Bubble tea was created in Taiwan during the 1980s. Its popularity grew throughout Asia and has continued here in North America. In order to understand the drink a bit better, there are a few science-y things about each of the 5 main ingredients we’ve got to become just a tiny bit familiar with …. So let’s get to it!
What is bubble tea?
There is no “standard” definition of what bubble tea is, as there are many possible combinations that exist. You can get drinks from bubble tea shops that don’t even have tea in them! Bubble tea is also known as boba, pearl milk tea, boba nai cha or tapioca tea.
The most common ingredients in bubble tea are simple:
- Black Tea
- Milk/Non-dairy milk
- Ice
- Sweetener
- Tapioca Pearls and/or additional toppings (jellies, custards, foams, etc.)
Ingredients in Bubble Tea: Tea
As you could imagine, there is a lot of science that goes into the perfect cup of tea. Bubble tea is known for its unique colors, which contrast against the additional toppings. Because bubble tea’s colors are so iconic, let’s focus on what causes the color in popular varieties of tea.
Bubble tea most frequently incorporates black tea as its base. When brewed, black tea takes on a dark brown color with a hint of orange and red. Black tea is made by fermenting tea leaves, allowing for the development of black tea pigments, including theaflavins (TFs, golden yellow) and thearubigins (TRs, orange brown), which are largely responsible for brightness, briskness, color, and strength. For more information on these, see the post on Tea for Boba Lovers.
Oolong tea sits between black and green tea on the spectrum of tea oxidation levels. Oolong is a fermented tea made from oxidizing black tea leaves until they create a rich delivery of flavor compounds.
Green tea is produced by heat fixation and rolling of green tea leaves. The process enables the preservation of the tea leaves and allows them to keep their rich green color. This rich green color comes from chlorophyll, a naturally occurring pigment that enables a plant to convert light into glucose. When green teas are steeped, they can range from deep green, such as in the case of matcha, to a yellowish color in the case of jasmine. The more characteristic yellow colour is due to the presence of water-soluble flavonols (kaemperferol, quercetine,myrecitin) and flavones (apigenin, isovitexin, saponarin),which represent 1.3 to 1.5% and 0.02% of the tea leaves (drybasis), respectively.
Ingredients in Bubble Tea: Milk
The most popular variety of Boba is milk tea.
Many people utilize the term creaminess to describe both flavour and texture (even though flavor and texture are two different things). In Boba tea, we care about both.
Milk is largely composed of fats, proteins and sugars which enhances bubble tea’s “mouthfeel” or its texture. However, it’s just as common for non-dairy creamers to be used INSTEAD of milk (either for personal preference or to avoid dairy). The purpose of adding either milk or a milk-alternative is to give Boba tea its characteristic mouthfeel. Milk has a higher viscosity than water because it contains caseinate micelles and fat globules. These reduce the flow of the liquid because they are solid particles. Solid particles reduce the flow of something because there are internal forces at work such as hydrodynamic, Brownian and colloidal forces. There is much more at play… but what you need to know is that it causes your bubble tea to seem thicker when milk is added!
And of course, there is flavor! Milk balances the astringent, tannic compounds in brewed tea, making the beverage taste “smooth” and less harsh. Boba tea ALWAYS contains some sort of ingredient to balance these components of brewed tea and the most common is a milk or dairy-free substitute.
Ingredients in Bubble Tea: Ice
Ice is liquid water that has been frozen. But you knew that. I hope.
What you probably didn’t know is that the shape and size of the ice in your bubble tea will affect its flavor, just like with any other drink. Why? There are two reasons: dilution and sweetness intensity.
The size and density of the ice determine the dilution factor, and when you order bubble tea, you’ll be asked how much ice you’d like (100%, 75%, 50%, 25%, or none). Bubble tea typically has cubed ice, and larger chunks mean a lower dilution factor because there’s less surface area to melt. A cube’s surface area is almost double that of a sphere, so it melts slower than pebble ice.
Why does this matter? The dilution of the ice is taken into account when designing the drink! Boba tea uses tea concentrates – not tea ready for immediate consumption. The melting factor of the ice dilutes the tea to the strength desired for the final product.
The amount of ice you receive will also affect the drink’s flavor, as colder drinks are less sweet and taste different as they melt. If the drink is not at the correct temperature (very cold!), it will taste “too sweet” and the flavors will not balance properly. The same thing happens with soda. Drink a room temperature Coke and it will taste WAYYYY too sweet and the flavors will be “off.” You might not be able to pinpoint what’s wrong.. but your taste buds will tell you something is not right.
This is why the ice ratio and shape matters: in Boba tea, the dilution rate of the melting ice and cooling effect are actually PART of the recipe.
Ingredients in Bubble Tea: Sweetener
Syrups are added to bubble tea to enhance its flavor and sweetness. Just like tea flavors, there are many options for sweeteners such as fruit syrups, floral syrups and sugar based syrups. Bubble tea is most classically known for adding melted brown sugar to it (although in the US, liquid sucrose is most commonly used).
Brown sugar is crystalline sucrose with added molasses. Molasses is a thick syrup that is a byproduct of the sugar-making process. It is derived from crushed sugar cane or sugar beets, which are boiled down to extract juice from sugar crystals. The remaining juice is used to create molasses. Molasses has a ton of flavor compounds that are a result of the sugar making process – rich, slightly bitter, with strong caramel overtones.
Ingredients in Bubble Tea: Boba
The thing we have been waiting for. The iconic pearls that give bubble tea it’s signature look, taste, and chew.
What are bubble tea bubbles made of?
The standard “bubbles” of bubble tea are made from tapioca starch. These tapioca balls are chewy, typically black spheres produced from tapioca, which is a starch extracted from the cassava root. Tapioca, when uncooked, is uncolored and doesn’t have much flavor. It isn’t until you cook them and add sugar (like brown sugar or cane syrup) that the flavor is improved.
So how does tapioca starch powder become squishy balls that are fun to chew?
Science of course!
Tapioca flour is activated by the addition of heat and water. When tapioca starch is heated in 180*F water is swells and begins to gel.
Starch molecules are essentially large polymer molecules made of glucose units. Heat and water trigger the gelatinization of tapioca flour, causing the starch particles to swell and break apart. These new pieces are able to create new connections and form a network that can hold water. As the solution cools, it becomes stiffer.
Scientifically, when you heat the tapioca balls, water is able to enter the randomly entangled amorphous regions of the starch molecules. As more water is added, it begins to flow into the polymer, causing the crystalline region to detangle. This allows the long-chain polymers from the crystalline regions to form hydrogen bonds with each other, initiating gelatinization. This gelatinization process is what gives tapioca balls their characteristic chewy texture.
“QQ” is a Taiwanese term that describes the chewy, springy, or bouncy texture of boba, or tapioca pearls, in bubble tea:
The term is similar to the Italian term “al dente” for pasta. The quality of boba is measured by its “Q power”, or how much QQ it has. Boba with the right amount of QQ is not too soft or too bouncy, but has just the right amount of toothiness. In order to achieve QQ, it is important to carefully follow the process for cooking boba.
