Many infused oils, honeys, vinegars, and liquors could pose significant health risks, but there are ways to make these popular holiday gifts much safer.
Foods that aren’t processed correctly or stored at the proper temperature can become a breeding ground for bacteria. The same is true for foods that are not sufficiently acidic. For example, garlic cloves in oil look lovely. But they have also been linked to botulism poisoning—which is not lovely.
It’s not that home cooks shouldn’t make infused food products for the holidays, but they should take proper precautions. With that in mind, food safety experts Natalie Seymour and Candice Christian offer basic guidelines for showing loved ones you care, but not making them violently ill:
Sterilize your containers
No matter what infused product you are making, you need to wash and boil your bottles or jars for 10 minutes in order to eliminate risk from residual pathogens on the container.
Use quality ingredients
Use fruits, vegetables, or other ingredients that aren’t bruised or scraped. This makes them less likely to harbor problematic bacteria. And don’t forget to wash them.
Refrigerate or freeze
We recommend storing the finished product in the refrigerator or freezer. This helps preserve the product’s quality—and makes it less likely that any bacteria in the product will reproduce.
For infused oil or honey
Oils create an environment with no oxygen, which is an ideal place for Clostridium botulinum bacteria to grow and produce botulism toxin (which is bad). Since produce items like garlic and herbs can harbor C. botulinum, it’s a good idea to destroy any bacteria on those items before adding it to oil. You can do this by soaking the products in a citric acid solution to reduce the pH and destroy bacteria that might be present.
Specifically, the citric acid solution needs to be strong enough to bring the pH level of the garlic, herbs, or other ingredients down to 4.2 or less within 24 hours. This paper outlines how you can do that. (This technique is also how manufacturers process infused oils that you can buy off the shelf.)
Skipping the acidification step is risky, so refrigeration is important to prevent the growth of bacteria. Based on the best available science, we recommend that, if you’re not using an acid solution to treat the ingredients in infused oil, the final product should be refrigerated—and thrown away within four days of being made. The only way around this is to freeze the oil until you’re ready to use it.
The oil or honey should also be heated to 180 degrees Fahrenheit before adding it to the other ingredients. Step-by-step safety instructions are available here.
If you make infused oils with properly acidified vegetables or herbs, you can keep them safely at room temperature, though you may want to refrigerate them in order to preserve their quality.
For infused vinegar
Heat the vinegar to 190 degrees Fahrenheit before adding it to the other ingredients, and be sure to fill the container to within 0.25 inches of the top of the container. If you’d like more details, you can find them here.
Once you’ve made them, infused vinegars can be safely kept in a cool, dark place for 2-3 months or refrigerated for 6-8 months.
(Note: If someone has given you infused vinegar, and it has started bubbling, that means that it is fermenting. Because any number of organisms could be causing the fermentation, and some of them are bad, you should throw it away. And, obviously, if the vinegar gets slimy, cloudy, or moldy, throw it away.)
For infused liquor
From a food safety standpoint, infused liquors get tricky. Many people think alcohol always kills pathogens, but it’s not that simple.
It depends on the pathogen, the fruit or vegetable, the alcohol content of the infused liquor, and how long the pathogens are exposed to the alcohol. For example, an infused liquor may be safe after being infused for six hours. Or it may be unsafe after six hours, but safe after 24 hours. Or it may never be safe.