Milk drinks
Milk drinks combine heated milk with coffee, often frothed by the steam of the espresso machine. Milk does more than mellow the coffee: its proteins bind to some of the coffee's compounds, and its foam changes the way the cup is drunk.
How does steam froth milk?
Start the scene or choose a stage. The animation simplifies the mechanism; what follows gives the details and the available references.
The steam wand does two things at once: its steam heats the cold milk, and when the tip skims the surface, it draws air in there, which makes foam. So you start just below the surface.
Read the stages without animation
- The tip at the surfaceThe steam wand does two things at once: its steam heats the cold milk, and when the tip skims the surface, it draws air in there, which makes foam. So you start just below the surface.
- The tip deeperThe tip is then pushed deeper: the milk starts to spin, and the large bubbles break. What remains of them, bubbles too small for the eye, can be poured and drawn with: this is microfoam.
- Proteins hold the bubblesMilk proteins settle around each bubble and hold it: the foam forms. More protein slightly increases its volume, more fat makes it less stable. The great enemy is lipolysis, the breakdown of milk fats: beyond about 2 milliequivalents of free fatty acids per 100 g of fat, the foam no longer holds.
- Stop at about 60 degreesThe pitcher becomes too hot for the hand. In Klimanova's study, which frothed with steam from 30 to 80 °C, the optimum lies between 50 and 60 °C, and it is at 60 °C that the bubbles of pasteurized milk are best distributed: beyond that, the foam gains nothing more.
- The milk meets the coffeeThe microfoam is poured into the espresso, more or less generously depending on the drink. Milk proteins form complexes with the coffee's polyphenols: the more protein there is, the more bitterness and astringency recede. Casein also binds part of the 5-caffeoylquinic acid, one of the chlorogenic acids.
To remember: Steam heats the milk and, at the surface, draws air into it; proteins hold the bubbles and, in the cup, bind to some of the coffee's compounds.
In history: In 1685, the Grenoble physician Monin recommends coffee with milk as a remedy, according to Ukers; milk foam comes with the steam of the Italian machines of the early 20th century.
Read the full article and its sources ↓History
Coffee with milk is older than any machine. Ukers attributes the first attempt at coffee with milk, around 1660, to Nieuhoff, Dutch ambassador to China, who imitated tea with milk, and reports that in 1685 a physician of Grenoble, Monsieur Monin, recommends it as a remedy: a bowl of milk put on to heat, a bowl of powdered coffee and a bowl of brown sugar thrown in when it rises, and it is boiled for some time (source 1). It is a decoction in milk, not a coffee topped up with milk.
In 1922, the same book makes the round of the tables: in France, breakfast is a bowl or a cup of café au lait; in Brazil, café au lait is the morning coffee, and milk never appears afterward; in Vienna, the Melange, meaning “the blend,” is café au lait, and Viennese coffee is served two parts coffee to one of hot milk under whipped cream, which the war replaced with condensed milk and saccharin (source 1).
The name cappuccino, the “little Capuchin,” comes from Vienna. Drinks called Kapuziner, coffee with a few drops of cream, the color of the Capuchins' habit, appear on the menus of the cafés of the Habsburg monarchy in the late 18th century; the Italian form appears in texts of the 19th century (source 2). Milk foam comes later, with the steam of the Italian machines of the early 20th century, of which Ukers cites Desiderio Pavoni's patent of 1907 (source 1).
The two other names come from the New World. Lino Meiorin, co-owner of the Caffe Mediterraneum in Berkeley, said he invented the caffè latte in 1959, literally “coffee with milk” in Italian, for customers who found Italian cups too small and too strong (source 3). The flat white is disputed between Sydney and Wellington: Alan Preston put one on the menu of the Moors Espresso Bar in Sydney in 1985, a Wellington bar claims one in 1989, and a restaurant critic of the Sydney Morning Herald cites a “flat white coffee” as early as May 1983 (source 4).
The motion
The steam wand does two things at once: its steam heats the milk, and when the tip skims the surface it draws air in there, which makes foam. You start near the surface to let the air in, then push the tip deeper to spin the milk and break the large bubbles; what remains of them, bubbles too small for the eye, can be poured and drawn with: this is microfoam.
The stopping temperature matters. In the study by Klimanova and her colleagues, who frothed with steam from 30 to 80 °C, the optimum lies between 50 and 60 °C, and it is at 60 °C that the bubbles of pasteurized milk are best distributed (source 5). The milk is then poured into the espresso, more or less abundant and more or less foamy depending on the drink.
The settings
- Grindthat of the base espresso; not applicable to filter café au lait
- Dosenot standardized in the sources read
- Brew ratiotwo parts coffee to one of hot milk in the Viennese coffee of 1922; a bowl of milk to a bowl of powdered coffee for Monin in 1685 (source 1)
- Temperaturemilk frothed between 50 and 60 °C, optimum of the Klimanova study (source 5)
- Timenot documented in the sources read
- Pressurethat of the boiler steam, not quantified in the sources read
What it has going for it
- Milk proteins soften bitterness and astringency: in a 2025 study, the overall rating goes from 3.88 out of 10 for black coffee to 7.40 for the coffee with the most milk protein (source 6).
