Homemade Rosemary Infused Oil

Rosemary infused oil is olive oil that has been warmed with fresh rosemary and strained. It takes a cup of oil, four sprigs and ten minutes over the lowest heat. The part that matters most comes afterwards: an oil made with fresh herbs belongs in the refrigerator and is used within four days, because herbs in oil at room temperature are a botulism risk.

Why rosemary in oil is kept cold

The University of Georgia Extension explains the risk. Oil shuts out oxygen, and garlic and herbs are low-acid foods that can carry spores of Clostridium botulinum. Without oxygen, with little acid and at room temperature the spores can grow and produce a dangerous toxin.

The same publication gives the rule for oils made with fresh, untreated herbs: they must be kept in the refrigerator and discarded 4 days after being made. It adds that dried herbs do not guarantee a safe oil either.

Recipe

Rosemary Infused Oil

Olive oil warmed gently with fresh rosemary, cooled and strained — a cooking and dipping oil to keep in the refrigerator and use within 4 days. One cup, sixteen servings of 1 tablespoon.

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Prep

5 min

Cook

10 min

Total

45 min

Serves

16

Cuisine

Mediterranean

Ingredients

• 1 cup olive oil
• 4 sprigs fresh rosemary (each about 5 inches)

Instructions

1. Wash the rosemary and dry it completely with a towel. Any water left on it goes into the oil.
2. Put the oil and the rosemary in a small saucepan and warm over the lowest heat for 10 minutes. The oil should reach about 140°F and must not sizzle; small bubbles around the sprigs are the sign to lower the heat.
3. Take the pan off the heat and let the oil cool with the rosemary in it for 30 minutes.
4. Strain the oil through a fine sieve into a clean, dry jar and discard the rosemary.
5. Close the jar and put it in the refrigerator at once. Use the oil within 4 days and discard what is left.

Nutrition

Calories:

120

Calculated from the ingredient quantities above using the USDA FoodData Central database, then divided by the number of servings. It is an estimate and will vary with the exact products you use.

Rosemary infused oil that keeps at room temperature

The extension describes one home method that allows storage at room temperature, developed at the University of Idaho for garlic, basil, oregano and rosemary. The herb is soaked for 24 hours in a citric acid solution, 1 tablespoon of citric acid in 2 cups of water, with ten parts of solution to one part of herbs. The acidified rosemary is then added to oil heated to 140°F, one part herb to ten parts oil, and removed once the oil tastes strong enough.

That is the method to follow for a bottle that stands in the cupboard or is given away. The recipe in the card is the simple one, for an oil that is used up within days.

Gentle heat

Rosemary gives its flavour to warm oil within minutes. Hot oil fries the leaves and turns the flavour harsh, and olive oil itself tastes burnt once it smokes. Low heat and half an hour of standing give a clear, green-tasting oil.

Smaller batches make more sense than large ones: half a cup of oil and two sprigs is enough for a few days of cooking.

What it is used for

• Bread: a small dish of the oil with a pinch of coarse salt, for dipping.
• Potatoes and vegetables: toss them in it before roasting.
• Meat: brush it on chicken, lamb or steak in the last minutes on the grill. A dry seasoning for steak is the coffee rub on this site.
• Pizza and focaccia: a spoonful over the top after baking.

In the refrigerator olive oil turns cloudy and thick. A few minutes at room temperature make it pourable again.

Not an essential oil

An infused oil is a cooking oil with a herb's flavour in it. Rosemary essential oil is a different product, obtained from the plant by steam distillation, and it cannot be made in a saucepan.

Other things to mix at home for the pantry are the McCormick Italian seasoning and the Weber Kick'n Chicken seasoning.