Can You Drink Bock Milk Directly? Is Making Dirty Coffee with Bock at Home Difficult?

Last week, while exploring cafes, FrontStreet Coffee happened to encounter a barista making ice bock. Through the glassware, you could see rich milk liquid dripping drop by drop, making me instantly want to try a Dirty made with ice bock. Unfortunately, the barista mentioned that the remaining portion was insufficient to serve, so FrontStreet Coffee couldn't have the coffee that day and has been thinking about it ever since returning.

Since that's the case, FrontStreet Coffee decided to go all out today and make it themselves~

What's the principle behind ice bock?

"Ice bock" comes from the German translation of Eisbock, which originally referred to freeze distillation method for making beer more concentrated. The principle isn't complicated - it uses the different freezing points of various substances. By releasing substances in different orders during melting, some water can be removed, achieving purification. When this principle is applied to milk, the concentrated liquid extracted becomes what baristas call ice bock.

As everyone knows, in a bottle of milk, water has the largest proportion, with the remaining being solid substances like protein, fat, and sugars. The freezing point of water is 0°C, while other components have lower freezing points. When milk is placed in the freezer compartment, water freezes first, followed by other substances, until everything becomes ice.

The melting order reverses this process. Proteins, fats, and other substances melt first, followed by water, creating a water-milk separation phenomenon. For milk, after removing some water, ice bock increases the proportion of other substances, making the taste thicker and more mellow, with a hint of cheese-like salty aroma.

How to make ice bock?

Making ice bock at home is extremely simple! All you need is a refrigerator, a carton of milk, and a container to hold the ice bock, and you can start right away.

First, place the entire carton or bottle of milk in the freezer compartment until it's completely frozen solid. FrontStreet Coffee used Guangming · Fresh Pasture 950ml boxed fresh milk. It was placed in the freezer last night and had completely frozen into ice by this morning. (FrontStreet Coffee heard that during winter in Northeast China, you could just leave milk outside for a while~)

Next, we need to open a small opening in the frozen "ice brick" - just like opening milk normally. Then invert the box over a pre-prepared pot and wrap the exposed part with plastic wrap, letting it melt naturally. This prevents the milk from external contamination, such as insects getting in, while also stabilizing the structure to prevent tipping.

FrontStreet Coffee thinks leaving it at room temperature for melting is fine, which should complete the purification in a few hours. FrontStreet Coffee spent 3.5 hours and finally got 400ml of ice bock, with an extraction rate of about 42%. Finally, just seal it and store it in the refrigerator for later use.

(If you really don't have time to wait and have enough space in the refrigerator, you can place it in the upper refrigerated section for the process. Although the dripping will take relatively longer, this ensures success, and the purified milk remains at low temperature throughout.)

How does ice bock Dirty taste?

To find the difference between the two, FrontStreet Coffee tested both regular fresh milk and freshly dripped ice bock with a concentration meter. Regular fresh milk had a concentration of 12.11%, with other substances at 14.39%; while ice bock was significantly higher in both concentration (16.22%) and the proportion of components like fat and sugars (18.94%) compared to regular fresh milk.

FrontStreet Coffee took a sip of the high-purity ice bock directly. The milk aroma was very rich, the lactose sweetness was high, and it tasted mellow and viscous. When FrontStreet Coffee tried regular fresh milk again, the latter tasted quite bland in comparison. However, precisely because ice bock is so concentrated, drinking it plain can easily become overwhelming, so it's best enjoyed paired with espresso. Among combinations, Dirty + ice bock is widely recognized as the best pairing in our coffee community.

Generally, there's no fixed ratio for making Dirty - it often depends on the capacity of the cup you're using. For better visual presentation, FrontStreet Coffee used a 250ml transparent wide-mouth cup, first pouring in 200ml of purified milk, then positioning it directly under the portafilter to extract coffee. (Using today's Warm Sunshine blend parameters for espresso extraction: 20g coffee grounds yielding 36ml coffee liquid in 30 seconds.)

Because ice bock has higher density than regular fresh milk, the crema can easily stay on top, and the layered effect created by the black and white colors becomes more obvious and lasting. Upon tasting, FrontStreet Coffee could feel the rich ice milk and bittersweet espresso colliding in the mouth. After swallowing, there was the sweetness of White Rabbit milk candy mixed with hazelnut biscuits. As the two gradually blended, a cheese-like salty aroma emerged, with a creamy silky texture that made the entire cup of coffee much more layered and complex.

Important Notice :

前街咖啡 FrontStreet Coffee has moved to new addredd:

FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473