+198. Removing the whey.+--To permit the normal changes in the curd to take place naturally, two and one-half hours from the time the rennet extract is added is ordinarily required before the whey is drawn. The time of removing the whey is determined by two factors: one, the acid development, and the other, the firmness of the curd. For the best results, it is better to have the firmness of the curd a trifle ahead of the acid development. When the proper acid development has been reached, the whey must be removed, regardless of the firmness of the curd. If the curd has not become firm enough by natural forces, when the acid development has reached the proper stage to remove the whey, it must be firmed by other means. If it is not firm enough, either by natural or artificial means, when the whey is removed, a sour cheese is the result.
The acid development should not be allowed to go beyond 0.16 to 0.19 of 1 per cent acidity in the whey by the acid test or 1/16 to 1/8 of an inch of acid on the hot-iron test, before the whey is removed.
+199. Hot-iron test.+[89]--This test is employed to determine the amount of acid in the curd. A piece of iron, such as an iron pipe two feet long, is heated in the fire to proper temperature. If the iron is too hot it will burn the curd, and if not hot enough the curd will not stick to the iron. When hot, it is taken from the fire and wiped clean with a cloth. A handful of curd is taken from the vat and squeezed dry, either in the hand or in a cloth. This curd is carefully pressed against the hot iron and drawn away. If the iron is at the right temperature and the curd has sufficient acid development, the curd will stick to the iron and when pulled away will form fine threads. The length of these threads determines the amount of acid in the curd. The acid is usually spoken of in terms of the length of threads, as 1/8 inch of acid, inch of acid and the like. The curd must have a slight development of acid before it will stick to the iron. This test takes advantage of the peculiar properties[90] of curd which are produced by the action of the acid on the casein.
+200. Firmness of the curd.+--The cheese-maker must be able to judge the firmness of the curd by physical examination. The particles of curd should have shrunken to about one-half their original size and should be of uniform consistency throughout; they should not have any soft centers. The curd should be firm and springy. When a double handful is pressed and suddenly released, the curd particles should spring apart.
The curd should have a "shotty" feeling when in the whey. If the curd has attained the proper firmness, and the acid has not reached the correct stage to remove the whey, it may be left in the whey until sufficient acid development has been attained. This is liable to cause the curd to become too firm and to result in a hard dry cheese. If there is no evidence of the presence of undesirable organisms, such as bad odors, or gas holes in the curd, it is better to remove the whey and develop the acid when the curd is in the "pack." The pack refers to the first piling of the curd.
[Ill.u.s.tration: FIG. 36.--Whey siphon with strainer.]
The whey may be removed either by means of a faucet or gate in the vat or by a siphon (Fig. 36). With either form of removal a whey-strainer (Fig. 37) should be used to prevent loss of curd particles. It requires considerable time for the whey to escape from a large vat. After the curd has been heated to the proper temperature, it is well to remove a portion of the whey. In doing this the surface of the whey should not be drawn down quite to the top of the curd. When ready, the remaining whey can be quickly removed.
[Ill.u.s.tration: FIG. 37.--Whey strainer with spout to fit into the gate in the vat.]
If it is decided that the curd is not firm enough, when the whey is drawn down to the surface of the curd and the acid has developed sufficiently, the curd should be firmed up in the whey by stirring it vigorously by hand before the remainder of the whey is removed. This is commonly called "hand stirring." This difficulty results either from the use of too much starter or from holding the milk until too much acid development has taken place before adding the rennet. Hand stirring accomplishes what natural forces would accomplish if given sufficient time. If the curd does not firm naturally in the whey, there is a large loss of fat and other solids, because the pieces of curd will have to be broken up to allow the water to escape from the soft centers of these ma.s.ses. This loss can usually be reduced by firming the curd in the whey or adding water rather than by stirring without either water or whey. If the curd is not properly firmed, it carries extra whey into the cheese.
With the increase in whey, the amount of milk-sugar carried into the cheese increases. This extra milk-sugar attacked by bacteria produces an excess of lactic acid, which results in "sour" cheeses. This explains why the curd is placed beyond the danger of over-development of acid by removing so large a portion of the whey. If the curd is properly firmed in the whey and the whey is removed before too much acid has developed, it is impossible to make a sour cheese.
