I was amazed to read from a book on growing Garlic by Penny Woodward that it is dangerous to store garlic in oil in the fridge. Apparently there were some serious cases of botulism in the USA and Canada in the 1980's. Laws have been passed in these countries plus Australia to ban storing any herbs, spices or vegetables with a PH of no greater than 4.6 being stored in oil in a fridge. Foods with a PH of below 4.6 will not usually support the growth of bacteria that cause food poisoning.
Anyone who bottles fruit or veges needs to know of the risk of bacterial infection. Garlic is prone to these problems because it is a low acid vegetable of between 5.3 and 6.3. This means that with the right conditions, along with other low acid/low salt fruits and vegetables it is capable of causing botulism. Conditions that can cause its growth are moisture, lack of oxygen, room temperatures and low acidity. These are all conditions that occur when garlic is preserved in oil at ambient temperatures. Garlic can be added to oil and kept in the fridge but should be disposed of if not used in a few days.
Botulism can be fatal and so all of our garlic which was being stored in olive oil in the fridge has been dumped. As the season for harvesting Garlic is nigh we are not concerned as we will soon have loads of fresh garlic which we will hang under the verandah to dry.
We had the same problem with chillies in oil, they went off so we don't do that any more.
As it happens I was interested in upping my garlic intake by adding it to my lunchtime fare. But prepping garlic TWICE per day -- much as I love garlic -- is not my preferred domestic labour.
So why not infuse the garlic in oil and add that oil, maybe, at the end of cooking? I love adding olive oil then--so why not have some garlic in it?
Ditto re Roger: there are problems with the marriage. As with herbs stored in oil for flavour.
After researching the DIY I was about to give up entertaining the option when I came upon this article:Making Garlic- and Herb-Infused Oils At Home from a team at the University of Idaho.
The trick is to acidify the garlic or herbs first and then add them to the oil.
Raw, chopped garlic or fresh herbs (basil, oregano, or rosemary) are immersed in a 3 percent solution of citric acid. After soaking for 24 hours, the acid is drained away and the acidified garlic or herbs are ready for addition to your vegetable oil of choice
Details in the article.
This might also be helpful, from Penn University in commenting on the Idaho article.
You can get powdered citric acid in the baking section of most grocery stores.
Ascorbic acid vitamin c powder would also work if not 'buffered' vitamin C