+193. The milk.+--It is the usual practice to deliver the milk to the cheese factory each morning (Fig. 29). The night's milk is cooled and kept clean and cold until delivered at the factory. It is advisable not to mix the cold night's milk and the warm morning's milk, but to deliver them in separate cans to the cheese factory at the same time. The milk is weighed, sample for fat test taken and then run into the vat (Fig.

30). The receiving or taking in of the milk is one of the most important parts of the cheese factory work. It is practically as important as the actual manufacturing of the cheese.

+21 CHEESE.+ This card must remain with lot ........... from the milk room until the finished product is ready to leave the building, then it should be handed to instructor.

+MAKING+ Day and Date ................................ Vat ...............

+Milk

Used+

+Milk+ ........................

............

Appearance of Milk ................

........................

............

Odor ..............................

........................

............

Taste .............................

Total pounds

............

Weather conditions ................

------------------------+------------+------------------------------------ ...........% fat ...........lbs. fat

+Starter+

Kind used..........................

....% solids not fat ....lbs. s.n.f.

Flavor.............................

Acidity............................

....% casein ....lbs. casein.

Amount used.......... % used.......

-------------------------------------+------------------------------------ +Time of Minutes+

+% Acid+

+Temperature+ adding starter }......

_In Milk_

of milk when received }

when starter added...

adding rennet }......

when received............

when rennet added....

}

before adding starter....

when whey removed....

coagulation }......

after adding starter.....

at pressing..........

}

when rennet added........+---------------------- cutting }......

+Rennet Test+ }

when milk received...

turn'g on steam }......

_In Whey_

after adding starter.

}

after curd is cut.......

when rennet added....

turn'g off steam}......

at dipping.............. +---------------------- }

at packing..............

+Hot Iron Test+ dipping }......

at milling

at dipping...........

}

at milling

at packing...........

packing }......

at salting

at salting...........

} +--------------------------+---------------------- milling }......

+Condition of Curd+ }

salting }......

when cut........................................

}

when packed.....................................

hooping }......

when milled.....................................

}

when salted.....................................

pressing }......

when pressed....................................

} +------------------------------------------------- dressing }......

Amount per

+Color+

+Rennet+

+Salt+

1000 lbs. milk

.........

..........

........

Total time from }....

setting to pressing}

Total Amount

.........

..........

........

------------------------+-------+-----------+---------+----------+-------- % fat in lbs. fat estimated

If comments are added on .......whey ....... so lost.

reverse side, put cross here............

% of total milk

Work and ....fat lost in whey

Observations by.........................

a.s.sisted by...............................................................

-------------------------------------------------------------------------- +YIELD+ Day and Date......................... Time.......................

Serial Weight of cheese when removed from press to curing room,......lbs. No....

lbs. milk for Kind of cheese made lbs. cheese per ..........one lb. cheese. ................... ......100 lbs. milk lbs. cheese for one No. of cheese made. lbs. cheese for one ..........lb. fat in milk. ................... ....lb. total solid If comments are added on reverse side put cross here...........

Work and observations by..................................................

-------------------------------------------------------------------------- Arranged by W. W. Hall.

[Ill.u.s.tration: FIG. 30.--Receiving, sampling, weighing and running the milk into the cheese vat.]

Any milk high in acid or with a bad flavor should be avoided. It is often bad policy to reject the milk, for a neighboring factory will accept it and the factory not only loses the milk but also the patron.

Factories should have an agreement to prevent this. The acidity can be determined by the acid test, but the detection of flavors must be made by the cheese-maker himself with the aid of smell and taste. Many of the bad flavors in the cheese can be traced to the poor quality of the milk. One of the worst qualities in milk and cheese is the presence of gas-producing organisms.[88] Any milk which shows ga.s.sy fermentation should be rejected, for it is difficult to make cheese from this and at best there will be a large loss during the manufacturing process. The cheese may have a bad flavor and develop "pin-holes" and in extreme cases may puff up like a ball. The person receiving the milk should talk to the farmers or dairy-men about the proper care of the utensils and milk. He must see that the cans are kept clean. One very bad practice is to deliver milk and take home whey in the same cans. The cans, as they are brought back from the cheese factory full of whey, are often left in the barn or near a hog-pen until the whey is fed. Unless such cans are emptied immediately on returning to the farm and then rinsed out with cold water, thoroughly washed and scalded, bad flavors may develop in the cheese. It is thought that this causes "fruity" or sweet flavor, which resembles that of fruits such as raspberries, strawberries or pineapples.

