Hi Amie, 

There are currently no research-based instructions for canning diced tomatoes at home. 

Unfortunately you cannot safely use the processing times recommended for other tomato products (like whole tomatoes) because diced tomatoes would have a very different density when packed in the jar. Denser products take longer to heat up, and diced tomatoes would in theory need a longer processing time. This time has not been established in a lab. Attempting to guess at the right time could lead to underprocessing and an unsafe product.

When the Extension tomato recipes were developed diced tomatoes were excluded, most likely because they do not hold their structure well when canned using home kitchen equipment and ingredients. The researchers instead included options for larger tomato segments or for crushed tomatoes to give canners a variety of options that work well at home.

Extension publications (like PNW 300 Canning Tomatoes) provide safe instructions for canning a variety of tomato products, such as crushed tomatoes, whole tomatoes, tomato juice, and more. We recommend that you stick with those options for safety!

Thanks for using Ask Extension.

Jared