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Preserving Tomatoes after a Fall Frost or Freeze

Posted on by Karen Blakeslee

Tomato plants may still produce fresh tomatoes into the Fall season. But, if the tomato vine is dead or killed by a frost or freeze, those tomatoes are not safe for canning. The pH, or acidity, changes in this situation to increase the pH above 4.6. Therefore, the safest choice to preserve these affected tomatoes is by freezing or dehydrating.

Unripe, or green, tomatoes can be preserved just like ripe tomatoes. So when canning them they still require acidification. Here are some ideas to can green tomatoes.

Tomatoes

Learn more about pre-frost tomato harvest at https://www.johnson.k-state.edu/programs/lawn-garden/agent-articles-faqs-and-resources/agent-articles/vegetables/Pre-Frost-Harvest.html.

Tips for Canning Tomatoes

Posted on by Karen Blakeslee
tomatoes
Photo: USDA Flickr

Many gardeners plant tomatoes and they are starting to ripen. Preserve them by canning, freezing or dehydrating to use later in many recipes. While it is fun to make salsa, spaghetti sauce or even a barbecue sauce, having basic options such as whole tomatoes, tomato juice or tomato sauce allows you to use tomatoes in many more recipes.

Here are some reminders about tomatoes:

  • Although tomatoes are usually considered to be acidic in flavor, most have pH values slightly above 4.6, which makes them a low-acid food. As such, tomato products must be acidified to a pH of 4.6 or below with bottled
    lemon juice, vinegar, or citric acid. Properly acidified tomatoes can be safely processed in a boiling-water canner or pressure canner as an acid food. Learn how to acidify tomatoes in Preserve it Fresh, Preserve it Safe: Tomatoes.
  • Pressure processing instructions are equivalent in heat treatment to water bath processing. Caution: Both methods require acidification. There are no recommendations for processing tomatoes without acidification. The chart in the above publication provides the options for acidification.
  • Tomato-based recipes for products such as salsa, barbecue sauce, ketchup and others will also include added acid. Do not reduce the amount of added acid in these recipes.
  • Tomatillos can be substituted for tomatoes in the same amount stated in a recipe, such as in salsa.
  • Salt is for flavor only and can be omitted, if desired.

Tomatoes

Preserve the Best Tomatoes

Posted on by Karen Blakeslee

TomatoesWhen preserving any food, use the best food possible for the safest results. This includes tomatoes. During the fall, many gardeners still have tomatoes on the vines. But once a frost or freeze happens, these tomatoes are not safe to preserve by canning.

When tomatoes are left on the vine towards the end of the growing season, the pH increases above 4.6. This is the dividing point whether a food is a high acid or low acid food. When the pH is above 4.6, it is a low acid food. These tomatoes are also more susceptible to other microbial damage. Tomatoes that have signs of blight or other fungus related infestations have a higher pH making them a low acid food. All of these are not safe for canning.

For information on preserving tomatoes, see www.bookstore.ksre.ksu.edu/pubs/MF1185.PDF.

 

Do Tomatoes Need to be Peeled Before Canning?

Posted on by Karen Blakeslee
peeling tomatoes
Peeling tomatoes
Photo: K-State Research and Extension

Yes! That extra time is important and time well spent for safely canned tomatoes. This is true for any produce that is canned. For example, potatoes, peaches, and apples are also peeled before canning.

According to the National Center for Home Food Preservation, “Most bacteria, yeasts, and molds are difficult to remove from food surfaces. Washing fresh food reduces their numbers only slightly. Peeling root crops, underground stem crops, and tomatoes reduces their numbers greatly. Blanching also helps, but the vital controls are the method of canning and making sure the recommended research-based process times found in the USDA’s Complete Guide to Home Canning are used.”

Easily peel tomatoes by dipping them in boiling water for 30-60 seconds or just until the skins split. Then dip in ice water, slip off the skins and remove cores. See how at https://youtu.be/diZGx8RZAd0. This method can be used for peaches or nectarines.

 

Canning Previously Frozen Tomatoes

Posted on by Karen Blakeslee

So you saved your tomato crop in the freezer. Can those frozen tomatoes be canned?

It is not recommended to can tomatoes that froze on the vine. This is because the acid content changes too much, while on the vine, making them unsafe for canning.

