is made from cream which is further concentrated so that the final product is more than 80% fat. In this form it keeps for longer than fresh milk or cream, and has therefore been used since antiquity (although not everywhere—the ancient Greeks, whose usual cooking medium was olive oil, seem not to have used butter except as an ointment).
Butter is made not only from cow's milk but from water-buffalo's milk in India, and sheep's milk in various parts of Asia. It is only exceptionally made from camel's milk. Milk from the dri (female yak) is rich in butterfat; and that from a dzomo (yak/cow hybrid) can also be used. Goat's milk butter, made on a small scale in France, is delicious.
Structurally, butter is a water-in-oil emulsion. It is made from cream, which is an oil-in-water emulsion containing, in the richest grades, over 40% fat (the words ‘fat’ and ‘oil’ are interchangeable in this context). When cream is churned, by some kind of revolving paddle, this disturbs the emulsion, forcing the fat globules together until they join up into a continuous mass with water droplets trapped in it. Much of the water, with milk sugar dissolved and proteins dispersed in it, is forced out in the form of buttermilk.
Most butter is made from cream which has ‘ripened’ by the action of lactic acid-producing bacteria, which are present naturally in unpasteurized milk and cream. Since one can never be certain that the right bacteria are there in adequate strength, it is usual to add starter cultures of bacteria chosen to produce substances which give desirable flavours. Streptococcus spp, in addition to fermenting the lactose (milk sugar) to lactic acid, convert the citrates in milk to diacetyl and acetyl methyl carbinol, of which the first is a major and the second a minor contributor to butter flavour. Leuconostoc spp also produce acid and other flavouring substances such as alcohols and esters. Some of the latter, the delta lactones, are the chief factors in the flavour of foods cooked in butter. Butter made from unripened cream is called ‘sweet cream butter’ and has less flavour.
Naturally, butter from different species of animal differs in flavour, but another effect comes from the diet of the animal, in particular from aromatic herbs. This is why butter from certain areas, for example Normandy, has such a high reputation.
After churning, the butter is further worked, and also washed in plain water, to remove as much of the buttermilk as possible and improve the texture and flavour. (Most of the lactic acid is in the buttermilk and if it were all retained the butter would taste too sour.) This also improves keeping quality, as does the addition of salt, which discourages the growth of bacteria.
Butter, whether salted or not, is not a fully preserved food; indeed, it begins to deteriorate (albeit slowly) at once. The fat is broken down by oxidation (the effect of the oxygen in the air) and hydrolysis (the effect of the water) so that it becomes rancid. One way of making butter keep longer is to clarify it: that is, to remove all the water. This is done by heating it gently so that the emulsion breaks down and the fat rises to the top of the water. The fat may then be left to solidify and be lifted off the water, or, more usually, the water evaporated by continued heating. The latter method is the one used to make ghee. The prolonged heating develops a slightly burnt taste, caused by reactions between the small amounts of proteins and sugar remaining in butter from the original milk; but the taste is quite pleasant. The heat also completely eliminates bacteria, further improving keeping quality.
Butter is a fine cooking medium; the excellent flavour which it imparts to food is matched by no oil or other fat. This is due partly to lactones, as mentioned, and partly to protein-sugar reactions brought about by heating. These reactions also give an attractive brown colour to food cooked in butter. However, butter stands up to heat less well than oils; if it is overheated, protein breakdown goes too far, resulting in a strong burnt taste and too dark a colour. (This problem is lessened by mixing butter half and half with oil, or by using ghee.)
Butter has a lower melting point than hard white fats such as lard and hardened vegetable cooking fat. It is therefore more difficult to make good pastry with butter than with these fats. Moreover, the latter also have larger fat crystals, better able to hold the flour grains well apart and prevent them from coalescing into a dense mass. Despite this, butter's superior flavour balances its disadvantages in other ways and it is often used for rich shortcrust, and almost always for the flaky and puff varieties.
Alan Davidson was a distinguished author and publisher, and one of the world's best-known writers on fish and fish cookery. In 1975 he retired early from the diplomatic service—after serving in, among other places, Washington, Egypt, Tunisia, and Laos, where he was British Ambassador—to pursue a fruitful second career as a food historian and food writer extraordinaire. Among his popular books are Seafood of South-East Asia, North Atlantic Seafood, and Mediterranean Seafood. In 2003, shortly before his death, he was awarded the Erasmus Prize for his contribution to European culture.
