Page:1902 Encyclopædia Britannica - Volume 27 - CHI-ELD.pdf/390

 [cheese AND CHEESE-MAKING. D A I R Y - F ARMING is deposited in the cheese- or store-room—which should be moder- mena—the production of flavour and the breaking down ately warm and sheltered from the access of air, lest the cheese of the casein (that is, the formation of proper texture) should crack—and turned every day, until it has become suffi- —used to be regarded as different phases of the same ciently hard and firm. These cheeses require to be kept a con- process. As subsequently shown, however, these changes siderable time. As a matter of fact, there are three different modes of cheese- are not necessarily so closely correlated. The theories making followed in Cheshire, known as the edfly ripening, the formerly advanced as explanatory of the ripening changes medium ripening, and the late ripening processes. There is also in cheese were suggestive rather than based upon experia method which produces a cheese that is permeated with “green mental data, and it is only since 1896 that careful scienmould” when ripe, called “Stilton Cheshire ; this, however, is confined to limited districts in the county. The early ripening tific studies of the problem have been made. Of the method is generally followed in the spring of the year, until the two existing theories, the one, which is essentially Euromiddle or end of April; the medium process, from that time until pean, ascribes the ripening changes wholly to the action late autumn, or until early in June, when the late ripening pro- of living organisms—the bacteria present in the cheese. cess is adopted and followed until the end of September, changing The other, which had its origin in the United States, again to the medium process as the season advances. The late ripening process is not found to be suitable for spring or late asserts that there are digestive enzymes — that is, unautumn'make. There is a decided difference between these several organized or soluble ferments — inherent in the milk methods of making. In the early ripening system a larger quan- itself that render the casein soluble. The supporters of tity of rennet is used, more acidity is developed, and less pressure the bacterial theory are ranged in two classes. The one, employed than in the other processes. In the medium ripening process a moderate amount of acidity is developed, to cause the led by Duclaux, regards the breaking down of the casein natural drainage of the whey from the curd when under press. In as due to the action of liquefying bacteria (Tyrothrix the late ripening system, on the other hand, the development of forms). On the other hand, Yon Freudenreich has ascribed acidity is prevented as far as possible, and the whey is got out of these changes to the lactic-acid type of bacteria, which the curd by breaking down finer, using more heat, and skewering when under press. In the Stilton Cheshire process a larger quan- develop so luxuriantly in hard cheese like Cheddar. With regard to the American theory, and in view of tity of rennet is used, and less pressure is employed, than in the medium or late ripening systems. the important practical results obtained by Babcock and Wisconsin experiment station, the followIt is hardly possible to enunciate any general rules for Bussell at the 2 the making of Stilton cheese, which differs from Cheddar ing account of their work is of interest, especially as and Cheshire in that it is not subjected to pressure. Mr the subject is of high practical importance. In 1897 they J. Marshall Dugdale, in 1899, made a visit of inspection announced the discovery of an inherent enzyme in milk, they named galactase, and which has the power of to the chief Leicestershire 1dairies where this cheese is which digesting the casein of milk and producing chemical deproduced, but in his report he stated that every Stilton cheese-maker worked on his own lines, and that at no two composition products similar to those that normally occur dairies did he find the details all carried out in the same in ripened cheese. The theory has been advanced by manner. There is a fair degree of uniformity up to the them that this enzyme is an important factor in the point when the curd is ladled into the straining-cloths, but ripening changes j and as in their experiments bacterial at this stage, and in the treatment of the curd before action was excluded by the use of anaesthetic agents, salting, diversity sets in, several different methods being they conclude that, so far as the breaking down of the in successful use. Most of the cheese is made from two casein is concerned, bacteria are not essential to this curds, the highly acid curd from the morning’s milk being process. In formulating a theory of cheese - ripening, have further pointed out the necessity of considermixed with the comparatively sweet curd from the even- they ing the action of rennet extract as a factor concerned in ing’s milk. Opinion varies widely as to the degree of tightening of the straining-cloths. No test for acidity the curing changes. They have shown that the addition appears to be used, the amount of acidity being judged of increased quantities of rennet extract materially hastens rate of ripening, and that this is due to the pepsin by the taste, feel, and smell of the curd. When the the which is present in all commercial rennet extracts. They desired degree of acidity has developed, the curd is broken it easily possible to differentiate between the proteoby hand to pieces the size of small walnuts, and salt is find added at the rate of about 1 oz. to 4 lb of dry curd, or 1 oz. lytic action—that is, the decomposing of proteids—of pepsin and galactase, in that the first-named enzyme is to 3^ lb of wet curd, care being taken not to get the curd incapable of producing decomposition products lower than pasty. If a maker has learnt how to rennet the milk properly, and how to secure the right amount of acidity the peptones precipitated by tannin. They have shown at the time of hooping—that is, when the broken and that the increased solubility—the ripening changes—of salted curd is put into the wooden hoops which give the the casein in cheese made with rennet is attributable to the products peculiar to peptic digestion. The cheese its shape—he has acquired probably two of the solely addition of rennet extract or pepsin to fresh milk, does most important details necessary to success. It was formerly the custom to add cream to the milk used for not produce this change, unless the acidity of the milk is making Stilton cheese, but the more general practice allowed to develop to a point which experience has shown now is to employ new milk alone, which yields a product to be the best adapted to the making of Cheddar. cheese. apparently as excellent and mellow as that from enriched The rationale of the empirical process of ripening the milk before the addition of the rennet is thus explained. milk. As a cheese matures or becomes fit for consumption, In studying the properties of galactase it was further not only is there produced the characteristic flavour found that this enzyme, as well as those present in peculiar to the type of cheese concerned, but with all rennet extract, is operative at very low temperatures, varieties, independently of the quality of flavours de- even below freezing-point. When cheese made in the veloped, a profound physical transformation of the casein normal manner was kept at temperatures ranging from occurs. In the course of this change the firm elastic 25° to 45° F. for periods averaging from 8 to 18 it was found that the texture of the product curd “breaks down”—that is, becomes plastic, whilst months, chemically the insoluble casein is converted into various simulated that of a perfectly ripened cheese, but that soluble decomposition products. These ripening pheno- such cheese developed a very mild flavour in comparison with the normally-cured product. Subsequent storage at

354

1 “The Practice of Stilton Cheese-Making,” Journ. Roy. Agric. Soc., 1899.

2

Experiment Station Record, xii. 9. Washington, 1901.