How to Freeze Fresh Vegetables and Herbs
Home freezers are essential for maintaining a constant supply of ice cream and ice, but they're also good for preserving and storing an over-abundance of fresh produce and herbs. Used efficiently, the freezer can also help to cut down on food waste and reduce the frequent need to shop for fresh ingredients.
In the food science book On Food and Cooking, author Harold McGee describes the process of freezing as one which "stops cold the overall metabolism of fruits, vegetables and spoilage microbes," but, he adds, freezing also kills plant tissues. McGee goes on to explain how the water crystallizes and damages the cell walls of vegetables so that when food is thawed, the broken cell walls allow the liquid to leak out leading to food losing its crispness and becoming limp and wet. That's why it's better to freeze tomato sauce or puréed tomatoes rather than whole ones. Likewise, cucumbers, lettuce, and mushrooms do not freeze well unless fully cooked before freezing.
What Produce Freezes Best?
The vegetables that freeze best are some of the sturdiest ones such as asparagus, Brussels sprouts, peas, corn, broccoli, cauliflower, green beans, and some dark leafy greens including spinach, kale, Swiss chard, mustard greens, and collards. While carrots, onions, peppers, celery, and winter squash can also be frozen, they also will last a relatively long time in the refrigerator or pantry without freezing.
Two Methods for Freezing Produce
The way to freeze fresh produce is a four-step process: blanch, cool, pack, and freeze. The blanching process, which typically consists of boiling or steaming for two to three minutes, inactivates the enzymes in vegetables, thereby preserving the vitamins and color. Once you've blanched and chilled your vegetables in a bowl of ice water, pack them in a freezer zip top-style bag, or pack in a freezer safe plastic or glass container. Another technique is to freeze blanched produce on a baking sheet. Once it's frozen solid, transfer it to a bag or container. When each piece is individually frozen in this way, the final product is not frozen into a solid block, making it easier to retrieve smaller portions of the frozen produce.
How to Freeze Fresh Herbs
Fresh herbs can also be frozen, in oil or in pastes and though some herbs can be frozen in ice cubes, when they are defrosted, they will lose their vibrant color. Because they are dry and don't have much water content, fresh thyme and rosemary freeze well, while softer herbs, such as basil, parsley, and cilantro, are better when blanched and frozen in cubes.