previous page: 14.1.5 Factors Influencing Safety
page up: Food Preserving FAQ
next page: 14.1.5 Fruits and Vegetables

14.1.5 Tomato Products


This article is from the Food Preserving FAQ, by Eric Decker ericnospam@getcomputing.com with numerous contributions by others.

14.1.5 Tomato Products

Tomatoes and tomato products are very hard to categorize. Tomatoes are
borderline acidic. Lemon juice or other acid (vinegar, citric or ascorbic
acid) must be added to all tomato products to insure adequate acidity. Added
acid is necessary whether the product will be pressure canned or boiling water
bath processed. Bacteria and spores die faster in an acidic environment, and
the recommended process times for pressure canning assume that the tomatoes
are acidic. The times would not be reliably adequate to insure safety if the
tomatoes were low-acid.

Green tomatoes are more acidic, and may be used safely in any recipe calling
for red tomatoes. Overripe and frosted tomatoes are less acidic and can not
be safely home canned. They can be frozen.

Addition of salt, while optional, does give a miniscule margin of safety. For
dietary information, one teaspoon of salt added to 1 quart of juice or sauce
adds about 526 mg sodium per cup.

Addition of low-acid vegetables to tomatoes decreases the acidity. The
amount by which the acidity is lowered depends on which vegetables, how much,
how finely they are chopped, if they are boiled in the tomatoes or not, if
seeds and skins remain in or are removed, and if the chunks of vegetable and
tomato remain, if they are ground together or sieved out. The initial
acidity of the vegetables and tomatoes depends on maturity, growing conditions,
post-harvest holding conditions, and soil/location of growth.

It is impossible to test every recipe. It has so far been impossible to
develop a set of proportions or an equation that would take into account all
the variables and give a reliable assessment of the acidity or the necessary
process times. The only safe recommendations can be made by comparing the
recipe in question with the USDA guide recipes. If more vegetable or less
acid (vinegar or lemon juice) is added than the USDA recipe, the recipe in
question can be changed or the product should be processed according to the
process times for the vegetables. Alternatively the product may be frozen
or refrigerated.

These proportions of vegetables have processing times in the USDA Home
Canning Guide:

  Tomato-vegetable juice   22 lb tomato : 3 C chopped vegetable
  Spaghetti sauce          30 lb tomato : 8 C vegetable : no acid
  Ketchup #1               24 lb tomato : 3 C onion : 3 C vinegar
  Ketchup #2               24 lb tomato : 1 C peppers : 2.6 C
  Ketchup #3               24 lb tomato : 9 C vegetables : 9 C

Use the equivalencies above to convert the amount of vegetables to cups be-
fore a recipe is evaluated for safety.

The tomato-vegetable juice recipe specifies "chopped vegetables". Up to but
no more than 3 cups of mixed vegetables may be safely added to tomatoes to
make 7 qts of juice. Which vegetables are used is not important, the margin
of safety is large enough to tolerate the variations in this recipe. BUT,
after boiling, this recipe is pressed or sieved, so the chunks are removed,
and a smooth juice is canned. These proportions can not be used for a chunky

The spaghetti sauce is pressure processed, so the proportions can be
different. The tomato acid and the long boiling prior to canning are
sufficient. These proportions and procedures can be used with different
spices to make a taco or barbecue sauce type product.

Ketchups 1 and 2 are pressed or sieved so skins and seeds are removed. The
proportions are similar, #2 with less added vegetable has a little less added
vinegar. Ketchup #3 is a blender ketchup, skins are not removed prior to
canning. The amount of added vegetable and of added acid is much greater
relative to the amount of tomato.

If these proportions are maintained, the amounts of sugar and spices may be
varied to suit one's taste without endangering the safety of the product, and
processing times given in the USDA Guide can be used. If other proportions
are used, if the product is canned chunky instead of sieved smooth, or
blended raw (uncooked) or any other variation, the processing times are not
valid: the recipe must be changed, or the product must be frozen or held


Continue to:

previous page: 14.1.5 Factors Influencing Safety
page up: Food Preserving FAQ
next page: 14.1.5 Fruits and Vegetables