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Aug 30, 2009 08:52 AM

Storing Pesto without Freezing

I made pesto cheese and all. Boiled up some canning jars and lids. Filled the jars and eliminated air pockets wherever possible. I then topped off the jars with olive oil to 'seal' out air and closed them.

My plan is to cellar them, not freeze them.

Will this work to preserve the contents? More importantly, am i creating a health risk?!

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  1. oh gosh, you've got fresh garlic in there. that's a problem. i'd freeze them today -- as in, now.

    2 Replies
    1. re: alkapal

      Paraffin is no longer considered to provide an optimum seal, much less oil. I believe I've read that botulism is a risk when raw garlic is stored in oil - perhaps someone knows for sure. Freezing is needed for long-term storage. I haven't had a problem with pesto that was just refrigerated, but not frozen, for 3-4 weeks.

      1. re: greygarious

        Think of it this way. Basil, garlic, oil, cheese and a salt. How long would those ingredients last on the shelf? Not very. Mashing them together does nothing to change that.

        Paraffin's the least of the OP's worries. As it stands, there's nothing preserving his/her pesto - it's just sitting in jars and at room temperature will go BAD very quickly. Bad as in they'd be lucky if it ferments and becomes obviously non-edible before they taste it and die of botulism poisoning. There's nothing preservative in pesto except the nominal amount of salt. All the ingredients are low-acid and on top of that, there's dairy in it. Even processing in a water bath wouldn't be safe, let alone just putting it in jars. Paraffin will keep mold spores out of jam or jelly, but that's about it. And jams and jellies are both high-acid and contain a huge amount of sugar - a preservative.

    2. I second the recommendation to freeze. If space is an issue, pour into freezer bags, remove as much air as possible and lay flat. to form a thin layer. You'll be able to break off small pieces if necessary.

      Not use how long you've had them stored as is, but the issue is that sealing out air doesn't rule out anaerobic bacteria and the toxins they produce that can seriously sicken you.

      2 Replies
      1. re: 4Snisl

        i think it is the very fact that it's an anaerobic (airless) environment that is the problem with botulism.

        i know we've had long threads on this issue in the past, but i just did a quick google search and came across this posted by claraB :

        12-14-2004, 07:46 AM
        I found this information on the Colorado State University's extension service website:

        Flavored Oils
        Safety Concerns
        Infused oils and oil-based mixtures of garlic, herbs or dried tomatoes can pose a health hazard if not kept refrigerated. There have been a number of cases of botulism poisoning traced to commercially and home prepared mixtures of garlic in oil that were not refrigerated. Refrigeration is necessary because all other conditions that favor growth of C. botulinum are met: low acid environment with pH higher than 4.6, anaerobic conditions (oil), food and moisture source (garlic), not boiled before eating.

        Garlic in oil
        For added safety, the Food and Drug Administration (FDA) now requires that all commercial garlic in oil products contain specific levels of microbial inhibitors or acidifying agents such as phosphoric or citric acid. Although most garlic products do contain these additives, some boutique or specialty mixes may not. Always check the label to be sure.

        As for home-prepared mixtures of garlic in oil, the FDA recommends that these "be made fresh for use and not left around at room temperatures." Refrigerate left-overs for use within 10 days, freeze or discard.

        The reason for the concern is that unrefrigerated garlic in oil mixtures lacking antimicrobial agents have been shown to permit the growth of C. botulinum bacteria and its toxins, without affecting the taste or smell of the products. Toxin production has been known to occur even when a small number of C. botulinum spores were present in the garlic. When the spore-containing garlic is bottled and covered with oil, an oxygen-free environment is created that promotes the germination of spores and the growth of microorganisms at temperatures as low as 50 F.

        Botulism is a potentially fatal food poisoning characterized by blurred or double vision, speech and breathing difficulty, and progressive paralysis. Without prompt and correct treatment, one-third of those diagnosed with botulism may die. C. botulinum spores are widespread in the environment but cause no harm as long as oxygen is present. Also, the toxin produced by C. botulinum bacteria is readily destroyed by heat. Boiling a potentially suspect mixture for 10 minutes, plus one minute for each 1,000 feet above sea level, will destroy any botulism toxin that may be present.

        Vegetables and herbs in oil
        Less has been documented on the dangers of storing whole chilies, fleshy vegetables or herbs in oil, but they, too, are best made fresh, with leftovers stored in the refrigerator for use within 10 days. Vegetables have a high water activity level which further encourages the growth of C. botulinum bacteria in an anaerobic environment. Even when dried, there is still the potential for risk, unless the vegetable has been acidified to a pH of 4.6 or lower.

        Dried tomatoes in oil are less of a safety concern than other mixtures in oil because the pH of tomatoes is generally 4.6 or lower. In addition, by drying the tomatoes, conditions become even less favorable to growth of C. botulinum due to a decrease in water activity. Dried herbs in oil also are less of a safety concern because of their low water activity. However, to ensure safety, it is recommended that all tomato in oil and herb in oil products be stored at refrigerator temperatures.


        i think every hound should read this publication from the colorado state university about flavored oils and vinegars:

        1. re: alkapal

          Fair enough - in the freezer it goes. Thanks all.

          Now...who wants a jar for thanksgiving! :-)