Freezing spinach lets you take advantage of your garden's summer and fall bounty well into the cold depths of winter. To successfully freeze spinach and preserve as much of its nutrients and texture as possible, blanch your greens prior to freezing, and wrap them well to ensure that they don't develop freezer burn. Use frozen spinach as you would fresh spinach in everything but fresh salads and in the juicer.
Blanch the Greens
You can blanch your spinach either with boiling water or hot steam, although steaming helps preserve more of the nutrients. To blanch in boiling water, bring a 1-gallon pot of salted water to a rolling boil, and then add in the cleaned spinach leaves in 1-pound increments. To steam blanch, boil 1 to 2 inches of water in a large pot, and lower a steaming rack filled with 1 pound of spinach into the pot, keeping the basket out of the water by at least 1 inch. It will take roughly 10 seconds to boil blanch spinach, and 30 to 60 seconds to steam blanch.
Cooling and Wrapping
Immediately after blanching, dunk the cooked leaves into a large basin of ice water to cool the leaves rapidly and stop the cooking process. Rapid cooling is crucial for high-quality frozen spinach. Drain the leaves and spin them dry with a lettuce spinner, or pat them dry with a towel. To prevent freezer burn, minimize the amount of exposure the leaves have inside the container. Freezer bags that have leaves layered individually inside work well, although vacuum-seal bags work best by removing all the oxygen.
Freezing and Storing
Place the packaged spinach in the coldest part of your freezer. Do not put more spinach in your freezer than can be fully frozen in a 24-hour period -- usually no more than 2 to 3 pounds of prepared spinach per cubic foot of freezer capacity. Keep your packets separated to ensure rapid freezing. If stored at zero degrees Fahrenheit or lower, the spinach can keep for 12 to 18 months when properly wrapped.
Defrosting and Using
Defrost frozen spinach in its package in the refrigerator, placing it on a plate or in a bag to capture any water that may leak out as the leaves melt. Defrosted spinach can keep in the refrigerator for several days. You can also defrost the spinach at room temperature. To ensure the packages defrost quickly, do not stack them together because this slows down the process. If you want to use a microwave to defrost the spinach, microwave it for 2 to 3 minutes per 1 1/2-pound package. Use defrosted spinach as is -- there is no need to squeeze or drain the spinach unless you're using it in a quiche or omelet, where the excess liquid would ruin the dish.