Freeze Fresh Herbs for Long-Term Storage

20150401-freezing-herbs-best-method-1.jpg

Freezing herbs in oil in an ice cube tray will preserve their flavor. [Photographs: J. Kenji Lopez-Alt]

There's no herb storage method I know of that can faithfully retain the flavor and texture of completely fresh herbs, but if you find yourself with more than you can possibly use, there are some methods that will work better than others. Drying them in the microwave is a great method if you want to have dried herbs on hand in the pantry. Want to have something that more closely resembles fresh herbs for sauces, soups, and stews? In that case, the freezer is your friend.

It's a given that texture is going to go out the window when you freeze herbs—the formation of ice crystals inside them destroys cell walls, turning the herbs limp after defrosting—but you can go a long way towards preserving flavor.

Poke around the internet or in books and you'll find many different methods that claim to be the best for freezing herbs. To figure out which ones really work, I tried freezing herbs using four different methods:

  1. Chopped and frozen with nothing added, stored in a zipper-lock bag for two weeks.
  2. Chopped, placed in an ice cube tray, and frozen covered with water. Transferred to a zipper-lock bag and stored for two weeks.
  3. Blanched briefly in boiling water, chilled, chopped, placed in an ice cube tray, and frozen covered with water. Transferred to a zipper-lock bag and stored for two weeks.
  4. Chopped, placed in an ice cube tray, and frozen covered with oil. Transferred to a zipper-lock bag and stored for two weeks.

I also included a set of freshly chopped herbs in my taste tests as a control.

20150401-freezing-herbs-best-method-6.jpg

To taste the herbs, I added equivalent amounts of herbs from each storage method to a batch of Quick and Easy Italian American Red Sauce, as well as a in a Hearty Winter Vegetable Soup, tasting them for potency as well as fresh flavor.

The good news? All of the methods worked pretty darn well, producing flavor that, while not quite perfectly fresh-tasting, was at least as intense as any herb that you've cooked in a sauce for a few minutes.

The herbs frozen in oil fared the best, while unblanched herbs packed in a solid block of ice had the weakest flavor of all. Why is this the case?

20150401-freezing-herbs-best-method-4.jpg

Fresh herbs are living things with active enzymes and flavor compounds that change dramatically when heated or damaged. Herbs stored in an ice cube take much longer to melt and incorporate into a sauce than herbs stored in frozen oil, which means that while you're waiting for the core of that ice cube to melt, the herbs that have already melted into the sauce are busy overcooking and losing fresh flavor. Of course, it also means that your herbs will simply take longer to cook into your soup or sauce.

Blanching herbs can deactivate enzymes, which goes a long way towards maintaining flavor, but more importantly, blanching the herbs first means that they can be packed into a smaller volume. The equivalent amount of herbs takes less space and therefore melts faster.

20150401-freezing-herbs-best-method-5.jpg

If quick melting is the goal, then shouldn't just plain old frozen herbs be your best best? Not quite. With such a high surface area to volume ratio, fresh herbs lose moisture and get freezer burn very rapidly (freezer burn is caused when ice crystals in food sublimate, that is, they go directly from solid ice form to gaseous water vapor form). Even after two weeks of storage, there's a significant textural difference in the herbs, giving them a papery feeling on the tongue.

The Best Way to Freeze Herbs: Freeze Them in Oil

20150401-freezing-herbs-best-method-3.jpg

For my money, covering chopped herbs in a neutral oil and freezing them solid is the best method to keep your fresh herbs tasting fresh for a long time. To do it, place chopped herbs in an ice cube tray, then top up the wells with a bit of neutral oil like canola or light olive oil. Alternatively, if you have lots of herbs, place the whole leaves in a food processor, add a few tablespoons of oil, and process until finely chopped. Transfer this mixture to an ice cube tray and freeze.

Once frozen solid (this will probably take overnight), transfer the cubes to a zipper-lock bag for long-term storage. Use cubes of herbs wherever you'd add chopped fresh herbs to a cooked meal, such as in soups, stews, or pan sauces. Even directly out of the freezer, an oil-based cube of herbs will soften and melt much faster than a ice cube of equivalent size.

Even Better: Store Them Flat

20150328-freezing-herbs-best-method-7.jpg

Here's another quick tip: Instead of using ice cube trays, place your chopped herbs and oil inside a zipper-lock bag. Seal the bag, leaving about a half inch of space open, then carefully squeeze out excess air before sealing the bag completely. Now place that bag on a large plate or baking sheet, spreading out the herb mixture to a thin, even layer and place it in the freezer until completely frozen solid. It'll freeze in record time, and even better, it's much easier to use than solid ice cubes of frozen herbs. Just cut off as much as you need with a knife or kitchen shears, reseal the bag, and store the rest for later.

Because of its high surface area to volume ratio, herbs frozen this way freeze and melt much faster. You can drop them into your pasta sauce or soup, and within seconds they'll be ready to go.