unsalable as a first-class article. The process of sourcream butter-making is therefore, at the bottom, a question of keeping the fermentations during the ripening of the cream in the right track, of controlling the same so as to exclude all but lactic-acid-producing bacteria. The old original way of reaching this end was to allow the cream to sour spontaneously, trusting to luck to obtain the desired fermentation of the cream by leaving it standing in a warm room for a couple of days. Later on, a buttermilk starter from a preceding churning or a skim-milk starter was added for the purpose of ripening the cream; by this means the lactic-acid bacteria contained in the starter were introduced in such large numbers that they generally were able to crowd out other kinds of bacteria that might be found in the cream, and which, if left alone, would produce undesirable fermentations in the cream and bad flavor in the butter. The next step in advance was the introduction of pure cultures of lactic-acid bacteria; these consist of one or a few forms of bacteria, and when introduced in milk or cream will be apt to overpower all other forms of bacteria therein, and thus produce the pure mild flavor of sourcream butter desired.

The honor of having first introduced pure cultures in butter-making belongs to Dr. V. Storch, the chemist of the Danish state experiment station in Copenhagen; the bulletin describing Dr. Storch's investigations of this subject, "On the Ripening of Cream," was published in 1890. Other bacteriologists in Europe and in this country have worked along this same line, and as a result we find that pure cultures are at the present time used almost universally in the manufacture of sour-cream butter in the creameries and dairies of northern Europe, and also in this country their use has become general and is spreading. The expected result of adding a pure culture-starter, viz., that of excluding all undesirable fermentations in the ripening of the cream, will not, however, follow with any certainty unless the seeding with the pure culture is preceded by pasteurization or sterilization of the cream, that is, at least a partial destruction of the bacteria already found therein. In Europe, notably in Denmark and the

other Scandinavian countries, pasteurization of the milk (or of the cream) is practised regularly in all the best creameries, in the former country at present in perhaps 90 per cent of the creameries in operation. In this country the firms manufacturing and selling pure cultures have unfortunately not insisted on this point, and where pure culture-starters are used with us it is nearly always without previous pasteurization. One reason why pasteurization has not been adopted in the manufacture of butter in this country is that the market demands a higher flavored, ''stronger" butter than is wanted by the European market, and the pure cultures on the market, when used with pasteurized cream, do not produce such a butter. The expense of pasteurization of the cream and the absence of proper apparatus, or non-introduction of such as have proved successful in European practice, furthermore tend to explain why our butter-makers do not generally pasteurize the cream in using pure culture-starters.

The three pure cultures now on the market in this country are Chr. Hansen's Lactic Ferment (Chr. Hansen's Laboratory, Little Falls, N. Y.), Conn's culture (B. 41, Conn Butter Improvement Co., Philadelphia, Pa.), and the Boston Butter Culture (Boston Butter Culture Co., Boston, Mass.). The first one is of Danish origin, and is one of the standard pure cultures used in the Scandinavian countries; the second was described by its originator in the author's Dairy Calendar for 1896. These cultures are placed on the market in dry form as a powder, or as pellets. Directions for using the cultures accompany each package sold. In general, the method to be followed is to seed the culture in a quantity of sterilized skim-milk or cream; this is kept for one to two days at a temperature below 90° (B. 41 70°, Lactic Ferment 86°); the starter is then mixed with the cream to be ripened, generally adding about 2 per cent. The cream will be ready for churning the next day. A portion of the starter prepared is used for the seeding of a new lot of sterilized skim-milk, which will make the starter for the following day, and the same process is continued until deterioration of the starter sets in, as shown by lack of flavor in the ripened cream and in the butter; a fresh batch is then prepared from a new package of ferment. If proper

care in sterilizing the skim-milk and in handling the starter is taken, the pure culture may be propagated in this manner for months. With lack of cleanliness and care it must be renewed every other week or oftener.

While the use of pure cultures has not as yet become general in American creameries, the agitation caused by their introduction and the discussions in dairy papers and dairy meetings which they have brought about have doubtless been of great benefit to cur dairy industry in emphasizing in the minds of butter-makers the necessity of thorough cleanliness in the creamery and the importance of the proper conduct of the ripening process for the manufacture of high-grade butter. They have enabled us to make butter of uniform fine flavor and of greater keeping quality than was previously possible.

