Sweet, creamy, and refreshing, this Thai red rubies dessert is perfect for a hot, summer day. The red rubies are chewy on the outside and crunchy in the middle, giving this dessert a wonderful and unexpected texture. Served with cold, sweet coconut milk, it's as beautiful as it is delicious.
I was captivated by this Thai red rubies dessert from my very first taste of it. I love most Thai desserts that are served with sweetened coconut milk. But this one is particularly special. The "red rubies" have such a unique texture -- delightfully gummy on the outside, much like boba, but with a surprisingly crunchy center.
The first time I ate this dessert, I don't think I would have guessed that it's made from water chestnuts. Indeed, the bite-sized red rubies are made by coating small pieces of water chestnut with tapioca starch. Once they are boiled and cooled, they magically transform into delightful little gems that are chewy on the outside and crunchy in the middle. Paired with sweet, cold coconut milk, they make a unique, delicious, and very pretty dessert.
Why is it called Red Rubies Dessert?
In Thai, this dessert is known as Tub Tim Grob. Tub Tim is the Thai word for ruby (as well as pomegranate seed, presumably because they look like rubies). Grob means crunchy. So this dessert literally translates to crunchy ruby or crunchy pomegranate seed. Since the rubies are red, it's not much of a stretch to call this dessert Red Rubies in English.
Ingredients
- Water chestnuts: For this dessert, you can use either fresh or canned water chestnuts. If you are using fresh water chestnuts, you'll want to cut the top and bottom off, then peel the remaining skin off. Then proceed with either variety by cutting them into bite-sized pieces.
- Red food coloring: The bite-sized pieces of water chestnut are soaked in red food coloring to give them their distinctive ruby red color. If you prefer natural coloring, you could try beet root or pomegranate juice.
- Tapioca starch: Tapioca starch is what transforms these water chestnuts into beautiful gems. It can be found at Asian grocery stores and online. Other flours or starches cannot be substituted.
- Granulated sugar: White sugar is used to sweeten the coconut milk. Palm sugar could be used, if you prefer, although it will turn the coconut milk a darker color.
- Coconut milk: Coconut milk forms the base of this dessert, so it's important to use a good quality milk. Fresh, homemade coconut milk would be ideal, but canned works as well. The coconut milk is traditionally flavored with pandan leaves.
- Crushed ice: The dessert just isn't the same without crushed ice.
NOTE: This red rubies dessert is sometimes also served with small slices of tropical fruits or other jellies. Jackfruit, young coconut meat, lychee, longan, and toddy palm are common choices.
Step by Step Instructions
- Prepare the Water Chestnuts: If using fresh water chestnuts, cut the top and bottom off and peel them with a vegetable peeler. If using canned, simply rinse. Cut each water chestnut into very small bite-sized pieces (~¼" cubes).
- Add the Red Color: Mix 20 drops red food coloring with a little water. Coat the water chestnut cubes in the food coloring mixture and let them sit for about 10 minutes until they are all evenly red.
- Coat with Tapioca Starch: Add the water chestnuts to the tapioca starch and mix until they are coated well. Strain them with a mesh sieve or colander to get rid of the excess flour. If you prefer a more gummy texture, add another layer of tapioca starch by misting them with water and coating them with the starch again.
- Cook the Red Rubies: Place the coated water chestnuts in a pot of boiling water and cook for approximately one minute. Once they float to the surface, they are done. Remove and plunge into a pot of ice cold water. Once in the ice water, they'll transform into shiny, clear red rubies. If you notice spots of white (uncooked tapioca starch), put them back into the boiling water to cook for a minute longer.
- Make the Coconut Syrup: Make a simple syrup by heating equal parts water with white granulated sugar. If you like, you can add a bruised and knotted pandan leaf to the syrup mixture while it cooks to infuse the syrup with pandan flavor. Once it cools, add the coconut milk and stir together.
- Serve over Crushed Ice: Allow the coconut syrup to cool to room temperature. Add crushed ice and the prepared red rubies. Stir and enjoy immediately!
Storage
The red rubies tend to stick to each other if they are not submerged in a liquid. You can store them in a little simple syrup to help keep them separate.
They can be kept at room temperature for several hours, but after that, they'll need to be refrigerated. Be warned - they will harden in the fridge, so it's really best to make them within a few hours of serving this dessert. The coconut syrup, however, can be made days in advance and kept in the fridge with no problems.
This Thai Red Rubies Dessert is wonderful on a hot, summer day. It'd be a great end to a backyard meal with your favorite Thai grilled foods, or just as wonderful as a refreshing mid-day snack. The chewy, crunchy red rubies with sweet, cold coconut milk is just so delicious whenever you serve it!
