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Dangers of Adding Herbs to Oil

post #1 of 6
9/20/08 at 9:44am
Thread Starter 
I posted a technique for oven drying tomatoes and then packing them in olive oil. I suggested that some fresh herbs might be added to the oil for a flavor enhancement. It was suggested that doing such a thing could be dangerous as some sort of bacteria could grow and cause people to become ill.

This seems a little odd to me because I've been adding herbs to dried tomatoes for years with no ill effects and because I know of at least two California companies that make oil-packed sun dried tomatoes that use herbs in their product. In addition, I have been using a French oil - Moulins de la Brague - for many years that is shipped with fresh rosemary and other herbs and peppers in the bottle, and they've been making the product for a few hundred years.

So now I'm curioius. Is there a potential for a health problem when using fresh herbs in oil products? If so, how do the aforementioned companies add the herbs safely?
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post #2 of 6
9/20/08 at 10:24am
I just found this info on the UC Davis Extension site for Calaveras County.

FLAVORED OILS
"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 the growth of C. botulinum are met: low acid environment with pH higher that 4.6, anaerobic conditions (oil), food and moisture source (garlic), not boiled before eating. 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 three weeks. 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 insure safety it is recommended that all tomato in oil and herb in oil products be stored at refrigerator temperatures.

Avoid Rancidity
In addition to reducing the potential for growth of C. botulinum bacteria, storing flavored oils in the refrigerator helps keep the oils from becoming rancid. A putrid "off" odor indicates the development of rancidity. All fats and oils will become rancid given enough exposure to air, sunlight and heat. Polyunsaturated fats, like vegetable oils, are especially prone to such deterioration. Eating rancid food won’t make you sick, but it may be unhealthy in the long run. Rancid fat contains chemicals called peroxides and aldehydes that can damage cells and may even encourage cholesterol to clog arteries.

It is important to note that rancidity and the presence of botulinal toxins are not necessarily related. Toxin may be present without any hint of an off-odor. Likewise, an off-odor does not necessarily indicate the presence of botulism toxin. It does, however, indicate the product may have been left for long periods at room temperature, which would promote the growth of C. botulinum. Therefore, it’s best to discard any oil-based mixtures that have become rancid so they’re out of reach of humans or animals."

And here's the whole article at the site:
Flavored Vinegars and Oils
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post #3 of 6
9/20/08 at 10:46am
Shel -

/q
cause people to become ill.
/uq

if you are thinking about botulism, it can be fatal - which is an extreme case of "ill" and can easily ruin your whole day.

....."the commercial guys do it ......"
if you have the process control - especially time, temperature and pH, to do what they do, you too can produce a safe product. most home kitchens do not have the proper controls.

and do not count on "refrigerated" to "keep you safe" - low temperatures will discourage / slow down / inhibit botulism, but it does _not_ kill botulism.
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post #4 of 6
9/20/08 at 2:07pm
Yes, all of the above. And I remember reading that if something is infected with botulism, it doesn;t smell different, but that just putting your finger in and tasting it can kill you. I don't remember where i read that, but it made me very afraid of botulism.
However, I also remember, back maybe in the 60s, there was a shipment of vichyssoise locally that had botulism and some people died. There were lots of articles on the newspaper then and they explained that other soups were not so risky because boiling them in an open pot kills botulism but vichyssoise was eaten cold. Same for tuna that a couple of years later also was found with botulism after someone died, and we usually eat tuna unheated.
So, i imagine that heating the oil to 212F should kill it, right? So if you use it as a base for a sauce it should be safe? or not?
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post #5 of 6
9/20/08 at 2:36pm
botulism is a bacteria.
it reproduces via "spores" - which one might typically associate more with fungus.

neither form is detected by smell or taste.

if the bacteria is actively growing, 100'C temperature is an adequate kill level.
in spore form, 116'C is required for a kill temp

a minimum 10 minute boil is recommended for anything that may remotely contain active botulism. this is, in my opinion, a rather loose definition of "how to get the whole pot up to 100'C"

the FDA/USDA now require all commercial operations preparing stuff like canned/jarred garlic & herbs to add chemical acidifiers - not just relying on "vinegar" being innately sufficiently "acid" - to ensure the pH level is so acid any botulism spores cannot become active.

I'm not trying to blather out a bunch of scare tactics - but you absolute must realize that botulism is not something to approach with a "well, maybe it'll work" approach. research what you want to do and apply the appropriate measures to the iota.
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post #6 of 6
9/21/08 at 8:59am
Sure people have been making herb oils for years and you don't really hear about people "getting sick" from it. Sure it might be a very slim possibility that you get botulism from your herb oil, but botulism kills, not sometimes, but most times. So while the possibility is slim do you really want to risk death? Flat out, if you want to make herb flavored oils, then keep them in the fridge and use them up in a decent amount of time.
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