Is Dirty Coffee Always Made with Boke? What Are the Differences in Taste Between Dirty Coffee and Latte?

Dirty coffee has long existed as a secret menu item at FrontStreet Coffee, because in FrontStreet Coffee's view, Dirty is simply a "special" way to drink latte. Until one day, FrontStreet Coffee无意间听到客人对他的朋友科普，总结起来就是「Dirty就是用冰博克奶做底，然后淋入espresso形成分层效果，喝的时候不用搅拌，直接喝。」

This customer's explanation of Dirty coffee was generally correct, but there was ambiguity about whether Dirty must be made with Eisbock milk. When you open a search engine and type "dirty coffee," the indexed terms also include "Does dirty coffee have to use Eisbock?" It seems this isn't an isolated case. So FrontStreet Coffee wants to explain what's really going on with Dirty coffee and Eisbock.

The Origin of Dirty Coffee

Dirty coffee is essentially a latte presented with a layered effect. It originated from the popular "dirty food" culture of 2018, where chocolate powder was basically used to create a "very dirty" visual effect. When applied to coffee, the "dirty" effect comes from the visual of deep black espresso slowly seeping down and "contaminating" the pure white milk.

After the dirty food trend faded, people discovered that this layered "latte" drinking method—first experiencing the hot, rich coffee flavor, followed by the mild milk coffee taste, and finally the cold lactose sweetness—had its own unique charm, so it was preserved. To distinguish it from iced lattes that are stirred, the name Dirty coffee was also retained.

Dirty Coffee vs. Iced Latte

The ingredients for Dirty coffee and iced latte are basically the same—espresso + milk. However, iced lattes include ice cubes and don't emphasize the layered effect. Dirty coffee, on the other hand, doesn't add ice cubes and deliberately creates a layered effect (some coffee shops might use slightly less milk than in a regular latte to balance the coffee-to-milk ratio).

What is Eisbock?

Eisbock is a process originally used by Germans to purify (ice distill) beer, making it richer and higher in alcohol content. The principle involves freezing beer into ice blocks, then thawing it, utilizing the different melting points of various substances in beer to remove some water (ice), resulting in higher beer concentration.

At the 2017 World Barista Championship, a Canadian barista first applied ice distillation technology to the coffee field. At the 2018 World Barista Championship, a Chinese barista applied Eisbock technology to milk, increasing the original milk concentration from 11-12% to 20-21%. After the competition, some coffee shops in China also introduced Eisbock lattes.

Actually, the process of making Eisbock milk isn't very complicated. Early coffee shops made Eisbock milk by hand. The process was as follows: first freeze the milk, then make a small opening in the milk carton, invert it over a container, and let the frozen milk thaw. Since ice (solid H₂O) melts slowest, when 1L of frozen milk melts to produce 0.5L of milk, the remainder can be discarded. The melted milk is Eisbock milk that's twice as concentrated as the original milk.

Eisbock milk is more viscous and richer than regular milk, with a more prominent lactose sweetness, and you can even taste a hint similar to light cheese.

The Connection Between Dirty Coffee and Eisbock

Dirty coffee and Eisbock milk were born around the same time but developed in parallel without much intersection. It wasn't until 2020 that these two truly became connected when industrially produced Eisbock appeared. The original Eisbock milk was handmade by coffee shops using fresh milk, resulting in low yield, high cost, and difficult storage, so it never became widespread. Industrial production solved this problem, and with the product positioning targeting coffee shop supply, Eisbock milk became popular after several promotions.

Since Eisbock is just purified milk, it can also be used to make lattes, cappuccinos, flat whites, and other milk-based coffee drinks. So why is it specifically Dirty coffee and Eisbock milk? The reason is that Dirty coffee pairs better with Eisbock.

Other milk-based coffee drinks involve full integration of coffee and milk, so the combination of coffee flavor and milk flavor is emphasized. Eisbock milk would overwhelm and mask the coffee's taste. But when presented as Dirty coffee, the coffee flavor isn't masked by the overly sweet milk.

The collision between rich coffee and rich milk also makes the flavor changes in dirty coffee more varied. More importantly, using Eisbock milk makes it easier to achieve the layered effect of Dirty and extends the drinking time.

Of course, using Eisbock for Dirty coffee is just one option, not a necessity. Coffee shops also match different types of milk based on the flavor characteristics of coffee beans. For example, FrontStreet Coffee has seen a coffee shop that is flavor-result-oriented, using different coffee beans to make Dirty coffee, with corresponding different milk choices. Some coffee shops have different understandings—regular milk is too watery and weak, while Eisbock milk is too rich and overwhelmingly sweet—so they make their Dirty coffee milk with 2 parts regular milk + 1 part Eisbock.

Important Notice :

前街咖啡 FrontStreet Coffee has moved to new addredd:

FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473