Which jam recipes are safe to use, and how do you tell a tested recipe from an untested one?

A safe jam recipe for canning is one whose ingredients, proportions and processing time were checked in a laboratory, and the dependable places to find one are USDA's jam and jelly guide, the National Center for Home Food Preservation (NCHFP), the book So Easy to Preserve, university extension publications, and recipes from canning publishers such as Ball, followed exactly. Blog, family, magazine and old recipes may taste wonderful, but nobody has measured whether their processing works. This page explains what "tested" means, where tested recipes live, how to judge a recipe in front of you, and what to do with a favorite that fails the check.

What a tested recipe has been through

University of Wisconsin food scientist Barbara Ingham puts it plainly: "A tested recipe is one where we have data, or prior knowledge, that supports food safety" [1]. For home canning, that data comes from a laboratory. Researchers measure the temperature of the food inside the jar and at different places in the canner, then use heat penetration models to set a processing time that reliably reaches every jar [1].

For jam, three things are being checked at once:

• The heat treatment. The minutes in boiling water have to destroy the yeasts and molds that spoil jam and give the lid a strong vacuum seal. That depends on jar size, how thick the jam is and how hot it goes into the jar.
• The chemistry. Fruit, sugar, acid and pectin in the stated amounts make a product acidic and sugary enough to keep. Changing the proportions changes the product the time was tested on.
• The method. Pan size, batch size, the order ingredients go in and the boiling time all affect the set and the final sugar concentration. That is why extension specialists warn against doubling jam recipes [2].

So "tested" applies to the whole recipe as written. A recipe can be tested for one pectin, one batch size and one jar size, and untested the moment you change any of them.

Where tested jam recipes live

Two cautions apply across this table. First, use one source's recipe with that same source's processing time and altitude chart. Mixing a USDA recipe with a Ball altitude chart, or the other way round, gives a number neither source tested. How long to process jam lays the two systems out side by side. Second, a source being reputable doesn't make every recipe in it tested. A newspaper column by an excellent cook is still a newspaper column.

Recipes that are probably untested

Blogs, social media and celebrity cooks

Wisconsin Extension says Pinterest, celebrity chef websites, cookbooks, magazines and newspaper articles "can not be counted on" to share tested recipes [1], and SDSU Extension tells readers never to use canning recipes from Pinterest, blog posts or old family recipe files [7]. Some blogs do reprint tested recipes and credit them. Look for the original source by name, then go and read the original, because a reprint can drift.

Family recipes

A recipe that has worked for forty years has shown that it tastes good and usually sets. It hasn't shown that its processing is enough, because the failures nobody traced back to the jar don't make it into the family story. University of New Hampshire Extension starts its list of questions with "Was the recipe handed down through the generations?" [8]. If the family version matches a tested recipe closely in fruit, sugar, acid and pectin, use the tested recipe's method and time and keep your grandmother's spice blend.

Old recipes and old books

SDSU Extension says recipes older than 1994 may be unsafe [7], and UNH Extension advises recipes "no earlier than 1994" from recent, research-based sources [8]. Guidance has moved since then. Paraffin seals are "no longer considered safe" because the wax shrinks and lets mold and yeast in [5]. Some fruits once canned freely are now flagged: Penn State recommends freezing white peaches, and says elderberries are low in acid and safe to can only as jam or jelly made with specific sugar ratios [5], while the North Central extension network's substitutions bulletin says no tested home canning recipes exist for elderberries [2]. Fruits that need extra acid sorts out that disagreement. Paraffin, inverting jars and other old methods covers what changed and why.

UK, European and other overseas recipes

Many British recipes seal hot jam in jars that were sterilized in the oven, sometimes under a wax disc, with no boiling water process. US guidance requires processing in a canner for shelf storage, and Penn State notes that it is not safe to use canning jars in dry oven heat, which can crack them [5]. Their fruit and sugar ratios may be fine; their method is a different tradition. Also watch the units: a UK recipe written in grams and British pints doesn't convert to US cups without a scale.

A recipe check you can run in two minutes

Read the recipe with this list beside it. One "no" doesn't make the recipe dangerous, but it does mean nobody can tell you it is safe for the shelf.

