Cream ripening.—­Passing from milk to butter, we find a somewhat different story, inasmuch as here bacteria are direct allies to the dairyman rather than his enemies.  Without being aware of it, butter makers have for years been making use of bacteria in their butter making and have been profiting by the products which the bacteria have furnished them.  Cream, as it is obtained from milk, will always contain bacteria in large quantity, and these bacteria will grow as readily in the cream as they will in the milk.  The butter maker seldom churns his cream when it is freshly obtained from the milk.  There are, it is true, some places where sweet cream butter is made and is in demand, but in the majority of butter-consuming countries a different quality of butter is desired, and the cream is subjected to a process known as “ripening” or “souring” before it is churned.  In ripening, the cream is simply allowed to stand in a vat for a period varying from twelve hours to two or three days, according to circumstances.  During this period certain changes take place therein.  The bacteria which were in the cream originally, get an opportunity to grow, and by the time the ripening is complete they become extremely numerous.  As a result, the character of the cream changes just as the milk is changed under similar circumstances.  It becomes somewhat soured; it becomes slightly curdled, and acquires a peculiarly pleasant taste and an aroma which was not present in the original fresh cream.  After this ripening the cream is churned.  It is during the ripening that the bacteria produce their effect, for after the churning they are of less importance.  Part of them collect in the butter, part of them are washed off from the butter in the buttermilk and the subsequent processes.  Most of the bacteria that are left in the butter soon die, not finding there a favourable condition for growth; some of them, however, live and grow for some time and are prominent agents in the changes by which butter becomes rancid.  The butter maker is concerned with the ripening rather than with later processes.

The object of the ripening of cream is to render it in a better condition for butter making.  The butter maker has learned by long-experience that ripened cream churns more rapidly than sweet cream, and that he obtains a larger yield of butter therefrom.  The great object of the ripening, however, is to develop in the butter the peculiar flavour and aroma which is characteristic of the highest product.  Sweet cream butter lacks flavour and aroma, having indeed a taste almost identically the same as cream.  Butter, however, that is made from ripened cream has a peculiar delicate flavour and aroma which is well known to lovers of butter, and which is developed during the ripening process.