Illustration | Coffee newbies, you need a guide to making layered latte

Click to follow | Daily boutique coffee culture magazine

There is a common sense in making latte. If you want to make a beautiful latte, you should pour milk into espresso, not the other way around. But what happens if you do it the other way around? This will make another kind of latte: layered latte . To make a layered latte, you pour espresso into a cup of milk.

| What’s the secret to a perfect layered latte?

If the espresso is poured into the milk too slowly, the denser fluid will mix too evenly with the less dense fluid, and the latte will not be layered. A faster pouring speed allows the denser fluid to impact the less dense fluid and cause rapid movement as the density equilibrium is established, resulting in the desired layering.

Even with a gentle agitation, such as sipping a layer, the layers will form and remain for minutes, hours, or even days. As long as the latte is warmer than the surrounding air, stirring will create another density gradient, similar to the density gradient created by pouring espresso. But if the latte is stirred after it reaches room temperature, the layers are gone forever. They published their findings in Nature Communications.

| Why is it important to understand the stratification principle of liquids?

Stone and doctoral student Nan Xue and others used a set of LED lights and cameras to capture the stratification process, observing that when coffee is poured into heated milk, a phenomenon called double-diffusive convection occurs, creating different density layers in the liquid.

After recreating the latte with their own espresso and milk, they developed a simulated drink by injecting heated, dyed fresh water into a denser, heated salt water containing particles that scatter a green laser beam, mixing to test the scientific parameters that make this spontaneous layering possible. They then ran simulations to compare various models of different systems using the data they collected.

They found that pouring hot coffee into hot milk at a certain speed caused an interaction between temperature and density that caused the beverage to separate into layers of different densities. The same basic phenomenon, called double-diffusive convection, forms water layers in the ocean. Salt water with different concentrations has different densities, just like the espresso and denser milk in a latte.

As the liquids try to mix, the temperature gradient causes one part of the liquid to heat up, become lighter and rise, while the other, denser part sinks. This sinking and rising motion stops when the local density of a region in a latte approaches equilibrium. As a result, the fluid must flow horizontally, rather than vertically, resulting in different layers.

The following is the recipe we used when we used the VST 20g colander

▼

– Water temperature | 93-94℃

– Pressure | 9 ba

– Freshly ground coffee | 19-20 g (use a digital scale)

– Total weight of coffee | 36-40 grams (using a digital scale)

If you are using a 22g filter bowl, please use 22g of freshly ground coffee powder, the total weight of coffee should be 44g, the ratio is 1:2. .

Maple Iced Latte

Maply Syrup Latte

1. Fill a glass half full with ice and add 10 grams of maple syrup.

2. Pour the fresh milk into the cup until it is 70% full, then stir evenly to make the syrup melt into the fresh milk to increase the proportion of fresh milk.

3. Let the coffee slowly pour into the cup along the spoon. Do not pour too fast to avoid destroying the layering.

4. Completion