Onions are simple to prepare and very useful dried, but they have one catch: the smell. Volatile sulfur compounds leave with the water vapor and get into the chamber, the door gasket and anything else on the trays. Owners routinely dry onions alone, then air the machine out.
Dried diced onion goes straight into soups and sauces. Ground, it becomes a fresher-tasting onion powder than the jar from the store.
Prep and loading
- Peel and dice ¼ to ⅜ inch. A food processor saves tears, but keep pieces even.
- No blanching needed.
- Run onions in their own batch. Wipe the chamber and leave the door open for a few hours after.
- Garlic, shallots and leeks are handled the same way.
How to tell it’s done
- Pieces are crisp and papery, not bendy.
Not sure? The weight check compares two weighings and the expected dry weight for onions.
Problems and fixes
The next batch tasted of onion
Odor carryover. Clean the chamber and gasket with warm soapy water and run an empty dry cycle with the door open after if needed.
Onion powder turned into a brick
Onion powder is very hygroscopic. Store in small jars with an absorber and close them fast.
Rehydrating and storing
Rehydrate: Add dry to cooking; soak 10 minutes for raw uses. By weight, 100 g of dried onions takes back about 782 g of water to return to fresh weight; the rehydration calculator does any amount.
Store: Jars or small mylar bags with oxygen absorbers.
Ways to use it
- Soups, sauces and stews
- Onion powder
- Dip mixes with sour cream powder
- Seasoning blends
How much fits per batch
At a normal single layer, onions load at roughly 2.2 lb of fresh food per square foot of tray. That works out to:
| Machine | Fresh per batch | Dried per batch |
|---|---|---|
| Harvest Right Countertop 360 | 5.5 lb | 9.9 oz |
| Harvest Right Small | 6.6 lb | 12.0 oz |
| Harvest Right Medium | 10.3 lb | 1.17 lb |
| Harvest Right Large | 16.9 lb | 1.92 lb |
| Harvest Right X-Large | 34.4 lb | 3.90 lb |
Sources
- USDA FoodData Central: onions, raw (water content)
- Utah State University Extension: Can I Freeze-Dry That? (2026)
- Penn State Extension: Let’s Preserve: Freeze-Drying
- National Center for Home Food Preservation: freezing (blanching times)
- Iowa State University Extension AnswerLine: Preserving by home freeze drying
Water content rounded from USDA FoodData Central (onions, raw). Cycle times are typical ranges at default settings; thickness, load and your room change them. How we put these together.