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Cheese and Cheese-Making
THE PRINCIPLES OF CHEESE-MAKING
PROFESSOR HENRY, of the Wisconsin Agricultural College, recently stated that the loss of the American cheese trade with Great Britain was owing to the fact that his countrymen did not make the best article, and that in many cases imitation cheese was produced for the sake of a possible temporary profit, but to the ultimate loss of all concerned. Whatever may be the immediate gain effected by the addition of foreign fat to milk, or by the removal of a portion of the cream it contains, the permanent value of the cheese industry to the producer is maintained only by the manufacture of the best, and of its production in the largest possible quantity. To obtain both quantity and quality necessitates a close study of the subject and a recognition of the principles which underlie the practice of cheese-making. To obtain quantity of cheese it is essential to have rich milk. We are told by those who oppose the institution of a standard in this country that the solids present in milk do not exceed 11 to 12 per cent., but the cheese-maker who produces or buys milk of this quality will not find his returns very satisfactory. The value of rich milk to the cheese-maker is twofold. In the first place, cheese is chiefly composed of the fat and casein of the milk — its two most important solids — and water; therefore, the more fat milk contains — and this is by far the most important constituent — the more cheese we produce per gallon, for three reasons: first, because the fat itself adds to the weight of the cheese; next, because with the increase of fat there is an increase of casein, which follows in an almost constant ratio; and last, it is a fact worth knowing that cheese produced from rich milk, i. e. milk containing a high percentage of fat, retains more water, and consequently weight is obtained from this source also. Every good cheese is mellow in its texture, and to some extent this mellowness depends upon the proportion of fat the cheese contains. Recognizing these facts, we come to the first principle which it is essential to remember, that in order to produce rich milk the cattle must be well selected, for quality depends rather upon breed than upon food. Nor is it entirely necessary to go to the Channel Islands for rich milkers. There are milkers of a very high order, as regards both quality and quantity, to be found in every British breed, particularly among Shorthorns and Devons.
It is, therefore, by selection and by testing the milk of cows retained in the herd, and excluding those which produce poor milk, that quality is maintained. Although, as we have remarked, breed has more influence than food upon quality, yet the production of fat in milk depends largely upon good feeding, inasmuch as good feeding improves the yield — although it may not increase the percentage of solids — and consequently it increases the fat. Thus we get to the soil, and it is usually found that in those districts where the most luxurious crops are grown — grass in particular, for it is the commonest food of cows — the cattle are best, and the milk they produce most abundant. Soil, however, has another influence which it is essential to mention. As we shall show, acidity plays an important part in the process of cheese-manufacture. But acidity is to some extent controlled by the alkaline properties which are present in milk, and as a proportion of these properties depends to a large extent upon the soil from which they are obtained, so does the soil indirectly influence the quality of the cheese, unless, by the exercise of the highest skill, sufficient allowance is made and the acidity controlled. Similarly, water exercises an influence when it contains an abnormal quantity of lime, and it is next to impossible to produce fine-flavoured cheese where such weeds as garlic are common on the pasture. The dairy, too, must be constructed with the object of providing perfect ventilation, the maintenance of an even temperature, and the exclusion of every possible means of conveying a taint to the milk.
Upon the first part of the process of manufacture in the dairy — that of the coagulation of the milk — a great deal depends. The period of the formation of the curd varies in accordance with the variety of the cheese produced. In the manufacture of soft cheese it is prolonged, sometimes for a considerable period; in the manufacture of pressed cheese it is usually short. The period of coagulation is influenced by the quality of the milk, the condition at the time the rennet is added, its temperature, and the strength and quantity of the rennet employed. The curd produced in a short time is elastic and comparatively firm; that produced after a prolonged period of coagulation is tender, it will scarcely bear cutting, and it parts with its fat, which is carried off in the whey unless it is very carefully handled. Thus it will be recognized that mellowness in cheese is obtained in different ways, but without sufficient moisture we can have no mellowness. Hence, if too large a quantity of rennet is used, if too much acidity is developed, or if the temperature is raised too high, the whey may be so rapidly and so completely expelled, that an insufficient amount of water will remain, either for the purpose of producing the necessary mellow condition, or even of ripening the cheese. In the manufacture of pressed cheese the whey is expelled by cutting the curd — and the finer it is cut the larger the surface exposed for its removal, — by heating to a high temperature, by the development of acidity — which causes the curd to contract — and by pressing. In the manufacture of soft cheese, however, the curd is not cut, except in such large slices as are essential for its removal into the moulds; but the whey drains off slowly by gravitation, and subsequently more is lost by evaporation. The cheese is soft because it retains more water than pressed cheese, while its flavour is largely influenced by the fact that it retains more sugar — the sugar being in solution in the whey — and because, in consequence, more acid (which is produced from the sugar) is developed. A tender curd, then, such as is generally used in soft cheese-making, is obtained by setting the milk at a low temperature and by the employment of a small quantity of rennet. In this way coagulation will be delayed. It is also essential that the milk used should be sweet, for if, as in pressed cheese-making, a portion of the milk used has been allowed to stand for a number of hours, acidity will have commenced to develop, which hastens coagulation, and will in time actually produce it.
