(1) Weak rennet extract or too small an amount.

(2) Low temperatures due to inaccurate thermometers.

(3) Pasteurized milk.

(4) Presence of abnormal bacterial ferments.

(5) Presence of preservatives.

(6) Heavily watered milk.

(7) Use of badly rusted[29] cans.

(8) Milk containing small amounts of casein or calcium salts.

_Causes of uneven coagulation:_

(1) Uneven temperature of the mix in the vat, due to lack of agitation.

(2) Uneven distribution of the rennet extract.

(3) Adding rennet to vat too soon after heating, while the sides and bottom are still hot, causes curd to stick to sides and bottom of the vat making cutting difficult.

(4) Sloshing after the milk begins to thicken breaks the curd and causes it to whey off.

+98. The curdling period.+--The time allowed for rennet action also affects the texture of the curd. The enzymes of rennet (rennin and pepsin) do not cease acting with the thickening of the milk. In many cheeses, the handling process begins as soon as the curd has become solid enough to split cleanly before a finger thrust into it. If let stand further, the same curd ma.s.s will continue to harden with the progressive separation of whey; this shows first as drops ("sweating") on its surface, which then increase in number and size until they run together and form a sheet of whey. The limit of such action is difficult to measure. The solidifying process ceases in a period of hours. The further action of the enzymes is digestive in character and goes on slowly. It requires a period of weeks or even months to accomplish measurable results at the working temperatures in use in the trade.

Other ripening agents with more rapid action intervene to shape the final result. It follows that the rennet factor in the ripening changes found at the end of the period is almost negligible for most varieties of cheese, although it appears to be measurable in some varieties.

+99. Cutting or breaking[30] the curd.+--As soon as curd is formed, separation of whey begins upon the surface and perhaps around the sides of the vessel. This is accompanied by shrinkage and hardening of the ma.s.s. If the curd remains unbroken, the separation is extremely slow. In cheese-making practice, such curd ma.s.ses may be dipped at once into hoops as in Camembert, dumped in ma.s.s into cloths for drainage as in Neufchatel or, as in the larger number of cheeses, cut or broken in some characteristic manner. After the curd ma.s.s is firm, the rate at which subsequent changes take place depends largely on the size of the particles into which the curd is cut. The smaller the particles, the quicker the water is expelled. Consequently the development of the acidity and other changes take place more slowly. For this reason the curd should be cut into pieces of uniform size. If the work is not properly performed, the pieces of curd of various sizes will be at different stages of development. The fine particles will be firm and elastic while the larger particles are still soft and full of whey and may be developing too much acid. The knives should be inserted into the curd obliquely so that they will cut their way into the curd and not break it. The horizontal knife is used lengthwise of the vat and cuts the curd into layers of uniform thickness. The perpendicular knife then is used lengthwise and crosswise of the vat. It first cuts the curd into strips and then into cubes. The knives may have wire blades or steel blades, some operators preferring one and some the other.

Whichever is used, the blades should be close enough together to give the fineness of curd desired.

After the knife pa.s.ses through, the cut faces quickly become covered with a smooth coating, continuous over all exposed areas. This surface has the appearance of a smooth elastic coating or film. This can be seen by carefully breaking a piece in the hand. It is this film which holds the fat within the pieces of curd. If the film is broken, some of the fat globules are lost because the rennet extract acts only on the casein and that in turn holds the fat. All the fat globules which come in contact with the knives as they pa.s.s through the curd will be left between the pieces of curd and will pa.s.s off in the whey. If care is exercised in cutting, the loss of fat will be confined to what may be called a mechanical loss. This is similar to the loss of the sawdust when sawing a board. This loss in American Cheddar is about 0.3 per cent and cannot be avoided. If it is greater than this, it is due to negligence on the part of the cheese-maker or the poor condition of the milk. The cutting of the curd into small pieces may be considered a necessary evil. If the moisture could be expelled from the whole ma.s.s without disturbing it, this fat loss could be prevented. The cutting, breaking or turning should be done with the greatest care, that the loss may be as small as possible.

+100. Curd knives.+--For cutting curd, special knives have been devised (Fig. 11). They consist of series of parallel blades fixed in a frame to make cuts equidistant. The blades run vertically in one, horizontally in another. They are s.p.a.ced according to the demands of the variety of cheese to be made. Wires stretched in a frame take the place of blades in some makes of curd knife.

[Ill.u.s.tration: FIG. 11.--Blade and wire curd knives: horizontal, perpendicular, horizontal, perpendicular.]

+101. Heating or "cooking."+--Curdling by rennet has already been shown to be markedly hastened by moderate heating. After the coagulum or curd is formed, the making process may be completed without the application of further heat, as in Neufchatel, Camembert and related forms (Fig. 12) and in some practices with Limburger. In other forms and especially in the hard cheeses in which cutting of curd is a prominent part of the process, the curd after being cut is reheated or "cooked." The cooking process hastens the removal of the whey, thus shortening the time required to reduce the water-content of the ma.s.s to the percentage most favorable for the type of cheese desired. The process also produces marked changes in the physical character of the curd ma.s.s. With the rise in temperature the casein becomes elastic first, then approaches a melting condition and a.s.sumes a tough, almost rubbery consistency. The final texture is the result of the combination of the amount of rennet added, the temperature, the acidity reached during the process, and the final water-content of the ma.s.s.

[Ill.u.s.tration: FIG. 12.--The heat relation. See pages 77 and 87.]

