Cookbook:Cheese

| Dairy

Cheese is a dairy product made from the curdled milk of various animals (most frequently cows, but often goats, sheep, and water buffalo). In some locations, as a response to the loss of diversity in mass-produced cheeses, a cottage industry has grown up around home cheesemaking.

Production
All cheeses are made by curdling milk to separate the solid fat and protein from the liquid whey. Milk is a suspension of many components in water, including sugars, fat globules, proteins, and more. Most salient to the cheesemaking process are the fat globules and a group of proteins called caseins. In plain milk, caseins are grouped together into bundles called micelles, held together by calcium with a bunch of negative charges on the outside. These negative charges prevent the bundles from all clumping together, which keeps them suspended in the milk. Interfering with the negative charges and/or disrupting the casein micelles causes the proteins to bind together in a network, trapping the fats and separating them out from the liquid portion. These curds are then processed into cheese. Now, there are multiple ways to go about these processes, and the varied combinations of ingredients and techniques are what generates the sheer variety of cheeses available across the world.

Culturing
When making some varieties of cheese, you start out with a culturing step much like when making yogurt. Here, the milk is warmed and (often) inoculated with specific strains of "starter" and "finishing" microbial cultures. This mixture is kept warm for a period to allow the starter cultures to begin fermenting the milk, which contributes both flavor and the acidity needed to help curdle the mixture in subsequent stages. Higher temperatures cause faster fermentation (to a point) and help weaken the casein bundles. The finishing cultures will start playing a bigger role in later stages (e.g. aging) and contribute to the specific characteristics of the cheese.

Curdling
While several stages of cheesemaking are optional, depending on the desired outcome, the curdling stage is required for every kind of cheese. This is achieved through any combination of acidity, temperature, and enzymes. In direct acid cheesemaking, a large amount of acid like citrus juice or vinegar is stirred into heated milk, which causes curds to rapidly form. Alternatively, the addition of rennet—a mixture of protein-cleaving enzymes —to cultured milk chews off the negatively-charged portions of the casein micelles, which similarly disrupts the proteins and causes a stable curd network to form.

Cutting
After the curd network forms, the curd may be cut into small pieces order to drive out more moisture and solidify the texture—this can be done with a variety of tools such as a knife or harp. The smaller the pieces, the more whey can be lost through surface area and the drier the final product—some curds are cut to the size of rice grains, which tends to produce hard cheeses.

Cooking
Once cut, curds can be heated to induce further changes. For example, slowly stirring and heating the curd for a period further denatures the protein, causing it to shrink and release more water —this too helps decrease the moisture of the final product. Heating may also help activate some microbial cultures that were added earlier, preparing them for the aging process—one example of this is the gas bubbles formed from heating the bacteria used to make Swiss cheese. A few cheeses are formed by heating and stretching the curds at 60°C (140°F), making an elastic and sometimes stringy final product that can be shaped by hand (e.g. mozzarella, provolone).

Draining
In order to fully separate the curds from the way, the cheesemaker must drain them. The most basic way to do this is by gravity, where the curds are transferred to a mesh or perforated container and let drip for anywhere from hours to weeks. This removes relatively little moisture, often yielding a softer, moister cheese like brie. In order to remove more moisture, the curds must be pressed —this can be done by stacking the curds in layers, topping them with weights, or using pressing machines.

Forming
If it has not already taken place during the cooking or draining stage, the curd must be shaped to give it its final form. A variety of forms are available in different sizes, shapes, and materials.

Aging
Unless making fresh cheese (e.g. ricotta), the last step in the cheesemaking process is aging or ripening. In this stage, the shaped cheese is allowed to rest in a controlled environment, where it is carefully tended to—sometimes for years —in order to ensure correct development. It is here that cheeses start taking on their final distinct character, adopting a variety of flavors, textures, and appearances according to the steps taken in prior stages.

