coffee science : everything you need to know about milk -2

fat, aka do you want flavour & foam or mouthfeel ?

fat is both your best and worst friend. on one hand, it tastes frikkin’ fantastic, but on the other hand, fat is detrimental for foam stability and too much of it will mask the flavour of the coffee.

as i mentioned earlier, milk is a type of emulsion, i.e. it’s a combination of fat and liquid. vinagrettes and hollandaise sauce are common examples of culinary emulsions. there are also temporary emulsions (salad dressing) that split over time and permanent emulsions (mayonnaise) that don’t. unprocessed milk falls into the former category and processed milk into the latter.

butterfat, the primary type of fat found in milk, is a pretty hefty globule. more than 95% of the total milk lipid is in the form of a globule ranging in size from 0.1 to 15 µm in diameter. this triglyceride (an ester made up of three fatty acids) is so large and heavy that it weighs down air bubbles, making foam collapse. butterfat is usually broken up in the homogenising process, to prevent a layer of fat forming on the top of your milk and eventually forming a solid layer when chilled – a common phenomenon in unpasteurized farm-fresh milk.

fat separation in raw milk. credit: grassfood

another reason why a fattier milk shouldn’t be your one-stop solution to a better tasting latte is its flavour-masking properties.

since fat globules are so huge, it physically blocks the other solubles in the water from reaching your tongue. in other words, it coats your tongue and forms a film that repels certain flavours.

to best understand this effect for yourself, try making three cappuccinos: one with non-fat milk, one with whole milk, and one with half-and-half. try to identify which one tastes more of coffee.

all that being said, you shouldn’t reach for the skim just yet – because what fat delivers more than anything else is the magical factor of mouthfeel.

recent scientific studies have shown that the reason why fatty foods taste so satisfying has very little to do with the actual flavour of fat, but instead with the mouthfeel of it. imagine drinking unsalted melted butter… now imagine the taste of cold butter spread over hot toast. that creamy mouthfeel is what seals the deal, baby!

human tasters working for food companies report on the sensation of fat by rubbing their tongue against the roof of their mouths. alternatively, they use a machine called a tribometer and make quantitative measurements of mouthfeel with it.

the effect of fatty emulsions on the touch receptors in the tongue’s papillae. credit: ediblegeography.com

something else you should know about fat is that, while is does block off certain flavours, it accentuates others. in a study of how flavor is released in low-fat versus high-fat ice cream, food scientists found that fat could have different effects depending on the flavor. cherry, for example, becomes less intense in the presence of fat, but the opposite is true for vanilla.

flavour is made up of these things called volatile components, and fat affects how these volatile components reach your tongue. some flavours like to stick to fat and so make for a more prolonged release. this explains why adding milk to coffee brings out certain nutty, or caramel-esque, flavours.

understanding milk labels

so now that you know about each individual component of milk, it’s time to bring the whole family together!

make it a habit to read milk labels. i urge you to go to a supermarket and literally read every single different milk carton. you might look eccentric doing it, but you’ll learn so much.

as an example, let’s take two of the most common brands of milk in singapore and compare the nutritional contents – using precisely what we’ve looked at so far in this article

exhibit a: meiji whole milk. credit: fairprice.com.sg

exhibit b: magnolia barista milk. credit: magnolia.com.sg

comparing the two, it’s easy to see the immediate differences: meiji has a much higher lactose content but a lower protein content. it also has a higher fat content and added sodium.

meiji was designed to be drunk, and it’s the most common brand in singaporean cafes. it’s easy to see why, because it’s deliciously buttery, and the slight saline content adds an extra dimension to the milk.

barista milk, on the other hand, was a type of milk specifically designed to be used with coffee. hence the higher protein content (more stable foam) and less fat (to draw out more of the flavours of the coffee). the modest lactose content might have something to do with the desire to not throw the flavours of the coffee off-balance, too.

that said, the taste of milk – as with coffee – is highly subjective. deciding what brand of milk to use in a cafe is almost as big a decision as the type of bean to use!

however, with an in-depth understanding of the different components of milk, that decision doesn’t need to be guesswork anymore.

article written by christine s.

edited by t. newton and

feature photo credit : chris pelliccione