Lucinda Hutson, author of The Herb Garden Cookbook (Gulf Publishing), offers these tips for perfect pesto every time:
Tender-leaf, cold-sensitive herbs such as basil, oregano and sage may be stored in airtight containers in the refrigerator. Hardier herbs including cilantro and parsley can be placed in a glass of water in the fridge, covered loosely with a plastic bag.
Make certain herbs are free of moisture before grinding, and don't skimp.
Select top-grade imported cheese, and grate it yourself. Make sure all nuts are fresh, as they have a tendency to become rancid if improperly stored.
When tossing pesto with hot pasta, add a few tablespoons of the water used to cook the noodles.
Pour a 1/8-inch layer of olive oil over pesto before storing to prevent its darkening.
When freezing pesto, for best flavor, leave out the garlic and cheese; add these after thawing and just before using pesto.