+201. Gathering the curd together.+--Before the last of the whey has been removed, the curd should be pushed back from the faucet into the upper two-thirds of the vat and spread in an even layer. This layer should be six to eight inches thick. The curd can be pushed back with the rake or a board which will fit crosswise in the vat, in which are many holes. As soon as the whey has been removed so that there is not enough to wash the curd into the lower part of the vat, the vat should be tilted and a ditch eight to ten inches wide cut in the curd through the center. The curd from the ditch should be removed to either side and spread evenly. As soon as all the whey has been removed, the pieces of curd scattered about in the vat should be gathered up and placed with the remainder.
In some factories, instead of matting the curd in the vat, a curd sink is used. This is a wooden receptacle about the size of the vat but not so deep, with a slatted false bottom. It is fitted with castors so that it can be easily moved about. A cloth is placed in the sink and the curd and whey are dipped upon the cloth. The whey escapes very rapidly through the cloth. The curd sink is an advantage in those cases in which it is desirable to remove the whey from the curd quickly, such as high acid curds which have to be hand stirred to firm the curd. The disadvantage lies in the work required to keep the sink and the large cloth clean.
+202. Matting or cheddaring+ is the distinctive feature of the Cheddar process. It is the piling and matting of the curd. Whether the curd is matted in the vat or in the curd sink, the process is practically the same. The object of cheddaring is three-fold: (1) to control the incorporation of moisture; (2) to control undesirable ferments, if present in the curd; (3) to develop the texture desired in the cheeses.
[Ill.u.s.tration: FIG. 38.--A cheese knife.]
After the curd in the vat has become matted so that the particles stick together, the ma.s.ses on either side of the central channel are cut crosswise into strips with a cheese knife (Fig. 38). The width of the strip depends on the water-content of the curd at this stage. The more water, the smaller should be the pieces of curd. This allows the whey to drain away much more rapidly. As soon as the strips of curd are cut, they should be turned over or stood on edge. A drain should be left along the middle line of the vat and on each side. This permits the whey to run away freely. If, on the other hand, the outlet is dammed up, the curd may become "whey-soaked." This produces a soft mushy cheese which sometimes is "acidy" or sour. After the curd is turned each time, all crumbs of curd broken off should be brushed underneath the ma.s.ses of curd so that they will mat with it. They should never be placed on top of the curd because they will not unite but will become dry and hard. If the crumbs are not kept brushed up, they become dry and will cause an open textured granular cheese and possibly lumps in the cheese. After the pieces of curd have been turned several times, and the whey has fairly completely drained away, they may be piled first two deep, then three deep and so on, the depth of the piling being gauged by the softness or amount of water in the curd and the temperature. The higher the curd is piled, the more water it will retain (a.s.similate), so that the amount of moisture in the curd is regulated by the size of the pieces into which it is cut and the rapidity and depth to which it is piled.
The curd should not be left too long from the time it is turned until it is turned again. This period is usually about ten to fifteen minutes.
The moister the curd, the more often it should be turned. In turning, care should be taken to keep the ends at the same temperature as the remainder. This can be done by piling them inside, thereby keeping them warm. There is a tendency for the ends of the pieces of curd to remain granular and so cause an open-textured cheese.
During the cheddaring process, the temperature should be reduced uniformly and gradually. If there is danger of the curd becoming too cold, the vat should be covered and a pail of hot water may be placed inside, if it is deemed necessary. The temperature of the curd should not be allowed to go below 85 to 90 F. If kept too warm, the curd will become soft and plastic, and if too cold, it will not mat together.
While the curd is being turned and piled, its physical properties are changing. The acid develops. When the cheddaring process is completed, the curd should be elastic, smooth and fibrous. The curd should have the close meaty texture desired in the cheese. If this step in the process is neglected, defects may appear later in the body, texture and flavor of the cheese. Attempts to pile the curd too fast result in a soft, mushy, open-textured product. Such cheese has mechanical holes, in which moisture collects, and so is likely to cause rot while curing.
If gas is detected either before or during the cheddaring process, the curd should be piled until the gas holes are no longer round but flat.
If the gas holes are not flattened or obliterated during this process, the cheeses will be very liable to puff on the shelves in the curing-room. The curd should be handled until the gas holes flatten out evenly, although this may require considerable time. At best, ga.s.sy curd will never produce the highest grade of cheese.
