How to Make Onion paste
Fermented onion paste transforms pungent raw onions into a sweet, complex, umami-rich condiment. The fermentation process caramelizes the natural sugars while adding probiotic tang, creating an incredibly versatile cooking base.
Category: Pastes & Sauces · Method: Lactic Acid · Time: 7-30d · Difficulty: 1/5 · Yield: varies · Temp: 18-22°C
History
Onion fermentation appears in cuisines worldwide, from Indian onion pickles to Eastern European preparations. The paste form concentrates these flavors for use as a foundational ingredient in sauces and dishes.
Ingredients
- 1 kg Yellow onions — Peeled, quartered
- 20g Sea salt — 2% of onion weight
- 4 cloves Garlic — Optional
- 1 tsp Thyme — Optional, dried
Equipment
- Food processor
- Fermentation jar with airlock
- Kitchen scale
- Large bowl
Instructions
Process onions
Pulse onions in food processor until finely minced but not pureed. Reserve any liquid.
Time: 5 min
Tip: Work in batches to ensure even texture.
Salt and mix
Combine minced onions with salt. Mix thoroughly. Add optional garlic and thyme.
Time: 5 min
Tip: Onions will weep significantly over the next hour.
Rest and release
Let salted onions rest 1 hour, stirring occasionally, until very wet.
Time: 1 hour
Pack and ferment
Transfer to fermentation jar, pressing out air. Liquid should cover onions. Ferment 7-14 days.
Time: 7-14 days
Tip: Onions ferment well and develop remarkable sweetness.
Blend smooth
Process fermented onions to smooth paste. Adjust consistency with brine.
Time: 5 min
Fermentation Timeline
- Day 1-3: Initial fermentation — Bubbles form. Onion smell intensifies then mellows.
- Day 4-7: Active phase — Steady bubbling. Sweet notes emerge.
- Day 7-14: Maturation — Complex, sweet-savory flavor develops.
Signs of Success & Spoilage
Good signs
- Golden-tan color
- Sweet, mellow onion aroma
- Complex sweet-sour taste
- Smooth, spreadable texture
Warning signs
- Pink or grey color
- Alcoholic smell
- Slimy strings
- Mold growth
Troubleshooting
- Still too pungent
- Cause: Insufficient fermentation time Solution: Continue fermenting - onions need time to mellow.
- Alcoholic smell
- Cause: Fermented too long or too warm Solution: Refrigerate immediately. Still usable but past peak.
- Separated layers
- Cause: Normal settling Solution: Stir to recombine before using.
Storage
Refrigerate in sealed jars Keeps 4-6 months refrigerated. Sweetness continues developing slowly when cold.
Health Benefits
- Rich in quercetin
- Prebiotic fiber
- Contains sulfur compounds
- Probiotic cultures
Serving Suggestions
- Soup and stew base
- Gravy enrichment
- Burger spread
- Dip foundation
- Marinade ingredient
Related Pastes & Sauces Ferments
Other Lactic Acid Ferments
- Sauerkraut — Vegetable
- Kimchi — Vegetable
- Kefir — Dairy
- Pickles — Vegetable
- Yogurt — Dairy
- Hot Sauce — Condiment
- Water Kefir — Beverage
- Kraut-Chi — Vegetable