Frederic Melton
Swiss cheese is known for its distinctive holes, smell, texture, and flavour, which are created through a combination of bacteria, temperature control, and specific production techniques. The process involves coagulating and curdling milk, cutting and heating curds, moulding the cheese, and creating holes through the release of carbon dioxide by bacteria. The size of the holes and the flavour profile of the cheese are influenced by the type and amount of bacteria used, as well as the temperature at which the cheese is made.
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What You'll Learn
Bacteria, milk, and curds
The first step in making Swiss cheese is to produce curds from milk and bacteria. Fresh milk is brought in and poured into a vat, where it is gradually heated. Then, lactic acid bacteria and rennet are added to the milk to begin the coagulation process. This mixture is gently heated to between 30°C and 32°C, causing it to curdle and form a gelatinous substance. The addition of bacteria and the increase in temperature also increase the milk's acidity, which enhances the effect of the rennet. The milk is left to stand for 35 to 40 minutes, during which time the rennet curdles the milk.
The curds are then cut into small pieces using a cheese harp, which can feature wires or blades. The size of the curd pieces determines the type of cheese that will be made—smaller pieces will result in a harder cheese. The cheese harp is used to stir the curds, and the longer the stirring duration, the smaller the curd pieces become. This step also reduces the water content in the cheese, as the finer the curds, the less water they contain.
After the curds are formed, they are stirred and heated again. The temperature is adjusted according to the desired water content and texture of the final cheese. For harder cheeses, the curds are heated to approximately 51°C to 58°C, while softer cheeses are heated to around 35°C. During this stage, the curd granules contract and separate from the whey, a green liquid that is considered a waste product. The whey is removed and can be further processed into various products, such as whey drinks, butter, or quark.
The curds are then ready to be moulded into cheese. The mixture is poured into perforated moulds, allowing the whey to continue draining off. The moulds are compressed to remove any remaining liquid and give the cheese its desired shape. This step also helps to remove additional whey. Finally, the cheese is soaked in a brine bath, where it absorbs salt and releases any remaining whey.
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Rennet and coagulation
Rennet is a crucial ingredient in cheese-making, including Swiss cheese, and plays a vital role in transforming milk into cheese. Rennet is an enzyme that is found in the lining of a cow or goat's stomach and is added to milk to assist in the coagulation process. This process separates the curds from the whey. The earliest rennet was made by extracting the enzyme chymosin from the fourth stomach of a young ruminant several thousand years ago. Today, rennet is available in different forms, including animal, vegetable, and microbial rennet.
In Swiss cheese-making, the milk is first gently heated to produce thermised (warmed to 63°C) or pasteurised milk (warmed to at least 72°C). The milk is then poured into a vat and stirred as it is gradually heated. The lactic acid bacteria and rennet are added to begin the coagulation process. Just a few grams of rennet are needed to curdle around 1,000 litres of milk. The milk is left to stand for 35-40 minutes, during which time the rennet curdles the milk.
The choice of rennet can affect the cheese's flavour, texture, and traditional authenticity. For example, animal rennet is prevalent in many European cheeses, especially those with traditional production methods. On the other hand, microbial rennet, also known as vegetarian rennet, is commonly used in commercial creameries in the US and UK. In some cultures, vegetable and plant rennet has been used to coagulate milk, such as in India, where fruit trees were used as a source of rennet due to the cow being revered as a religious symbol.
While rennet is a key component in coagulating milk for cheese, there are alternative methods to achieve coagulation. Some cheese recipes use acids like vinegar or lemon juice, culture, or heat to coagulate the milk. These methods produce cheeses such as queso fresco and cream cheese. Additionally, microbial rennet or FPC (a milk-clotting enzyme) is often used in cheese production, constituting 90% of the cheese in the United States.
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Cutting and shaping curds
Cutting the Curds
Once the milk has been heated and curdled, the cheesemaker must determine the optimal time to cut the curds. This can be done manually by inserting a flat blade at a 45-degree angle and slowly raising it to test if the curd is ready. Cutting the curds at the right time is crucial, as early or late cutting can lead to the loss of fines (small curd particles). For Swiss cheese, cutting often begins early when the curd is still soft to prevent over-setting. After cutting, the curds are stirred and gently heated to release more whey and create firmer curds. Drier cheeses are typically cut into smaller curds to remove more moisture, while larger curds are retained for softer cheeses.
