The Chemistry Behind Cheese's Unique Flavors And Scents

Cheese is a dairy product made from the same basic ingredient — milk. However, there are over a thousand types of cheese, each with its own distinct flavour and aroma. So, what gives each cheese its particular character?

The flavour of cheese is influenced by many factors, including the type of milk used, the bacteria and mould present, and the length of ageing. During production, bacteria turn milk sugars into lactic acid, and enzymes break down proteins and fats, creating a complex mix of amino acids, amines, and fatty acids that contribute to the flavour and aroma of the cheese.

The perception of cheese flavour is a complex sensation, comprising aroma, taste, and texture. The aroma compounds in cheese are derived from the breakdown of lactose, lipids, and proteins during ripening. The type of bacteria and mould in the cheese, as well as the processing steps, also play a significant role in developing the flavour and aroma.

Microorganisms and enzymes

The distinct flavours and aromas of cheese are influenced by many factors, including microorganisms and enzymes. Microbes and enzymes break down casein proteins and milk fats into amino acids, amines, and fatty acids, which give cheese its flavour. This process is called proteolysis.

Cheese flavour is a complex sensation that includes aroma, taste, and texture. The aroma components are usually the predominant determinants of the characteristic flavour of cheese products. The perception of cheese texture also contributes to its general flavour.

During cheese production, milk is typically acidified, and enzymes from rennet or bacterial enzymes are added to cause the milk protein casein to coagulate. The solid curds are then separated from the liquid whey and pressed into finished cheese.

The type of bacteria and enzymes used, as well as the cheese-making conditions and ripening conditions, will influence the flavour and aroma of the final product. For example, the addition of brevibacteria, which contains the enzyme methionine lyase, improves cheddar cheese flavour.

The flavour of cheese is also influenced by the length of ageing or ripening. As cheese ages, microbes and enzymes break down proteins and fats, intensifying the flavour and changing the texture.

Different types of bacteria produce different flavour compounds. For example, the genus Pseudoalteromonas, originally from the sea but now found in many types of cheese, produces a wide range of flavour compounds, including esters, ketones, and sulfur compounds, which impart fruity, mouldy, and oniony flavours to cheese.

Type of milk

The type of milk used is a key factor in the distinct flavours and aromas of cheese. While most cheeses are made using cow's milk, milk from other animals, especially goats and sheep, is also used. The composition of milk varies according to the type and breed of animal, the season and geographic location, and the health and nutrition of the animal.

Goat's milk cheese has a distinctive flavour and higher water content than cow's milk, yielding softer cheeses. Sheep's milk, on the other hand, is higher in fat and produces a creamy-textured cheese. It has a higher percentage of milk solids, resulting in almost twice the yield of cow's milk cheese.

The butterfat content of milk also influences the flavour and texture of cheese. For example, cheeses with higher butterfat content, such as Brie or Camembert, tend to have a softer texture and a richer, buttery flavour. In contrast, low-moisture cheeses like Parmesan have a harder texture and a longer shelf life.

The origin of the milk, including the animal's diet and geographic location, can also impact the flavour of the cheese. For instance, cheeses made with milk from specific breeds of cows, goats, or sheep in certain regions may have unique flavour profiles due to the specific characteristics of the milk produced in those areas.

Additionally, the processing techniques applied to the milk can further enhance or modify the flavour and aroma of the resulting cheese. For example, the cutting and stirring of curds, heating, and pressing can affect moisture content, texture, and flavour development during ripening.

Ageing and ripening

The ageing or ripening period is when cheese develops its flavour and texture. Freshly made cheese usually tastes salty and quite bland, but as it ages, microbes and enzymes break down the casein proteins, intensifying the flavour and changing the texture. This process is called proteolysis.

The length of the ripening period can vary from several days to two or more years. As the cheese ages, it loses moisture, develops a stronger flavour, and becomes harder and more crumbly. The rate of ripening is carefully controlled by temperature and humidity.

During the ageing process, bacteria and moulds intentionally introduced to the cheese before or during the ageing process break down milk components, producing volatile and non-volatile compounds that give the cheese its flavour. These include fatty acids, methyl, ethyl and higher esters, methyl ketones, aliphatic and aromatic hydrocarbons, alcohols, aldehydes, amines, amides, phenols, and sulphur compounds.

