Manufacturing of Cheddar cheese
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The name Cheddar cheese originated because cheddar was first made in a small English village named Cheddar. Cheddar cheese has become so widespread that the term no longer refers to a cheese made in this village, however. The process of cheddaring makes cheddar unique when compared to other cheeses.
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[edit] Food ingredients used during manufacture
[edit] Milk
Generally, the milk is raw milk (whole or 3.3%). The milk must be "ripened" before adding in the rennet (see below). The term ripening here means allowing the lactic acid bacteria to lower the pH of the solution, which aids greatly in the coagulation of the milk.
[edit] Lactic acid bacteria
Lactic acid bacteria (LAB) are responsible for turning lactose into lactic acid, thereby reducing the pH of the solution. When the pH is lower, the protein is more easily precipitated. This is vital for the production of cheese curds that are later formed into cheddar.
[edit] Rennet/chymosin/rennin
Rennet is an enzyme that is collected from the stomach of a milk-fed calf. In more recent years, this enzyme is commonly produced by using modified bacteria and has adopted the name Chymosin and Rennin. This enzyme is responsible for the coagulation of the milk proteins to produce curds. Coagulation can also be achieved using acids, but the resulting cheddar will not be as high quality.
[edit] Equipment
This is not a comprehensive list of equipment, but includes some of the less mundane items commonly used in cheddar cheese making operations
Stainless steel wire knives
These knives are used to uniformly cut the curds at various points during the process. Basically a stainless steel frame with stainless steel wires, that will cut the curd cleanly.
Vat
Vats will vary depending on a variety of factors. Generally oval or rectangle shaped with hollow walls that are used for holding warm water to keep the curds at desired temperatures. This part of the vat is referred to as the jacket.
Milling machine
A milling machine is used to cut the matted curds that are formed during the cheddaring process. This allows the curds to be easily salted.
[edit] Ripening the milk
The milk is ripened by adding in a culture of LAB. Generally 1% starter culture is used by volume. The milk is done ripening when the acidity changes a significant amount. The best way to determine acidity is by measuring the titratable acidity using an acid-base titration. Acidity will raise anywhere from .01-.02% compared to the original milk. After addition of the starter culture, the milk is mixed thoroughly. Ripening may take anywhere from 30–60 minutes, depending on the time of year and the conditions under which it’s made.
[edit] Add rennet
Generally 3–4 ounces of rennet are added per 1000 pounds of mix. The rennet will serve to coagulate the milk protein and form curds. The vat must be mixed thoroughly after the addition of the rennet to ensure equal mixing, and it also helps to dilute the rennet to make it easier to spread around.
Pure water is used when diluting the rennet as any pH that is not near 7 will rapidly decrease the effectiveness of the rennet, as will chlorine. Thus, water with impurities will result in a vastly decreased yield of cheese.
[edit] Setting the curd
Once the rennet is added, the mixture must be allowed to set and form curds. The mixture is kept at around 84–88 degrees Fahrenheit. Generally temperature is controlled by flowing warm water through the jacket of the vat. Setting time varies, and allowing a proper amount of time is vital. It commonly takes anywhere from 30–40 minutes to set the curd.
The most common way to determine when the curd is set is by inserting a flat blade at a 45 degree angle into the curd and raising it slowly. If the curd breaks cleanly leaving a glassy fracture, it is ready for cutting. In a large cheddar manufacturing facility, this may also be tested using a viscometer.
[edit] Cutting the curd
The curd is cut into 1/4 to 5/8 inch cubes using stainless steel wire knives. A smaller cube size means the cheese will be lower moisture whereas a larger cube size will result in a high moisture cheese.
It is important that cutting time is minimized and that the cuts be clean. The best way to determine how efficient the cutting job was is to determine the fat content of the whey. The optimal level of fat content of whey is .3% fat or less.
The curds are handled gently after cutting to prevent fat and protein loss to the whey. The curd is prevented from sticking to the sides of the vat, but minimal agitation is desired. The curds are allowed to set again for 10–15 minutes. Fat and protein loss may affect the ability for the cheese to be considered cheddar cheese depending on the region where it is created (See Code of Federal Regulations for US standards)
[edit] Cooking the curd
The curd is cooked by adding hot water to the jacket of the vat (up to 102 degrees Fahrenheit). The curd is stirred constantly during this step to avoid uneven cooking or overcooking, and the cooking will only take 20–60 minutes. The whey's pH will be around 6.1–6.4 by the end of the cooking.
[edit] Draining the curds
Whey is removed from the curds by allowing it to drain out of the vat. A gate is generally present to prevent curds from escaping. When most of the whey is gone, the curds are raked to either side of the vat, allowing whey to drain down the middle of the two piles.
[edit] Cheddaring
Cheddaring is the unique step to making cheddar. It is a multi-step process that gives cheddar its unique flavor.
[edit] Setting
The curds are allowed to set for a few minutes. By the end of the setting, the acidity of the whey will be somewhere between .15 and .17.
[edit] Cutting loaves
"Loaves" of curds are cut about 6 inches wide along each side of the vat. After 10 minutes, the loaves are turned and stacking begins.
[edit] Stacking loaves
Every 10 minutes when the loaves must be turned, they are stacked. The first time, two loaves are stacked together. The next time the loaves are turned, two stacks of two are put together. When the stacks get large enough (generally 4 high), stacking stops but the loaves are still turned every 10 minutes. This process is complete when the acidity of the whey is between .5 and .7, so it is checked constantly.
[edit] Milling the curd
When the turning process is complete, the loaves must be cut down into a size that fits in the mill. The mill will cut the matted curd into about 1/2 inch pieces. During this process, the milled curds are constantly stirred to avoid re-matting.
[edit] Salting
When all of the curd is milled, salt must be added. The amount of salt varies, but it will be between 1% and 3% by weight. The salt must be mixed thoroughly. Salt will help remove some of the whey from the cheese which will lower moisture content. Salt will also add to the flavor of the cheese.
[edit] Packaging and pressing
The curds are placed into molds that will be used to press the curds and form the blocks of cheddar. At this point, the cheddar cheese will be aged.
[edit] Aging
Mild cheddar is generally only aged for 1–2 months, but sharp cheddar can age for a year or more. Aging time depends on the type of cheddar being made.
