Ideally, you'd "store" fresh herbs in the garden, never snipping more than you needed. The chives on your scrambled eggs, the cilantro on your tacos, and the basil on your pizza would always be bright, fragrant, and bursting with life. Alas, the real world doesn't work that way. To avoid wasting nature's herbaceous gifts, we must use our ingenuity.
There are multiple complex factors influencing produce's longevity, and most of us don't have the means, the time, or even the inclination to precisely control for all of them. Conjuring maximum herbal freshness is therefore more art than science. Rather than recommend one approach, let's discuss the basic elements of freshness, then look at how things can go wrong so that you can respond based on what you observe in your kitchen.
What influences herb freshness?
There are multiple factors that determine how long herbs will stay perky, vibrant, and fresh. These include the date of harvest, cleanliness, the type of herb, and the nature of the storage environment.
Of course, when buying herbs from the grocery store the date of harvest is unknown, and out of our control. However, if you've done all you can to keep your parsley lively and it still doesn't last, it might be time to find a new source. Assuming you trust your supplier, let's look at the other factors.
Should you wash your herbs?
There's no debate as to whether you should wash fresh herbs before consumption. But should you wash them before storage? If you think you'll need to store the herbs for a while, the answer is yes. A bath in cold water will remove some of the bacteria and mold spores that are ubiquitous in a natural environment, and subsequent refrigeration will dramatically slow the growth of any microbes that remain. However, if your refrigerator isn't clean, or if you just put the washed herbs back into the same bag they came from, you're simply putting them back into a less-than-ideal environment.
Even if done properly, an initial wash may not be worth the effort. That's because moisture has a big influence on successful longer-term herb storage. Once you've soaked the herbs, you'll need to return them to an optimal moisture level: dry, but not too dry. If you know you will only need to store your herbs for a couple of days, it might be better to skip the pre-wash.
What types of herbs are you storing?
Herbs are not all created equal. There are two basic categories of herbs: soft herbs and hard herbs. Soft herbs are fine to use on a casual basis, whereas hard herbs should only be used on the weekends, and then only in moderation (just kidding). All jokes aside, soft herbs are the ones with tender green stems and delicate leaves. Herbs like chervil, parsley, tarragon, cilantro, and basil are soft herbs. Hard herbs have hardier leaves and tougher, woody stems. Examples of hard herbs are rosemary, thyme, sage, oregano, and savory.
Because they are less woody and more delicate, soft herbs lose moisture much more easily. Unless you manage this tendency, soft herbs will quickly become tired, limp, and wilted. Hard herbs hold their moisture better, and their ligneous stems and hardy leaves resist wilting. With hard herbs, you still have to manage the moisture level, but it's not as critical.
Storage environment
The storage environment is the biggest factor under your control, but it may not be as under control as you think. Do you know the exact temperature in different parts of your refrigerator? Do you know the humidity? Do you monitor and account for the levels of oxygen, CO2, and ethylene? We didn't think so, and neither do we. Worse, because you store many different things in your refrigerator, there's no way to dial in your conditions. The perfect environment for one food may be suboptimal for another. So rather than talk about perfection, let's look at what can go wrong and how you might address it.
Herbs turning brown or black?
This problem is due either to excessive oxygen or excessively cold temperatures. Basil, for example, is particularly sensitive to the cold, as well as oxidation. If your basil is turning black, your refrigerator, or the part of the refrigerator where you put the basil, is too cold, usually below 40 degrees F. You can try storing your basil at room temperature in a manner similar to fresh-cut flowers, or try a different spot in your refrigerator.
To reduce browning caused by oxidation, try storing herbs in sealed containers, like plastic tubs, glass jars, zip-top bags, or vacuum sealed containers. You can even experiment with an oxygen absorber made for food storage.
Herbs turning yellow?
Yellowing is a natural part of the aging process in leafy plants. If your herbs turn yellow right away, they simply may not have been very fresh to begin with. It's also possible that the storage climate is accelerating the aging process. Two things that can do this are higher temperatures and ethylene gas. To keep your herbs green, try moving them to a colder spot, and/or away from ethylene-producing fruits and vegetables. The way your refrigerator is organized plays a significant role in the shelf life of your foods. You can also purchase ethylene gas absorbers.
Wilting herbs
Wilting is drying, which happens when the humidity of the surrounding air is too low, leading to evaporation. To prevent this, keep herbs in a plastic bag or other sealed container. For extra humidity, try wrapping the herbs loosely in lightly dampened paper towels before placing them inside the bag or container.
Some folks like to treat their herbs like cut flowers, keeping them in a jar with the stems submerged in water. If you try this, be sure to trim the stems first; it will improve the capillary action responsible for moving the water through the stem and into the leaves. If the humidity in your refrigerator is very low, you may need a barrier to evaporation as well. Cover the jar with a lid or an upside-down plastic bag.
Slimy herbs
Maintaining a proper moisture level is a balancing act. Not enough moisture leads to wilting, but too much will speed decay. If your herbs get slimy, try taking steps to prevent the build-up of moisture. If washing the herbs, spin them in a salad spinner or lay them out on towels to absorb surface water. Loosen them from tight bunches to allow for more air circulation, and remove twist ties or elastic bands. Package them loosely for storage, perhaps with a dry paper towel to absorb condensation.
There's no magic bullet! Try as you might, there will be times when herbs spoil sooner than you'd like. It doesn't mean you've failed. Just keep these factors in mind, pay attention, and try different solutions. Odds are you'll find a method that works for you.
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