Cheddaring or piling the curd is not thoroughly understood by most cheese-makers. Because the moisture contains the milk-sugar, there is danger of having so much moisture present in the cheese that it will become sour from the action of the lactic acid-forming bacteria on the milk-sugar. A cheese may be sweet when made and later become sour because it contains too much moisture or milk-sugar. This is known as "shelf souring." For the proper cheddaring of a curd, it is necessary that it be properly firmed in the whey. If the moisture is not evenly incorporated, the cheese will have a mottled color. The pieces that have the more moisture will be lighter colored. If the proper amount of moisture is not incorporated, the cheese will be dry and hard, and if too much, soft and pasty.
+203. Milling the curd.+--The large pieces formed by the cheddaring process must be cut into small ones before the curd can be easily put into the hoop. This is called "milling." Properly milled curd can be salted evenly, cools more quickly and uniformly and can be distributed evenly in the hoops.
The proper time to "mill" the curd is determined by its physical condition. Some curds will cheddar much more rapidly than others, hence no definite length of time can be given. Curd, when ready to mill, should have a fibrous texture somewhat like the white meat of a chicken breast. The pieces of curd should split very easily. When cut, the curd should show a close, solid, smooth interior. The amount of lactic acid developed may vary within rather wide limits. The hot iron may show strings to 1 inch long. The acidity (by t.i.tration of the freshly separating whey) may be 0.45 to 0.65 of 1 per cent. If the curd has been properly made, that is, firmed up in the whey with the proper acidity so far, acid development during the cheddaring process will take care of itself. The physical condition remains the princ.i.p.al means of determining the time when the curd should be milled.
[Ill.u.s.tration: FIG. 39.--Gosselin curd-mill.]
[Ill.u.s.tration: FIG. 40.--Barnard curd-mill.]
[Ill.u.s.tration: FIG. 41.--Junker curd-mill.]
[Ill.u.s.tration: FIG. 42.--Harris curd-mill.]
There are many kinds and styles of curd-mills on the market. Gosselin, Barnard, Pohl, Junker, Victor, Harris are well-known kinds (Figs.
39-42). Some are hand, others power mills. Some of these tear the curd into pieces of unequal size, others cut it into uniform pieces. A mill that will do the work with the least possible pressure on the curd and which will cut it into small uniform-sized pieces is most desirable. The ideal mill should release the least fat and leave the curd in the best condition to receive the salt. It is impossible to run curd through any mill without exposing some fat on the freshly cut surfaces, and if the curd is put under pressure, more fat will be pressed out and lost.
Cutting in the mill, like cutting the curd after coagulation by rennet, may be called a necessary evil. There is an unavoidable mechanical loss which may be greater or less according to the mill used. If the curd has been properly handled so that the water in it has become thoroughly a.s.similated (properly incorporated), this loss will be reduced to the minimum. If the curd contains free moisture and many of the particles have soft interiors, a stream of white whey will run down the vat as the curd ma.s.ses are cut. Some samples of such white whey will test as high as 15 per cent fat. This not only causes a loss in yield but in quality of cheese, according to the amount of fat lost. White whey is an indication of loss of fat. If the proper amount of moisture is present and is so thoroughly incorporated in the curd that it can be separated only by evaporation, the ideal condition has been reached. While milling, the cut curd should be stirred as fast as milled to prevent matting again and to allow odors to escape. This stirring is usually performed with a curd fork (Fig. 43). At the same time the temperature will be lowered. The milled curd should be spread evenly over the upper three-quarters of the bottom of the vat. The flavor of the curd that has been made from tainted milk can be very much improved by stirring at this time so that air can enter.
[Ill.u.s.tration: FIG. 43.--A curd fork.]
A ga.s.sy curd, which has been held until the holes have become flattened, should be stirred very frequently during this stage to allow the gas to escape, thereby improving the flavor.
+204. Salting.+--Salt is added to Cheddar curd for several purposes: (1) for its taste; (2) to aid in the removal of the whey and to harden and shrink the curd; (3) to influence the fermentation by slowing down acidification, checking the growth of unfavorable organisms and delaying ripening. The salt should be pure. It should be coa.r.s.e-grained, because the large grains dissolve more slowly and permit its absorption to a much larger extent than the fine-grained salt. Salt that dissolves slowly is, therefore, to be sought for this purpose.
