On Butter: "Coagulated Sunlight"

Butter is one of life’s great blessings. Growing up, summer dinners meant platters of steaming sweet corn, smashed and spun into a stick of butter and sprinkled with salt. At Christmas, my mom’s tenderloin and crab leg dinner is accompanied by a ramekin of melted butter. And butter’s indulgent richness elevates simple foods to occasion-defining, from a stream of butter-flavored oil on popcorn at the movies to a smear of butter on a warm piece of bread on a good morning.

Butter is also literally sacred. Hindu scripture alludes to the presence of the Lord being like the hidden presence of butter fat in cream. An influential Zen Buddhist (Hakuin Ekaku) described meditation as the sensation of a scoop of butter slowly melting down from your scalp and warming your body. And the Bible only takes 18 chapters of Genesis to describe Abraham and Sarah improvising a quick meal for the Lord -- a spread of bread, calf, and butter. 

Splotches of butter also mark the pages of history. In the Medieval Christian church, butter was a controversial option for fasting days on which meat and dairy products were otherwise forbidden. While olive oil was a viable alternative for Rome, those further from the Pope’s reach likely only had lard and butter as cooking fats. Rome was happy to allow those without affordable olive oils to use butter while fasting -- but only for a price. Such paid permissions were another outrage for protestant pugilist Martin Luther, who complained that Rome made “a mockery of fasting, while forcing us to eat an oil they themselves would not use to grease their own slippers.” 

Had Luther been able to butter his brötchen, perhaps we’d all still be living under the pope!

That’s all to say nothing of butter’s sheer versatility: a pat of butter can enrich a sauce, fry a vegetable, moisten a cake, crisp a crust, or be spread gently across just about any carbohydrate. Butter is truly a foundational component of every cuisine developed alongside milk-producing animals. 

In this post, I walk through a few simple questions about butter -- its constitution, varieties, and uses. All of this is heavily drawn from Butter: A Rich History, an excellent book by Elaine Khosrova about this spreadable gold, as well as the Gastropod episode on the book.

What is butter?

Butter is isolated fat and protein from cream (which itself is the fattiest part of milk that floats to the top). That’s it! 

Milk itself is a relatively stable mix, jam-packed with nutrients for new calves. Cream is simply the fattiest part of whole milk, usually from Holstein cows, which naturally rises to the top (indeed, this is the origin of the Irish greeting “top of the morning” –– a wish for the very best). Cream is nowadays mechanically separated from milk.

But fat and water don’t like mingling, and are eager for the chance to split. Making butter is as simple as shaking cream to “break” the fat-in-water emulsion.

From goat bladders swung from a tree branch to my knockoff Vitamix, humans have found a lot of ways to churn cream into butter. Once the cream is agitated, the fat globules rip apart and collide with one another, gluing fat to fat and floating to the top. 

The agitated fat can then simply be strained and smashed together, removing as much as the liquid (whey) as possible (though finished butter contains 15-20% water by weight).

It is a miracle of nature that an animal eating nothing but grass can produce, in ample quantity, an end-product that’s over 80% fat.

Butter flavor and varieties

Irish poet Seamus Heaney once described butter as “coagulated sunlight,” capturing the two essential sensations of eating butter: a mellow sunny brightness anchored by a rich creaminess. 

On a molecular level, the “buttery” flavor of butter is primarily from diacetyl and acetoin, two small compounds consisting of a few carbons, hydrogens, and oxygens. These two compounds are prevalent in all butter, and also in synthetic butter-flavored foods like the jets of movie theater butter oil. 

These “butter” flavor molecules are themselves not produced by the cow directly – rather, they’re a byproduct of bacterial fermentation in the stomach of the cow. 

In addition to these base notes, butter makers transform flavor and texture through the following:

Animal Diet

Much of the ‘character’ in butter comes from the lifestyle of the cow that made the cream. This is especially true of the butter its color. The more green the animal’s diet, the more yellow the butter (this is why ‘spring’ butter is traditionally more yellow). The yellow color comes directly from the red-orange beta-Carotene in the cow’s grass (which we don’t see in grass as it is covered by the green pigments). The animal feed also greatly impacts the flavor. Isigny-sur-Mer butter from Normandy, for example, has a deep yellow color and mineral flavor from its cows grazing on seaside soil rich in clay and silt. More industrial butters, on the other hand, are blended from thousands of cattle eating a very consistent mix of grain and corn, resulting in a simple, ‘clean’ flavor.

A flight of butters — note the deep yellow culture of the unpasteurized butter on the right from a small farm in Brittany, where the cows feed on grass grown in clay-rich soil.

Pasteurization

Prior to churning, cream is typically pasteurized no higher than 160F / 70C to eliminate any spoilage microbes. This, however, makes a strong impact on flavor, resulting in a sweet and more ‘custardy’ cooked flavor. Look for ‘unpasteurized’ or ‘raw’ butters for a fresher flavor.

Culturing

Cream can also be lightly fermented by bacteria in the air or by the addition of lactic acid-forming bacteria strains. This historically was always the case, as cream would be pooled across multiple milkings prior to churning, exposing it to fermenting bacteria. This fermentation process, like the fermentation in the cow’s stomach, produces diacetyl, making cultured butter taste even more buttery. However, the main note of cultured butter is a light acidity and funkiness, which can range from very mild to deeply cheesy. Nowadays, most ‘cultured’ butter simply have lactic acid and diacetyl added. The difference between live-cultured and shortcut instant-cultured butter is imperceptible to most consumers.

Ripening

In order to make a finished butter more spreadable and chewy, butter makers often ‘ripen’ or temper the butter by raising and lowing its temperature. This causes some of the liquid in fat globules to leach out of the fat, sticking the fat together and creating a more cohesive butter (this step is the main reason why home-churned butters are more firm and crumbly).

Salt

Salt plays its familiar role in butter, acting as both flavoring and preservative. Everyday salted butter is usually 1.6-1.7% salt by weight, making it slightly less salty than, say, pickled vegetables. French butters are either demi sel, up to 3% salt, or fully salted and up to 8% salt. Some French salted butters (usually from Brittany) are salted with flakes of sea salt, which retain a pleasant crunch in the final butter. 

With skillful control of these factors, butter makers are able to express a tremendous range of butters, from incredibly sunny and deep-yellow salted raw spring butter to a neutral-tasting, low-moisture, unsalted industrial butter that is perfectly consistent for baking. 

As we continue to spend far too time confined to our homes, I think butter offers us a sacred, small luxury. Butter is a chance to enjoy something profoundly delicious, entwined with a thousand food memories of better days behind. It requires no cooking and little prep (or dishes!), just a knife and a good loaf of bread. 

So go buy two or three fine butters of different styles (unpasteurized, cultured, imported, maybe a different animal), let them come up from fridge temperature, and sit down for a moment of sunshine in these short, dark winter days. 

If you care to experiment with butter-making yourself, I shared a few ideas on this post. Enjoy!