Freezing

Why blanch

Freezing stops microbes from growing but doesn’t stop the vegetables’ own enzymes, which keep slowly breaking down flavor, color, and texture in the freezer. Blanching, a short scald in boiling water or steam, stops that enzyme action; it also cleans off dirt and microbes, brightens color, and slows vitamin loss ¹.

Timing matters both ways: under-blanching stimulates the enzymes and is worse than no blanching at all, while over-blanching loses flavor, color, vitamins, and minerals ².

Water blanching

From NCHFP and UNH Extension ^{1 2}:

1. Wash, sort by size, trim, and cut the vegetables.
2. Bring 1 gallon of water per pound of vegetables to a rolling boil (2 gallons per pound for leafy greens).
3. Lower the vegetables in a basket, cover, and keep the heat high. The water should return to a boil within 1 minute; if not, you’ve added too much at once.
4. Start timing when the water boils again.
5. Cool immediately in ice water or cold water at 60 °F or below, about a pound of ice per pound of vegetables, for the same time as the blanch (corn on the cob, twice as long). Stir during cooling.
6. Drain thoroughly.

Steam blanching takes about 1-1/2 times as long, with the food held at least 3 inches above the water. Microwave blanching may not inactivate all the enzymes ¹.

Blanching times

From UNH Extension ²:

Beets are cooked until tender rather than blanched, then peeled and sliced; herbs are frozen raw ².

Packing

• Dry pack: pack tightly in containers or freezer bags, press out the air, and seal ².
• Tray pack: spread a single layer on a tray, freeze, then bag; the pieces stay loose and pour out ².
• Headspace: leave about 1/2 inch for most cut vegetables, since food expands as it freezes; none for loose-packed pieces like broccoli and asparagus ².
• Containers should be moisture-vapor resistant, leak-proof, freezer grade, easy to seal and label, and hold half a gallon or less; regular glass breaks in the cold, so use wide-mouth jars made for freezing ².
• Get the air out: lower a bagged food into water to push the air out before sealing ³; air left in the package causes freezer burn.

Freeze and store

Freeze at 0 °F or lower, and don’t overload the freezer at once, which slows freezing ²; spread new packages out until they’re solid. At 0 °F, frozen vegetables keep high quality 8 to 12 months ². Label every package with contents and date, and eat the oldest first.

Poultry and game go in the freezer the same way, flat and airless; poultry is chilled and rested in the refrigerator first (see the Butchering course’s poultry lessons) ³.

Try it

Put up a bushel of sweet corn: sort ears by size, blanch them at 7, 9, or 11 minutes, cool them twice as long, cut the kernels off, and dry pack them in pint bags with 1/2 inch of headspace. Freeze half a dozen ears whole for comparison.

What to take from this

Blanch vegetables before freezing to stop enzymes, timing from the return to a boil (within 1 minute with 1 gallon of water per pound), then cool in ice water for the same time and drain well. Green beans, broccoli, and cauliflower take 3 minutes, peas about 2, corn on the cob 7-11 by size. Dry pack or tray pack, leave 1/2 inch headspace for most, press out air, freeze at 0 °F without overloading, and use within 8-12 months.