Shaping the Curds
Once the desired level of dryness is achieved, the curds are ready to be shaped. This is typically done by pressing the curds into moulds, which can be baskets or hoops. Hoop moulds only wrap around the sides, while basket moulds are open at one end. The moulds give the cheese its signature shape and help remove any remaining whey. Most moulds are round or rectangular, resulting in cylinders or blocks of cheese. The cheese is then compressed to further remove whey and give the cheese its desired shape.
Aging the Curds
After shaping, the cheese is aged under controlled conditions to develop its distinct flavours, textures, and aromas. The aging time varies depending on the type of cheese. For Swiss cheese, the wheels are kept in maturing caves for 7-12 months, during which they are periodically washed with brine.
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Heating and cooling
The first step in making Swiss cheese is to heat the milk. The milk is typically delivered in tanker trucks and pumped into silos. It is then heated to at least 72 °C (161 °F) to produce pasteurised milk, which is safe for cheese-making. If making Swiss cheese with raw milk, the milk is heated to 86 °F. This is done slowly, with constant stirring.
Once the milk has reached the right temperature, lactic acid bacteria and rennet are added to begin the coagulation process. The milk is left to stand for 35-45 minutes. During this time, the milk thickens and curdles, resulting in a gelatinous substance. The curds are then cut into small pieces using a cheese harp, with the size of the pieces determining the hardness of the final cheese. The curds are then heated and stirred, with the temperature depending on the desired water content and hardness of the cheese. The curds are heated to around 30-32 °C for soft cheese and 51-58 °C for hard and extra-hard cheese.
After heating, the curds are stirred and allowed to settle. The whey, a green liquid that escapes from the curd, is then pumped away and the curds are pressed overnight to form blocks of cheese. The next day, the cheese is cut into blocks, salted, and placed in a cooler. It is then moved to a warm room for curing, where the starter cultures grow and generate gas, forming the characteristic holes of Swiss cheese. The cheese is then aged in a cooler to develop its flavour.
The ageing process involves moving the cheese to an ageing space of 65-70 °F and 80% moisture for 2-4 weeks, depending on the desired hole size. The cheese is turned daily to even out the moisture, which affects hole size and distribution. The cheese may be waxed or dry-brushed during this time. Finally, the cheese is moved to a cold room of 45-50 °F and 85% moisture for at least a month to develop its flavour.
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Salt and the brine bath
Salt is an essential ingredient in cheesemaking. It is important for drawing out whey, slowing the conversion of lactose to lactic acid, preserving the cheese, and adding flavour. Salting cheese also pulls moisture from the surface, drying it out for rind development. It also inhibits the growth of mould.
Brining is a common instruction in cheese recipes for adding salt, particularly for cheeses with a short ageing time. It is an efficient and reliable way to add salt to the cheese, as the salt absorption is quick and it is easy to get an even coverage. The density of the brine causes the cheese to float, so the top surface of the cheese will need to be salted. This can be done by sprinkling a small amount of salt on the top surface of the cheese. The cheese should be regularly turned over so that all surfaces are exposed to, and are able to absorb, the brine solution. Halfway through the brining process, the cheese should be flipped and re-salted.
Brine solutions can be made up with different ratios of salt to water, but anything less than 18% salt concentration is considered too low to keep the nasties at bay, and the upper limit of salt concentration is considered to be about 24%. Saturated brine is anything over 26% salt (or between 70-90% saturation).
Brine should be kept cool and stored in a non-reactive container. It should be stabilised at an acid level similar to the cheese being salted, typically around 5.4-4.9 pH. Fresh brine needs to have calcium chloride added, as low calcium in the brine will cause the calcium inside the cheese to be pulled into the brine, weakening the curd structure and softening the rind. When making fresh brine, you can add one cup of clear whey for every gallon of brine, as the whey will contain calcium.
If you are reusing brine, add more salt back in as required to maintain salt concentration levels. If you are concerned about undesirable bacteria in the brine, boil and cool it before using and storing.
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Frequently asked questions
Swiss cheese gets its holes from the carbon dioxide released by bacteria as the cheese absorbs salt and releases water during the brine bath. The type of bacteria and the temperature at which the cheese is made are key to the size of the holes and the flavour.
The cheese harp is used to cut the curd into small pieces. The size of these pieces determines the type of cheese that will be produced—the smaller the pieces, the harder the cheese.
Whey is the name given to the green liquid that escapes from the curd during the cheesemaking process. The majority of the whey produced is used as animal feed, but it can also be used in whey drinks, whey butter, cosmetics, and processed foods.
Cheese brands are applied to the cheese as a "cheese passport" for identification purposes.
