Return to the Harvest Forum | Post a Follow-Up

 o
Botulism in flavoured oils, honey and vinegars?

Posted by pdcraig 6a (My Page) on
Thu, Aug 25, 11 at 21:47

This is a bit long winded so please bear with me.

I know about botulism and ph levels and heat processing for fresh food but I thought/have read that it also required a fairly high level of water activity to germinate and produce toxins.

I wanted to make some herb flavoured oils, honey and vinegars and was reading up on various recipes and combinations. I was surprised to find lots of contradicting information on safety.

I thought, and have done this, that using dried herbs, sundried tomatoes and garilc to infuse oil was safe because it lacked the required water activity. Honey is similiar. I have made both and stored both at room temperature for months with no ill affects.

Using fresh herbs, if they were strained out, you had eliminated the "food source" for botulism to grow.

Have I just been lucky?

Following the hot pepper oil thread, it would appear so but most of the flavourings are fresh not dried. The rosemary oil thread kind of made it sound like different oils make a difference. Do they make a difference?

A lot of recipes on-line said to wash fresh herbs in a weak chlorine bleach solution to kill any bacteria but only a couple mentioned anything about refrigerating a finished product.

The reason I'd like to clarify this is beacouse I wanted to make some up as Christmas gifts and they require some steeping time but if it isn't safe..... Not such a great gift idea, especially if it has to be refigerated and has a short shelf life.

Any help is appreciated.


Follow-Up Postings:

 o
RE: Botulism in flavoured oils, honey and vinegars?

I don't think botulism can grow in vinegar no matter what, but I'd remove the flavorings after steeping. NCHFP says to refrigerate but BBB has a canning recipe for fruit vinegar. Shelf life might be as short as 4 months, but considering it takes a month to steep, that's 5 months. I would freeze the herbs/fruit and make the vinegars later.

Oil is a different story - personally, I'm not comfortable with oils, even if kept in fridge. Don't know about honey - sugar should keep it OK, but depends on what your flavoring is. I like the pollen to flavor the honey, not add anything later ;-)


 o
RE: Botulism in flavoured oils, honey and vinegars?

As you have discovered it is a very controversial topic and while there are many "recipes" out there, there are few approved instructions for the oil based products. Vinegars, yes. Honey, somewhat. But oil, no.

It is especially important to take great care when one is talking about gifting oil based foods. It is one thing to accept some risks for ourselves but something else entirely when we are talking about giving these marginally safe food as gifts to others. The potential negative consequences far outweigh the value of the gift IMO.

Vinegars, as aj said, have a built-in safety factor that oils do not have. Their acidity makes the development of toxin difficult if not impossible assuming the proper 5% is used and the herbs are first infused with vinegar.

Oils, as a general rule, are not allowed in home canned foods. There are a couple of tested exceptions but since we have no access to the many commercial safety products used to make these types of foods, I strongly discourage the gifting of ANY oil-based home prepped foods. The risk and consequences are simply too great.

Stick with the vinegars and encourage refrigeration of them once received or please reconsider the many other no-risk gift options that are available.

Dave


 o
RE: Botulism in flavoured oils, honey and vinegars?

Below is a reliable Extension document regarding herbs and other infusions for oil. The NCHFP and many Extension agencies have documents regarding vinegar infusions. Methods do differ slightly but the differences have more to do with shelf life and clarity than safety.

Basically dried herbs, peppers, etc. in oils are OK or something like fresh garlic which is infused in the oil then removed. Citrus, like lemon peel, is fine also.

Ellie Topp devised a method for heating the oil which increases safety as it further reduces water activity. Copies of her work can be found online and links have also been provided within this forum.

However, Christmas is still a good while ahead and there is a risk that an infused oil will turn rancid before then.

I would not recommend giving any infused oil which cannot be safely kept at room temperature (i.e. something like lemon infused) as my personal experience has been that recipients don't follow directions. I gave up on gift oils that must be refrigerated as I've seen friends ignore those instructions.