+194. Ripening the milk.+--A slight development of acidity is required: (_a_) to obtain the formation of a firm curd; and (_b_) to establish immediate dominance of a desirable type of lactic organism which will produce the large amount of acid required later in the cheddaring process. The development of this acidification before the addition of rennet is known as the ripening of the milk. The extent of ripening advised by different schools of makers has varied from an acidity of 0.20 of 1 per cent or even slightly higher percentage t.i.trated as lactic acid, to about 0.17 of 1 per cent as now preferred by some of the most successful groups of workers. The ripeness of the milk can also be determined by the use of the rennet test.

The milk may be ripened by allowing the lactic organisms already present in the milk to develop naturally. This requires considerable time and while the lactic acid-forming bacteria are developing, other and undesirable fermentations may be taking place, so that the good results which should follow the uninterrupted development of the lactic acid-forming organisms are lost. Starter is commonly used to produce the desired ripening of the milk. (For the preparation of starter see Chapter IV.)

[Ill.u.s.tration: FIG. 31.--Steel cheese vat.]

Some makers put the starter into the empty vat (Fig. 31) and add the milk as it is received; others add it to the total volume of cold milk and then begin to heat it. Whenever the starter is used, it should be strained to remove lumps. These lumps might cause a mottled color in the cheese. The best practice calls for an acidity or a rennet test of the mixed milk after it has been brought to the setting temperature in the vat. With milk tested at this stage and the volume of milk in the vat known, the cheese-maker is able to calculate closely the amount of starter needed. When the quant.i.ty of starter to use is in doubt, the amount added should be under rather than over the estimate, since the need of more can be determined by making frequent rennet and acid tests in a very few minutes without damage to the cheese. If too much starter has been used, acid or sour cheese is usually obtained, with loss in market quality.

An over-development of acidity at any stage of the manufacturing process affects the flavor, body and texture, color and finish of the cheese.

The product is known as a sour cheese, and can usually be identified by its sour taste and smell. A sour cheese while curing will seldom develop a normal Cheddar flavor and the texture will be hard and harsh and very brittle. The body will not be smooth but harsh and grainy. The over-development of acid will show by fading or bleaching the color. A sour cheese usually leaks whey for a few days after being placed on the curing-room shelves.

Ripening the milk is one of the most important parts of cheese-making.

Proper ripening places the acid fermentations under the control of the cheese-maker so that he may know what results will follow his labors.

The operator can control the acidity while ripening the milk, but after the rennet is added all control of the acidity is lost. From that time, the moisture must be regulated in proportion to the acidity.

Before setting, the milk should be ripened to such a point as to leave at least two and one-half hours from the time that the rennet extract is added until the acid development has reached the stage at which it is necessary to remove the whey. By the acid test the milk may vary from 0.16 to 0.18 of 1 per cent, but no definite statement can be given for the rennet test. This can be determined only by comparison from day to day. For operation of rennet test see Chapter V. During this period of two and one-half hours, the curd is formed, then cut, and the temperature is raised from 84 or 86 F. (the temperature at which the rennet extract is added) to about 98 to 100 F. The curd must be kept agitated so that the particles will not mat together; this is necessary to obtain sufficient contraction of the particles of curd with the proper reduction of water-content. If the milk becomes too ripe (too sour) before the rennet is added, there will not be sufficient time for these steps to take place naturally. In such cases special means are required to firm the curd. These result in a loss of both quality and quant.i.ty of cheese. On the other hand, if the milk is not ripened, but the rennet extract added, regardless of the acid development, one of the important natural forces for expelling the moisture is lost. The time required for the particles of curd to contract is much prolonged, the expulsion of whey is usually inadequate and the curd remains in a soft or wet condition. Using too much starter is almost equally bad, for although it hastens the making process, it produces a sour or acid cheese.

+195. Setting or coagulating.+--The milk for Cheddar cheese-making is heated to 86 to 88 F. or occasionally a slightly lower temperature.

This temperature is found by experiment to give the texture of curd most favorable for the desired results. Although some cheese-makers work as low as 84 F., the texture of such curd is too soft and coagulates too slowly. The very slight change of 2 F. produces curd which coagulates more quickly and is tougher and firmer.

