Fear of Botulism from Oil Infused Herbs
Question submitted by Kate: I was watching a video on canning that addressed botulism. It said that there is a danger when infusing herbs in oil, I do this often when I make salves and lotions. How can I do this safely?
Answered by Judith Fox Smith, MS,of Foxsmyth Herbal
Infusing herbs into oil is a wonderful way to extract an herb's phytochemicals, aromatics and culinary flavors. Depending on the composition, the infused oil can be used for therapeutic, cosmetic or culinary purposes. Yes, poorly prepared oil infusions do have the potential to be spoiled with botulism endospores or fungal spores. Botulism can result from either ingestion or through an open wound on the skin from contaminated oil.
To better understand these contaminants take a look at the reference links provided below. These include CDC and FDA guidance on safe food preparation. That said, globally, botulism is fairly rare, with approximately 1,000 cases yearly.
The Clostridium botulinum are abundant in the environment however they will only grow under anaerobic conditions; this is in a closed container (low oxygen) on low acid foods (below pH 4.6). Oils do not have a pH as they do not have water. Many herbs, berries and vegetables have pH >8. The addition of these to oil in fresh form add water as source of oxygen for the bacterium and make for a welcome environment for C. botulinum growth in a closed container. Heating foods above 121F does kill the bacterial rod form, however the endospores can still grow if the conditions are right.
The best practice is to use dried herbs for infusion and to heat the oil. Decant or filter out the herbs and store in cool environment, protected from light. The state of Maine provides a nice instructional bulletin for the preparation of herb infused oil, see references for a link. I also recommend James Green's book for instructions to a Folk Method and Hot Infusion Method.
Hot Infusion Method for Cayenne Oil:
Mix together in a closed bottle, 100 grams (4 oz.) Cayenne powder in 1 L oil. Place bottle in water bath and heat at 140F to 160F for 4 hours. Remove from heat and cool for 12 hours while the oil passively clarifies. Pour off the cleared oil into a clean bottle. Store in a cool environment and protected from light.
Generally speaking, follow these 5 Food Safety Rules in The Kitchen:
Rule 1: Wash hands between steps.
Rule 2: Sanitize work surfaces.
Rule 3: Use separate cutting boards: raw meats, vegetables, cooked foods.
Rule 4: Cook foods to safe temperatures.
Rule 5: Keep hot foods hot and cold foods cold.
1. Clostridium organisms https://en.wikipedia.org/wiki/Clostridium
2. What is Botulism? https://en.wikipedia.org/wiki/Botulism
3. Botulism in Infused Oils. https://wasabi.org/botulism-in-infused-oil/
4. Centers for Disease Control, Botulism. https://www.cdc.gov/botulism/index.html
5. FDA Food Safety Rule- RE: FDA Food Safety Modernization Act of January 26, 2016 https://www.fda.gov/food/food-safety-modernization-act-fsma/fsma-final-rule-produce-safety
6. FDA low acid canned food guidance documents: https://www.fda.gov/food/guidance-documents-regulatory-information-topic-food-and-dietary-supplements/acidified-low-acid-canned-foods-guidance-documents-regulatory-information
7. State of Maine, Bulletin #4385, Safe Homemade Flavored and Infused Oils https://extension.umaine.edu/publications/4385e/
8. James Green, The Herbal Medicine-Maker's Handbook, Chapter 17. The Crossing Press, 2000, ( tenspeed.com )
Judith Fox Smith, MS, is the founder of Foxsmyth Herbal, in Stoneham, MA. Judy is a biological research scientist and clinical herbalist. She is the founder and past president of the Eastern PA chapter of American Herbalist Guild, the Herb Gatherers of Lansdale, PA and past Vice President of San Antonio Herb Society. She combines her knowledge of biology and botany with her passion to provide practical herbal and lifestyle recommendations for a holistic balance in today’s techno-driven world.
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