Kohakutou is one of the most visually stunning candies you can make at home, and the crystallized sugar crust that forms overnight is pure magic with zero extra effort. Unlike gelatin-based gummies, this Japanese crystal candy is completely plant-based, sets up firmer, and develops a crackly exterior that gives way to a chewy, jewel-like center.
Quick Glance: Kohakutou Crystal Gummy Candy
- Recipe Name: Kohakutou Crystal Gummy Candy
- Why You'll Love It: These gorgeous Japanese crystal candies look like precious gemstones but require almost no skill to make.
- Time and Difficulty: 20 minutes active time + 2 to 3 days drying time | Easy
- Main Ingredients: Telephone brand agar agar powder, granulated sugar, water, food coloring, flavoring extract
- Method: Stovetop boiling, pour into molds or pan, unmold and slice, dry on rack
- Texture and Flavor: Chewy and firm interior with a crackly crystallized sugar crust. Flavor is entirely customizable based on the extract and coloring you choose.
- Quick Tip: Telephone brand agar agar is not optional here. Other brands will not crystallize correctly, and your candy will stay soft.
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I first saw this Kohakutou recipe on Emmymade in Japan's YouTube channel. I was fascinated by the crystalizing gummies and thought they would be great for a geode cake.
Kohakutou Ingredients
Here is everything you need to make kohakutou crystal gummy candy. The ingredient list is short, but quality and brand matter more in this recipe than almost any other.
Telephone brand agar agar powder sets the candy firm enough to unmold and slice cleanly while still maintaining a chewy interior. Do not substitute any other brand or type of agar agar.
Granulated white sugar creates the supersaturated solution that crystallizes on the candy's surface over time. Do not use powdered sugar or coconut sugar, as they will not crystallize the same way.
Water is the base of the entire mixture. Use filtered water if your tap water has a strong taste.
Gel food coloring gives kohakutou its jewel-toned appearance. Gel coloring is concentrated and will not add extra liquid that could affect the set. Liquid food coloring can make the colors appear washed out.
Flavoring extract is entirely up to you. Citrus extracts like lemon, lime, and orange work beautifully. Start with half a teaspoon and adjust to taste, since some extracts are stronger than others.
Luster dust or edible gold paint (optional) is brushed onto the finished candy to add a metallic shimmer. This step is purely decorative but makes a stunning presentation.
Why This Recipe Works So Well
The magic behind kohakutou comes down to two things: agar agar and supersaturated sugar.
Agar agar is a plant-based gelling agent derived from red algae. It behaves very differently from gelatin. Where gelatin only needs to bloom in cold water before dissolving, agar agar must be boiled in order to activate. If you do not bring it to a full boil, the agar will not gel properly and your candy will be soft and sticky instead of firm and sliceable. This is also why kohakutou is naturally vegan and why it sets up at room temperature rather than in the fridge.
The crystallization happens because of the extremely high sugar concentration in the recipe. When the candy is exposed to air over 48 to 72 hours, moisture slowly evaporates from the surface, and the sugar molecules begin to recrystallize into a thin, sparkling crust. The inside stays chewy and soft while the outside becomes crackly and opaque. This is the same principle behind rock candy and other supersaturated sugar confections.
Telephone brand agar agar powder is specifically required because of its particular gelling strength and purity. Other brands, including many commonly sold in health food stores, have different gel strengths that will not produce the same crystallization or texture. This is the one ingredient where substitution will not work.
Kohakutou Gummy Candy Step-By-Step
- Bloom the agar agar Pour cool water into a medium saucepan. Sprinkle the agar agar powder over the surface of the water and let it absorb for 5 minutes. Do not stir yet.
- Simmer the agar mixture Bring the mixture to a simmer over medium heat and cook for 2 to 3 minutes, stirring constantly with a spatula. The mixture will turn glossy as the agar activates.
- Add the sugar Sprinkle in the granulated sugar and continue cooking for another 2 to 3 minutes, stirring constantly, until fully dissolved.
- Add flavor and citric acid Remove the saucepan from the heat. Stir in your candy flavoring and citric acid.
- Pour into dish Pour the mixture immediately into a lightly oiled heatproof glass dish.
- Add color Drop a few drops of liquid food coloring on top and swirl with a toothpick. You can blend it fully for a solid color or leave it streaked for a more realistic gemstone look.
- Refrigerate to set Place the dish in the refrigerator for 2 to 3 hours until fully set.
- Cut into crystal shapes Remove the set gummy from the dish and place it on a cutting board. Use a sharp knife to cut it into irregular, angular crystal shapes.
- Dry at room temperature Place the cut pieces on a parchment-lined baking sheet and leave them at room temperature for 2 to 3 days. A hard crystallized crust will form on the outside while the inside stays chewy. Rotate them as needed.
- Finishing touches (optional) Once fully crystallized, you can brush the candy with edible gold or silver luster dust mixed with a small amount of clear extract or lemon extract for a metallic shimmer. This makes the gems look even more like precious stones.
Final Thoughts
When the crystals are fresh, they are very clear and super pretty. Very firm and pretty transparent. You could honestly use them on a cake just like this but they started getting a crystal skin on them fairly quickly.
These edible crystals would be amazing on a geode cake or as favors. I have so many ideas! We all were dying to try the crystal candy and I actually thought it was really good. The texture is not as chewy as regular gummy candy but still very good. I love the contrast between the gummy center and the crunchy exterior.