If the cheeses are to be colored, the color should be added after all the starter. It should be thoroughly and evenly mixed with the milk to insure an even color in the cheese. If the color is added before the starter, there are likely to be white specks in the cheese, on account of the coagulated casein in the starter. The amount of color to use depends on the tint desired in the cheese. It varies from 1/3 to ounce to 1000 pounds of milk for a light straw color to 1 to 2 ounces for 1000 pounds of milk for a deep red color.

Enough rennet should be used to produce a curd firm enough to cut in twenty-five to thirty-five minutes. The necessary amount will vary with the strength of the rennet extract itself, with the acidity, the temperature, the nature of the lot of milk, and with the individual aims of the maker in which he adjusts the other factors to his preferences as to rapidity of rennet action. With the usual commercial extract, the needed amount ranges from 2.5 to 4 ounces for 1000 pounds of milk. As for all varieties of cheese, the rennet extract should be diluted in cold water at about one part rennet to forty parts water and thoroughly stirred into the milk. (See Chapter V.)

+196. Cutting.+--The object of cutting is to obtain an even expulsion of the moisture from the curd. The curd is cut as soon as it becomes firm enough. To determine this, various tests may be used. Some operators test it by pressing it away from the side of the vat, considering it ready to cut when it separates cleanly from the metal. The test most commonly used is to insert the index finger obliquely into the curd, then to start to split the curd with the thumb and finally to raise the finger gently; if ready to cut, the curd will split cleanly over the finger and clear whey will separate to fill the opened crack. Another arbitrary but more or less satisfactory rule is that the time from adding the rennet until cutting should be two and one-half times that from the addition of rennet until the first sign of coagulation is observed.

The condition of the curd itself is the best guide to show when it is ready to cut. The condition of the curd is constantly changing, so that in a large vat, if the cutting is not begun until the curd is in the best condition, by the time the last of the curd is cut it will be too hard or firm. It is better to begin while the curd is a trifle too soft so that the cutting will be taking place while the curd is at the proper stage. At best the last of the curd may become too hard. If too hard, it will break ahead of the knife instead of cut. Breaking causes more fat loss than cutting because there is more surface exposed and hence more fat globules. The softer the curd when cut, the quicker and easier the moisture can be expelled.

If the curd is cut when soft, care must be exercised not to stir it too hard immediately after cutting. Soft curd breaks very easily. When the curd is cut soft and then stirred vigorously, there is a larger loss of fat than when the curd becomes hard before it is cut.

Two knives are used to cut the curd. (See Fig. 11.) These knives may have either wire or blades for cutting. The s.p.a.ce between the wires or blades varies from 5/16 to inch. Knives used should have blades or wires close enough together to cut the pieces as small as desired, without a second cutting. When the curd has to be cut a second time it usually results in pieces of uneven sizes, because the pieces already cut cannot be evenly split in two.

One set of knives has horizontal and the other perpendicular blades or wires. The curd is cut the long way of the vat with the horizontal knife and lengthwise and crosswise with the perpendicular knife so that the result is small cubes or oblongs of curd. Some cheese-makers prefer to use one knife first and some the other, but the result should be a curd cut into pieces of uniform size. The smaller the particles of curd or cubes are cut, the quicker the curd will firm up or cook. If not cut uniformly, the changes taking place later in the curd particles will not be uniform,--the small pieces will be hard and dry while the large ones will be soft and mushy.

[Ill.u.s.tration: FIG. 32.--The proper way to put the knife into the curd.]

Care should be taken to let the knife cut its way into the curd (Fig.

32). If the knife is pushed into the curd, it will break it and cause a large loss of fat. The same is true when taking the knives out of the curd. The loss of fat due to cutting is very similar to the loss of sawdust when sawing a board. It may be considered a necessary evil. The loss due to cutting is about 0.3 of 1 per cent of fat in the whey and the loss of casein about 0.1 of 1 per cent in the whey.

[Ill.u.s.tration: FIG. 33.--Acme curd rake.]

[Ill.u.s.tration: FIG. 34.--McPherson curd agitator.]

