How to Make Karasumi

History

Karasumi arrived in Japan via trade routes from China during the 17th century, when Nagasaki was Japan's main trading port. It became one of Japan's 'three great delicacies' (nihon sandai chinmi) alongside sea urchin and konowata (sea cucumber intestines). Nagasaki karasumi remains the most prized.

Ingredients

• 2 whole sacs Fresh mullet roe sacs — Membrane intact, from grey mullet
• Generous Sea salt — For curing
• 2-3 cups Sake — For soaking/rinsing

Equipment

• Shallow trays
• Pressing boards and weights
• Drying rack
• Sake for rinsing

Instructions

1. Prepare roe and remove blood

   Carefully extract intact roe sacs. Use a needle to meticulously prick the veins along the membrane and use the back of a spoon or your thumb to gently push all blood out towards the base. Rinse with cold water or sake.

   Time: 1-2 hours

   Tip: Residual blood is the primary cause of bitterness and bacterial spoilage; the roe must be completely clear of blood spots.

2. Salt cure (Refrigerated)

   Bury the roe sacs in high-quality sea salt. Store in the refrigerator (1-4°C). Change the salt every 2 days as it draws out moisture.

   Time: 1 week

   Tip: Keeping the roe cold during this phase is critical for food safety while the salt penetrates the center.

3. Sake soak and desalting

   Submerge the salted roe in sake (refrigerated). This removes excess surface salt and infuses the roe with amino acids. Change the sake if it becomes too cloudy.

   Time: 12-24 hours

   Tip: A longer soak results in a milder, more complex flavor profile.

4. Pressing and Sun-drying

   This is a dual process. During the day, place roe on bamboo mats in a cool, breezy, sunny spot (12-18°C). At night, place the roe between two boards with a light weight on top to maintain the flat 'inkstone' shape.

   Time: 2-4 weeks

   Tip: Wipe the surface with sake daily during the drying process to prevent mold and keep the membrane supple.

5. Final Aging

   Once the roe is firm and translucent (amber color), it can be aged further in a cool, dark place to develop deeper umami.

   Time: 1-4 weeks

   Tip: The total process from start to finish typically takes 4-8 weeks depending on the size of the roe and humidity.

Fermentation Timeline

• Day 1: Preparation — Roe sacs extracted and salted.
• Week 1: Salt curing — Moisture drawn out. Texture firming.
• Week 2: Sake soak and pressing — Rinsed in sake. Under weights.
• Weeks 3-5: Drying — Sun-dried daily. Amber color developing.
• Week 5+: Ready — Firm, amber, waxy. Intense umami flavor.

Signs of Success & Spoilage

Good signs

• Amber translucent color
• Firm waxy texture
• Intense savory aroma
• Gives slightly to pressure
• No cracks or tears

Warning signs

• Torn membrane
• Soft spots
• Off odors
• Too dry/cracked
• Mold

Troubleshooting

Cracking

Cause: Dried too fast or too long Solution: Dry more slowly. Wrap slightly to slow drying.

Too salty

Cause: Insufficient sake soak Solution: Soak longer in sake. Rinse more.

Soft texture

Cause: Under-dried Solution: Continue sun-drying.

Storage

Vacuum sealed or wrapped tightly in plastic/washi paper and refrigerated Keeps Up to 1 year refrigerated; 2 years frozen. If the surface becomes too dry, lightly brush with sake before serving.

Health Benefits

• High protein
• Omega-3 fatty acids
• Vitamin A and D
• Phosphorus
• Rich umami
• Prized delicacy status

Serving Suggestions

• Thinly sliced with sake
• Grated over pasta or rice
• With daikon radish
• On crackers as appetizer
• In traditional New Year celebrations
• With champagne or white wine

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• Garum
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• Hákarl
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• Bottarga

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