Page:Popular Science Monthly Volume 64.djvu/387

Rh nucleus of the international meeting. That such a unique fusion of scholarship will be productive in itself no one can doubt; but that these scholars are brought together and are doing their work under the control of the demand for unity in knowledge, for interrelation and synthesis—this thought will be the living force, the most powerful factor of the congress, and a tremendous influence in overcoming the pedantic and unphilosophic narrowness of specialists in every corner of the realm of science."

processes involved in the making and curing of cheese have been the subject of some of the most noteworthy dairy investigations which have been made. While the subject had been studied in a fragmentary way in this country and in Europe for some time, little real progress was made until several of the American experiment stations undertook a systematic investigation of the nature and causes of the changes involved and the chemical character of the products formed. This has gone on steadily for eight or ten years, and has resulted in the working out of the scientific principles underlying this very ancient art. The largest amount of work has been done by the experiment stations in Wisconsin, New York and Canada, and the names of Babcock, Russell, Van Slyke and Hart are especially prominent. The reports of progress have appeared in a series of bulletins from these stations, several particularly important ones having been issued during the past few months.

In the course of the chemical studies the product formed by the action of rennet on milk, about which there had previously been considerable doubt, was identified as paracasein. This was found to combine with acids to form mono and di-acid salts, quite different in character and in their effect upon the appearance of the curd. In normal cheese making the mono-acid salt is formed, the paracasein uniting in that proportion with the lactic acid produced in the curd by lactic-acid bacteria. These bacteria have invariably been found in the milk and green cheese in predominating numbers, but their true function has remained until now a mystery. They are indispensable to the formation of paracasein monolactate in cheese curd, and this compound is found to be the starting point of the ripening or curing process.

The first step in this appears to be a peptic digestion of the monolactate, the rennet ferment being the active agent. Rennet, which was formerly supposed to contain two enzymsenzymes [sic], is found to be in reality a peptic ferment and to act in all essentials like commercial pepsin in forming soluble nitrogen compounds. In fact, normal cheese has been made by the substitution of commercial scale pepsin for rennet extract. The chemical changes produced by both rennet and pepsin are confined mainly to the formation of paranuclein, caseoses and peptones, only small amounts of amids and no ammonia being formed. The action of these enzyms does not appear to