New updates available from Oregon State University on canning tomatoes safely

Last Updated: 
September 2, 2010

basket of tomatoes

CORVALLIS, Ore. —A highlight of late summer is when tomatoes picked fresh from the garden become an ingredient in almost every meal. But since we can't eat them fast enough, many people preserve them to enjoy throughout the year.

Home canning, one of the most popular preservation methods for tomatoes and tomato products, requires safe procedures, according to Carolyn Raab, Oregon State University Extension foods and nutrition specialist.

A revised OSU Extension publication, "Canning Tomatoes and Tomato Products," PNW 300, gives updated details on safe canning methods, from preparing the tomatoes to testing the seal, and is available online.

Revised recommendations include: replacing pressure canner gauges if they read high or low by more than two pounds (formerly one pound); pre-heating water in a boiling-water canner before processing; and waiting to remove jars from canners to promote lid seal.

A new section describes how to safely handle and detoxify spoiled food before disposal, and then how to clean the contaminated area.

Microorganisms that cause spoilage, such as molds, yeast and bacteria, are destroyed by heat processing, and because processing times are scientifically determined, Raab said, it is extremely important to follow a tested recipe for tomatoes and tomato products such as salsa.

"Changes in the amount or type of ingredients and method of preparation can influence processing conditions needed to guarantee safety," she said. "For example, addition of extra vegetables to a salsa recipe can change acidity, and overcooking can change consistency."

"Products not prepared according to instructions should be frozen."

In 1987, the U.S. Department of Agriculture completed extensive testing of tomato canning procedures to ensure that home-canned tomatoes and tomato products are safe to eat and can be stored on the shelf without spoiling.

Processing times were lengthened to ensure that tomato varieties with high solids content are adequately processed. Pressure canner recommendations were added as an alternative to boiling-water processing. Recommended pressures now differ for dial and weighted gauges. And, altitude corrections for both boiling-water canners and pressure canners were revised.

Author: Judy Scott
Source: Carolyn Raab