Published May 1, 2007. From Cook's Illustrated.
Can this product be reasonably substituted for fresh herbs?
We found Dorot frozen herbs—stabilized with water, soybean oil, starch, dextrose, and salt—at the supermarket, packaged in small ice cube tray-like containers. According to the label, one cube is equivalent to one teaspoon of fresh chopped herbs and doesn't need to be defrosted before use. To determine whether this product could be reasonably substituted for fresh herbs, we compared several versions head to head with the real stuff in six applications: salsa (cilantro), guacamole (cilantro), lemon-parsley pan sauce (parsley), sautéed zucchini (parsley), aioli (basil), and marinara sauce (basil).
In every application other than the marinara sauce (which had a high tomato-to-basil ratio), tasters overwhelmingly preferred the fresh herbs to their frozen counterparts. In addition to having "cleaner, brighter, fresher" flavors, the fresh herbs looked more vibrant, as well. The frozen herbs were noticeably darker in color and mushier in texture. Our conclusion? The convenience of these frozen herb cubes doesn't make up for their lackluster flavor. Fresh is best.
It is possible, however, to make decent homemade frozen herb cubes from parsley, sage, rosemary, or thyme. Simply place the chopped herbs in an ice cube tray, cover them with water, and freeze.