The flavour of cheese is a complex sensation comprising aroma, taste, and texture. The aroma is usually the first aspect of flavour encountered by a consumer. The aroma of cheese is due to volatile compounds, which can be detected orthonasally (by sniffing) or retronasally (by consuming).

The taste of cheese is another aspect of flavour. Tasting occurs in the oral cavity, primarily on the tongue, but also on the soft palate. The primary stimuli for taste are non-volatile compounds, which must make contact with the taste receptors. This contact creates perceptions of four distinctive taste qualities: sweet, salty, sour, and bitter. A fifth taste, umami, is accepted in some cultures. Compounds that contribute directly to cheese taste include lactic acid (sour), sodium chloride (salty), mineral salts of potassium, calcium, and magnesium (salty), and free amino acids and peptides of varying types (sweet, bitter, umami).

The final aspect of flavour is chemesthesis, which describes the sensory system responsible for detecting chemical irritants. This perception is related to the somatosensory characteristics of pain and temperature change and provokes a strong behavioural response. The sharpness of mature cheddar is an example of perceived chemical irritation.

Processing methods

The processing method used to make a cheese plays a significant role in determining its final characteristics, including its texture and flavour.

The first step in cheesemaking is to acidify the milk and then drain off the whey. This can be done by adding a starter culture of bacteria to the milk, which ferments the lactose and turns it into lactic acid. Different types of bacteria will produce different compounds, resulting in different flavours. For example, the bacteria Lactococcus lactis is responsible for the characteristic tang of cheddar cheese.

The amount and type of rennet, an enzyme derived from the stomach lining of young mammals, added to the milk can also affect the texture and flavour of the cheese. Animal rennet tends to produce a firmer texture and more intense flavour than vegetable rennet.

The curds are then cut and stirred, and the temperature is adjusted to release more moisture from the curds. The curds are then pressed and salted to arrest acid development.

For harder cheeses, such as cheddar, the curds are cut into small cubes and the temperature is raised to about 39°C to 'scald' the curd particles, releasing more whey. The curds are then stacked and pressed, and the acidity is increased to the desired level. The curds are then milled, salted, and pressed overnight.

For softer cheeses, such as Camembert, the curds are drained gently and left to age, allowing a white coat of mould to grow.

For washed-rind cheeses, such as Epoisses, the rind is washed frequently to encourage the growth of a sticky orange bacterium, giving a characteristic flavour and smell.

For blue cheeses, such as Stilton, mould culture is added during the initial cheese-making process or afterwards by piercing the cheese to allow air in.

The length of ageing also affects the flavour and texture of the cheese. As cheese ages, microbes and enzymes break down the casein proteins, changing the texture and intensifying the flavour. Harder cheeses, such as Parmesan, are aged longer, resulting in a stronger flavour and crumblier texture.

Bacteria and mould

The distinct flavours and aromas of cheese are influenced by many factors, including the type of milk used, the bacteria and mould, and the length of ageing. While all milk is made up of the same basic elements, its composition varies according to the type and breed of animal, the season and geographic location, and the health and nutrition of the animal.

Bacteria play a crucial role in shaping the flavours of cheese as it ripens. Specific types of bacteria produce flavour compounds that give cheese its distinct taste. For example, the bacterium Pseudoalteromonas, originally from the sea, has been found in many types of cheese and produces a wide range of flavour compounds.

The addition of mould to cheese also contributes to flavour development. Soft ripened cheeses such as Brie and Camembert have mould added to their surfaces, which produces a protein-digesting enzyme. This enzyme breaks down the curd during ripening, creating a runny texture and developing the characteristic flavour.

In traditional cheesemaking, bacteria and moulds might be present in the aging room, settling and growing on the stored cheeses. Today, prepared cultures are more commonly used, resulting in more consistent flavours and fewer constraints on the aging environment. These include soft-ripened cheeses like Brie and Camembert, blue cheeses like Roquefort and Gorgonzola, and rind-washed cheeses like Limburger.

The complex interplay between bacteria, mould, and other factors like milk composition and processing techniques ultimately determines the distinct flavours and aromas of cheese.

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