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I am infusing olive oil with truffles. How can I do it safely? Heating the oil destroys the truffle smell and pickling it is a sure way to do the same. Are there any other methods? Perhaps some type of filter that will eliminate the particulates?

Cascabel
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Seth
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2 Answers2

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Edit This answer assumes that you want a shelf-stable oil. If you are going to use up the oil immediately (or within 3 days and refrigerate), methods like the pressure charging from moscafj's answer don't pose a safety problem.

Simply, you can't. I am not sure how industrial oils are made, maybe they are irradiated or simply made under sanitized conditions and at the end microbiologically checked to ensure that a given batch isn't contaminated, but it isn't something you can do at home.

There are no methods accessible to home cooks to prevent botulinum in low-acid foods. Heat won't work, as botulinum bacteria don't just live like any other bacteria, they also form spores which will survive temperatures which would have incinerated other species with a single form. You can never reach these temperatures in a watery medium, e.g. in canning purees, in industry it is done in canners with much higher pressure than home pressure canners. In oil, you could theoretically reach the temperatures as you are not limited by the water's boiilng point, but as you pointed out, the flavor will change a lot. In the worst case, you will have to bring the oil to above smoking point to ensure safety.

Filters won't work, as any filters small enough to hold back bacteria are too tight to permit something as viscous as oil to flow through, and botulism toxin isn't "particulate matter", it is dissolved in the food.

rumtscho
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    Truffle oil have nothing to do with truffles, it is made by a synthetic aroma component of truffles. – Stefan Jan 30 '14 at 14:56
  • @rumtscho: Gamma irradiation is incompletely effective against botulism toxin: http://www.cdc.gov/biosafety/publications/bmbl5/BMBL5_appendixI.pdf (see table 1) Looks like pre-autoclaving your truffles is the way to go. That MIGHT be faked up with a pressure cooker. – Wayfaring Stranger Jan 30 '14 at 14:59
  • OK, I thought it was obviuos that my first sentence was pure speculation. The important part was to point out that, whatever they do, you can't do it at home. Thank you both @stefan and Wayfaring for giving the details of how it is actually done, they are interesting. – rumtscho Jan 30 '14 at 15:00
  • @rumtscho: sure, your speculation just made me curious. – Wayfaring Stranger Jan 30 '14 at 15:23
  • @WayfaringStranger the fact that there are no FDA approved recipes for home canning of certain low-acid foods like pumpkin puree makes me think that you can't reach the necessary water/steam temperature in a home pressure cooker. – rumtscho Jan 30 '14 at 15:37
  • @rumtscho I doubt FDA has looked deeply into such molecular gastronomy style esoterica. That's probably good, because if you try something like this without considerable research, and equipment testing, you could kill yourself. – Wayfaring Stranger Jan 30 '14 at 16:01
  • @WayfaringStranger it has certainly looked into home canning. I just inferred that, if you can't autoclave canned purees to a high enough temperature to kill botulin spores, then you probably can't autoclave truffles in your home pressure canner either. I doubt that the botulism spores in truffles would be somehow different to kill than the ones in pumpkin puree. – rumtscho Jan 30 '14 at 16:04
  • @rumtscho true, that. – Wayfaring Stranger Jan 30 '14 at 17:01
  • I don't understand the question or concern here -- in other foods (e.g., feta cheese) the oil is used to block oxygen and hence preventing the food from spoiling. Wouldn't that mean that anything you put into oil is safe anyway? – Robert Jan 30 '14 at 22:32
  • @Robert then read something on botulism, the Wikipeida article should suffice, or google the Big Bad Bug Book by the FDA. This is a bacteria which lives without oxygen and produces a toxin from which you can die even with proper medical care and will be in hospital for weeks else. Contamination is rare, but very dangerous. It grows in plant matter stored without access to air, unless it has been made very acidic (proper pickling). Feta doesn't come from plants, undergoes a fermentation in the presence of oxygen, and is also somewhat acidic. – rumtscho Jan 31 '14 at 13:34
  • Thanks. No wonder I have not heard about this -- 20 cases in 2011 in the US! Your initial answer makes it sound as if this was much more common and all home made infused oils would be dangerous. – Robert Jan 31 '14 at 17:07
  • @Robert it seems you don't understand how food safety works. For the FDA, there are only two categories, "safe", "dangerous" and nothing in between. The limit is something like "if there is more than 1x10^7 chance that bacteria survive in this food, it is dangerous". So both foods which have a 1 in 2 chance to send you to the hospital and foods which have a 1 in a million chance to send you to the hospital are dangerous. And all homemade infused oils are indeed *dangerous* by this definition. Now, you may have a very different personal definition of dangerous and think that you are OK (tbc) – rumtscho Jan 31 '14 at 17:21
  • (continued) with a risk of 1 in 1000. But the problem is that this cannot be calculated easily. Bacteria growth is highly non-linear and it can be that in food processed at 120 Celsius, only one bacteria in a billion remains alive, but that at 115, one in a million stays alive, and at 110, half of them stay alive. The only ones who have the actual data to calculate the conditions needed for ensuring that the risk is less than 1 in 1000 are the FDA (and international analogs), and they have not calculated them. So, by the only reliable definition in the world, all infused oils are dangerous. – rumtscho Jan 31 '14 at 17:24
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    @Robert: I don't know where you got 20 from, there's an average of 145 cases of botulism in the USA every year. Part of the reason that number is low is that most people do not attempt home canning; and most of those who do, use high-acid foods like tomatoes. *C.botulinum* is one of *thousands* of [anaerobes](http://en.wikipedia.org/wiki/Anaerobic_organism); you can probably get a dozen more examples from Wikipedia, including facultative anaerobes like Listeria, which affects 1600 people in the USA every year all by itself. All types combined easily affect tens or hundreds of thousands. – Aaronut Mar 02 '14 at 13:24
  • @Aaronut: There is indeed an average of 145 cases of botulism in the USA every year, but only approximately 15% of them are foodborne (*). Which makes 20 cases in 2011 cited by Robert a reasonable number. Source: http://www.cdc.gov/nczved/divisions/dfbmd/diseases/botulism/ (*) 15% according to CDC classification, which makes sense to me, but wasn't clear at first: they also have 65% of infant botulism that is technically foodborne, but different from adult one. – kdubinets Oct 06 '14 at 18:47
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Dave Arnold developed an effective way to infuse oil with aromatics that are heat sensitive. To employ it, you need an ISI or other brand whipper. Here is an example: https://www.starchefs.com/product_education/iSi/whipper/html/recipe-lemon-infused-extra-virgin-olive-oil-dave-arnold.shtml

