Hot Latte Coffee Tastes Awful When Cold: What's the Best Way to Reheat It?

Those who love milk coffee probably know that a freshly made hot latte offers the best taste experience. First, the crema brings rich aroma, and the first sip reveals a smooth, delicate foam layer. Then, at just the right temperature, the richness of coffee and the sweetness of milk complement each other in the mouth, creating a balanced and full-bodied experience.

In an article titled "What's the Best Temperature for Milk in Making Lattes?", FrontStreet Coffee also mentioned the importance of temperature in milk-based coffee. Once a well-made hot latte cools down, its aroma diminishes, the milk foam gradually solidifies, and the coffee underneath develops a rough, grainy texture, sometimes even with a greasy taste that lingers unpleasantly on the tongue. When it becomes completely cold, just a small sip will make you grimace, especially on a cold winter day when you wouldn't even want a second sip.

Out of the good habit of not wasting food, people usually have two approaches at this point: either force themselves to finish it (likely resulting in a pained expression) or reheat the coffee and then drink it. For those with the right equipment at home, various heating appliances are readily available, making the second option the preferred choice.

("Excuse me, could you please heat up my latte?")

Does Reheated Latte Still Taste Good?

This brings us to the question: Does a reheated latte still taste good? What's the appropriate temperature to reheat it to? And perhaps most importantly, how can we make it taste better when reheating?

Why Doesn't a Hot Latte Taste as Good When It Cools?

Our perception of taste results from chemical reactions between food elements and receptors on our tongues. As coffee changes from hot to cold, two main factors are affected: aroma and texture. Freshly brewed coffee continuously releases its aroma as it cools. When the coffee temperature drops below our body temperature, our taste buds' sensitivity to sweetness diminishes, while the perception of acidity and bitterness becomes more pronounced.

The same applies to hot lattes. When a well-integrated milk coffee drops from 65°C to below 45°C, the aroma of coffee oils and the sweetness of hot milk continuously dissipate. The milk foam gradually breaks down and separates from the coffee liquid. Additionally, because the structure of fat and proteins in heated milk has already changed, the flavors they present when cold differ from when hot, thereby diminishing the overall taste experience of the coffee.

Can a Cold Latte Be Reheated?

FrontStreet Coffee prepared a hot latte using their Nuanyang Blend (the same used in their store), measuring an initial temperature of 61°C. The first sip revealed notes of vanilla, creamy melon seeds, milk chocolate, and a subtle fermented wine-like flavor. The sweetness of milk and the aroma of espresso complemented each other perfectly.

When left outdoors for 20 minutes, the latte's temperature dropped to 38°C. It now tasted of chocolate and nutty cookies, with diminished aroma. The coffee's bitterness somewhat overpowered the milkiness, and the texture became somewhat sharp. After continuing to let it sit for another 40 minutes, the temperature measured 29°C. At this point, the coffee had lost its original sweet flavors and developed a slight burnt sensation in the mouth, resembling bitter cold milk.

Next, FrontStreet Coffee divided the remaining coffee into two equal parts. One portion was reheated using a steam wand, while the other was reheated using an electric stove until both reached 50°C.

After comparative tasting, FrontStreet Coffee found that both reheated samples had lost the characteristic aroma of the Nuanyang Blend, with relatively bland flavors. The latte reheated with the coffee machine's steam wand had a watery texture due to the high-temperature steam. Although it wasn't bitter, it left a slightly astringent aftertaste.

The second group, heated directly with an electric stove, maintained its concentration but the temperature increase intensified the coffee's bitterness while introducing a dry, walnut skin-like aftertaste.

By now, readers can probably conclude that for a cooled latte, whether reheated with steam or direct heat, it theoretically cannot return to its original delicious state as when first made, because irreversible flavor changes have already occurred in the coffee. However, compared to the jarring cold sensation, bringing the coffee back to near body temperature does make it more palatable and certainly prevents waste.

In addition to the two reheating methods mentioned by FrontStreet Coffee above, there's another common approach: using a microwave. For office workers or those at home, microwave heating is obviously the most convenient and quickest method. However, because microwave heating can cause uneven temperatures and may cause the liquid to boil and splash over, it's best to leave half the container empty. Be careful not to use too high a power setting—you can start with 30 seconds, test the temperature, and then decide whether to continue heating.

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