But tomatoes harvested prior to a fall freeze, then frozen, do not change in acidity. What does change is their texture and how they measure.

The best choice for canning previously frozen tomatoes is to make a well cooked product such as a stewed or crushed tomato product, or made into tomato juice or sauce.

It is not recommended to can them whole or quartered. They will pack into the jars differently, absorb moisture differently, and the heat transfers through the jars differently. This could lead to under processing and spoilage. Tomato canning recipes are based on fresh tomatoes.

Source: University of Georgia

 

Safely Preserving Tomatoes

Posted on by Karen Blakeslee
Canned tomatoes
Canned tomatoes, University of Georgia

Tomatoes are borderline in pH between acid and low acid foods, so the USDA preparation directions for these products call for acidification to allow a less severe heat treatment than would be required without it. To ensure safe acidity in whole, crushed, or juiced tomatoes, add two tablespoons of bottled lemon juice or ½ teaspoon of citric acid per quart of tomatoes. For pints, use one tablespoon bottled lemon juice or ¼ teaspoon citric acid. Add acid directly to jars before filling. Sugar may be added to offset an acid taste, if desired, but the acid cannot be decreased to taste.

No matter how you choose to can your tomatoes, all steps in preparing and cooking the foods still need to be followed for the process time(s) printed with them. The process times are very different for tomatoes packed in water compared to tomato juice or without added liquid. For many of these tomato products, there are canning options for both boiling water and pressure canning available in our directions.

Source: https://nchfp.uga.edu/tips/summer/canned_tomato_types.html

See KSRE Preserving Tomatoes for more information

 

Preserve the Best Tomatoes

Posted on by Karen Blakeslee

When preserving any food, use the best food possible for the safest results. This includes tomatoes. During the fall, many gardeners still have tomatoes on the vines. But once a frost or freeze happens, these tomatoes are not safe to preserve by canning.

When tomatoes are left on the vine towards the end of the growing season, the pH increases above 4.6. This is the dividing point whether a food is a high acid or low acid food. When the pH is above 4.6, it is a low acid food. These tomatoes are also more susceptible to other microbial damage. Tomatoes that have signs of blight or other fungus related infestations have a higher pH making them a low acid food. All of these are not safe for canning.

For information on preserving tomatoes, see www.bookstore.ksre.ksu.edu/pubs/MF1185.PDF.

 

High Antioxidant Purple Tomatoes

Posted on by Karen Blakeslee

Tomatoes with purple skins have been available for a while. Now there is a new purple tomato with purple flesh and high in anthocyanins.

Dark blue or purple foods such as blueberries are considered superfoods. These new purple tomatoes can add another option plus add color to many meals.

This tomato was developed by Norfolk Plant Sciences. The USDA Animal and Plant Health Inspection Service states it can be safely grown and used in the United States.

Learn more at the Big Purple Tomato website.

 

Preserving Unripe Tomatoes

Posted on by Karen Blakeslee
tomatoes
Source: https://preservingfoodathome.com/2019/10/
Photo: USDA Flickr

As fall approaches, those end of season unripe tomatoes are still usable. Be sure to pick them before a frost or freeze if canning them.

Unripe, or green, tomatoes can be preserved just like ripe tomatoes. So when canning them they still require acidification. Here are some ideas to can green tomatoes.

Don’t want to can them, or it is after a frost or freeze? Then freeze them for later use.

 

Preserving Overripe Tomatoes

Posted on by Karen Blakeslee

It is always best to preserve any food at its peak ripeness and freshness. Tomatoes that are overripe can be a problem if canned.

The acidity level in tomatoes varies during the growing season. If overripe, they are less acidic than when at the peak of ripeness.

Do not use damaged tomatoes or any that have mold growth. These may contain harmful pathogens that may not be destroyed during the canning process.

The best preservation method for these tomatoes is to freeze them.

Source: https://extension.umn.edu/preserving-and-preparing/canning-tomato-products-safety-guidelines

Treat all varieties and colors of tomatoes the same. They all require added acid for safely canned tomatoes. Learn more at www.bookstore.ksre.ksu.edu/pubs/MF1185.PDF.

 

Reference to any specific commercial products, process, service, manufacturer, or company does not constitute its endorsement or recommendation. Paid for by Kansas State University