I have had several calls the past few weeks on preserving produce. There are many ways to preserve produce such as canning, dehydrating, pickling, and fermenting but today I am going to talk about freezing your summer produce. Freezing is an excellent way to preserve fresh vegetables at home. Many of our fruits and vegetables can be frozen, but there are guidelines to follow for quality.
According to the National Center for Home Food Preservation (NCHFP), freezing produce does not sterilize the food; the extreme cold simply retards growth of microorganisms and slows down changes that affect quality or cause spoilage in food. The quality of frozen vegetables depends on the quality of the fresh products and how they are handled from the time they are picked until they are ready to eat. It is important, also, to start with high-quality vegetables because freezing will not improve the product’s quality.
The first step in freezing produce is to make sure you have the appropriate container. The selection of containers depends on the vegetable being frozen, personal preference and the types that are readily available. Containers should be moisture-vapor resistant, durable, easy to seal and should not become brittle at low temperature. Suitable containers for freezing vegetables include plastic freezer containers, flexible freezer bags, and their protective cardboard cartons, or glass canning jars. Foods packed in wide-mouth jars are easier to remove than those packed in narrow-mouth jars. Household containers NOT recommended for freezing include cardboard cartons that milk, ice cream or cottage cheese come in and regular (not canning) jars. Vegetables should be washed thoroughly in cold water prior to freezing.
The next step is to blanch vegetables. Blanching (scalding vegetables in boiling water or steam for a short period of time) is a must for almost all vegetables to be frozen. Blanching slows or stops the action of enzymes that can cause loss of flavor, color and texture. Blanching cleanses the surface of dirt and organisms, brightens the color and helps retard loss of vitamins. Blanching also wilts or softens vegetables and makes them easier to pack. Blanching time is crucial and varies with the vegetable and its size. Underblanching stimulates the activity of enzymes and is worse than no blanching. Overblanching causes loss of flavor, color, vitamins and minerals. You can water blanch or steam blanch vegetables for preservation. Microwave blanching is not recommended. Research has shown that some enzymes may not be inactivated. Flavors could be off and texture and color lost. If you choose to risk low quality vegetables by microwave blanching, work in small quantities, using the directions for your specific microwave oven. Microwave blanching has not been shown to save time or energy. For water blanching, use one gallon of water per pound of prepared vegetables. Be sure to lower vegetables into boiling water and for the specified time of that vegetable (this varies). Steam blanching is recommended for a few vegetables. Steam blanching takes about 1 ½ times longer than water blanching.
After you are finished blanching vegetables, cool vegetables quickly and thoroughly to stop the cooking process. To cool, plunge the basket of vegetables immediately into a large quantity of cold water, 60°F or below. Cooling vegetables should take the same amount of time as blanching. Drain vegetables thoroughly after cooling. Extra moisture can cause a loss of quality when vegetables are frozen.
For blanching times or more information on freezing vegetables, visit the nchfp.uga.edu or your local extension office.