Hi Les, 

Thanks for reaching out with your question about dandelion jelly!  The concern you raise is an important one. The high acidity of most canned fruits naturally inhibits the growth of botulism spores due to their acidity. Vegetables and proteins are naturally low acid, however, and so you have to be careful to select a canning recipe that accounts for that low acidity. Food scientists formulate recipes that either involve adding acid to lower the pH, adding lots of sugar to make water unavailable to microorganisms, or utilizing very high temperatures above the boiling point of water to kill botulism spores (i.e., pressure canning).  

Now to your dandelion recipes: I was able to find the recipes you reference in your email here (Wyoming) and here (California). It looks like the primary recipe posted online for dandelion jelly, including the U of California bulletin, ultimately comes from a 2011 publication from U of Wyoming which is no longer available on their website, although you can still find it elsewhere online. This U of Wyoming recipe does call for a large amount of sugar (1:1 ration of sugar to water) which is likely the reason the recipe was considered safe. If the sugar content is high enough in a jelly recipe , there is no water available for microorganisms to use, thus making it safe from botulism growth even if you have used low acid vegetable ingredients. You cannot "guess" at this proportion of sugar, however; the recipe needs to be confirmed by testing.

I am not sure why U of Wyoming seems to have pulled the recipe and replaced with a freezer jelly recipe. It has the hallmarks of a safe process, but because it does involve a low acid ingredient, we should be certain that the sugar proportion is tested and correct. I have emailed someone at the U of Wyoming to ask if they no longer stand by the recipe. If I hear back, I'll let you know. Meanwhile, freezing is a great option.

Jared

Thank you so much, I look forward to seeing if you can provide an update.

Hi Les, 

I heard back from U of Wyoming Extension (UWE) already, and it seems that the canning recipe for dandelion jelly is no longer considered safe. A food scientist at the National Center for Home Food Preservation flagged this recipe as potentially risky several years ago and Wyoming decided to pull the recipe. As I suspected, the acidity is not low enough to prevent growth of botulism spores, and the water activity is potentially high enough to still allow for microbial growth. UWE is asking other sites to remove the old canning recipe.

The new handout for refrigerator/freezer jelly is the replacement recipe, but it is not to be used for canning: https://uwyoextension.org/uwnutrition/category/food-preservation/

Best, 

Jared