Milk's Transformation: Cheese's Share Of Milk Production

Milk is a highly nutritious liquid formed in the mammary glands of mammals and is used to make cheese. The primary objective of cheesemaking is to remove most of the water from the milk and then acidify the remaining curds to preserve the solid mass. In 2012, cheese, along with whey, accounted for 37.1% of all milk in the US. According to a 2007 study, more than 35% of milk produced worldwide is used in cheese manufacture.

Milk production and the role of dairy farmers

Dairy farming is a class of agriculture for the long-term production of milk, which is then processed and sold as dairy products. The objective of good dairy farming practice is to produce safe, quality milk from healthy animals under generally acceptable conditions. Dairy farmers need to apply Good Agricultural Practice (GAP) in areas such as animal health, milking hygiene, nutrition, animal welfare, and environmental impact.

Animal health is a key constraint to increasing small-scale dairy productivity, as poor health leads to high morbidity and low production. To improve productivity, dairy farmers should focus on establishing a disease-resistant herd, preventing the entry of diseases, implementing effective herd health management, and using chemicals and veterinary medicines appropriately.

Milking hygiene is another critical aspect of dairy farming. While hand-milking is still common in small-scale dairy farms, especially in developing countries, milking machines are more common on medium to large dairy farms that use improved dairy breeds. Regardless of the method, avoiding contamination during and after milking is crucial. Good practices include ensuring that milking routines do not injure the animals, maintaining hygienic conditions, and handling milk properly after milking.

Nutrition, including feed and water, also plays a vital role in dairy farming. Providing the right feed and water is essential for the health and productivity of dairy animals, as well as the quality and safety of their milk. Factors such as the physiological state, milk production level, age, sex, body condition, weight, health, level of activity, climate, and season influence the feeding requirements of dairy animals. Access to water is particularly important, as dairy animals consume large amounts of water for milk production and pregnancy, which directly impacts milk production.

Animal welfare is another aspect of dairy farming that focuses on the well-being of the animals. Good dairy farming practices aim to keep animals free from hunger, thirst, malnutrition, discomfort, pain, injury, disease, and fear, while allowing them to exhibit relatively normal patterns of behaviour.

Environmental concerns in the dairy sector include land degradation, climate change, air pollution, water shortage, water pollution, and loss of biodiversity. Dairy production is a significant source of greenhouse gas emissions, and good dairy farming practices involve implementing sustainable farming systems, having appropriate waste management, and minimising adverse environmental impacts.

Socio-economic management is also integral to dairy farming, encompassing human resource management, financial management, and ensuring the financial viability of the enterprise.

To improve the profitability of dairy farms, it is crucial to maximise milk production by increasing the volume sold and optimising the sales price. This can be achieved through controlling milk composition, milk quality, diet optimisation, and maintenance fees. Additionally, factors such as reproductive and health issues, housing conditions, and herd performance should be considered to enhance productivity per cow.

Dairy farmers play a vital role in the milk production process by ensuring the health and well-being of their herds, implementing good agricultural practices, and contributing to the sustainability and profitability of the dairy industry.

The process of making cheese

• Preparing the Milk: The first step in cheese-making is to prepare the milk. This may involve processing the milk to standardize its composition, such as manipulating the protein-to-fat ratio. It often includes pasteurization or mild heat treatment to kill organisms that could cause spoilage. The milk is then cooled to the optimal temperature for the starter cultures to grow.
• Acidifying the Milk: The next step is to add starter cultures, which are lactic acid bacteria (LAB) that acidify the milk by converting lactose into lactic acid. This step helps to develop the flavour of the cheese and prevent the growth of undesirable bacteria. The milk is allowed to ripen, with its pH level dropping during this process.
• Curdling the Milk: To manipulate the texture of the milk, cheesemakers add rennet, an enzyme that causes the milk to curdle and form coagulated lumps known as curds. As the solid curd forms, a liquid byproduct called whey is produced.
• Cutting the Curd: The curds and whey mixture is allowed to separate and ferment until it reaches a certain pH level. At this point, cheesemakers use long knives to cut through the curds, creating more surface area and facilitating further separation of the curds and whey. The size of the curd pieces will influence the moisture level of the final cheese.
• Processing the Curd: The curds are further processed by cooking, stirring, or both, to continue separating them from the whey and to dry them. This step can also involve washing the curds, which affects the flavour and texture of the cheese.
• Draining the Whey: The whey is then completely drained from the vat, leaving only a mat of cheese curds. This step may be done naturally or with the help of a mould or press, especially for harder cheeses that require lower moisture content.
• Cheddaring the Cheese: For some cheeses, an additional step called cheddaring is performed to remove more moisture from the curd. This involves cutting the mat of curd into sections, stacking them, and periodically repeating this process. Cheddaring results in a denser, more crumbly texture and allows fermentation to continue.
• Salting the Cheese: To add flavour, cheesemakers can dry salt the cheese or brine it by submerging it in a salt solution. This step also acts as a preservative, making the cheese less accessible to microorganisms.
• Shaping the Cheese: With no more ingredients to add, the cheese is now ready to be shaped. Cheesemakers use moulds, such as baskets or hoops, to press and form the curd mixture into standardized shapes.
• Aging the Cheese: The final step is aging, which can take anywhere from a few days to several years. Aging occurs in a controlled, cool environment, during which molecular changes take place, causing the cheese to harden and intensify in flavour. Aging can also involve the development of mould, adding unique colour and flavour to the cheese.