The following factors must be considered in determining the amount of salt to be used: (1) the amount of curd from the milk; (2) the percentage of water in the curd; (3) the acidity of the curd; (4) the particular market form of cheese desired. The custom of determining the quant.i.ty of salt by the weight of milk is an inaccurate practice. The amount of salt should be based on the amount of curd. If the amount of fat in the milk is known, a fairly accurate estimate of the amount of curd can be made. It would be more accurate to weigh the curd before salting, but this is not practicable or necessary to insure a good quality of cheese. The amount of salt varies from 1 to 2 pounds of salt to the curd from each 1000 pounds of milk.
The salt should not be added directly after milling because, at that time, it would cause a large loss of fat. After milling there should be time before salting for the freshly cut surfaces to dry or "heal over."
When first milled the curd has a dry harsh feeling; when ready to salt it will feel soft and mellow and some moisture can usually be squeezed out easily. Fifteen to twenty minutes from the time of milling are required before the curd is ready for the salt. When ready, the curd should be spread evenly over the bottom of the vat. The salt should be carefully weighed, and then applied, evenly, over the surface of the curd, in two or three applications. The curd should be thoroughly stirred after each application of salt. While the salt is being dissolved and absorbed, the curd should be stirred occasionally to prevent lumps from forming.
[Ill.u.s.tration: FIG. 44.--Wilson press hoop. _A_, complete hoop; _B_, bottom cover with wide f.l.a.n.g.e; _C_, top cover with narrow f.l.a.n.g.e; _D_, closed body; _E_, bandager.]
[Ill.u.s.tration: FIG. 45.--Fraser press hoop. _A_, complete hoop; _B_, bandager; _C_, follower; _D_, fibrous press ring.]
+205. Hooping the curd.+--When the salt has become dissolved and the curd as soft and mellow as before the salt was added, it is ready to be put into the hoop. Various sized hoops may be used, depending on the desired size of the cheese. Two types are the Wilson and the Fraser (Figs. 44, 45). With either type, a dampened press cloth should be cut just to fit the bottom of the hoop. A starched circle may or may not be used; if used, it should be placed on top of the press cloth. The bandage now commonly employed is the seamless one which comes in the form of a tube of various sizes for different sized hoops. The lengths of bandage cut for each hoop or cheese depend on the height of the cheese plus about one and one-half inches" lap on each end. The bandage, after being cut the desired length, is placed on the part of the hoop made to hold it, so that it is suspended about the side of the hoop and laps about one and one-half inches on the bottom. The bandage should be free from ravelings and placed squarely in the hoop.
The hoop is now ready to fill with curd. Enough hoops should be prepared to hold all the day"s curd as fast as it is ready. In order to have all the cheeses as nearly as possible of the same size, it is advisable to weigh the curd into the hoops. The curd may be measured into the hoops, but this is not so accurate. The curd may be dipped with a flat-sided curd pail or a curd scoop into the hoops (Fig. 46).
[Ill.u.s.tration: FIG. 46.--Curd scoop and pail.]
+206. Pressing the curd.+--The natural changes sought in the curd require a period of at least five hours between the time of setting (addition of the rennet) and the pressing of the curd. Less time than this involves loss in yield and quality of the cheese. In other words, the time requirement for these changes cannot be ignored. The object of pressing is not primarily to remove whey but to produce the physical conditions essential to ripening the cheese in a ma.s.s and put it in convenient form for handling. The whey should have been removed during the cooking and cheddaring. When ready for the press, the temperature of the curd should be about 80 to 85 F.; it should be brought down to this point during the milling, salting and hooping processes. If the curd is put to press too warm or too cold, the following results may be expected:
Too high temperature during pressing produces several faults, as:
(1) Favors the development of undesirable ferments.
(2) Causes excessive loss of fat.
(3) Gives the curd pieces a greasy surface so that they will not readily pa.s.s into a compact cheese. If a cheese is greasy, the bandages will not stick.
(4) Favors the formation of mechanical holes in the cheese.
(5) Causes "seamy" color in the cheese by the collection of fat between pieces of curd.
Too low temperature has its difficulties, such as:
(1) The pieces of curd will not fuse together.
(2) The rind does not form properly.
(3) It appears to cause mottled cheese.
[Ill.u.s.tration: FIG. 47.--Continuous pressure gang cheese-press.]