There are a few important things to keep in mind to get the best results — including longest storage time and freshest thawed texture — when freezing asparagus. For traditional freezing methods, the goal is to freeze the asparagus as quickly as possible, meaning it should be very cold before being placed into the freezer. Vacuum-sealing the asparagus before freezing it can allow asparagus to be frozen without first blanching the spears. In some instances, chopping the asparagus into small pieces can help to preserve the texture for a longer period of time, especially when storing it for more than a few months. The amount of blanching time can make some difference when freezing asparagus, while not blanching the vegetables at all can lead to a better thawed texture but a shorter lifespan in the freezer.
When freezing asparagus, the first step often is to quickly blanch the asparagus in boiling water. Minimizing the length of time the asparagus is in the water can help to maintain the firm texture for a longer period of time in the freezer. Increased cooking times can make asparagus that will last longer once frozen but might not keep a firm texture. Freezing asparagus from a raw state can help to preserve its texture, but the enzymes in the asparagus also will cause it to go bad more quickly. One exception is with vacuum-sealed asparagus, because all the air is removed from the bag, preventing the enzymes from working.
After blanching, freezing asparagus in the traditional way will yield the best results if the asparagus is as cold as possible before being put in the freezer. This means placing it in an ice bath after blanching and then allowing the temperature of the vegetables to drop as much as possible. The asparagus should then be placed in a single layer on a baking sheet or plate so as much surface area as possible is exposed to the cold air in the freezer. Chopping the asparagus into smaller pieces allows them to freeze quicker.
The asparagus should be allowed to freeze completely, sometimes as long as overnight, before being removed from the freezer to be packaged. The spears can be placed in a container or freezer bag that has as much air removed as possible. Stacking the asparagus together tightly can help to keep the food as cold as possible and ward off freezer burn. In some cases, filling the container with some water and freezing asparagus inside the block of ice that develops will allow the spears to be stored for a very long time, although the texture will suffer after a few months.