adding to the pasteurized cream a culture of bacteria which will produce the type of fermentation desired. This enables the trained butter-maker to produce butter of more uniform character and better keeping quality.

Ripening of cream is an acid fermentation, the object of which is to produce a butter of desirable flavor and aroma. Ripened cream also churns more easily and completely than that which has not been ripened.

Different butter-makers use temperatures varying from 60° to 80° F. in ripening cream, the higher temperatures being employed when it is desired to complete the process as rapidly as possible. Ordinarily it is considered that a better type of fermentation is secured at 60° to 70° F. than at a higher temperature. The desired temperature is maintained by keeping the cream, during the ripening process, in a water-jacketed vat.

In the ripening vat the cream is mixed with (usually) one tenth to one fifth of its volume of "starter," which consists of clean skimmed milk in active lactic acid fermentation induced either by the addition of commercial cultures of lactic acid bacteria or by keeping a good natural milk at about 70° F. until it shows a clean pleasant acid odor and taste, and coagulates to a smooth uniform curd. Before the starter is added to the cream, it is strained or poured back and forth between sterilized cans until the curds which it contains are broken into very small particles; otherwise the lumps of curd may appear as whitish mottles in the finished butter. If necessary, the starter may be strained before mixing with the cream. The cream and starter should be thoroughly stirred together and the stirring should be repeated at intervals during the ripening process in order that the acid fermentation may predominate uniformly throughout and that the fat globules may have the most favorable conditions for absorbing the desired aroma.

In general, the degree of acidity reached by the cream in the ripening process is an indication of the degree of flavor that the

butter will have. Some markets require a more highly flavored butter than others.1

Churning consists in agitating cream in such a way that the fat globules stick together into masses of butter large enough to be separated from the buttermilk.

The churns now in general use in American butter factories, and which are being introduced into Europe, are the "combined churns," which are so arranged that they can be used not only to churn the cream and gather the butter, but also to wash, salt, and work the butter so that all these successive operations can be carried out without handling or exposure to flies and in an apparatus which permits of a controlled temperature.

In transferring the cream from the ripening-vat to the churn it is run through a tin strainer to remove any lumps of curd which might otherwise affect the appearance of the butter.

Butter color is usually also added to the cream before churning. Both annatto and synthetic colors are widely used. Different markets require different degrees of color. The commercial preparations used for coloring butter are employed in quantities varying from none in May and June (when the natural color of butter is highest) to about 2 ounces per 100 pounds of fat in winter when the butter would naturally have a much paler color than in early summer.

Churning is usually continued until the fat has gathered into irregular, flaky, granular masses between the size of a grain of wheat and that of a kernel of corn. The buttermilk is then drawn off and the butter washed with pure water, usually at a temperature about that at which the cream was churned or a little below. Warmer or colder water is sometimes used when it is desired to alter the texture of the butter.

1 Usually the ripening process is continued until 50 cc. of the cream neutralize about 35 cc. of tenth normal sodium hydroxide, using phenolphthalein as indicator. This is called 35 degrees of acidity. The acidity is also sometimes expressed as percentage of lactic acid, and is often measured by means of alkali tablets which contain a fixed amount of alkali along with enough phenolphthalein to serve as indicator.

Salting of butter has the object (1) of imparting the desired flavor, (2) of increasing the keeping quality, (3) of facilitating the removal of the buttermilk.

The amount of added salt desired in butter by different markets varies from o to 4 per cent, American markets tending as a rule to prefer a rather highly salted butter.

When the salting is done without removing the butter from the churn, the amount of salt added is calculated on the basis of the amount of fat known to have been contained in the cream.

The quality of the salt used is regarded as quite important. Good dairy salt should have a clean, white, silky appearance and should dissolve quickly. Woll' gives the following as the analysis of a sample of purest American dairy salt:

All of the salt contained in butter should dissolve in the water which the butter retains. Butter containing particles of undissolved salt is called "gritty." When the butter as packed contains undissolved granules of salt, these attract moisture and cause unevenness of appearance. This is one of the causes of mottles in butter. In order to avoid mottling of butter from this or other causes, the buttermilk should be washed out as completely as possible and the salt carefully applied and well worked in. The washing out of the proteins in the buttermilk also results in a butter of better keeping qualities.

Working. The butter, having been washed and salted, is next worked to distribute the salt evenly, to bring the butter into compact form, and to press out any excess of water or

1 Bulletin 74, Wisconsin Agricultural Experiment Station.

diluted buttermilk. The amount of water left in the finished product is largely determined by the working, since the more it is worked after it has become firm, the lower the percentage of moisture will be. For most markets the moisture must not exceed 16 per cent.

Packing. Extra quality butter is often put up in prints bearing the name of the farm or creamery where made. As the print butter must be firm in order to keep its shape well, it is apt to contain slightly less moisture than the butter put up in tubs. The butter is transferred from the churn or working table to the tub by wooden ladles which just before use are thoroughly scalded and then chilled in cold water. By means of the ladles, the butter should be smoothly and firmly packed into the tub so as to leave no air spaces either in the butter or between the butter and the sides of the tub or at the top.

Stored butter should be kept at 50° F. or below in as dry a place as possible and separate from any other foods or anything from which it might absorb an odor.

The expense of making butter from the whole milk was investigated in Iowa and is reported to range in the different factories from one and one fifth to six cents, with an average of two and one fourth cents per pound of butter produced. The cost of ordinary creamery butter depends therefore much more largely upon the cost of milk or cream than upon the expense of manufacture.

Judging butter is very important in the industry because the price is so largely dependent upon the grade given the butter by the butter judge.

On a scale of 100 the weight given to the different factors of quality in America is usually as follows:

For discussion of judging, grading, and the market classification of butter, see McKay and Larsen, Principles and Practice of Butter-making, Chapter XX. Under the recent Food Products Inspection Law, the United States Department of Agriculture has adopted an official system of classification and grading, the current rules of which can be obtained on application to the Secretary of Agriculture, Washington, D. C.

Composition of Butter. McKay and Larsen found the average composition of 221 samples of butter from 55 creameries in different parts of Iowa to be:

The figures for curd include any milk sugar which may sometimes be present. Under present conditions of manufacture the curd is the least variable constituent. It is very generally kept below 2 per cent because if more than this is present, the brine which exudes from the butter is apt to be noticeably milky, and such a butter would not be acceptable to the trade. In butter which is to be kept for some time special care is taken to keep down the protein as much as possible. Such butter will probably contain only 0.5 to 1 per cent of curd.

Preparations for increasing the amount of butter obtainable from a given amount of cream have been put on the market from time to time. Since in the ordinary manufacture very little fat is lost in the buttermilk, it is obvious that these butter increasers must act, if at all, not by a saving of fat, but by inducing the formation of a butter with a lower fat content. Usually the result is accomplished by the incorporation of an undue amount of curd and water by a sort of emulsification of buttermilk with the butter. Such a butter is of course fraudulent, and is also of very inferior keeping quality on account of