+102. Draining+ (including grinding, putting into hoops or forms and pressing).--The reduction of the water in the curd begins almost as soon as the curd becomes firm. It is aided by cutting or breaking, by the retention of the heat applied before renneting and by the secondary heating or cooking used in making certain groups of cheeses. In many varieties special apparatus is provided in the form of draining boards, draining racks or bags to hasten the removal of the whey as fast as it separates. The draining process continues until the cheese has reached its final form and weight. The intervening process of matting in the Cheddar group involves a combination of a souring process with the removal of whey, during which the cubes of curd become fused into semi-solid ma.s.ses. If such ma.s.ses are formed, they must be ground up before the cheese can be given its final form in the hoop. The draining process, therefore, may take any one of many forms varying from the direct transfer of freshly formed curd into hoops in which the entire draining process is completed, to an elaborate series of operations which end in pressing curd drained to approximately its final condition before it is placed in the hoop.

+103. Application to cheese.+--From the discussion of these factors, it is evident that the cheeses produced will differ widely with the differences in manipulation. If one considers essential const.i.tuent substances separately, the water-content of the finished product is found to vary from 30 per cent in Parmesan to 75 per cent in cottage cheese. The fat-content runs from a trace in some varieties to 60 per cent in some cream cheeses. The texture of the casein, which gives character to the product, varies from the tough or glue-like consistency of freshly made Swiss to the b.u.t.tery condition of a cream or Neufchatel cheese. Inside such limits the tastes of different peoples have led to the manufacture of many kinds of cheese. Each of these varieties represents some particular combination of curd-making factors and ripening conditions which produces a cheese suited to the taste of the maker and consumer of that country or community.

CHAPTER VI

_CLa.s.sIFICATION_

The literature of cheese-making contains reference to more than 500 names for varieties of cheese. Many of these can be thrown readily into great groups or families in which there are variations in unessential detail without modifying the characteristic texture and flavor of the product. Many varietal names are attached to the product of single factories or factory groups. Such varieties frequently differ only slightly in size or shape, or in stage of drainage or of ripening, from widely known varieties or other similar local forms. The descriptions recorded for such varieties commonly emphasize minor differences in manipulation without showing differences in essential factors. Vessels of particular size are prescribed to be made of wood, earthenware, or of a special metal. These details specify the exact size and shape of hoops, the use of particular styles of cutting or breaking instruments and of certain stirring tools, the material and construction of mats and draining racks.

The descriptions themselves are very commonly inadequate. The variable factors in cheese-making are fat-content of the milk, acidity, temperature of setting, amount of rennet, time allowed for curdling and the method of draining the curd. The differences in practice lie, with few exceptions, in the amount or intensity of particular factors, not differences in kind or quality of treatment. Such contrasts are quant.i.tative, not qualitative. A great number of combinations is possible by small variations of these factors.

Varieties selected as types of groups give marked contrasts in character, but comparison of large numbers of forms shows that almost every gradation from group to group can actually be found. Within groups frequently the same physical results in texture and flavor can be obtained by combinations or adjustments of factors for the purpose of offsetting or counteracting the effects of one change in practice by the manipulation of other factors. In ripening, an equally large range of practices makes possible the development of very different qualities in mature cheeses from the same lot.

Only a few of the large number of described varieties have obtained even national importance; fewer still are known outside the country of origin. In spite of the success of special products when properly advertised, the largest place in the market is clearly accorded to the standard forms which are widely known.

+104. Basis of cla.s.sification.+--A series of these widely known forms has been chosen as typical of groups in a system of cla.s.sification adapted from the French of Pouriau. No completely satisfactory scheme of cla.s.sifying all of these varieties has been devised. The grouping proposed here is based on the principles of curd-making already discussed together with consideration of the ripening processes to be discussed with each group. The factors that actually influence the quality of the final product are separated as completely as possible from non-essential operative details.

The common use of the terms "soft" and "hard" cheese is based on the single arbitrary fact of texture. The term "semi-hard" cheese may be conveniently applied to a miscellaneous group of unrelated families which are intermediate in texture between such soft forms as Neufchatel or Camembert and really hard cheeses like Cheddar or Parmesan. Although these terms are not made the main basis of the proposed grouping, their application to sections is indicated. Cla.s.sification based on the essential facts of manufacture is, however, really helpful.

a.n.a.lYTICAL TABULATION OF GROUPS

Section I. Cheeses with sour milk flavor only (Eaten fresh).

(Soft cheeses 45 to 75% water) PAGE

1. Curdled by souring, Cottage cheese and its allies in America, many related varieties in Europe 90

2. Curdled by souring and rennet--the Neufchatel group 95

a. Skim--Skim-milk Neufchatel 105

b. Part skim to whole milk--American or Domestic Neufchatel 106

c. With fat added--the cream cheeses of the Neufchatel group (both American and European)--such as Cream, Gervais, Malakoffs, etc. 108

Section II. Cheeses ripened.

Subsection A. Soft cheeses (40 to 50% water).

1. Curdled by souring, heated, then ripened.

Hand cheese, Pennsylvania pot cheese, Harz, etc. 112

2. Curdling by souring and rennet, ripened

Ripened (French) Neufchatel 114

3. Curdled primarily by rennet.

a. Ripened by mold--Camembert, Brie and their allies 117

b. Ripened by bacteria.

* Made from soft or friable curd--d'Isigny, Liederkranz, etc. 134

** Made from firm or tough curds--Limburger and allies 139

Subsection B. Semi-hard cheeses, firm, well-drained (38 to 45% water)

a. Curd not cooked, ripened by molds.

* Made from friable curd--Roquefort 150