I am not sure what you would want to infuse in honey. Walnuts can be bottled in honey. Lavender blossoms, vanilla beans, thyme are common options. According to Clemson, the average pH of honey is 3.9. While some honeys are less acid, the water activity is much lower than would be required for the growth of botulism. Honey is just not a hospitable medium for harmful agents.

Carol

Here is a link that might be useful: Herbs and Vegetables in Oil


 o
RE: Botulism in flavoured oils, honey and vinegars?

Thanks for the input everyone.

Here is my confusion. Botulism requires a ph greater than 4.6, an anaerobic environment and a water activity of 0.92 or greater to produce toxins. That is the information I have.

The danger with food packed in oil was/is the oil creates the airless condition, fresh food and herbs have the higher ph and the higher water activity so the toxins can be produced making the fresh food dangerous. My understanding is that the contamination was the food, not the oil, or vinegar or the honey. Is that right? I didn't think oil, honey or vinegar could support the growth of the toxins.

Carol, I read Ellis Topp's method previously in the hot pepper thread and thank you for the link for the other.pdf

Rosemary honey is delicious as a glaze for salmon or chicken. Lavender or rose for tea. Much like flavoured sugars.


 o
RE: Botulism in flavoured oils, honey and vinegars?

"Honey is just not a hospitable medium for harmful agents."
if that is true, then why do Dr's
say babies under 1 cannot have honey? I was told that there is a chance of botulism in the honey, and babies bodies couldn't handle it! Is that true?


 o
RE: Botulism in flavoured oils, honey and vinegars?

ahbee01 my understanding is honey can contain the spores and an infant's digestive tract is underdeveloped and rather than passing through harmlessly like an adult the spores can germinate and produce the toxins.


 o
RE: Botulism in flavoured oils, honey and vinegars?

Yes, that's true. But no responsible individual gives babies honey.

Botulism spores may exist in honey. Botulism spores exist in lots of things, including soil, and thus may reside in and on all kinds of produce. But until the right set of conditions those spores remain essentially inert. Honey does not provide those "right conditions." Therefore, the harmful toxins required to harm someone do not develop.

I'm not sure about pdcraig's confusion. Essentially if you have pieces of fresh low-acid product surrounded by oil, the oil creates a perfectly insulated little biosphere for the development of the toxins. It's not the oil per se, it's the vegetable matter in it.

I think it would take a microbiologist to explain further.

I have seen sources like the Herb Companion provide tutorials on infusing honeys and vinegars.

Carol


 o
RE: Botulism in flavoured oils, honey and vinegars?

Okay, one last shot at this,

Here is the last part of Ellie Topp's instructions, copied directly from the .pdf.

"Line a small strainer with a coffee filter.
Saturate coffee filter with regular
canola oil so that the flavoured oil is
not absorbed and lost in the filter.
Strain oil into a clean glass jar, cover
and store in the refrigerator at all
times. Use oil within a month."

So refrigerate and limited shelf life.

This is from the Herbs and Vegetables in Oil from the Oregon State University Extension Service.

"When raw or cooked vegetables or raw herbs are immediately removed after flavoring oil, the bacteria
will not have a "food source" for growth. The flavored oil can be stored safely at room temperature.

When vegetables or herbs are dried, water will not be available for bacterial growth. Therefore,
dried vegetables or dried herbs in oil can be stored safely at room temperature."

No refrigeration and no mention of shelf life.

I'm probably missing something painfully obvious but these two sources don't seem to agree.


 o
RE: Botulism in flavoured oils, honey and vinegars?

1) Different sources can't always be expected to agree. :)

2) This is, as mentioned at the beginning of the discussion, a controversial topic since it is only borderline safe at best. So disagreement is to be expected.

3) My interpretation of the Oregon document (linked below) is that they actually do agree for the most part. As an extension I would expect them to use the NCHFP guidelines. The issues are just stated differently and so cannot be taken out of context. There are exceptions and limitations included throughout the document.

4) The primary issue is fresh vs. dried foods being added. Using dried herbs and spices - no problem IF one can be assured of it being fully dried. Human error is invited - How would you know? How would you test moisture content? What is fully dried garlic to one is still 10-15% moisture content to another. Thus risk survives.

