When Should Fresh Herbs Be Added to a Dish?

Most fresh herbs are added during the last few minutes of cooking or immediately after the dish is taken off the heat; delicate herbs lose both their color and aroma quickly when exposed to heat for a long time. Parsley, dill, and mint are the best-known examples. When these herbs are added early, the dish also looks dull, as the vibrant green color gives way to a pale tone; this visual difference is noticeable even on the plate. In contrast, sturdier herbs such as thyme, rosemary, and bay leaves can be added at the beginning of cooking; their aromas develop slowly and they tolerate long cooking better. The difference between these two groups is directly related to the toughness of the herb's leaves; a thick, woody stem is generally a sign that it can withstand long cooking. Why are delicate herbs added at the end? The cell walls of thin-leaf herbs such as parsley and dill are delicate, so they quickly darken and may leave a bitter taste when exposed to high heat. This darkening also damages the herb's texture, and the leaves can look almost blanched. If these herbs are added after the dish is removed from the heat, as a final step before serving, they retain both their vibrant green color and fresh aroma. Adding chopped herbs just before serving preserves much of their aroma even as the dish is carried to the table. Why can sturdier herbs be added early? The aroma molecules in woody-stemmed herbs such as thyme, rosemary, and bay leaves are released slowly in oil or water; for this reason, these herbs can be added at the very beginning of cooking and simmered with the dish for a long time. Their thick leaf structure gives them natural heat resistance. Long cooking spreads their aroma more evenly throughout the dish. For this reason, in dishes that cook for hours, such as boiled dishes and casseroles, these herbs are generally added to the pot with the first ingredients. Why is mint considered an exception? Although mint is a delicate herb, it is also used at the beginning of cooking in some dishes (for example, in dolma filling); in this use, however, the aim is not to make mint a prominent flavor but to leave a subtle background aroma. Dried mint is generally preferred for this use because drying softens its aroma in a similar way. Recipes that aim to bring mint to the forefront generally add it raw or at the end of cooking. For salads or cold mezze servings, fresh mint is therefore almost always added last. Do the rules change for frozen and dried herbs? Dried herbs have a more concentrated aroma that is released more slowly than that of fresh herbs, so they are better added at the beginning of cooking; they behave in the opposite way from fresh herbs. For this reason, when a recipe substitutes dried herbs for fresh ones, both the amount and the timing should be reconsidered. Frozen fresh herbs soften as soon as they thaw, so they should also be added during the final stage of cooking as the closest equivalent to fresh herbs. Adding frozen herbs early causes them to lose their color and aroma early, just like fresh herbs.