Page:The story of milk.djvu/97

 *pensive 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").

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