Although you may not think it, there are a number of chemicals found in cheese, including lactose and whey protein.
Aside from a few food additives, the chemicals found in cheese can also be found in milk, but with different compound forms and molecular structures. The modern process of cheesemaking remains fundamentally the same as the methods used for thousands of years, with the main differences being hygiene standards and mass production.
In this post:
What is the Chemistry of Cheese?
While there are more than 1,800 varieties of cheese in the world, all different in terms of ingredients and preparation methods, the chemistry of cheese is pretty much the same across the board, with many varieties being chemically similar in terms of basic composition.
In general, the chemicals found in cheese, as well as the minerals and micronutrients, are the same as its source: milk. This makes it rich in:
- Vitamin B12
- Vitamin A
All cheese varieties are essentially fermented lactose. Lactose is a type of disaccharide found only in milk and its derivative products. It’s composed of galactose and glucose subunits, and has the molecular formula C12H22O11. With the help of lactic acid bacteria, lactose is converted into lactic acid, as shown in this balanced chemical equation:
C12H22O11 + H2O ⇾ 4CH3CHOHCOOH
The extra hydrogen and oxygen atoms are derived from the water content of the milk. Once the lactic acid is formed, the proteins in milk start to curdle as their tertiary molecular structures are denatured by the acid.
Most commercially available cheese is made from cow’s milk. The industrial standard is to pasteurise the milk, which involves briefly heating it up to 70°C in order to kill any potentially pathogenic bacteria.
Heating milk above 70°C causes it to prematurely curdle. It’s then cooled down before rennet mixture and starter bacteria is added (usually Streptococci and Lactobacilli). The lactose in the milk is digested by the bacteria for about an hour at the temperature range of 30-40°C.
This fermentation process produces lactic acid, which lowers the pH level of the mixture to 4.6. At this point, the casein protein in the milk will begin to coagulate. The process is sped up by adding an enzyme as catalyst. At the same time, the bacteria also metabolise citric acid, which helps in breaking down the protein. The curds are allowed to set for one to two hours in order to separate the whey liquid.
What Chemical Compounds Are in Cheese?
The chemicals found in cheese, particularly the proteins, are derived from milk. The two major types of proteins in milk are casein (which comprises about 80% of milk protein) and whey protein. Saturated fats and minerals are also present in cheese.
In milk, casein molecules are normally wrapped into compact spheres. They’re packed together with calcium and phosphate ions to form microscopic micelles, and are unpacked during fermentation.
In the mass production of cheese, rennet mixture is added. Derived from the stomachs of ruminant animals, this contains the active enzyme chymosin, and is used to speed up the curdling of casein protein. The hardness of the cheese will depend on how much protein coagulates and how much is compacted into a given volume.
Ultimately, the chemicals found in cheese are the product of fermentation, which breaks down the proteins in milk. These chemical compounds are responsible for the flavour, texture, smell, and colour. Adding cultures of molds or bacteria to age the cheese further breaks down its major components
For example, casein breaks down into ammonia, ethanoic acid, aldehydes, and alcohols, amongst other things, while milk fat breaks down into acids and ketones, and lactose breaks down into ethanol and ethanal.
Traces of these chemical compounds are relatively high in aged cheeses, and this is what gives them their strong flavour and smell.
Aside from proteins and breakdown products, cheese also contains fats, vitamin B complex, and other minerals such as iron, magnesium, and zinc.
What Chemical Reactions Occur in Cheesemaking?
The fundamental reactions in cheesemaking are complex microbial biochemical breakdowns of lactose and other major components of milk. Mainly, the conversion of lactose into lactic acid is the precursor to the curdling of milk protein (casein) into a solid that’s drained and processed to become cheese. Lactate and citrate are further broken down into other compounds that give cheese its buttery flavour. The breakdown pathway is shown in the illustration below:
How Are Cheeses Categorised?
While there are thousands of varieties, the chemicals found in cheeses are fundamentally the same. Types of cheeses only differ in minor aspects, such as the milk source.
The various cheese varieties can be classified based on the following:
- Source of milk: Most commercially available brands of cheese are made from the milk of cows, but other common sources include sheep, goats, buffalos, or a combination of each.
- Country or region: Many types of cheese are well known or associated with their place of origin. For example, parmesan cheese is named after Parma in Italy. Cheddar cheese originated in the English village of Cheddar, Somerset. Another well known cheese based on its place of origin is gouda, which was first traded in the Dutch town of Gouda.
- Age of cheese: Cheese is meant to have a long shelf life even without refrigeration. Some types of cheese, however, are purposely aged from a few months to a few years or more before they’re sold in supermarkets. A cheese is considered to be aged if it’s been cured for at least six months. Some examples of aged cheeses are cheddar, gruyère, manchego, gouda, and grana padano.
- Texture: The texture of cheese also plays an important role in its identity and categorisation. Cheese can be categorised as either soft, semi-soft, or hard. The texture is directly related to the age of the cheese. Aged cheeses have lower moisture content, making them harder.
- Flavour: Cheese flavours range from mild to sharp. Cheeses that have mild flavours are younger cheeses as compared to the aged cheeses with stronger flavours. Some types of cheese have strong flavour because of the mold or bacteria cultures introduced during the fermentation process.
- Preparation: Some types of cheese are ripened cheeses, or those to which cultures of mold or bacteria are added after being fermented. Blue cheese and limburger are examples of ripened cheeses, and are known for their strong flavours. Other types of preparations involve stretching, like the preparation of pasta filata cheeses, giving them a stringy, chewy texture, similar to mozzarella. Other examples of pasta filata cheeses are burrata provolone, queso Oaxaca, scamorza affumicata, and caciocavallo.
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