Drying- This is perhaps the most universally used method of preserving herbs. Nearly any herb can be effectively dried (though some may require different methods of drying), and dried herbs can be used for nearly any herbal application. This method works best for such herbs as sage, savory, rosemary, thyme, mint, lavender and oregano. Keep in mind, however, that the longer the drying process takes, the more flavor your herbs will lose. Some of the more popular ways of drying herbs are to lay them out on a drying rack; tie them upside down in bundles; placed in a paper bag, which you need to 'toss' the contents of periodically; in a dehydrator; in an oven on the very lowest setting or in the microwave (in one minute bursts until dry; the oven and microwave are the most effective methods if you live in a very damp or humid environment).
Herbs preserved by drying will last up to around a year; once their scent is gone, so is the majority of their flavor. Be sure to keep in airtight containers, preferably of dark glass or opaque material.
Freezing- Like drying, freezing herbs is highly effective both in the number of herbs that can be stored this way, and in the number of applications available for the frozen herbs; and has an advantage over drying in that most herbs will not lose their potency when stored this way. This method works best for such herbs as basil, cilantro, dill, parsley and tarragon. Most sources recommend lightly blanching the herbs, dipping them in ice water, and then laying on a cookie sheet to freeze. Another alternative is to roll them up in a paper towel and place in a ziploc bag, removing as much air as possible, and placing the whole bag in the freezer.
One rather novel approach to freezing herbs is to finely chop or blend them with a bit of water, and place them in an ice cube tray (make sure to add enough water to make a 'solid' cube once it freezes). This provides several advantages; one, the herbs themselves are not 'exposed' in the freezer, and thus will not suffer 'freezer burn'; and two, you can use cubes of various sizes, to provide yourself with custom-sized 'doses', without having to disturb any more than you need. Keep in mind, however, that some recipes will not take kindly to the extra water of this method; however, if chopped instead of blended, you can thaw, drain, and allow them to dry off before using them.
Herbs frozen quickly and kept in the freezer will last up to two years; perhaps more, in the ice-cube method.
Oil or Vinegar Infusions/Salts/Sugars- These methods are a bit limited in their application after preserving, but they can be highly effective where they can be used.
To infuse vinegar or an oil with your herbs, place them in an airtight container and cover completely with either oil or vinegar. Some sources claim it helps to gently heat the oil first. Allow them to sit at room temperature for a very minimum of two weeks, and shake them up every day or two. You can either strain when they have achieved the strength of infusion you want (this can take anywhere from 2-3 weeks for vinegar, or as much as 6 months for an oil), or you can simply leave the herbs in them. Olive oil infused with Rosemary is perhaps the most popular such infusion. Keep in the refrigerator to be on the safe side. You can also make a sort of infusion by adding finely chopped herbs to room-temperature butter, about 1 part herb to 4 parts butter. You may want to add in ¼ part lemon juice, as well. Store in the refrigerator or freezer in an airtight container (or formed in molds or into logs and then well-wrapped).
To make herb salt or herb sugar, partially dry the herbs you wish to use (until they have 'released' their own water; this is a very obvious point if you use the microwave to dry them). Then, layer the leaves (or flowers) with enough of either sugar or salt to cover them. Store in an airtight container for a minimum of two weeks before using.
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