Can You Freeze Basil? Leaves, Oil Cubes, Pesto and How Long They Keep

Got more basil than you can use before it blackens in the fridge? Freeze it. Basil is one of the herbs extension services say freezes well, and frozen basil can go straight from the freezer into a simmering sauce, in the same amounts as fresh.¹ It goes limp when it thaws, so save it for cooked dishes, sauces and pesto, not the top of a salad. If you freeze it in oil, handle it safely, because herbs in oil are a known botulism risk.

At a glance

Why freeze instead of refrigerating

Basil hates the cold. Rutgers Cooperative Extension gives 55°F as its ideal storage temperature and warns that basil is prone to chilling injury: blackened leaves, discolored stems and lost aroma.⁵ To keep it a few days, see how to store basil. For longer, you can freeze it or dry it.

Four ways to freeze basil

They all start the same way: rinse the leaves in clear water and pat them dry.

1. Loose leaves on a tray. Strip the leaves off the stems, spread them in a single layer on a cookie sheet and freeze. SDSU says that takes about one to two hours, until they’re frozen solid.² Then bag them. Since the leaves froze separately, you can grab just what you need.

2. Chopped basil in water cubes. Oklahoma State puts about a tablespoon of chopped herbs in each section of an ice cube tray and tops it up with water. SDSU fills the tray half full of water and adds a tablespoon of herbs.⁶² Once they’re frozen, bag the cubes and label them.

3. Basil in oil. Penn State and Oklahoma State both say herbs frozen in oil hold their color better than herbs frozen plain, and Oklahoma State says the method works well with basil.¹⁶ Their proportions are a little different:

Oklahoma State suggests a neutral oil like canola. NDSU Extension also suggests pureeing basil and freezing it in an ice cube tray. And Oklahoma State has a flat-pack version that saves freezer space: spread a thin layer of chopped herbs and oil in a zipper-lock bag and freeze it flat.

4. Pesto. NDSU Extension says pesto keeps up to six months in freezer containers.³ Freeze it in portions and you’ll never thaw more than one meal’s worth.

Should you blanch basil first?

It’s optional, and the sources don’t agree on how long:

You’ll often see an instruction to blanch for 1 to 2 seconds, but we found no published source for that figure. We haven’t averaged the times above.

Why blanch at all? NDSU notes that pesto may oxidize and turn brown, and that some people blanch the leaves for a few seconds to prevent it.³ For vegetables in general, USDA’s Food Safety and Inspection Service explains that freezing only slows enzyme activity in food but doesn’t stop it, and recommends blanching or partly cooking vegetables before freezing.⁷ You may read that blanching basil kills the bacteria that make it break down. None of these sources says so, and we found no study comparing blanched and unblanched frozen basil.

Safety: basil in oil

Herbs in oil are a known botulism risk. A 2011 review in Food Protection Trends explains that vegetables and herbs in oil provide the conditions botulinum toxin needs.⁴ Its guidance:

• Freezing herbs stored in oil is the safest bet. A frozen herb-in-oil mix wouldn’t support pathogen growth, though many oils don’t go solid in the freezer.⁴
• If you refrigerate it, use it within 4 days or toss it.⁴
• Never keep herbs in oil at room temperature. SDSU says to freeze the mixture right away.⁶²

For refrigerated pesto, the published limits differ:

When food-safety limits disagree, go with the shorter one. Anything you won’t eat in that window belongs in the freezer.

How long frozen basil keeps

Those are quality limits, not safety dates. FSIS says food kept constantly at 0°F will always be safe, and only quality suffers with long freezer storage.⁷ Freezer burn doesn’t make food unsafe either. It just dries it out in spots. Basil from the back of the freezer won’t hurt you, but it may not be worth using.

Using frozen basil

• Don’t thaw it first. Add it frozen to soups, sauces and stews. Dropping a cube into a simmering pan is the whole point.
• Use the same amount as fresh.¹
• Expect limp leaves. Frozen herbs go limp when thawed, so keep fresh basil for garnishes and salads.
• Wrap it well. Penn State suggests wrapping strong-smelling herbs in foil so their smell doesn’t creep into other foods.
• Refreezing. FSIS says food thawed in the fridge is safe to refreeze, though quality may drop from moisture lost in thawing.⁷ With basil, freezing in small portions sidesteps the question.

Not yet measured

• How long frozen basil keeps its aroma, measured on basil and not herbs in general.
• Whether blanching changes the flavor or color of frozen basil, and which blanching time works best.
• Whether Genovese, Thai, lemon or holy basil freeze differently. No source we found compares them.

Related

• Basil
• How to store basil
• How to dry basil
• Dried basil vs fresh
• Cooking with basil
• Can you freeze mint?
• Can you freeze cilantro?

Footnotes

1. Freezing Herbs, Penn State Extension. extension.psu.edu · Reference work ↩ ↩² ↩³ ↩⁴ ↩⁵

2. Preserving Herbs, South Dakota State University Extension. extension.sdstate.edu · Reference work ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸

3. Julie Garden-Robinson, Prairie Fare: Inspire Your Menus With Fresh Basil, NDSU Extension. ag.ndsu.edu · Reference work ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶

4. Nummer, Schaffner, Fraser and Andress, Current Food Safety Issues of Home-prepared Vegetables and Herbs Stored in Oil, Food Protection Trends, 2011. foodprotection.org · Peer-reviewed ↩ ↩² ↩³ ↩⁴ ↩⁵

5. Fact Sheet FS1283, Rutgers Cooperative Extension. njaes.rutgers.edu · Reference work ↩

6. Freezing Herbs, Oklahoma State University Extension. extension.okstate.edu · Reference work ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶

7. Freezing and Food Safety, USDA Food Safety and Inspection Service. fsis.usda.gov · Regulator ↩ ↩² ↩³