herbs) fully dried tomatoes may be safely stored in oil at room temperature. (Refrigeration may delay rancidity, however).” ^[7]Raab, Carolyn and Margy Woodburn. Herbs and Vegetables in Oil. Oregon State University Extension Service. SP 50-701. Revised Feb 2015. Page 2. https://extension.oregonstate.edu/fch/sites/default/files/documents/sp_50_701_herbsandvegetablesinoil.pdf

In 2001, The Commonwealth Scientific and Industrial Research Organisation in Australia said the following:

The pH of fresh tomatoes is normally just below 4.6. When the tomatoes are partially dried, the natural acid components are concentrated and the pH is reduced. It will often be closer to 4.0 in a fully dried product and the risk of food poisoning is largely eliminated. However, as recent incidents have shown, acid tolerant strains of Salmonella spp. and pathogenic Escherichia coli are able to survive long periods at pH levels below 4.6 and these vegetable products must be produced in accordance with good hygienic principles.” ^[8]CSIRO. Keith Richardson and Beverley George. Preservation of vegetables in oil and vinegar. Bulletin Nov. 2001. https://www.foodscience.csiro.au/fshbull/fshbull27d.htm

A 2011 study, partly co-authored by Dr Elizabeth Andress, project director at the National Center for Home Food Preservation, says the following:

Several of the publications from Cooperative Extension sources reviewed in this publication (Table 2) recommend storing dried tomatoes in oil at room temperature. While fresh tomatoes are considered a borderline acid food (33), the drying process concentrates the available acid, making dried tomatoes an acidic food with a pH of approximately 4.0 (9). Sun-dried tomatoes stored in oil are considered low risk as long as sufficient moisture is removed in the drying process (9). A few of the recipes reviewed (Table 2) mix low-acid foods with tomatoes, either before or after drying, and are not clear with regard to potential hazards of these foods when they are stored in oil. One recipe (19) assumes that mixing fresh tomatoes with low-acid spices before drying will acidify the spices, but no evidence or peer-reviewed citations support this claim.” ^[9]Nummer, B.A., Schaffner, D.W., Fraser, A.M., and Andress, E.L. Current food safety issues of home-prepared vegetables and herbs stored in oil. Food Protection Trends 31:336-342, 2011. https://www.foodprotection.org/files/food-protection-trends/Jun-11-Nummer.pdf

[Ed: for their 4.0 pH number, they cite the CSIRO paragraph we noted earlier above.]

Again, to be clear, despite the above snippets, many Extension Services are still not backing storing home-dried tomatoes in oil, and that is not our practice, either.

Recipe for Dried Tomatoes In Olive Oil with Herbs

Note that all sources say that if you add any garlic or herbs, all bets are off, and you must refrigerate. No room temperature shortage. Oregon says:

Dried tomatoes-in-oil mixtures with garlic and/or herbs MUST be refrigerated and used within 4 days or frozen for long-term storage.” ^[10] Raab, Carolyn and Margy Woodburn. Herbs and Vegetables in Oil. Oregon State University Extension Service. SP 50-701. Revised Feb 2015. Page 2. https://extension.oregonstate.edu/fch/sites/default/files/documents/sp_50_701_herbsandvegetablesinoil.pdf

This recipe comes from: Tomatoes Basic & Fancy. UCCE Master Food Preservers of El Dorado Country. Undated.

• 100 g dried tomatoes (1¼ -1½ cup / 3 oz )
• 1 bay leaf
• 1 Tbsp red wine vinegar (5% or higher)
• 2 Tbsp water or wine
• ½ tsp salt OR salt sub (optional)
• ⅓ tsp cayenne OR Tabasco
• ¼ tsp dried marjoram
• ½ tsp dried thyme
• ½ tsp dried rosemary
• 1 to 4 cloves of garlic (to your taste)
• 250 ml olive oil (1 cup / 8 oz)

Put dried tomatoes and bay leaf into a litre / quart jar. Set aside.

Put everything from the vinegar down to and including the garlic into a blender; blend until smooth.

Pour into jar with the tomatoes.

Shake jar.

Let stand 6 to 8 hours, shaking lightly occasionally until all the liquid has been absorbed.

Add the oil.

Recipe notes

Instead of fresh cloves of garlic, you could use ½ to 1 teaspoon of minced garlic from a jar.

Vary herbs and spices as desired. Black peppercorns and dried basil can be interesting additions.

Further reading

How to Use Dehydrated Tomatoes. UUCCE Master Food Preservers of Orange County. (Link valid as of Dec. 2017)