Recipe
Red Rubies Dessert | Tub Tim Grob | ทับทิมกรอบ
Ingredients
- 1 cup water chestnuts
- 20 drops red food coloring
- 2 tablespoons water
- 1 cup tapioca starch
- ½ cup water
- ½ cup granulated sugar
- 1 cup coconut milk
- crushed ice
Instructions
- If you are using fresh water chestnuts, cut the tops and bottoms off and peel them with a vegetable peeler to remove the skin. If you are using canned water chestnuts, simply rinse them. Then cut each water chestnut into very small bite-sized pieces (~¼" cubes).
- Mix 20 drops red food coloring with 2 tablespoons water. Coat the water chestnut cubes in the food coloring mixture and let sit for approximately 10 minutes until they are all evenly red.
- Add the water chestnuts to the tapioca flour and mix until they are coated well. Take them out of the flour and then, using a spray bottle, mist them with water and coat them with flour again. Strain them with a mesh sieve or colander to get rid of the excess flour.
- Place the coated water chestnuts in a pot of boiling water and cook for approximately one minute. Once they float to the surface, they are done. Remove and plunge into a pot of ice cold water. If they still have small spots of white, this indicates uncooked tapioca starch, so they should be boiled for another minute.
- Make a simple syrup by heating ½ cup water with ½ cup sugar until the sugar is completely dissolved. Cool to room temperature, then add 1 cup coconut milk and stir until mixed. Add the red rubies and crushed ice and enjoy!
aley
hi! may I know why my red rubies have a bitter aftertaste 😊
Jacqueline Low
Bring coconut milk to boil, add in sugar and pandan leaves. Add in jasmine tea leaves and salt. Infuse for 15mins. Leave to cool n refrigerate. It brings out the frangrance.
Jacqueline Low
Bring coconut milk to boil, add in sugar and pandan leaves. Add in jasmine tea leaves and salt. Infuse for 15mins. Leave to cool n refrigerate. It brings out the frangrance.
Jacqueline Low
After cutting the chestnuts into cubes, can also use rose syrup to soak it in fridge for 2hrs. Coat w 1 layer of tapioca flour, sieve off the excess flour n bring to boil. Thats what i just did!
Jacqueline Low
After cutting the chestnuts into cubes, can also use rose syrup to soak it in fridge for 2hrs. Coat w 1 layer of tapioca flour, sieve off the excess flour n bring to boil. Thats what i just did!
sarazi
Hi Rachel... For how many days can i keep/ store the water chesnut that have been boiled.... can i put it into freezer for a long time? Btw i love ur blog and all the recipes!!
Rachel
Hi Sarazi, that's a really good question, and I'm not sure... We tend to eat all of them pretty quickly 🙂 If you do experiment with storage timing, please let us know how it goes...
sarazi
Hi Rachel... For how many days can i keep/ store the water chesnut that have been boiled.... can i put it into freezer for a long time? Btw i love ur blog and all the recipes!!
Rachel
Hi Sarazi, that's a really good question, and I'm not sure... We tend to eat all of them pretty quickly 🙂 If you do experiment with storage timing, please let us know how it goes...
Zainab
Hi I dyed the chestnuts in beet root juice. But the coating of tapioca and the colour came off completely while boiling. Any suggestions
Rachel
Hmm, I haven't run into this problem before, so I'm not exactly sure how to guide you. My only suggestion would be to try coating the water chestnuts in several layers of the tapioca flour (dip in flour, then spritz with water, then more flour, etc). Best of luck!
Zainab
Hi I dyed the chestnuts in beet root juice. But the coating of tapioca and the colour came off completely while boiling. Any suggestions
Rachel
Hmm, I haven't run into this problem before, so I'm not exactly sure how to guide you. My only suggestion would be to try coating the water chestnuts in several layers of the tapioca flour (dip in flour, then spritz with water, then more flour, etc). Best of luck!
Bhandari
Hi mam its a great dessert can we add a flavour of rose petals or pandan leaf while boiling coconut milk...
Bhandari
Hi mam its a great dessert can we add a flavour of rose petals or pandan leaf while boiling coconut milk...
Ana Fernandez
Oh y God the cup with the coconut milk and the red rubies looks great!
Ana Fernandez
Oh y God the cup with the coconut milk and the red rubies looks great!
Irina @ wandercrush
Such a beautiful dish! Have you ever tried dying the water chestnuts with beetroot juice?
Rachel
Thanks Irina! I've read about it, but haven't tried it yet... soon 🙂
Irina @ wandercrush
Such a beautiful dish! Have you ever tried dying the water chestnuts with beetroot juice?
Rachel
Thanks Irina! I've read about it, but haven't tried it yet... soon 🙂