Blanching is an important step for vegetable quality.
Blanching is a heat process in which vegetables are scalded in boiling water or steam for a brief (but specific) amount of time. It is a very important step in the freezing procedures for most (but not all) vegetables. Blanching stops enzymatic actions which can cause loss of flavor, color and texture during freezing. It also brightens colors, helps retard the loss of vitamins, and it wilts or softens certain vegetables making them easier to pack. The process can also help clean the vegetable surfaces of dirt and destroy microorganisms.
Blanching is not required for safety but rather ensures quality frozen vegetables. It is crucial to blanch vegetables correctly, including for the specified amount of time for each vegetable. Underblanching stimulates enzyme activity and is actually worse than no blanching. Overblanching causes loss of flavor, color, vitamins and minerals. Blanching in boiling water is generally the preferred process, although a few vegetables do best with steam blanching. Microwave blanching is generally not recommended.
A summary of the boiling water process follows (a chart with blanching times for each vegetable is in the link below).
- Bring a large pot of water to a full rolling boil; maintain high heat.
- Lower vegetables into the water in a basket and cover.
- Start timing when the water returns to a full boil (this should occur within 1 minute; if not, you’ve added too many vegetables – generally add no more than 1 pound of prepared vegetables to 1 gallon of water). Note: Add 1 minute to the blanching time at altitudes of 5,000 feet or more.
- When the time is up, remove the vegetables and place them in an ice bath or very cold water. The chill time is the same as the blanching time.
- Drain the vegetables well and pat dry as much as possible before packing.
Note: The process for blanching vegetables before dehydrating is essentially the same; however there are some differences, including blanching times. Be sure to follow the appropriate procedures/charts.
For further details on blanching before freezing, including a blanching time chart for specific vegetables, visit the National Center for Home Food Preservation website or your local Extension office.
Brought to you by the UC Master Food Preservers of El Dorado County
Last updated July 2025