Butter-Fat
Aiton's Encyclopedia (1910)
in dairying, the fatty or butter-producing portion of milk. Butter-fat exists in the form of small globules from 1/15000 to 1/2500 of an inch in diameter. The globules can be seen in a drop of milk placed under a microscope. The globules weigh .93 as much as water; the rest of the milk weighs more than water, If milk be allowed to stand quietly, the settling of the milk forces most of these globules to rise to the surface, where they form cream. The amount of fat in the average milk of the different breeds of cattle, expressed in percentages, according to tests made at the New York Agricultural Experiment Station, is: Holstein-Friesian 3.4 Ayrshire 3.6 Shorthorn 4.4 Devon 4.6 Guernsey 5.3 Jersey 5.6 Jersey milk is richest in butter-fat. Twenty-five Jersey cows exhibited for 120 days at the Louisiana Purchase Exposition at St. Louis, 1904, produced a daily average of 1.9 pounds of butter-fat per cow. This made an average of 2.3 pounds of butter or 6,841.6 pounds of butter for the twenty-five cows in 120 days. There is great diversity in the richness of the milk produced by different cows of the same breed, in the milk produced at different times of the day, and in the milk produced by different kinds of feed. The milk of some Holsteins contains more fat than the milk of some Jerseys. A famous Holstein cow, Colantha 4th's Johanna, tested by the Michigan Agricultural Experiment Station, produced 28.176 pounds of butter-fat in 7 days; 110.883 pounds in 30 days; 208.398 pounds in 60 days, and 998.256 pounds in a year. Morning milk ordinarily contains a larger percentage of fat than evening milk. Clover and bran and green bluegrass pasture favor the production of milk having a high percentage of fat. The creameries that buy milk pay for the butter-fat. Farmers sending milk to a cooperative creamery are credited with the amount of butter-fat in contains.
What Has Changed in the Last Century
The physical description Aiton's gave in 1910 still holds: butterfat rides in globules a few microns across, lighter than the surrounding milk, and Jerseys and Guernseys still test richer than Holsteins and Ayrshires. What has moved is the arithmetic. The Babcock test that made the entry's payment-by-butterfat system possible has been largely displaced in commercial labs by infrared spectrophotometry, which reads fat, protein and lactose from a sample in seconds, and yields have climbed so far that the 998 pounds of fat in a year set by Colantha 4th's Johanna, a record worth naming in 1910, is roughly what a good ordinary Holstein now gives in a lactation. Butterfat's reputation has swung too, from the prized fraction of the milk, to the thing skimmed out during the low-fat decades, and back to a premium ingredient.
Written for this edition, 2026.