What does a coffee enthusiast need for homemade Eisbock?

Homemade Eisbock purified milk is made by freezing whole milk and then slowly thawing it so the concentrated, sweeter portion drips out first. The technique traces back to German brewing and later reached the World Barista Championship stage. Home brewers can use a 200ml bottle or a 1-liter pack and collect the first 40 to 60 percent of the thawed liquid for the richest flavor.

Thawing at room temperature is faster, while refrigerating the milk slows the process and limits bacterial growth. Coffee enthusiasts typically store the finished Eisbock in a sealed container in the fridge and use it within a few days, since the concentrated milk has no preservatives and spoils faster than regular milk. Always discard the leftover icy residue.

In the world of milk coffee, espresso is certainly the soul, but the choice of milk is equally important. In recent years, Eisbock purified milk, with its rich, sweet, and fragrant taste, has moved from specialty coffee shops into home kitchens, becoming a staple ingredient for many coffee enthusiasts. This article addresses common questions about homemade Eisbock: from its German origins and appearance on the WBC stage, to the specific steps of freeze purification; from the choice between 200ml small bottles and 1-liter packs, the impact of 40% to 60% milk extraction ratios on flavor, to the time differences and hygiene considerations between room temperature and refrigerated thawing; finally, it also compiles recommended storage periods for homemade Eisbock. Front Street Coffee, combined with comparative experiments, provides a complete guide for friends who want to recreate Eisbock milk coffee at home.

For a delicious milk coffee, espresso is certainly the soul, but milk also plays an irreplaceable role. Choosing the right milk not only brings a smooth mouthfeel and natural sweetness, but also highlights the cocoa-like aroma in the espresso, significantly enhancing the layering of the entire drink.

In recent years, the concept of purified milk has become increasingly popular, and Eisbock milk coffee has almost become a regular on specialty coffee shop menus, often appearing on bestseller lists. Front Street has noticed that this type of milk is not complicated to make and does not have strict requirements for ingredients, so it has long been more than just a dairy product for coffee shops. Many coffee enthusiasts also keep it at home, and making homemade Eisbock has become a basic skill for home coffee players.

Today, Front Street has specifically compiled the most frequently asked questions about making Eisbock. For those who want to learn how to recreate it at home, follow along and read on~

How Eisbock Came to Be

The name "Eisbock" originates from Germany. It is said that a brewer accidentally discovered that beer becomes particularly sweet and rich after freezing and then thawing, so he began repeated experiments and optimized the freezing and thawing process, eventually forming this ice-drip purification technique. Later, this technique was named "EISBOCK," also translated into Chinese as "冰馏博克." Among them, "eis" means "ice" in German, while "bock" refers to a native German beer.

At the 2017 WBC competition, Canadian competitor Ben Put first introduced the method of purifying milk by freezing to the industry.

Eisbock milk, also called ice-drip milk, works on the principle of using the differences in freezing points and melting points of various components in milk for purification. After the water content is reduced, the proportions of fat, protein, lactose, and other substances relatively increase. Therefore, compared with milk before freezing, the purified Eisbock tastes thicker and sweeter.

The process of making Eisbock is actually not complicated: first put a carton of milk into a freezer below -18°C and freeze it for more than 6 hours. After confirming it has completely frozen into a solid block, take it out and place it at room temperature or in the refrigerator's cold storage compartment. Then cut a small opening, invert it over a container, patiently wait for it to slowly melt, and after collecting the desired amount of milk, remove the ice milk block.

The finished Eisbock can be drunk directly, but because of its high concentration, drinking a large cup can easily feel sweet, cloying, and bloating. Therefore, it is best paired with freshly extracted espresso: the rich milk brings a thick sweetness to the coffee, while the mellow, slightly bitter coffee just balances the viscosity of the milk liquid, and it also has a natural cheese-like flavor. It can be said to be a combination where 1+1>2.

What size carton of milk should be used? How much milk liquid should be released?

Various online tutorials for homemade Eisbock usually recommend releasing 40%-60% of the milk liquid. This is because this range can both obtain the substances in milk relatively completely and ensure that most of the ice has not yet melted into water.

If you just want to drink an Eisbock coffee temporarily, such as a Dirty, Front Street suggests using a small bottle or small carton of milk around 200-300ml, which can yield about 100-150ml of base, and it will not be too much to finish and waste. If you drink it frequently and want to make several cups at once, then buy 1-liter milk to make it, and try to finish it as soon as possible.

As for the specific release ratio, Front Street also conducted a small comparative experiment: after freezing two bottles of 250ml fresh milk, they were melted at ratios of 40% and 60%, respectively, yielding one cup of 100ml and one cup of 150ml purified milk, which were then paired separately with espresso extracted from a dark-roast espresso blend to make Dirty for tasting.

In comparison, the Eisbock milk coffee with only 40% extracted had a more substantial mouthfeel. In every sip, you could feel both the warm espresso crema and the cold milk liquid, and it was just finished before the espresso sank to the bottom (the drawback is that more is discarded, which feels a bit wasteful...). The Eisbock Dirty with 60% extracted was also much thicker than an ordinary latte, but as you drank further, the milk flavor became more dominant, more like a concentrated iced latte without ice.

So Front Street suggests that when making Eisbock at home, if you want to pursue the richness of a Dirty, only extract 40-50% of the liquid weight; if you want to make a latte, you can release 50-60% of the milk. In short, as long as it tastes good.

Room temperature melting or refrigerator melting?

Actually, the frozen "milk block" can melt whether placed at room temperature or in the refrigerator's cold storage compartment. But in terms of time consumption, the melting environment directly determines the drip filtration time of the Eisbock. For example, in Front Street's small experiment above, even when obtaining 40% purified milk, it took nearly 5 hours to finish dripping in the cold storage compartment, while at room temperature (about 25°C) it melted in only 2 hours. Because the room temperature in Guangzhou, where Front Street is located, is relatively high, the milk liquid that drips down will also gradually approach room temperature. If you want to make iced milk coffee, it still needs to be put back in the refrigerator to cool down.

So if you are not in a hurry to drink it, Front Street suggests carrying out the melting process in the refrigerator and wrapping it well with plastic wrap. First, it can keep the milk liquid cold; second, it can avoid contamination by flies and mosquitoes, and also prevent mixing odors with other foods.

How long can finished Eisbock be stored in the refrigerator?

Although Eisbock milk is not complicated to make, the actual operation is still quite time-consuming. You have to freeze it for most of a day and also wait most of a day for it to melt, so many people make more at once and keep it in the refrigerator for later use.

Many people know that commercially available Eisbock products can be stored for 28 days under unopened and refrigerated conditions; after opening, to ensure quality and taste, it is recommended to finish it within three days. As for our homemade purified milk, it has already come into contact with air during the melting process, and when put into the refrigerator, it easily absorbs the odors of other foods. To avoid gastrointestinal discomfort, Front Street recommends drinking it within 48 hours.

- END -

The above content is compiled by CoffeeHunters, a coffee news website.