The step that preserves quality
Blanching (brief boiling followed by immediate ice-water cooling) stops enzyme activity that causes flavor, color, and nutrient loss during freezing. Without blanching, frozen vegetables become tough, discolored, and off-flavored within weeks.
The USDA and university extension services provide specific blanching times for each vegetable (peas: 1.5 minutes, corn on the cob: 7 to 11 minutes, green beans: 3 minutes). Under-blanching is worse than no blanching because it stimulates enzyme activity.
Air is the enemy
Freezer burn is dehydration caused by air contact. Use airtight packaging: vacuum-sealed bags, freezer-weight zip bags with air pressed out, or rigid containers with tight lids. Regular sandwich bags and containers without tight seals allow moisture to escape.
Label every package with the contents and the date frozen. Follow the FIFO principle: first in, first out.
Different rules
Most fruits do not require blanching. Spread pieces on a baking sheet in a single layer (flash freeze) until solid, then transfer to bags. This prevents pieces from clumping into a solid block. Add sugar or ascorbic acid to light-colored fruits (apples, peaches) to prevent browning.
- Blanch vegetables before freezing (specific times per vegetable)
- Cool immediately in ice water after blanching
- Use airtight packaging: vacuum bags or freezer-weight zip bags
- Label with contents and date. Use oldest first
- Fruits: flash freeze on a sheet tray, then bag
- USDA Home Food Preservation — NCHFP freezing guidance.