Where abnormal fermentations appear, and the butter produced is diseased or "off flavor," the evil may be remedied by the use of pure cultures. In case of the establishment of an export trade of American butter of high quality, the pure cultures used in connection with previous pasteurization of the milk or cream will prove of great benefit, insuring uniform goods and perfect keeping quality in the product.

The use of pure culture-starters in the manufacture of Cheddar cheese is of recent date, and but limited experience has so far been gained in this line. According to the testimony of some of our leading cheese-makers, and of recent experiments conducted at Wisconsin experiment station, their use for this purpose is very beneficial, cheese of improved, clean flavor and high keeping qualities being produced. Pure cultures may therefore be safely recommended for this purpose. The general method of application is similar to that followed in the manufacture of pure culture butter. The starter is propagated in sterilized milk and kept at 90° F. for one day, when it will be slightly lobbered, having an acidity of about .8 per cent. Prof. Decker, late of the Wisconsin Dairy School, gives the following hints on the use of the starter by the cheese-maker: "The starter is introduced into the milk by rubbing it

through a fine hair sieve so as to break up curd particles. If too large quantities of starter is used, there is a tendency to produce a sour cheese. The best results are obtained when a 2 per cent starter, of the acidity given, is added.

"In propagating the starter from day to day care must be taken to keep it free from contamination. It should always be prepared in a covered vessel that has previously been sterilized, and the milk used should first be pasteurized (or sterilized) and chilled before adding the 'seed.' Some of the original starter should be taken for 'seed,' not the whole milk after the starter has been added.

"The starter cannot be used for cheese-making if the milk is overripe, which is the case when the rennet test is 65 seconds or under (see p. 282). In sweet milk, testing by the rennet test 120 seconds, the addition of a 2 per cent starter will increase the acidity, so that the rennet test will act in 70 seconds.

"With sweet milk the use of a pure lactic starter will result in the saving of 3-5 hours in time. With tainted milk in which the acid develops imperfectly the addition of the starter aids in producing the acidity required for the manufacture of Cheddar cheese."

BOYD'S PROCESS OF CREAM RIPENING.

By JOHN BOYD, Chicago, Ill.

It is an accepted fact that the fine aromatic flavor and also the keeping properties of butter depend largely upon the treatment of the cream from the time it is separated from the milk until it is ready for the churn, that is, in the best possible condition to yield the maximum quantity and the best quality as to flavor, texture, solidity, etc., free from casein and other undesirable substances. This perfect condition of cream is understood by the term "ripened cream," and when this condition can be produced by the butter-maker with uniformity, regardless of the seasons of the year or extremes of climate, the process may be reckoned as nearly perfect as possible, and not until then. It is most desirable that the process be as sim

ple as possible, in fact within the reach of every creamery and dairyman in the country, and all the means required to attain these results can and should be a part of every dairy and creamery, large or small.

Boyd's process or system of ripening cream or milk is the result of years of practical work in a private dairy of about 40 Jersey cows. After it had been thoroughly tested and used, during all the seasons of the year, it was patented in the United States, Canada, and Great Britain, and given to the public in the year 1889, a very considerable time in advance of any of the artificial methods of ripening, now being advocated under the representations of "pure cultures of bacteria."

When first introduced it was met by a sea of opposition from the experts, who would see nothing good in it, but gradually it has been making its way in a quiet manner into popularity until at present it is being successfully practised in every state in the Union, and is gaining favor every day with the most practical butter-makers.

The apparatus necessary to practise the process supplies all the conditions required to produce a uniform result every day in the year, the temperature of the lactive ferment and also of the cream being entirely under the control of the operator during the entire process.

The directions for using the process, which go with every purchase of the apparatus, are as follows:

To make the Best Ferment.-Take milk from fresh-milking cows (that from pregnant cows will not answer); submerge the milk warm from the cows in Cooley cans in ice water. Skim at twelve or twenty-four hours, as most convenient, and use this skimmed milk for making the ferment; or select milk as above, run it through a separator, and save the skimmed milk for making the ferment.

The skimmed milk so selected is then brought to a temperature of 90°, in a water bath, being constantly stirred during the operation of heating. As soon as the temperature of the milk reaches 90°, place it in the fermenting-can and close the cover tightly, having first rinsed out the can with warm water. Allow the can to remain closed for