Cheese making Cheesemaking
Traditionally, cheese was made as a way of preserving milk as a food.
- Milk and whey tanks
- VAT - tank used for incubating the milk
- Cheese milk Pasteuriser - designed to heat and cool to the milk to the desired cheesemaking temperature
- Separator - To remove fat from the milk.
- Standardiser - to give desired fat in milk %
- Draining belt or draining table - te seperate the curds and whey and facilitate, cooling, matting and salting the curd
- Cheese Moulds or moulding system
- Brine system or dry salting
- Packing machines
- Standardising and Heat treatment of Milk
- Additives and colours
- Inoculation and Milk Ripening / Incubation
- Coagulation / Acid and Enzymes
- Whey removal
- Curd Handling & Treatment
- Cheese ripening & storage
Treatment of Milk for Cheesemaking
The milk is first clarified / separated and standardised. The milk may then be subjected to a heat treatment of 64.5° C for 16 sec. This thermisation treatment results in a reduction of initial bacteria counts and it should be followed by a full pasteurisation process. HTST (High Temperature Short Time) pasteurisation (72.3° C for 16 sec) is often used, other heat treatments may be used and they are calculated based upon the characteristics of the liquid being pasteurised as some more dense fluids may require a greater time temperature combination.
Homogenisation breaks up the fat globules and increases the fat surface area where casein particles attach which may give a weaker / softer curd.
The following may be added to cheese milk (Check your country regulations):
- Calcium choride
- Hydrogen peroxide
Calcium choride is added to replace calcium lost during heat treatment and also lost during the cheesemaking process. The calcium assists in coagulation and reduces the amount of rennet required giving an improvedyield and firmer curd.
Sodium or potassium nitrate is sometimes added to the milk in certain types of cheese to improve keeping quality
Annato, Beta-carotene and other natural colours are often used to colour cheese.
The addition of hydrogen peroxide is sometimes used to reduce microbial counts in cheese milk.
Lipases, normally present in raw milk, are inactivated during pasteurization. Lipase is used for flavour development through fat hydrolysis.
Inoculation and Milk Ripening
Cheesemaking relies on the fermentation of lactose by lactic acid bacteria. The lactic acid lowers the pH and aids coagulation, promotes syneresis, helps prevent spoilage and pathogenic bacteria from growing, contributes to cheese texture, flavour and keeping quality.
After innoculation with the starter culture, the milk is held for 45 to 60 min at 25 to 35° C to allow the bacteria to develop, The time and temperature is dependant upon the type of cheese being made and tailoring to suit the bacterial strains being used. As the bacteria grow in the vat they produce lactic acid. The type and strains of bacteria will depend on the type of cheese you are manufacturing and they are rotated on a regular basis to reduce the chances of Phage attach which can "kill" the lactic acid starter bacteria in the cheese milk.
Adding the enzyme Rennet causes the casein micelles to agglommerate and form a network which locks in the the water (whey) and traps the fat globules in the milk matrix. A cheesemaker will test the set of the vat prior to cutting and this is usually done with a sharp blade where two cuts are made in the set cheese milk and using the knife blade on its side lifts the curd to ensure a clean cut.
Setting the vat may be achieved using:
- Enzymes (Chymosin or Rennet)
- Acid treatment
- Heat-acid treatment
Lowering the pH of the milk results in casein micelle destabilization and aggregation. Acid curd is more fragile than rennet curd due to the loss of calcium. Acid coagulation can be achieved naturally using starter culture, or artificially with the addition of gluconodeltalactone (GDL). Acid coagulated fresh cheeses may includeMozzarella Cheese, Cottage cheese, Quark, and Cream cheese. A combination of processes is also often used as acid cogulated cheese does not have the starter cultures to produce the flavours required in cheesemaking. GDL is mostly used in Feta Cheese manufacturing which allows the use of a a continuous process where the cheese can be filled as a liquid into cans or even into Tetra Bricks where the GDL is injected immediately prior to filling and the cheese sets in the package.
Heat treatment results in the denaturation of the whey proteins. The denatured whery proteins interact with casein. By the addition of acid, the casein precipitates along with the whey proteins. In rennet coagulation, only 76-78% of total protein is recovered, while in heat-acid coagulation, 90% of protein can be recovered. .
Cutting and stirring
The set milk is gently cut into small pieces with knife blades or wires. The results in the expelling of water (whey) The size and speed of cutting is dependant upon the type of cheese bing manufactured and the design of the vat. As the curds are cut the curd particles firm up and shrink as a result of expelling mositure. This wheying off process is enhanced by raising the tempoerature of the vat slightly referred to as "Scalding" This process causes the protein matrix to shrink. The acidity also contributes to more rapid shrinkage of the curd particles. The final moisture content is dependant on the time and temperature of the cook stage. The cook stage is important as id decides the final moisture content of the curd and also affects amount of fermentable lactose remaining and affects the final pH and quality of the cheese.
When the curds have reached the otimum moisture and acidity they are separated from the whey. The whey is usually first removed from the top using a "Pre-draw". Gentle handling of the curd throughout the process otherwise the curd may shatter and result in fines losses to the whey. The curd & whey can also be placed directly into moulds for draining. Some cheeses are also washed curd cheeses and this process increases the moisture content, washes out residual lactose and reduces acidity giving a softer mor open textured cheese..
Curd handling from this point on is very specific for each cheese variety. Salting may be achieved through brine as with mozzarella or surface salt as with Feta, or vat salt as with Cheddar or a combination of methods. When producing Feta using the UF method where the cheese sets in the packaging if this was salted prior to filling then it would rapidly kill off the bacteria resulting in a very bland cheese. To acheive the characteritics of Cheddar, a cheddaring stage (curd manipulation), milling (cut into shreds), and pressing at high pressure are crucial. Commercial Cheddar manufacture is most often pressed in a Cheddar tower which allows for the automation of the whole process. The curds and whey are pumped or blown to the top of a high towe shaped to the shape of the final cheese block and the weight of curd in the tower causes the pressing to take place during its residence time in the tower.
The finished cheese is matured, at different temperatures, times and humidities to give the required flavour, body and texture profile. During ripening, degradation of lactose, proteins and fat are carried out by ripening agents.
Some of the ripening agents in cheese are:
- The bacteria and enzymes in the milk
- Lactic cultures
- Added moulds as with blue cheese
For more information or to discuss your requirements please contact us.