University of California Agriculture and Natural Resources announced on Apr. 30 that canning previously frozen tomatoes is not always safe, depending on the intended use and condition of the fruit. The organization said that while freezing tomatoes is a practical way to preserve them for future cooking, certain precautions must be taken if they are later canned.
The guidance highlights that recipes for canning typically assume the use of fresh tomatoes. Frozen tomatoes tend to become mushy, which may cause them to pack too densely in jars. This can interfere with heat penetration during processing, potentially leading to spoilage or safety concerns. As a result, using previously frozen tomatoes is not recommended for products such as whole or quartered canned tomatoes or salsa.
However, the organization reports that well-cooked products like juices and sauces may be suitable for canning with previously frozen tomatoes if all thawed juices are included. Tomatoes that have frozen on the vine should never be canned due to their lower acidity levels, which make them unsafe for preservation. Overripe or previously overripe frozen tomatoes should also not be used in home canning.
University of California Agriculture and Natural Resources secures funding through public contributions to support its programs, according to the official website. The institution promotes sustainable practices aimed at strengthening resilient ecosystems and economic vitality according to its official website. It utilizes nine research and extension centers as laboratories representing California’s diverse ecosystems according to its official website.
The university has gained recognition for providing trusted services linking research directly with community needs according to its official website. It manages Cooperative Extension services as part of the University of California system according to its official website, conducting more than 33,800 educational events annually and engaging over 18,400 volunteers in various initiatives according to its official website.
For further information about safe tomato preservation methods or other food safety topics, residents are encouraged by UC Agriculture and Natural Resources staff members in El Dorado County Master Food Preservers program to consult resources from the National Center for Home Food Preservation.