What Are Sea Grapes Filled With?

January 6, 2026 •

4 min read

Over a third of Okinawa's population is known to be over 100 years old, with many attributing their longevity to a healthy diet that includes sea grapes, or 'longevity seaweed'. This marine algae is not only a nutritional powerhouse but also a culinary delight that prompts the question: what are sea grapes filled with, and what gives them their signature pop?

Quick Summary

This article explores the unique characteristics of sea grapes, revealing that their tiny, edible bulbs are filled with a briny liquid that delivers a satisfying popping texture. The content of these 'bubbles' consists of minerals, vitamins, and other beneficial nutrients.

Key Points

Salty Liquid: The tiny bubbles of sea grapes are filled with a briny, oceanic-tasting liquid.
Popping Texture: The signature 'puchi-puchi' pop occurs when the turgid, water-filled cells are bitten, releasing the liquid.
Rich in Nutrients: They are packed with minerals like calcium, iodine, and iron, along with vitamins A, C, and E.
High in Omega-3s: The liquid also contains healthy omega-3 fatty acids and vegetable protein.
Antioxidant Properties: Sea grapes have antioxidants that combat oxidative stress and inflammation.
Best Served Raw: To preserve the delicate texture, sea grapes should be eaten raw and rinsed in cold water.
Nicknamed 'Green Caviar': Their appearance and popping texture often lead to them being called 'green caviar' or 'longevity seaweed'.

Unpacking the Unique Structure and Composition

Sea grapes, scientifically known as Caulerpa lentillifera, are a type of green macroalgae characterized by tiny, bubble-like structures growing on a central stem, or frond. These glistening nodules are actually the edible leaves of the plant, and it's their unique cellular structure that gives them their distinct character. The 'bubbles' are filled with a salty, marine-flavored liquid that is released with a satisfying pop when chewed. This sensation is so beloved in Japan that it has its own onomatopoeia: "puchi-puchi".

The secret behind the pop lies in the process of osmosis. When dehydrated sea grapes are soaked in cool, fresh water, the water rushes into the cells, causing them to plump up and become taut. When these turgid cells are crushed in the mouth, they burst, releasing the salty liquid. This creates the delightful, crunchy texture that is a hallmark of this delicacy.

Nutritional Richness Inside Every 'Grape'

Beyond the unique texture and briny flavor, the liquid and tissue within sea grapes are packed with a wide array of nutritional benefits. This is why they have earned the nickname "longevity seaweed" in places like Okinawa, Japan. Their low-calorie nature, combined with a dense nutrient profile, makes them a valuable addition to a healthy diet.

Nutrients Found in Sea Grapes:

Minerals: A fantastic source of essential minerals like calcium for strong bones, iodine for thyroid health, and iron for oxygen transport. They also contain potassium, magnesium, and zinc.
Vitamins: Rich in vitamins A and C, which boost the immune system and support skin health. They also provide vitamins K and E, which have antioxidant properties.
Antioxidants: The liquid contains antioxidants that help neutralize free radicals, reduce inflammation, and may offer protection against chronic diseases.
Protein and Omega-3 Fatty Acids: Sea grapes provide vegetable protein and healthy omega-3 fatty acids, promoting heart and brain health.
Dietary Fiber: The seaweed offers dietary fiber, which aids in digestion and gut health.

Sea Grapes vs. Other Seaweed: A Comparison

While many seaweeds are nutritious, sea grapes stand out for their unique texture and nutritional composition. A comparison helps highlight their distinct qualities.


Feature	Sea Grapes (Caulerpa lentillifera)	Kombu (Saccharina japonica)	Nori (Pyropia yezoensis)
Texture	Crunchy, popping, and succulent when fresh; famously described as "puchi-puchi".	Tough and chewy when fresh; often dried and used for broth, soft when cooked.	Thin, crisp, and papery when dried; becomes pliable when wet.
Best Use	Best eaten raw in salads, as a garnish, or with dipping sauce to preserve its texture.	Ideal for making dashi (broth), stews, and as a flavoring agent.	Common in sushi rolls, as a wrap for rice, or as a crunchy snack.
Flavor Profile	Briny, ocean-like, with umami notes and a refreshing crispness.	Strong, savory, and rich umami flavor.	Mild, slightly sweet, and toasty when roasted.
Nutritional Highlight	Rich in antioxidants, vitamins (A, C, E, K), and omega-3 fatty acids.	High in iodine and glutamic acid, which contributes to its umami flavor.	Contains vitamins A, B, C, and protein; often fortified with iodine.
Cultivation	Primarily farmed in shallow, warm waters of the Indo-Pacific region, including Okinawa and Vietnam.	Typically harvested wild or farmed in colder coastal waters of Japan and Korea.	Extensively farmed and processed for commercial use globally.

Preparing and Enjoying Sea Grapes

To fully appreciate the flavor and texture of sea grapes, proper preparation is essential. Since high heat destroys their signature pop, they are almost always consumed raw.

Rehydrate: If using dehydrated sea grapes, soak them in a bowl of cool, clean water for about 3 minutes until they plump up.
Rinse: Rinse the rehydrated or fresh sea grapes a few times in fresh water to remove excess saltiness.
Chill: For the best and crispiest texture, briefly soak them in ice-cold water before serving.
Serve Immediately: To prevent them from shriveling, eat them within a few minutes of preparation.

They pair wonderfully with simple dipping sauces like ponzu, soy sauce with vinegar, or miso. Their oceanic flavor and unique texture make them a fantastic garnish for seafood, sushi, and salads, providing a delightful culinary experience.

Conclusion: The Secret of the Sea Grapes

In conclusion, what are sea grapes filled with is not just seawater, but a briny liquid contained within their specialized cellular structure, which is the source of their famous popping texture. This unique 'puchi-puchi' sensation is complemented by a surprising wealth of nutrients, including vitamins, minerals, and antioxidants, justifying their reputation as a superfood and a delicacy. For those who seek a healthy, low-calorie, and texturally exciting addition to their diet, the humble sea grape offers a refreshing taste of the ocean and a burst of nutritional goodness with every bite.

Authoritative Resource on Seaweed

For further reading on the potential of seaweed like sea grapes as a sustainable food source, the Leibniz Centre for Tropical Marine Research offers insight into their 'SeaGrapes' project.

Frequently Asked Questions

The scientific name for the type of sea grapes known for their popping texture is Caulerpa lentillifera, a species of green algae.

No, sea grapes are a type of seaweed (algae) and are not related to the fruit grapes that grow on vines. They are called 'sea grapes' due to their visual resemblance to small clusters of green grapes.

Yes, sea grapes are considered a healthy superfood. They are low in calories and rich in vitamins A, C, E, and K, as well as minerals like calcium, iodine, and iron. They also contain antioxidants and omega-3 fatty acids.

If starting with dehydrated sea grapes, first rinse them well, then soak in ice-cold water for a few minutes until they plump up. If fresh, simply rinse them thoroughly. Always serve them raw to maintain their texture.

Sea grapes are native to the warm, shallow coastal waters of the Indo-Pacific, and are commonly farmed and consumed in Southeast Asia and Japan, particularly Okinawa.

Sea grapes are often called 'green caviar' because their small, bead-like appearance and the way they pop in your mouth are reminiscent of fish roe, or caviar.

"Puchi-puchi" is the Japanese onomatopoeia used to describe the delightful, popping sound and sensation that occurs when you bite into the fresh sea grapes.