Study finds online salsa recipes for home canning lacking food safety standards

Homemade salsa recipes are abundant on food blogs, but the majority of them fail to follow USDA home canning guidelines and are a cause of food safety concern, according to a new University of Maine study.

In the study, “Adherence of Food Blog Salsa Recipes to Home Canning Guidelines,” UMaine Extension professor Kathy Savoie and Jen Perry, an assistant professor of food microbiology, examined 56 recipes for home canning of salsa from 43 food blogs. They found that in 70 percent of the recipes, USDA home canning guidelines were not included in four categories: acidification, thermal processing, contaminants and vacuum sealing.

Of the blogs evaluated for this study, the number of Facebook followers ranged from 719 to 3.2 million. 

“Traditionally, salsas are mixtures of low-acid foods, such as onions and peppers, with acidic foods, such as tomatoes. Depending on ingredient ratios, the natural acidity of salsa mixtures may not be high enough to safely process in a boiling water bath, which is still the most common method for canning in American homes,” says Savoie, who has been providing home food preservation education since 1996. 

Historically, home-canned vegetables have been the most common cause of botulism outbreaks in the United States. Two recent botulism outbreaks in 2015 and 2018 in the United States involving improperly home canned foods demonstrate that this risk continues, as well as the need for continued education to those who want to preserve foods at home, Savoie says.

In the recipes posted on the blogs, analysis of acidification volume to tomato volume revealed that 12 (21 percent) of the 56 recipes failed to meet the minimum USDA acidification guidelines for tomato volume. In addition:

  • Five recipes (9 percent) actually contained sufficient quantities of acid to account for the volume of vegetables used.
  • Fourteen percent of the recipes provided information regarding necessary adjustments for altitude.
  • Although more than half of recipes (34, or nearly 61 percent) correctly specified the length of time to process jars in a boiling water bath, only 10 (29 percent) of these indicated that processing time should start after a rolling boil is achieved, representing a critical risk of under-processing.
  • Four (7 percent) of the 56 recipes reviewed provided correct information on all of the following three measures: total processing time, when to start processing time and altitude adjustment.
  • Eight (14 percent) specified the correct type and strength of acid(s) to ensure safety.
  • The mean acidification ratio across all recipes in this study was 0.94 tablespoons per cup of peppers and onions — less than half the recommended level to ensure safety during extended anaerobic storage.

To ensure the food safety of canned homemade salsa, the UMaine researchers recommend accessing resources from USDA, UMaine Extension and the National Center for Home Food Preservation to know the latest techniques and guidelines to safely preserve foods at home. Those doing home canning should use recipes that have been tested to ensure that the salsa is properly acidified to ensure safety.

And when searching for recipes online, look for science-based information by typing at the end of your query term. This will help to direct your search towards educational institutions. You can use the same strategy and to search for government information, ending your query with (For example: “canning salsa”)

University of Maine Cooperative Extension publications include the “USDA Complete Guide to Home Canning” and “So Easy to Preserve”; and the National Center for Home Food Preservation salsa recipes. UMaine Extension also offers workshops in home canning and food safety.

Contact: Kathy Savoie,