1. Does it name a tested source (USDA, NCHFP, So Easy to Preserve, an extension office, Ball, a pectin manufacturer) and match that source when you look it up?
2. Is it dated 1994 or later, or reprinted from a current edition? [7][8]
3. Does it give a processing time in a boiling water or steam canner, with an altitude adjustment? A recipe that says to pour hot jam into jars and let the lids seal is on UNH's list of warning signs [8].
4. Does it give jar sizes and headspace (1/4 inch for cooked jam and jelly [3])?
5. Does it name a specific type of pectin, or say plainly that no pectin is added?
6. Are the sugar and acid amounts exact rather than "to taste"? Sugar shapes the set and the keeping quality as well as the flavor.
7. Is it free of thickeners such as flour or cornstarch? UNH flags extra starch, flour or thickener because it slows heat penetration [8].
8. Does it keep to fruit, sugar, acid and pectin? Peppers, onion, garlic, pumpkin, dairy, butter beyond a small antifoam amount, or extra spirits push a recipe toward foods with different safety rules. Can jam give you botulism? explains where that line sits.
9. Is the batch the size the source wrote? A doubled or tripled batch is no longer the tested recipe [2].

When a favorite recipe fails the check

You have three honest options.

1. Find its tested twin. Most family jams are strawberry, peach, apricot, plum or grape with sugar and lemon. A tested recipe for the same fruit is almost always out there. Use its proportions and processing, and carry over small flavor touches within what the guidance allows: the extension network's guidance permits adding a small amount (1 teaspoon or less) of an herb or other flavoring to a fruit jam or jelly [2]. What you can change in a tested recipe sets out the rest.
2. Make it as a refrigerator or freezer jam. An untested jam that you keep cold and eat within a few weeks avoids the question of shelf processing. Label it as untested and refrigerator-only, and don't give it away as a shelf jar. Refrigerator jam gives the storage limits.
3. If you plan to sell it, have it reviewed. A recipe outside the tested sources usually needs a process authority's review before it is sold, and some products need one by law. Process authorities and scheduled processes explains what that involves.

What you should not do is can an untested recipe "just this once" and store it on the shelf. Mold and fermentation are the usual results of underprocessed jam, and the jar may look fine until it is opened.

Picking your first tested recipe

For a first batch, choose a recipe from USDA's guide or a pectin insert for a fruit that is in season now, at the batch size printed, and read it through twice before you start. Then gather the tools it calls for with Equipment for your first batch, and follow the method on How to make jam, start to finish.

References

1. University of Wisconsin-Madison Extension, Ingham, What Does "Use a Tested Recipe" Mean in Home Food Preservation?, February 20, 2019. https://winnebago.extension.wisc.edu/2019/02/20/14333
2. North Central Food Safety Extension Network (Blakeslee, Garden-Robinson, Ingham, Geiger), Play It Safe: Safe Changes and Substitutions in Tested Canning Recipes (FN2102), rev. March 2024. https://www.ndsu.edu/agriculture/sites/default/files/2024-03/fn2102.pdf
3. USDA and National Center for Home Food Preservation, Complete Guide to Home Canning, Guide 7: Preparing and Canning Jams and Jellies, rev. July 2015. https://nchfp.uga.edu/papers/guide/GUIDE07_HomeCan_rev0715.pdf
4. National Center for Home Food Preservation, Do I need to pre-sterilize my jars before canning?, May 21, 2014. https://nchfp.uga.edu/blog/do-i-need-to-pre-sterilize-my-jars-before-canning
5. Penn State Extension, Hassani, Why Some Old Canning Recipes Are No Longer Safe, updated September 13, 2024. https://extension.psu.edu/why-some-old-canning-recipes-are-no-longer-safe
6. National Center for Home Food Preservation, Testing Jelly without Added Pectin (adapted from So Easy to Preserve, 6th ed., 2014; Andress and Harrison). https://nchfp.uga.edu/how/make-jam-jelly/jams-jellies-general-information/testing-jelly-without-added-pectin
7. South Dakota State University Extension, Kleine and Botzet, A Guide to Water Bath Canning (P-00255), 2022. https://extension.sdstate.edu/sites/default/files/2022-10/P-00255-v2.pdf
8. University of New Hampshire Extension, Hamilton, Questions to Ask Before Trying a Canning Recipe, February 20, 2023. https://extension.unh.edu/node/16922
9. National Center for Home Food Preservation, Extracting Juice for Jelly (adapted from So Easy to Preserve, 6th ed., 2014, Bulletin 989, University of Georgia; page notes the 6th edition was reviewed and updated in 2020), accessed October 22, 2026. https://nchfp.uga.edu/how/make-jam-jelly/jams-jellies-general-information/extracting-juice-for-jelly/