Replenishing Infused Olive Oil
I have a bottle I use that came with olive oil and spices in it (that I pour new olive oil into when needed), such as rosemary, bay leaf, thyme, peppercorns etc. Do those spices need to be changed out every so often? The same spices are in it that came w/the bottle.
Bacteria cannot grow in olive oil, but can grow in herbs added to the oil if they retain moisture or if water is added to the spiced oil. In addition, without fully draining all of the old oil from the bottle, you run the risk of the olive oil turning rancid.
Over time, adding more olive oil to the same bottle will cause it to be less flavorful. The process of adding new herbs and spices to fresh oil is called infusion, which will provide you will fresh, aromatic, flavorful oil.
Olive oil can be infused with fresh or dried herbs. Fresh herbs that retain moisture, such as garlic, fresh peppers, basil or lemon peel, can attract bacterial growth such as botulism - even in the olive oil. Soaking the fresh herbs in white vinegar overnight will raise the Ph and help decrease water, making it harder for bacteria to grow.
Three methods of infusion are hot, cold and simply placing the herbs and oil in a sealed bottle for at least a week or until it reaches flavor/aroma intensity you desire.
The cold method involves placing fresh or dried herbs in a blender or food processor and adding olive oil. The agitation of the processor will slowly instill the flavor(s) with the olive oil.
The hot method involves heating the herbs/spices in olive oil over low heat for no more than five minutes. The heat will gradually allow the essence of the herbs to infuse with the olive oil. Take it off the heat and once cooled, cover for at least one hour.
Regardless of the methods, you may leave the herbs/spices in the oil or strain them. Using and leaving fresh herbs will provide a stronger scent and taste; however, keep in mind infusions made with fresh ingredients need to be refrigerated and will not last as long as those made with dried herbs/spices.
The infusions should be poured into a clean container and sealed for storage. Depending on the ingredients, infused olive oils can be kept anywhere from a few weeks to six months to well over a year.