Milk or creamer are widely used by coffee drinkers throughout the world. From Latin America’s cafe con leche to South India’s filter coffee, many recipes call for adding dairy to coffee. Dairy products were likely added to coffee in the Ancient World for much-needed calories and nutrition. Today, though, they’re primarily added for flavor. Some coffee enthusiasts may insist on black coffee, but adding milk or cream may actually make coffee taste better.
Milk is largely made up of fats and proteins, and both affect the way a cup of coffee tastes.
The fats in milk enhance a cup of coffees “mouth feel.” While coffees can have little or large bodies, all brewed coffee is primarily water — and it feels like drinking water. Adding fats from milk change the texture of coffee, making it thicker and, when done well, giving it a velvety smoothness.
The proteins in milk soften coffee’s bitterness by binding to polyphenolic compounds, such as tannins. Although good for the body, tannins have an astringent taste that detracts from coffee. When proteins bind to these molecules, their flavor is covered up.
Milk proteins also help lessen a coffee’s acidity, or brightness. Just as they bind to tannins, proteins will also react with chlorogenic acids (CGAs), which are largely responsible for coffee’s brightness. When the CGAs react, the coffee tastes less acidic. Acidity is largely a prized characteristic in coffee, but not all coffee drinkers appreciate extremely bright coffees. Adding milk is one way people can lessen a brew’s acidity.
Because the fats and proteins in milk are the molecular structures that affect how coffee tastes, milks high in protein and fat have the greatest impact on a cup of coffee. Soy, rice, coconut and other “milks” that are mostly made with water will never enhance a cup of coffee in the same way that cow’s milk will, because they don’t have as many fats and proteins. Soy milk and these other selections have a place in coffee shops, as some people are allergic to dairy milk, and they can be used to create good-tasting beverages. The flavor of any coffee drink made with soy rather than dairy will be different, though, because of soy milk’s different fat and protein content.
Similarly, heavy cream will produce a richer- and smoother-tasting cup than skim milk, because heavy cream has a lot more fat. (Most cow milks have the same amount of proteins.) Heavy cream is, of course, also much less healthy than skim milk. As with every other food and beverage, each person must find their own balance between flavor and health.
Cow milk, however, isn’t the only suitable milk to use in coffee. It’s the most available and affordable option in the United States, but goat and even water buffalo milk are good choices.
Cow milk has a sweet flavor, especially when it’s heated to around 130°F. At this temperature, the sugars in the milk are especially sweet, which is why properly made cortados, cappuccinos and lattes taste sweet even without adding sugar. Because cow milk has a natural sweetness, it pairs well with any roast level.
Goat milk has a salty, tangy flavor. Because it’s not sweet like cow milk, goat milk goes best with medium roasts that are roasted to the Maillard reaction’s peak.
A Maillard reaction is simply the breaking down and browning of sugar. It’s the process that makes a cut apple turn brown if left out, turns bread into toast and transforms sugar into caramel. As with toast and caramel, when the Maillard reaction peaks, the sugars in coffee add sweetness. If the roast progresses beyond the reaction’s peak, which darker roasts do, the sugars begin to burn and become bitter (like burnt toast).
By pairing goat milk with medium-roasted coffee, some sweetness comes across in the cup. The sweetness is provided by the coffee, not the goat milk, so it’s important to choose a sweet medium roast.
Water buffalo milk is rare and expensive, but it’s a luxurious indulgence that’s worth trying in coffee. Water buffalo milk has many, many fats, a lot of proteins and a natural sweetness. In large amounts, it will overpower a coffee’s flavor. In small quantities, however, it is able to improve coffee in ways that no other milk can.
To see how different kinds of milk affect the flavors of different roast levels, get a few milks from the grocery store and order the tasting kit as part of the subscription. We’ll send you four different roast profiles (Fruity, Balanced, Classic and Bold), and you can try each milk in each coffee.
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