What Is Blanching?

• Blanching refers to subjecting fresh fruits and vegetables to high temperatures – typically via boiling or steaming – to inactivate the enzymes responsible for aging. This prevents the flavor and appearance of the fruits or vegetables from changing while frozen. Although freezing slows the enzyme action, even if the food is not blanched, unblanched frozen produce develops off-colors and flavors over time.

Stopping Enzyme Action

• Enzymes like peroxidase and catalase regulate plant growth and maturity. When the vegetables reach maturity, these enzymes continue to work to age the fruit in an attempt to develop viable seed for reproduction. Blanching fresh fruits or veggies in hot water inactivates peroxidase and catalase, stopping the maturation process. This prepares the veggies for freezing for winter storage.

Blanching Vegetables

• To prepare vegetables for boil blanching and freezing, wash them gently and cut them into the desired finished size if necessary. Fill a saucepan with water and bring it to a roiling bowl over medium heat. Submerge the vegetables in the boiling water and return it to a boil. Blanch for the appropriate time for your vegetable, beginning when the water returns to a boil. Vegetable blanching time varies depending on the type of vegetable and the size of the sections. For example, a small ear of corn requires 7 minutes in boiling water to blanch, while a large ear of corn requires 9 minutes to blanch. Other vegetables, such as green beans or summer squash, blanch in 3 minutes.

Taking the Plunge

• Blanched fruits and vegetables require quick cooling to halt the cooking process and maintain their bright color and crisp texture. This means plunging the blanched produce into a bowl of ice water to cool. It takes the same amount of time to cool the vegetables in ice water as it takes to blanch them. For example, corn that is blanched in boiling water for 7 minutes requires 7 minutes in an ice bath to cool completely. Freezing fruits and vegetables immediately after blanching keeps them fresh and retains their color.

Common Problems

• Although blanching times vary depending on the type of fruit or vegetable and the size of the portions, improper blanching times alter the quality of the fruits or vegetables. Blanching too long overcooks the fruit or vegetable and may cause faded color, nutrient loss and an overcooked texture. Underblanching fails to stop the enzyme activity and may result in fruit or vegetables that discolor or lose flavor while frozen. Failing to cool the fruits or veggies completely may result in produce that continues to age while frozen, potentially causing color, flavor and texture to degrade over time.