I had a caller last week with 180 tomato plants, yes, you read that right ... 180! Her questions about bottling them got me thinking that maybe a short update on tomatoes might by a good idea. Things have changed a bit from when my mom was canning tomatoes and tomato mixtures, and since many of us learn to can from our moms, it might be time for an update.
First, let’s discuss a few basics. When bottling food, there are a few key points to consider. In order for a food to be safe for water bath canning procedures, it must contain enough acidity — be at least a 4.6 pH or higher. When a food is higher in acidity, the pH number is actually lower. So a pH reading of 3.0 makes the food quite acidic — like an orange.
The cutoff pH for water bath canning, and whether the food now needs to be pressure cooked, is 4.6 pH. Where do tomatoes fall as far as their acidity? Well, that depends — on variety, growing conditions, etc. The majority fall between 4.1 and 4.6 pH. I have even tested some that come in at 4.7 pH. Because there are so many varieties and growing conditions that the USDA came out with the recommendation to acidify your tomatoes by using lemon juice concentrate (2 tablespoons/quart) or citric acid (1/2 teaspoon/quart), just to make sure they are safe for water bath canning.
The main micro-organism we are wanting to safeguard against is the botulism spore — and keep it from producing its deadly botulism toxin. This organism likes to produce its toxin in low acid and anaerobic (no air) conditions — just what I have created inside a bottle of low acid foods. In order to eliminate the risk, we need to make sure foods are high enough acid, OR, that the spore itself is killed, through pressure canning. Then it can’t produce its toxin in a low-acid environment. That is why we pressure can meats and veggies.
Acidity is especially important to keep in mind when adding vegetables of some sort to tomatoes. This addition of some low-acid foods will bring the pH (acidity) down of the tomatoes. Lots of folks want to add “just a little bit of onion and pepper.” I hear it all the time. Now what have we just done to the acidity? The same with salsa recipes that we don’t know whether they are from a tested source — and no, the “recipe I’ve used for years” isn’t the kind we are talking about here.
There are a number of recipes and options to choose from when canning tomatoes. Everything from a plain stewed tomato, to salsa, to tomato sauce. For me, the method that makes the most sense for the way I use stewed tomatoes is “Crushed with No Liquid Added—Hot Pack”. Here are the details for water bathing that type tomato:
Wash tomatoes and dip in boiling water for 30-60 seconds or until skins split. Then dip in cold water, slip off skins and remove cores. Trim off any bruised or discolored portions and quarter.
Heat about 1 pound of the quarters quickly in a large pot, crushing them with a wooden mallet or spoon as they are added to the pot. This will draw off some juice. Continue heating the tomatoes, stirring to prevent burning. Once the tomatoes are boiling, gradually add remaining quartered tomatoes, stirring constantly. These remaining tomatoes do not need to be crushed. This will soften with heating and stirring. Continue until all tomatoes are added. Then boil gently 5 minutes. Add bottled lemon juice or citric acid to hot jars according to the size bottle you are using. (See above.) Add 1 teaspoon salt to each quart (1/2 teaspoon/pint), if desired. Fill jars immediately with hot tomatoes, leaving ½ inch headspace. Remove air bubbles. Wipe jar rims. Adjust lids and process in a boiling water bath. Pints: 35 minutes (sea level); Quarts: 45 minutes (sea level). Make necessary altitude adjustments to time. For my altitude (4,500 feet), I add an additional 10 minutes to these times.
If you and I are going to go to the bother of canning, we should “bother” with safety, too. So before you get ready to can your season’s harvest of tomatoes, be sure to check out the National Center for Home Food Preservation’s website, www.uga/nchfp for updates and recipes. They have plenty of great ones to choose from when it comes to canning — not just tomatoes. They also have a terrific book, "So Easy to Preserve", that has such great information it will soon become your canning favorite. Many of the USU Extension offices in the state of Utah carry these books — check with yours.
Feel free to check out my county website for the Utah State University Extension in Weber County, Utah, at www.extension.usu.edu/weber. Go to Family and Consumer Sciences and then to Food Preservation.