Estimated reading time: 5 minutes
Cheese is a naturally fermented dairy product. The cheesemaking process has a reputation of being a complex craft which can produce all sorts of pleasant, and some rather foul-smelling, flavours and textures. These are all created during the fermentation process which involves a biochemical reaction that is usually driven by multiple micro-organisms.
A complicated process
Fermentation is a complex process during which bacterial cultures are used to turn milk lactose into lactic acid. Fermented products, particularly cheese, have been used for thousands of years to preserve milk to make it more transportable and readily available, as well as more digestible because of the breakdown of lactose during fermentation.
In food processing, fermentation takes place under oxygen-free conditions through the conversion of carbohydrates to alcohol or organic acids using micro-organisms such as yeasts or bacteria. In view of this, the Dairy Standard Agency (DSA) asked Hans Keller, an expert in cheesemaking and a well-respected judge at dairy competitions, to give an account during an online webinar, of the most important types of fermentation and the effect it has on different cheese products.
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Fermentation processes
Lactic acid fermentation: This type of fermentation is unique in the cheesemaking process where lactose is turned into glucose and galactose; lactic acid enzymes convert these two sugars into lactic acid, with the latter playing a big role in the suppression of unwanted bacteria.
Lactic acid is used in most cheeses, except haloumi and paneer, among others. It is a crucial ingredient in Cheddar, Gouda, mozzarella and Grana Padano, as well as cottage cheese, mould cheese and hard cheeses such as Parmesan.
In the process of lactic acid fermentation, it is important to achieve the right acidity and to ensure all goes according to plan with proper control and no contamination.
Citrate fermentation: Citrate-positive bacteria are used as mesophilic starter culture. The addition of citrate by lactic acid bacteria stimulates the production of diacetyl (a chemical used to add butter-like and other flavours) and acetoin (an external energy store of fermentative bacteria). This creates the flavour or butter-like component in cheese such as Gouda, continental types, cottage cheese and soft cheese. Citrate fermentation is slow and the CO2 that is produced in the process forms small holes.
Propionic acid fermentation: This type of slow to very slow fermentation involves CO2 and propionic acid which inhibits the growth of mould and bacteria. It produces Swiss-type cheeses such as Emmentaler, Gruyère and Bergkäse, which is sometimes an acquired taste since the acetate and propionic acid create a slightly sweet, nutty flavour.
Ethanol fermentation: Yeasts turn lactic acid into CO2 and ethanol and the yeasty flavour plays a role in the flavour of surface ripened cheese.
Fermentation of milk fat: The milk fat in cheese contributes to its texture, colour and flavour. There are many enzymes in raw milk, of which lipase is one of the most important – lipase converts milk fat into fatty acids and glycerol. This is important for the flavour in pecorino, Parmesan and hard cheese. Pasteurisation destroys the lipase enzyme and therefore it must be added during the cheesemaking process.
Protein breakdown
Protein is broken down to peptides, amino acids and eventually to ammonia. The ripening of Camembert is a good example of the process – as the proteins break down, the texture will gradually get softer.
More important tips
- Non-iodate salt must be used when making cheese. Salt is a preservative, and the correct type and amount must be used. Any cheesemaker knows the worth of salt. It slows the lactic acid formation process as well as the breakdown of protein. In addition, it helps to improve the overall flavour profile of cheese as it ripens.
- The types of cheese that benefit from a slower ripening process are hard types such as Grana Padano, Parmesan and the like.
- When ripening cheese, temperature control is important because it gets the process going. The temperature should preferably be around 13°C. In terms of cheese that is ripened at higher temperatures, it is recommended to salt it early in the cheesemaking process.
- Humidity also plays a role and the right amount of moisture in cheese is vital. The higher the moisture, the faster the cheese will ripen. In a hard cheese with a very low moisture content such as Parmesan, patience is a virtue since the ripening process can take as long as three years.
- Sanitation is essential in the cheesemaking process, as contaminated equipment will not yield the desired results. Cheese moulds should also be kept as clean as possible, and all equipment and cloths must be thoroughly sanitised.
Can anyone make and sell cheese?
Anyone who is interested in making and selling cheese must first obtain a certificate of acceptability (COA) from the local health authority before they can sell cheese to consumers. It is also important to refer to the Foodstuffs, Cosmetics and Disinfectants Act, 1972 (Act 54 of 1972): Regulation R638 of 22 June 2018, which contains the regulations governing general hygiene requirements for food manufacturing premises, the transportation of food and related matters.
An environmental health practitioner will conduct an inspection, based on R638, at the premises where cheese will be manufactured, after which a COA will be issued. Correct labelling of the cheese must also be taken into consideration. – Carin Venter, Plaas Media
For more information, contact The Dairy Standard Agency on 012 665 4250 or visit www.dairystandard.co.za.