During ripening, the microbial cultures introduced earlier continue to act, breaking down the fats and proteins into smaller molecules. If added before curdling, the cultures will work homogeneously from the inside-out, creating a uniform texture throughout. On the other hand, if cultures are introduced to the outside after forming, they will break down the cheese from the outside-in, often creating a microbial rind.

The cheeses must be closely monitored and tended to during this stage. One key task is to regularly turn the cheese, which controls microbial growth and evens the shape. The cheese may also be washed or brined. It is also important to note and control any undesired microbial growth or pest infestations such as mites or maggots—infected cheeses must be discarded and prevented from contaminating the rest.

Salting
Salt may be added to the curds at varying points during the cheesemaking process, and in varying forms. In some types of cheese, the curds or molded forms are simply seasoned with salt crystals after draining. Other cheeses are salted by soaking in or washing with brine. Both methods remove further moisture from the curds, helping preserve it and regulating the type of microbial growth possible. It also contributes flavor of its own and helps enhance the final flavors of the cheese.

Characteristics
A huge number of factors come into play when determining the ultimate final characteristics of a cheese, ranging from diet of the animal producing the milk to the final moisture content, microbial strains, and much more. These factors and the specific ways in which they are combined are how we get the large variety of cheeses available today.

Rind
Aged cheeses can either develop their own rind or have one applied to the exterior. In bloomy rind cheeses, microbes grow on the outer layer of the cheese and develop into a soft, edible rind. Another variety—the washed rind—is made by repeatedly applying a brine to the outside of the cheese. Inedible rind varieties include wax, which holds in moisture very well,

Color
Unless they are colored, cheeses tend to be a creamy or mild yellow color that darkens over the course of the aging process. If a stronger yellow/orange color is desired, annatto may be added to the milk before curdling.

Texture
Ultimately, the texture of a finished cheese depends on the moisture content and the enzymatic activity of the microbes breaking down the fat and protein in the curd. Unripened, fresh cheeses tend to have a higher moisture content and softer texture.  On the other hand, cheeses like parmesan that have been aged for a long time become much drier and harder. 

Additionally, some cheeses melt well when heated—these tend to be rennet-based cheese with high to medium moisture levels, which have stable but not-too-tangled proteins. In acid-curdled cheeses like paneer, the proteins are tightly tangled together and cannot melt.

Flavor
There are as many flavors of cheese as there are varieties. Fresh cheeses tend to be very mild in flavor, though some are tangy if significantly cultured before curdling. On the other hand, aged cheeses develop a wide range of flavors and aromas from the microbial breakdown of nutrients. Initially, proteins are broken down into amino acids, which all have their own flavor profiles. Over time, these amino acids are then broken down into strong-smelling amines, and eventually even smaller, diverse flavor molecules. A similar process takes place with fats, and low-fat cheeses tend to be less flavorful and aromatic.

Selection and storage
Each variety of cheese will have its own individual criteria for selection. Storage-wise, the shelf life of cheeses is highly variable—low-moisture and long-aged cheeses keep on the order of weeks, while soft and fresh cheeses may only keep for a few days. No matter what, cheese should be stored in the fridge, well-wrapped to prevent moisture loss.

Use
Cheese is both eaten plain and incorporated into a variety of cooked preparations, where it provides salt, fat, and a lot of flavor. When serving aged cheese plain, make sure it has fully come to room temperature before eating—this allows for optimal flavor and texture. It pairs well in a cheese plate with fruits, nuts, and preserves. When cooking cheese, use the lowest possible heat to prevent undesirable stringiness and curdling. If incorporating it into a sauce, adding starch (such as flour) helps it properly incorporate; a small amount of sodium citrate can also keep it from separating.

Substitution
Different kinds of cheese in the same class can often be substituted for each other. For example, parmesan and pecorino make reasonable substitutes for each other if one is not available. In addition to traditional dairy-based cheeses, there are also non-dairy cheese facsimiles.