Introduction:Both cappuccino and flat white are made with espresso and milk—so why is one more bitter while the other smoother? The key actually lies in the difference between the coffee base used and the thickness of the milk foam. This article delves into how ristretto and traditional espresso differ in flavor extraction, and through actual weighing comparisons, explores how milk foam affects overall mouthfeel, helping you better understand the essential distinctions between these two classic Italian coffees.

Many people, when tasting cappuccino and flat white, often notice that although both are based on espresso and mixed with milk, their flavors are quite different—especially in terms of bitterness. In fact, the main factors behind this lie in two aspects: the difference in the coffee base used, and the impact of milk foam thickness on overall mouthfeel.

Among common Italian coffee drinks, latte has the highest proportion of milk, hence usually the sweetest, because the large amount of milk effectively softens the intensity and bitterness of the coffee. However, since cappuccino and flat white have similar serving sizes, why does cappuccino often taste more bitter? The answer is directly related to the base they use.

Traditional cappuccinos and lattes typically use standard "espresso" as the base, then add varying proportions of steamed milk according to need to adjust the overall body and balance of flavors. Flat white, on the other hand, uses a different brewing method—the base is not regular espresso, but rather "ristretto," which evolved from the espresso technique.

To understand the difference, it’s first necessary to know that during coffee extraction, the three main flavor compounds—acid, sweetness, and bitterness—are released gradually as hot water contacts the coffee grounds, but their dissolution rates vary. Acidity and sweetness are usually released abundantly in the early to middle stages of extraction due to their high solubility, while bitterness is released more slowly, typically emerging only after the acidic and sweet components have largely dissipated, as the later stages tend to extract more bitter elements.

Espresso extraction is considered a more complete method—we use appropriate parameters to achieve a certain balance among acid, sweetness, and bitterness, supporting the coffee’s richness and enabling it to harmonize with milk. Ristretto, however, has a different goal: it aims to preserve the intense coffee flavor while minimizing bitterness. Therefore, ristretto typically extracts only the early and middle stages of flavor, omitting the tail end that tends to produce bitterness.

Simply put, if using the same amount of coffee grounds to brew both espresso and ristretto, the former will have more total liquid and thus relatively more noticeable bitterness, while the latter, with less liquid and higher concentration, feels milder in bitterness. This explains why, at the same serving size, a cappuccino based on espresso tastes more bitter than a flat white based on ristretto.

Beyond the difference in base, the thickness of the milk foam is also a key factor affecting the flavor expression of cappuccino and flat white. Many shops, when making flat white, if not specifically adjusting for its base, often simply use standard espresso instead of specially brewing ristretto. In such cases, what truly creates the noticeable difference in mouthfeel between cappuccino and flat white is the thickness of the milk foam.

One of the most well-known features of cappuccino is its thick and velvety milk foam—this cloud-like, delicate layer provides a unique textural experience; in contrast, flat white has noticeably thinner foam, which has good fluidity and is often described as having a silky-smooth, velvety mouthfeel.

Generally speaking, the foam thickness of a cappuccino is about 1 to 1.5 centimeters, while that of a flat white is often less than 0.5 centimeters. This seemingly small difference actually has a significant impact on the proportion of milk used. Taking a common 240 ml cup as an example, a cappuccino is usually made with foam slightly spilling over the rim, presenting an eleven-tenths full appearance; whereas a flat white is required to have the liquid level even with the rim.

According to actual weighing comparisons, a standard cappuccino weighs about 195 ml in total liquid volume—with 40 ml of espresso, the remaining milk portion is about 155 ml; a flat white, meanwhile, weighs about 225 ml in total, and after deducting the same 40 ml of espresso, its milk portion reaches 185 ml, about 30 ml more than that of a cappuccino.

This additional 30 ml of milk effectively reduces the ratio between coffee and milk, thereby decreasing the overall perception of bitterness, making the flat white smoother and softer compared to the cappuccino. Similarly, latte, with its higher milk proportion, has become the preferred choice for many consumers who enjoy sweetness and a silky texture.

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