There is no tested method for safely home-canning some foods, and without a method, they should not be canned. These include eggplant except when pickled, zucchini and pumpkin purée, milk and dairy products, flour-thickened soups and sauces, and mixtures containing rice or pasta. Store these foods frozen or in the refrigerator instead of canning them.
A canning recipe is not just an ingredient list; it is a process established by measuring how many minutes it takes for the center of the jar to reach a specific temperature. There is no processing time to give for a product that has not been measured. That is why some foods are not canned at home: the problem is not the recipe, but the fact that no measurement has ever been made. Applying a number from a similar product to these foods produces a jar that looks safe but is based on nothing. The jar looking perfect from the outside does nothing to make up for this gap.
Eggplant is at the top of the list. There is no tested canning method for eggplant except for pickling; it can be pickled with vinegar acidification, but there is no published processing time for plain eggplant or eggplant canned in oil. Zucchini and pumpkin purée are in the same group: purée is dense and thick, and heat does not reach the center at any reliably predictable rate. If these vegetables are to be canned, they are processed cubed according to their own tested directions, not as purée. The pieces should also be cut to the size specified in the directions.
The second group consists of thickening ingredients. Soups and sauces thickened with flour, starch, whipped cream, or grated cheese are not home-canned; thick liquids do not transfer heat well, and the center of the jar can lag behind in an unpredictable way. Mixtures containing rice, bulgur, pasta, or orzo are on the list for the same reason. These grains absorb liquid, form a mass, and unpredictably lower the temperature at the center. The same soup can be made with the grain added at serving time.
The third group is milk and dairy products. There is no recommended method for home-canning milk, cream, butter, cheese, or milk-based desserts. Nut butters, egg mixtures, and mashed bananas are also in this group. What they have in common is low acidity and a thick consistency; heat does not penetrate, and the product also creates an environment favorable to bacteria. The right answer for these products is not a longer processing time, but a different storage method.
The alternatives are clear. Store these foods frozen, keep them in the refrigerator for a short time, or dry them. Divide zucchini purée into portions and freeze it, freeze soup without grains, and roast eggplant before freezing it. If you want a product in a jar, turn the recipe into a pickle and follow the acidification measurement written in the recipe. There is no recommended method for canning unpickled vegetables in a boiling-water bath; this list is the other half of that statement. If you are unsure about a product, do not prepare it for canning at all. The list is short but not flexible; if a product appears here, canning is not an option.
A Note for Readers
This content is for informational purposes only and is not a substitute for medical advice. Consult your doctor before making any decision about your health.
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