I have read much information available on the internet regarding making flavoured oil infusions; chili oils, herbs flavored oils, garlic oil, and so on – most of it is wrong or ill informed. The ridiculous mystique and aura of classy snobbishness surrounding containers of flavoured oils adorning your kitchen shelves to enhance the culinary moment is only perhaps surpassed by that of wine or schnapps snobs at a tasting. While many people believe it to be a good idea, often little thought is given to the issues of food safety and hygiene. I am quite alarmed at the ‘folklore’ as opposed to real science that is being posted by many people on the internet and the ignorance with regard to the high risk of botulism affecting these oils. A simple search on Wikipedia and elsewhere for botulism will make you think and question why so many people are still in the gene pool.
I recommend you visit this site to download and read the information related to home canning. Here.
Without being alarmist in any way:
There is a real and genuine risk of botulism from oil infusions. If you think otherwise then you are simply being blind and foolish. The effects arising from botulism as it attacks the nervous system are a real leveler in the common sense and longevity department. Vegetables and herbs preserved by covering in oil potentially provide the four conditions necessary for botulinum toxin production:
1. Absence of oxygen
2. pH greater than 4.6
3. The presence of Clostridium botulinum spores
4. The presence of water.
For the cook and food preparer there are some simple steps you can take to limit the risks involved with home prepared infusions. I still prepare both fresh and preserved infusions with the fresh being the preferred and (I believe) best method. There is no real advantage to be gained in terms of flavour and quality by extended storage of any produce suspended in oil regardless of what many others say. The likelihood of spoilage is very high, different food materials have different chemical properties and water content, and contaminants from commercially grown produce (herbicide, pesticide, fetilisers…) as well as natural soil borne particulates cannot be easily isolated. As a very important note, botulism can be present without any visible signs (mould. cloudiness).
I hate to be a party pooper but those posters who write about putting garlic and fresh peppers into oil are at a raised risk of dropping out of the evolutionary process and ending up as prime fertiliser for a piece of land somewhere. Great for gardeners but not too good when it affects you personally.
Ask yourself the really honest question: “Do I want the oil infused product for consumption or do I really want it for display on a shelf in the kitchen to get a rustic look and feel (to show off your kitchen credentials)?” Having said that, you are also at risk walking down the street and even more so while at home.
IF the answer regarding usage is consumption, then, while “fresh is best”, you can make some rather tasty oils for culinary use that do keep for extended periods but caution is required.
IF the answer is display, then use brine or vinegar instead. Not only does it look better, the product will last longer AND still (hopefully) be edible.
So, rant and caveats out of the way, what CAN you do to limit/reduce the risk of botulism while still enjoying ‘oil infused’ produce that is ‘aged’ and ensure a good taste experience.
Simple rule, exercise caution. The primary cause of infection is with garlic and fresh herbs.
Here are some suggestions on preparing infusions.
1. Ensure the product to go into the oil is clean and free from dirt and bugs – see methods.
2. Avoid fresh or ‘wet’ products if possible (see below) and exercise the same caution you would with any fresh produce.
3. Dry chilies and herbs completely before use – either in the sun or in an oven on a low heat (chilies should rattle when properly dried) – or blanch fresh herbs in a brine or vinegar solution. The capsaicin in chili peppers will not spoil or lessen as a result – if anything, the flavour will be enhanced. As a note, the ‘hot’ in chilies is NOT in the seeds; the seeds happen to be hot due to their proximity to the capsaicin glands near the top of the pepper itself – to reduce the hotness in a chili simply slit open lengthwise, fold open, and using the flat edge of the knife scrape the white membrane ‘rib’ away in one movement from bottom to top.
4. Only keep oil infusions with fresh ingredients for up to a week in a clean and sealed container. Any more than this and there is no real flavour benefit. The ‘aged’ myth is best kept for port, wine, single malts, and properly treated infusions. If there is any cloudiness, bubbles, or an ‘off’ smell then THROW IT OUT.
5. IF you still think otherwise and are confident in your own risk assessment then you can preserve for longer if:
A: The ingredient to be added to the oil is dry AND/OR (for garlic) prepared in a brine solution (sterilising aid)
B: AND – This is a MUST for long term infusions… You need to add something to increase the acidity level and reduce the pH level to a level that inhibits (note the word is not ‘prevents’). This can be lemon juice (fresh only), vinegar (I use cider or white wine vinegar), or a culinary form of phosphoric (E338) or citric acid (E330). This should be at a ratio of about one tablespoon of vinegar/lemon/acidity regulator to one cup of oil – with all of these additives it is important to understand their role in ensuring their effectiveness as a mould inhibitor. A simple search of the FDA web site will point out the risks involved. In addition it should be noted that the inclusion of an acidity regulator has been a mandatory requirement for commercially produced oil infusions. The level of deaths and serious illness from home-prepared oil infused products is still very high.
C: Use glass containers in preference over metal and avoid aluminum containers altogether to prevent leaching and tainting. Ensure the containers are properly sterilised immediately prior to use and, if storing for an extended period, the closure provides a good seal to prevent air contamination. Refrigerate.
My personal favourite oil infusion recipes can be found here.