I've had great success with the technique and see no reason why you couldn't use it with truffles. From a brief google search, it looks like you should refrigerate this oil and use it within a month to avoid any risk from botulism.

moscafj
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  • That example is of using lemon, which is acidic. The doesn't seem like an equivalent of the problem faced with other flavors. – Caleb Mar 02 '14 at 08:04
  • It is an intriguing infusion method though. [Low End](http://www.amazon.com/Mosa-Whipped-Cream-Dispenser-500ml/dp/B00BSYNZMC/ref=sr_1_16?ie=UTF8&qid=1393756773&sr=8-16&keywords=isi+whipped+cream+dispenser)- [High End](http://www.amazon.com/ISI-Gourmet-Whip-Quart-PLUS/dp/B004GFS2I2/ref=sr_1_4?ie=UTF8&qid=1393757147&sr=8-4&keywords=isi+whip)- [Chargers](http://www.amazon.com/iSi-10-Pack-Cream-Whipper-Chargers/dp/B000RZRYF2/ref=sr_1_3?ie=UTF8&qid=1393757233&sr=8-3&keywords=isi+chargers) It's worth experimenting. Refrigerate and use quickly. – Jolenealaska Mar 02 '14 at 10:49
  • @Caleb: No, it uses lemon *zest*, which is pretty much inert. It's like using dried spices; you can even buy it as a shelf-stable product. You can't acidify oil; the whole concept of an acid or pH only makes sense in aqueous (water) solutions. – Aaronut Mar 02 '14 at 13:28
  • @Caleb the original question asked how to infuse an aromatic ingredient in olive oil. Acid has nothing to do with it. One could heat the lemon zest in the olive oil to infuse it, but that would destroy the aromatic nature of the olive oil. While the original poster was concerned about losing the aroma of the truffle by heating, I believe the ISI method would accomplish his goal. Safety is a secondary issue, but one would simply need to refrigerate and use in the near-term. – moscafj Mar 02 '14 at 16:34