Freezing
Freezing is an easy, convenient and quick method of preserving food. Most vegetables should be blanched before frozen to inactivate enzymes which would otherwise cause color and flavor changes and loss of nutrients. Blanching is scalding vegetables in boiling water or steam for a short time which cleanses the surface of dirt and organisms, brightens the color, helps slow nutrient loss, and makes packing easier. Consult any of the references listed above for the amount of time specific vegetables should be blanched. Not blanching long enough actually stimulates the activity of enzymes and is worse than no blanching. But blanching for too long will affect flavor, color, and nutrients. Once blanched, the vegetables should be quickly cooled in ice water to prevent cooking.
Since we generally prefer the texture of raw, uncooked fruits, they are not usually blanched. Enzymes in fruits can cause browning and loss of vitamin C, so they are often treated with ascorbic acid (vitamin C). Less effective ways to prevent browning in frozen fruits include placing them temporarily in citric acid or lemon juice solutions or in a sugar syrup. Ultimately, fruits can be frozen plain or with sugar or syrup, depending on personal preference.
The reason the texture of frozen produce is much softer when it thaws is because as the water in the food itself freezes, it expands, and the ice crystals formed cause the cell walls to rupture. This is quite evident in foods with high water content and those usually eaten raw. Faster freezing produces smaller, less-damaging ice crystals than slower freezing. If the food is going to be cooked before eating, it’s not as noticeable.
Drying:
One of the oldest preservation methods, drying is simple, safe, and easy. Modern dehydrators make the process even easier. It is critical to follow instructions for a safe final product.
Canning:
Currently, the two safe ways of canning are in a pressure canner or boiling water bath canner, depending on the food being canned. Fruits, tomatoes, pickles, jams, jellies and other fruit preserves can be safely canned with the boiling water bath method, so long as the research-based recipe is followed exactly. Vegetables, some tomato products with added ingredients, meats, poultry and seafood must be pressure canned. Each year the dial gauge on a pressure canner should be checked. Our office provides that service.
Source: So Easy to Preserve, Sixth Edition, 2014.
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