+197. Heating or "cooking" the curd.+--After the curd is cut, the pieces (cubes) rapidly settle to the bottom of the vat and tend to mat together. To prevent this, the curd must be kept stirred. When stirring first begins, the curd is soft and very readily broken. Some cheese-makers prefer to stir by hand for the first few minutes after cutting, while the curd is soft. The importance of careful handling can hardly be over-emphasized. No matter how well the curd has been cut, if the stirring is performed in a careless manner in the early stages, it will be broken into uneven sized pieces and a considerable loss of fat will result. A wooden hay rake or a McPherson curd agitator (Figs. 33, 34) may be used to stir the curd. Mechanical curd agitators are used in some cheese factories. There are several makes. (See Fig. 35.) These agitators save much hand labor, although some stirring by hand must be done in connection with them. The mechanical agitators do not stir the curd in the corners of the vat; this must be done with the hand rake. It is the usual practice to stir the curd immediately after cutting for five to ten minutes before the mechanical agitators are used. This is necessary to give the curd a slight chance to firm as the mechanical agitators tend to break it up. After cutting, a thin film forms on each piece of curd. This film holds the curd particles, especially the fat.

Breaking the films on the cubes causes loss of fat. If lumps form at the early stage, by matting of the curd particles, violent stirring is required to separate them. When such lumps are broken up, new cleavage lines are formed with loss of fat, because the original films surrounding the soft curd fuse so firmly that the curd cubes do not separate but actually break. New surfaces are thus formed with consequent fat loss. Rapid shrinkage with expulsion of whey takes place during the first few minutes of gentle agitation. Before any heat is applied to the vat, sufficient whey should have separated or formed to float each piece of curd separately. This will require ten to fifteen minutes from the time of cutting.

[Ill.u.s.tration: FIG. 35.--Two types of mechanical curd agitators.]

Thus far the first of three distinct factors which expel the moisture from the curd has been considered: (1) the action of the rennet; (2) the development of the lactic acid; and (3) the application of heat. These forces must have time to act naturally. If heat is applied too soon after the curd is cut or if the temperature is raised too rapidly, it causes a thick film to form on the pieces of curd which interferes with the escape of the whey. The outside of the curd becomes firm but the inside remains very soft. A curd which is cooked on the outside only feels firm when stirred by hand in the whey, but when a handful is squeezed the soft centers are noticed. To firm such curd ma.s.ses requires violent stirring, which will break the thick tough film. This allows the moisture to escape and also increases the fat loss. The rapidity of heating should depend on the condition of the curd and the amount of acid developed. The heat should keep pace with these. When ready to raise the temperature, the least amount of steam possible should be allowed to pa.s.s through the valve. This should raise the temperature very gradually. If heat is applied too quickly at first, it will cause the curd to lump. A safe rule is to raise the temperature one degree in the first five minutes after the steam has been turned on. The heating should progress slowly until the whole ma.s.s of curd in the vat has reached a temperature of 90 to 92 F. The usual temperature to which the curd is heated or cooked is 98 F. to 100 F. The lower the temperature that can be used and properly firm the curd, the better will be the body of the cheese. If the curd is heated too high, it will become hard, which causes a dry hard "corky" cheese. After this temperature has been reached, there is not such a tendency for the curd particles to stick together nor are they so easily broken in stirring.

It should require, under normal conditions, not less than thirty to forty-five minutes, from the time the steam is turned on, to raise temperature of the curd from the setting temperature to that necessary to "firm" the curd. If a shorter time is allowed to raise the temperature, the curd will not have opportunity to contract naturally.

The temperature required to expel the moisture properly varies with the percentage of fat in the milk. If rich in fat (4.5 to 5.5 per cent) milk requires a temperature of 98 to 104 F. to firm the curd, while the same result can be accomplished with milk testing 3.0 to 3.5 per cent fat at a temperature of 94 to 96 F. A higher temperature is needed in winter than in summer because the milk is usually richer in fat. In a water-jacketed vat, allowance must always be made for the rise in temperature due to the water surrounding it. The water may be removed if there is danger of the temperature going too high. However, it is better to gauge the heat so that the water may be left, as this helps to hold the curd at an even temperature, especially in cold weather. In a steam-heated vat there is not so much danger of the temperature running up.

The stirring must be kept up after the steam has been turned off until the curd has reached such a stage of contraction that it will not readily pack or mat in the bottom of the vat. After the curd reaches this stage it may be allowed to settle to the bottom and stirred only occasionally until it is time to remove the whey. If the cheese room is not warm and there is danger of the curd cooling, a cover should be placed on the vat. The curd should not be allowed to settle for more than fifteen minutes without stirring to keep each piece separate. This is necessary to obtain uniform contraction of all curd ma.s.ses.