Variations in the Cheese-Making Process

While the above steps provide a general overview of the cheese-making process, it is important to note that there are variations depending on the type of cheese being made. For example, in the production of blue cheese, mould spores are added to the milk at the beginning of the process, and the cheese is then pierced to create air channels for the mould to grow. Additionally, different types of cheese may require different processing times, temperatures, and pH levels.

The use of milk fat in cheese

Milk fat, also known as butterfat, is a crucial component in cheesemaking. It contributes to the opaque white colour of milk and is composed of triglycerides, which break down into fatty acids that enhance the flavour of cheese as it matures. The fat content in milk varies depending on the type of milk and the source animal's breed, weight, and diet. For instance, Holstein Friesian cows produce milk with around 4% butterfat, while Channel Island breeds yield 6-8%.

The fat content in milk significantly impacts the resulting cheese's texture and flavour. A higher fat content in milk leads to cheese with a higher fat and moisture content, while lower fat milk tends to produce harder cheeses. For example, skim milk is typically used for making hard cheeses like Romano and Parmesan, while whole milk is used for most cheeses, including soft and semi-hard varieties.

During the cheesemaking process, milk fat becomes entrapped in the curd formed by the coagulation of casein proteins. The curd is then cut into small pieces to release the whey, and the size of these pieces determines the amount of whey released, influencing the final texture of the cheese.

Furthermore, the milk fat content affects cheese yield. Studies have shown that increasing milk fat content leads to higher cheese yields, with actual and dry matter yields increasing at rates of 1.16 ± 0.15 and 0.93 ± 0.10 kg/kg of fat, respectively. However, at very high milk fat percentages, the proportion of milk fat lost to the cheese whey also increases.

In summary, milk fat plays a vital role in cheesemaking, affecting cheese texture, flavour, and yield. Cheesemakers carefully consider the fat content of the milk to achieve the desired characteristics of the final product.

The importance of casein in cheese-making

Casein is a crucial component in cheese-making. It is a family of related phosphoproteins that are commonly found in mammalian milk, making up about 80% of the proteins in cow's milk. Casein is the primary emulsifier in milk, helping to mix oils, fats, and water. It is secreted into milk from mammary cells in the form of colloidal casein micelles, which are suspended in the liquid phase of milk.

The process of cheese-making involves coagulating the casein protein in milk and then separating the milk into solid curds and liquid whey. Casein proteins are special because, in milk, they are invisible to the eye, but when acid or rennet is added under the right conditions, they clump together to form curds, which are then removed from the remaining liquid (the whey) and pressed into cheese. This curdling process is the destabilization of casein micelles.

Casein plays a key role in determining the texture and flavour of the final cheese. It is relatively hydrophobic, making it poorly soluble in water, and its behaviour can be influenced by factors such as the impact of calcium concentration, salt content, and the composition of the milk itself. The addition of extra calcium, for example, can help form more stable cheese curds.

Casein also continues to impact the cheese during its shelf life. Many cheeses are ripened, and during this time, changes in the casein may occur, such as the breakdown of some types of casein proteins and the reorganization of the proteins, which can affect the consistency and even the flavour of the cheese. Additionally, some cheeses become stringy when melted, which is caused by casein proteins linking together into long fibres.

In summary, casein is essential to the cheese-making process as it is the component that forms curds when coagulated, and its behaviour can be manipulated to influence the final texture, flavour, and consistency of the cheese.

The types of milk used for cheese

Cheese can be made from almost any kind of milk, including cow, goat, sheep, skim, whole, raw, pasteurized, and powdered. The only type of milk that should not be used for cheesemaking is ultra-pasteurized milk, as it has been heated to such a high temperature that all the native bacteria and enzymes are destroyed, and it will not form a curd.

Skim milk is mostly used for making hard cheeses like Romano and Parmesan, while Monterey Jack and Mozzarella are sometimes made with a portion of skim milk, blended with whole milk.

Raw milk, whether from a cow or a goat, can be used to make many familiar cheeses. It has beneficial bacteria and enzymes that add complexity and character to the cheese. However, it is important to ensure that the milk comes from healthy animals and has been properly handled, as tainted milk can transmit infections and cause serious illnesses.

Cow milk is typically used for cheesemaking and is composed of 88% water, 5% lactose, 3.5-5% protein, and 3-5% fat, which supplies flavor and texture to the cheese. The breed of animal, stage of lactation, geographical location, environmental conditions, and seasons influence the balance of these components and affect the final outcome of the cheese.

Goat milk is similar to cow milk but has smaller fat globules that are more easily digested, resulting in a whiter cheese. Goat milk is also naturally more acidic, which can lead to a slight reduction in ripening times and a softer curd.

Sheep milk has twice the solids content of cow milk, resulting in a higher cheese yield. It has a butterfat content of 9%.

While any milk from any breed can generally be used for making cheese, certain breeds of cows and goats are better suited for specific types of cheese. For example, Jersey and Guernsey milk have the largest fat globules, making them great for soft and semi-soft cheese varieties, while Ayrshire milk has the smallest fat globules and is preferred for sharp Italian cheese and long-aged Cheddars.

More than 35% of milk produced worldwide is currently used in cheese manufacturing.

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