Kohakutou Crystal Gummy Candy FAQs
Kohakutou (also spelled kohakutoh or kohaku-to) is a traditional Japanese candy whose name translates roughly to "amber sugar." It is made by simmering agar agar with a high concentration of sugar, pouring it into a mold, refrigerating until set, and then allowing the cut pieces to dry at room temperature for 2 to 3 days. During the drying period, the outer layer crystallizes into a sparkling, crackly crust while the interior remains soft and chewy. The finished candy resembles colorful gemstones or geodes.
Not all agar agar is the same. Different brands are processed with different gel strengths. Telephone brand has been consistently tested to produce the correct crystallization for kohakutou. Other brands, even those labeled as pure agar agar powder, often have a different gel strength that produces candy that either stays permanently soft or sets too hard without ever developing the crystal crust. It is available on Amazon and in many Asian grocery stores.
The crystallization process takes 2 to 3 days at room temperature after the candy has been cut. You will notice the exterior beginning to turn opaque and sparkly within the first 24 hours. The exact timing depends on your environment since lower humidity speeds up crystallization and higher humidity slows it down.
No. Agar agar is the only ingredient that will produce the correct texture and allow crystallization to happen. Gelatin will not work because it has a different protein structure and will not crystallize. Pectin will also not produce the same results.
Yes. Agar agar is derived from red algae, making it completely plant-based. Traditional gelatin gummies are made from animal collagen and are not vegan, but kohakutou is a fully vegan candy.
The most common causes are using the wrong agar agar brand, not simmering the agar mixture long enough, or storing the candy in an airtight container after cutting. Make sure you are drying the pieces uncovered at room temperature in a relatively dry environment. High humidity can significantly slow or prevent crystallization.
There is no right or wrong way to cut kohakutou. The irregular, angular cuts are what give it the gemstone appearance. Use a sharp chef's knife and make confident cuts at varying angles. Jagged and uneven is actually what you want here.
Properly stored at room temperature in a dry, open container, kohakutou will last up to 2 weeks. The crystal crust helps preserve the candy by sealing out moisture. If the candy becomes sticky, it has absorbed humidity and the surface crystals have dissolved.
Yes. Candy flavoring is stirred in after removing the mixture from the heat. Citrus flavors are especially popular because the bright, tart flavor pairs well with the sweet candy. Rose, lychee, and other floral or fruity flavors also work beautifully.
Citric acid adds a subtle tartness that balances the sweetness of the candy and enhances fruit-based flavorings. It is the same ingredient that gives sour candy its pucker. You can find it in most grocery stores in the canning aisle or online.
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Recipe
Equipment
- Saucepan
- Container
Ingredients
- 12 grams agar agar (telephone brand)
- 14 ounces cool water
- 24 ounces sugar
- ¼ teaspoon candy flavoring
- ⅛ teaspoon citric acid optional - adds a tart flavor
- 3 drops liquid food coloring I used Americolor airbrush color
Instructions
- Place cool water into a medium-sized saucepan
- Sprinkle agar agar powder over the water and let it absorb for 5 minutes
- Bring the mixture to a simmer and cook for 2-3 minutes stirring constantly with a spatula
- Sprinkle in your sugar and continue cooking for another 2-3 minutes
- Remove from the heat and add in candy flavoring and citric acid
- Pour the mixture into a heatproof, glass dish that has been lightly oiled to prevent sticking
- Add a few drops of liquid food coloring on top and swirl with a toothpick. You can blend fully or leave it streaked
- Place the container into the fridge for 2-3 hours until set
- Remove the set gummy from the container and cut into crystal shapes using a sharp knife
- Place the crystal gummies onto a parchment covered cookie sheet and let dry at room temperature for 2-3 days until a hard crust forms on the outside
Fable says
Where do you recommend getting the agar agar? I'm finding it hard to locate some online that is consistent in price and the right brand (telephone).
Elizabeth Marek says
I got mine at an asian grocery store or you can get it online
Zoe says
Can I use gel food coloring instead of liquid?
Elizabeth Marek says
Yes but you might have to water it down
Jessica says
Just took mine out of the fridge and they are AWESOME! I am so excited to bake some cupcakes and show these off at work. My students are going to go nuts! I used LorAnnOils green apple flavoring with the citric acid, and I would definitely use more of both next time (I like a super pronounced sour flavor) and I think I overdid it on the food coloring, but they worked beautifully and I am so pleased!
Maria says
What brand of Citric acid can I use? And where can I purchase?
Sugar Geek Show says
Any brand is good, I got mine in the canning foods section of my grocery store. Or you can probably find it on amazon.
Amy Estes says
I want to love this but it flopped,
Not once but three times. Followed the recipe exactly and weighed my ingredients. So bummed.
Elizabeth Marek says
Did you by chance use a different brand of agar agar? This recipe will not work at all unless you use the telephone brand. I tried to make that super clear in the blog post and the recipe. I'm sorry it didn't work for you
Dawn says
1tablespoon = 12.78 grams, if that helps any.
Becky says
Great recipe! Followed to a “T” but used the agar powder I had in my cabinet instead of telephone brand. Turned out awesome! Would suggest increasing citric acid and flavoring up to 3x the amount as turned out weak tasting. Great visual affect though 🙂
Thanks for the awesome recipe!!
Caroljup says
Love All Your Work, You Are The Best Girrlll!!!, Can You Add The Flavored Candy Oil!!!, Thanks Again!!
Elizabeth Marek says
you can add flavoring extracts