- A fine foam can be poured and drawn with, which only a microfoam with even bubbles allows, best achieved around 60 °C on a pasteurized milk (source 5).
- Whole milk gives a foam that drains less, even if it lasts less long than a skim milk foam (source 7).
- The drink can be adjusted endlessly, from a few drops of cream to a large bowl, which explains why it took its own form in each country described by Ukers (source 1).
What is held against it
- Milk binds to some of the chlorogenic acids: casein strongly binds 5-caffeoylquinic acid, and in humans less of it is found in the urine after a coffee with milk than after a black coffee (sources 8 and 9).
- Foam is capricious: the free fatty acids released by lipolysis, the breakdown of milk fats, make it collapse, and a summer milk froths less well than a spring milk (sources 10 and 11).
- Heating too high serves no purpose: beyond 60 °C, you leave the range where the foam is at its best (source 5).
- The milk is tasted as much as the coffee: a panel tells a pasteurized milk from a UHT milk, that is, one sterilized at very high temperature, moderately to strongly, in the foam (source 5).
What it gives in the cup
Milk changes the chemistry of the cup before it changes the taste. Its proteins form complexes with the coffee's polyphenols, through weak bonds and strong bonds; the more protein there is, the more bitterness and astringency recede, and the higher the foam rises, while holding up slightly less well (source 6).
Foam depends on the composition of the milk. More protein delays the formation of a distinct foam layer and slightly increases its volume; more fat makes it less stable but makes it drain less (source 7). Pasteurization, homogenization and standardization clearly improve frothing, and spring milk froths better than summer milk, which is fattier and lower in protein (source 10). The great enemy is lipolysis: beyond about 2 milliequivalents of free fatty acids per 100 g of fat, the foam no longer holds (source 11).
Anecdotes
- In 1984, an article in the Sydney Morning Herald claimed that Italian-style café au lait and the “flat white” were one and the same drink (source 4).
The sources for this sheet
- William H. Ukers, All About Coffee, New York, 1922, ch. XXXIV (Pavoni patent of 1907), ch. XXXV (customs of France, Brazil and Vienna) and ch. XXXVI (Nieuhoff, Monin) · online · secondary
- English-language Wikipedia, “Cappuccino,” accessed October 21, 2026, citing G. McNamee (Encyclopædia Britannica), G. H. Oberzill (1983), K. Baedeker (1893) and F. Angiolini (1897) · online · secondary · reading: relay read; original sources not read
- “Remembering Latte Birthplace and Quintessential Counterculture Destination Caffe Med,” Daily Coffee News, December 12, 2016, citing Kenneth Davids · online · press
- English-language Wikipedia, “Flat white,” accessed October 21, 2026, citing the Sydney Morning Herald (May 6, 1983, April 16, 1984, September 27, 2015) and The Dominion Post (January 13, 2015) · online · secondary · reading: relay read; original articles not read
- Klimanova et al., “Effect of steam frothing on milk microfoam: Chemical composition, texture, stability and organoleptic properties,” International Dairy Journal, 2022, article 105476 · online · primary · reading: article abstract (Europe PMC)
- N. Chen et al., “Milk protein modulates antioxidant activity and metabolome stability in coffee beverages during thermal processing,” Journal of Dairy Science, 108 (11), 11919-11939, 2025 · online · primary · reading: article abstract
- M. Münchow et al., “Steam-frothing of milk for coffee: Evaluation for foam properties using video analysis and feature extraction,” International Dairy Journal, 51, 84-91, 2015 · online · primary · reading: article abstract (Europe PMC)
- D. Tagliazucchi et al., “The type and concentration of milk increase the in vitro bioaccessibility of coffee chlorogenic acids,” Journal of Agricultural and Food Chemistry, 60 (44), 11056-11064, 2012 · online · primary · reading: article abstract
- G. S. Duarte and A. Farah, “Effect of simultaneous consumption of milk and coffee on chlorogenic acids' bioavailability in humans,” Journal of Agricultural and Food Chemistry, 59 (14), 7925-7931, 2011 · online · primary · reading: article abstract
- T. M. Ho, B. R. Bhandari and N. Bansal, “Foaming properties of milk samples collected at various processing stages in a dairy processing factory across two seasons,” Journal of the Science of Food and Agriculture, 104 (3), 1470-1478, 2024 · online · primary · reading: article abstract
- D. Hummel et al., “Reproducing high mechanical load during industrial processing of ultra-high-temperature milk: Effect on frothing capacity,” Journal of Dairy Science, 107 (12), 10452-10461, 2024 · online · primary · reading: article abstract