Water, fat, and milk solids determine a butter’s quality. Nearly everything else is a matter of taste.
Good butter is at least eighty-two percent butterfat and no more than sixteen percent water, a ratio that yields flaky pastries and sturdy sauces. It also happens to be the legal threshold in France for a dairy product to be considered as “butter,” France being the global heavyweight of butter consumption, where people eat on average nearly eighteen pounds per year (two-thirds more than what Americans eat).
In the United States, butters of even eighty-five percent fat have been common for years now, although the exact composition of any particular brand remains mysterious. That isn’t the kind of thing listed on a Nutrition Facts label, for instance. I have more to say on this issue below.
Butter is the most elementary of sauces—a sauce being nothing more than fat and water joined together by emulsion in which tiny droplets of one liquid disperse throughout another without actually dissolving.
A sauce is a simple thing, in principle. In practice, the challenge is to keep the two substances from pooling back towards themselves. Without an emulsifier every sauce would look like a puddle of water in a parking lot, dotted with iridescent blobs of oil.
The emulsifier of home-made mayonnaise, for example, is egg yolk. When oil and yolk are whisked together, various proteins in the yolk coat the minute droplets of the vegetable oil along with those of the water in the yolk itself. The result is a gob of mixed-up oil and water droplets, like a wad of magnetic ball bearings, each trying to regroup with its own kind but unable to do so because of a thin smear of egg protein that coats everything.
Butter is an emulsion of fat and water held in place by the proteins of milk solids, which are the remnants of the milk from which the butter was churned.
Milk solids also happen to give butter its distinctive flavor. Whenever you melt butter, therefore, the best way to do so is the one that keeps this tasty dairy essence evenly distributed. Otherwise, all you end up with is a pool of flavorless butterfat.
This action simply reverses the ordinary emulsion of butter, so that water contains fat.
The colder the butter you have and the gentler the heat you use, the more gradually your butter melts, which gives the minuscule quantity of liquid in your bowl the time it needs to incorporate all of the fat.
You could achieve the same result in a number of ways. You could do it in a skillet over low heat (demonstrated in this video on how to sauté chicken). For a liquid, you could use wine or vinegar or anything else.
In fact, any recipe that instructs you to melt butter in a little liquid over low heat is referring to this technique, which often goes by the French terms beurre monté and beurre blanc.
I recommend using a bowl over steam only because it’s the easiest way to achieve consistently gentle heat.
Once the emulsion is in place, you can add as much butter as you like without any additional liquid. You could make a whole panful of sauce without a single extra spoonful of water.
Streaks are a sign that the emulsion is breaking, which occurs when the butter gets a little too hot. Whisking in a little cold water should restore the balance.
Cream is loaded with the same milk solids found in butter.
The more wholesome the milk was that produced your butter in the first place, the greater quantity of emulsifying milk solids that you’ll have at your disposal. The easier it will be for you to make a sturdy sauce without having to add something like cream. That’s one reason why it’s important to buy good-quality butter.
In that regard, at least.
“Milk solids” doesn’t appear on any label, neither does “water content.”
“Fat” is listed, but its quantity is obscured by the way that American nutritional labels quantify things. In the United States, the official serving size of butter is one tablespoon, which is 14.2 grams, a number that’s typically rounded down to fourteen. The overall fat content is also rounded to the nearest whole number, so that nearly every brand of butter sitting on the store shelf states the same “11 grams” of fat.
Your best guide is your own instinct. The more deliciously wholesome a butter tastes, the better it will function in your cooking. It’s that simple.
“Unsalted” butter is something that recipe-writers constantly recommend, mainly because it’s versatile. With it, you can make sweet as well as savory dishes.
As a matter of quality, the presence of salt on an ingredients label does indicate that the butter is less rich, because regulations (even in France) permit salt to displace fat by up to two percent.
“European style” butter sold in the United States is often cultured, which means that it was made from fermented milk. (A lot of butter sold in Europe is produced this way, in fact.)
Fermented milk possesses aromatic compounds that intensify the basic buttery flavor. It doesn’t result in “tangy” butter. Food-writers who say that are probably confusing fermentation with rancidity. Their butter isn’t fresh.
And yet freshness is the most important factor of all. Your butter could be churned from the milk of cows reared on a remote mountain monastery, nourished on a diet of rose petals, whatever qualities these impart being lost if the butter is stale.
Finding truly fresh butter in the United States, however, is a matter of trial and error, since, according to the Department of Agriculture, no rules exist here to govern whether or how expiration dates appear on food (unless that food is infant formula).
To answer this very question, an online news site, SFgate, commissioned a laboratory to analyze unlabeled samples of butter. Two nationwide brands passed muster:
That study was done way back in 2000, however. It’s all we have to go on for the moment, it seems. One brand that nearly made the cut, Plugrá, has changed ownership since then. (It was a rich butter with just a little too much moisture, at 16.30%, and fewer milk solids than the two above.)
Other brands give me good results, but I’m waiting until I can get some numbers to verify my own impressions. I’ll update this article as soon as I’m able.
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Your own taste is paramount. The integrity of your supplier is important, too. If your butter tastes stale or weird, then the place where you bought it is likely to blame.
Once you find a reliable purveyor, put your butter into something air-tight, and keep it in the fridge.
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