5) Using fresh ingredients and IF fresh foods are used ALL of it MUST be filtered out. Filtering ALL of it out invites human error once again. How does one know ALL has been removed, that none remains? Microscopic examination?

So, given the potentially lethal level of risk and to eliminate the role of human error as much as possible, freezing or limited 3 week refrigeration is the guideline. No shelf storage.

And IMO, certainly no gift giving of flavored oils. You have no control over how long they would keep it or store/use it. Accept the risk for yourself if flavored oil is so important to you. Do NOT pass that risk on to others.

Hope this helps but the bottom line with flavored oils is it is risky, not worth the risk to most, and not recommended.

Dave

Here is a link that might be useful: Oregon Ext. on Flavored Oils


 o
RE: Botulism in flavoured oils, honey and vinegars?

Here is the recipe for flavoured oil copied directly from the Oregon Extension office document I keep getting referred to

Garlic, Vegetable, or Herb Flavored Oils
2‐3 heads of finely chopped garlic or
3 cups of: finely chopped vegetables, or a combination of vegetables and herbs,
or loosely packed coarsely chopped herbs
3 cups olive or vegetable oil

Heat the oil over medium heat until you see a few bubbles rise from the bottom of the pan. Reduce
heat to low and let steep for about 2 hours. Keep the temperature around 170F. Do not allow oil to
get too hot or it may develop a bitter flavor. Use a candy thermometer to regulate temperature.
After 2 hours, remove the pan from the burner and strain hot oil through a coffee filter into a heat
resistant container. Let it cool to room temperature for about 30 minutes. Re‐strain oil into clean
storage jars.
The strained oil can be stored at room temperature indefinitely, but the quality will be better if kept
in the refrigerator or freezer for long‐term storage.

I am not taking anything out of context, there is no mention of specialized equipment for straining or microscopic checking of the final product. Double strained through a coffee filter. There is a qualifier on quality if left at room temperature not safety.

According to Ellie's directions this recipe isn't safe. It is heated 130 degrees lower than hers, not refrigerated and has no shelf life.

This is why I'm confused, you all keep pointing me to two sources that say completely different things.


 o
RE: Botulism in flavoured oils, honey and vinegars?

It also says at the top of page 2:
Garlic‐flavored Oil
Oil can be flavored by heating finely minced raw garlic in it (at a very low temperature). Remove the
garlic by pouring the cooled oil through a fine‐meshed sieve lined with several layers of cheesecloth
or a foodgrade paper towel. If all of the garlic is not removed, the flavored oil must be stored in the
refrigerator (for no more than 3 weeks)
.
Underlining is mine and that is the context i was referring to. How would you know it was all removed?

I don't keep referring you to any source. :) I wouldn't make these oil items for any reason simply because the associated risk far outweighs any benefits. Vinegars I make, honey I have made. Oils - no way.

Carol "offered" it as an alternative info source for you if you were interested. If, despite all the controversy surrounding them, you insist on making these oil products then the choice is yours of course. But you are not going to find any source which guarantees you shelf storage safety without reservations and qualifications. The only guaranteed safety comes with refrigerated for a max of 3 weeks or frozen.

Dave


 o Post a Follow-Up

Please Note: Only registered members are able to post messages to this forum.

    If you are a member, please log in.

    If you aren't yet a member, join now!


Return to the Harvest Forum

Information about Posting

  • You must be logged in to post a message. Once you are logged in, a posting window will appear at the bottom of the messages. If you are not a member, please register for an account.
  • Posting is a two-step process. Once you have composed your message, you will be taken to the preview page. You will then have a chance to review your post, make changes and upload photos.
  • After posting your message, you may need to refresh the forum page in order to see it.
  • Before posting copyrighted material, please read about Copyright and Fair Use.
  • We have a strict no-advertising policy!
  • If you would like to practice posting or uploading photos, please visit our Test forum.
  • If you need assistance, please Contact Us and we will be happy to help.


Learn more about in-text links on this page here