About 1860 the deep tin can was introduced, set in cold running water or, where ice was available, in ice water. This was a great improvement over the shallow setting system. It was now possible to raise most of the cream in 24 hours leaving not to exceed ½% butter-fat in the skim milk, and to have both cream and skim milk sweet.
Centrifugal Creaming.—But the climax of perfection was not reached until the separator (see under Cream) was invented about 1879 and cream was raised instantaneously. For a long time it was the object of the manufacturers to produce power separators of larger and larger capacity, handling from 6,000 to 10,000 lbs. of milk an hour.
Co-operative Creameries were established, taking in 20,000 lbs. of milk and more a day. But in thinly settled sections where the roads were poor it was expensive to haul the milk a long distance to the creamery and hand separators were introduced, each farmer skimming his own milk fresh from the cows and delivering the cream, only, to the creamery. This system has the advantage of leaving the skim milk on the farm in the very best condition for the calves and hogs and of saving time and expenses in transportation. It has the disadvantage that many farmers can hardly be expected to handle all of these separators as skilfully and cleanly as the creamery expert can run his one or few machines, and consequently that the skimming is more or less imperfect—more butter-fat being left in the skim milk and more impurities in the cream than in the whole-milk creamery. But in practice the advantages of the hand separator and cream-gathering system seem to be greater than the disadvantages and it is rapidly taking the place of the whole-milk creameries.
Ripening the Cream.—Butter may be made by churning whole milk, but usually it is made from cream that has been “ripened” or soured by standing for about 10 hours at a temperature of from 65° to 75° F. Modern buttermakers often pasteurize the cream and then add a “starter” to sour it. By preparing the starter with a pure culture of lactic acid bacteria one can get the desired acidity and aroma, and exclude undesirable flavors (as to Pure Cultures and Starters, see under “Bacteria” and “Commercial Buttermilk”).
Sanitary Cream Ripener showing coil swung up into cleaning position
The process of ripening requires considerable skill and attention and is one of the most delicate functions the buttermaker is called upon to perform. In the first place the cream must be faultless, sweet and pure before it is set to ripen, so the buttermaker will have full control of the fermentation. For, if it is already turned or partly fermented, no skill will avail to bring it back to perfection. But with a first class, pure cream the operator has it in his power to turn out perfect butter. In the big western creameries cream is often collected from farms at a distance of a hundred miles or more and in warm weather such cream is likely to arrive at the central plant in more or less advanced condition. It is therefore difficult for the centralizers to make really first-class butter while the “whole-milk creamery” as well as the farmer handling his own milk are in position to control the ripening from the beginning,—starting with pure material and being able to develop the desired flavor and acidity in the cream.
After adding the starter to the cream it must be kept at a uniform temperature of 65 to 75° during the ripening process and it must be watched carefully and occasionally stirred gently until the consistency, aroma and acidity are as desired. Then it should be cooled quickly to stop further fermentation and if it is not to be churned at once it should be kept cold until churning time. Usually it is safer to set the cream in the morning and hasten the ripening so it will be completed in the evening rather than to leave it overnight warm. For, if it is finished in the evening, the cream may be cooled and placed in ice water overnight and one is sure to have it in good condition for churning in the morning. But it is quite feasible for the experienced operator to regulate the process so the cream will not be fully ripened in the morning until he is on hand to watch it and see that the process does not go too far. Taste and smell will tell when it is just right, and the acid test may also be applied to determine when to stop the fermentation. An acidity of .5% is usually desired. When the condition is right, chill the cream, cooling it to below 50°—preferably down towards 40°—and leave it in ice water or in the refrigerator until churning time; then temper it to the proper temperature for churning.
Even if it is to be churned soon after the ripening is completed it is best to chill it and then raise the temperature to the point wanted for churning. This gives a better “grain” and “body” to the butter than if the ripened cream is just cooled to the churning temperature, and is especially desirable when the cream has been pasteurized.
