Freezing an overabundance of fruits or vegetables saves the bounty until you can use it, but frozen raw vegetables can develop an off taste or texture if they aren't properly prepared. Blanching, the process of cooking the food slightly before freezing, prevents these changes. Properly blanched and frozen vegetables and fruit are the next best thing to fresh.
Blanching preserves the flavor and texture of frozen vegetables. Enzymes within the vegetable are constantly breaking it down. This enzyme action initially aids in proper ripening and flavor development, but it will eventually cause the vegetables to decline. Slowing down the enzymes with a quick heat treatment allows you to freeze your vegetables with minimal loss of flavor, texture, nutrients or color.
The brief exposure to heat used for blanching partially cooks food, but not enough to cause a quick decline in quality. Blanching softens the fibers, making the vegetables easier to pack and improving their texture after freezing and thawing. Without blanching, frozen vegetables become soft and mushy when you thaw and prepare them.
Some vegetables, like tomatoes, are easier to peel after blanching. Blanching also works well for peeling soft fruits, such as peaches. The hot water softens the outer peel so it slips off the fruit without the need for a knife or vegetable peeler. When blanching for easy peeling, heat the food only until the skin begins to break, then immediately place it in ice water to cool before you slip the peel off.
Blanching provides the most reliable method for preparing most vegetables for freezing. Cut or separate the vegetables into even-sized pieces, then plunge them into a pot of boiling water just until their color brightens and they begin to soften. Blanching times vary, with thin or tender vegetables, such as spinach, requiring as little as one minute, while denser vegetables, like carrots, may require five minutes or more. After blanching, submerge the vegetables in an ice water bath so the cooking process is stopped. You can also blanch vegetables by steaming, using a steamer basket over a pot of boiling water.