The reason why curd which has been cut fine in the manufacture of large pressed cheese is left in the whey and heated, is that unless this were done it would not be sufficiently acid, for the curd when drawn from the whey is tough and dry as compared with the curd used in the manufacture of soft cheese. Unless this process were carried out the whey would not be expelled, and the cheese would not acquire its mellowness of texture or its fine nutty flavour. In soft cheese-making the curd is placed in small moulds; small cheeses are, indeed, essential, otherwise the whey would be unable to find its way to the surface; but unless the temperature is sufficiently high, it even then refuses to move, and for this reason soft cheese-making is conducted at specific temperatures which are applied to each variety of cheese. Theoretically, the time of coagulation is in inverse ratio to the quantity of rennet employed, but in practice this axiom is not entirely borne out, although the reasons do not detract from its truth. The same conditions do not, for example, apply to large quantities of milk, or to entirely fresh milk, which apply to small quantities or to milk which has been practically ripened by exposure. Thus, in the manufacture of small cheeses small quantities of milk are employed, and this milk parts with its heat more rapidly than is the case with a large volume. Again, when acid is developed slightly in milk, less rennet is required, and a milk rich in fat does not produce the same result with the same quantity of rennet as a milk poor in fat. It is important, therefore, in cheese-making to understand the quality of the milk employed, and, where it has been exposed for any number of hours, to ascertain the quantity of acid which it contains. Where small quantities of milk are set for curd, wooden vessels should be used, as wood is a non-conductor of heat; lids should be employed, and the whole covered with a blanket or any other non-conducting material.
We have referred to the nature of the solid matter of milk. The cheese-maker should early learn to understand that only a portion of these solids find their way into the cheese, the bulk of the sugar of milk, which forms a large proportion of the total solid matter, remaining in the whey, together with portions of the mineral matter, the casein, the albumin, and the fat. Almost the whole of the casein is, however, extracted in cheese-making, this being coagulated by rennet or by acid, whereas the albumin passes into the whey in almost all varieties of curd which are not submitted during manufacture to a high temperature, as it is coagulated only by heat. There is, however, a material which has been described by chemists as albumose, which always passes into the whey, not being coagulated either by heat, rennet, or acid. In accordance with the very extensive results obtained at the New York State Experiment Station, which we have had the advantage of inspecting, the average percentage of solids lost in cheese-making, i. e. by passing into the whey, amounts to 6.20, while the percentage of solids recovered from the milk, i.e. retained in the cheese, amounts to 6.30. The actual figures — from my The Elements of Dairy Farming — may, however, be quoted, as they are of considerable value —
Milk-Constituents lost in Cheese-making.
Lost in Whey for 100 lbs. Milk.
recovered in Cheese-making;
Retained in Cheese for 100 lbs. Milk.
The term "nitrogen compounds" indicates casein and albumin; The largest proportion of solids which passed into the whey was in the months of August and September; The smallest proportion of fat lost in the whey was in June and July, whilst the smallest proportion of casein and albumin lost was in the months of July and August; Upon the basis of the work carried on at forty-eight cheese-factories, it was ascertained that 50.6 per cent; of the total solids of milk were recovered, including 90.98 of the fat and 75.71 per cent. of the casein and albumin. It has been supposed that a larger proportion of fat is lost when the milk is rich than when it is poor or of but moderate quality. But this is not the Case, and the following table will show that the percentage of fat lost when the milk is rich is positively lower than when it is of lower quality; also that the percentage of cheese made is enormously increased as the milk increases in quality.