Cheese production
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I. GENERAL DESCRIPTION:
- 1. Definition
- (Dairy science and Technology, University of Guelph, http://www.foodsci.uoguelph.ca/dairyedu/home.html)
Cheese is the fresh or ripened product obtained after coagulation and whey separation of milk, cream or partly skimmed milk, buttermilk or a mixture of these products. It is essentially the product of selective concentration of milk. The essential ingredients of cheese are milk, coagulating enzyme (rennet), bacterial cultures and salt.
- 2. General Flowsheet
Figure 1: Manufacture of cheese LITERATURE: BAT for Food, Drink and Milk Industries, June 2005
- 3. Description of techniques, methods and equipment
- (Dairy science and Technology, University of Guelph, http://www.foodsci.uoguelph.ca/dairyedu/home.html)
- General:
- The process of cheese manufacturing is described in Figure 1. Cheesemilk must first be clarified, separated and standardized. :Homogenization is not usually done for most cheesemilk. After innoculation with the starter culture, the milk is held for 45-60min at 25-30°C to ensure the bacteria are active, growing and have developed acidity. This stage is called ripening the milk and is done prior to renneting. Then, the next step is milk coagulation. After the milk gel has been allowed to reach the desired firmness, it is carefully cut into small pieces with knife blades or wires (Dairy science and Technology, University of Guelph, :http://www.foodsci.uoguelph.ca/dairyedu/home.html). When the curds have reached the desired moisture and acidity they are separated from the whey. Curd handling from this point on is very specific for each cheese variety. This final stage varies from weeks to years according to the cheese variety (Dairy science and Technology, University of Guelph, http://www.foodsci.uoguelph.ca/dairyedu/home.html).
- A further process in the cheese production involves melting. Milled cheese and other ingredients are put into a processing kettle and heated to a temperature normally not less than 75oC to ensure a complete pasteurization of the processed cheese. Agitation during processing is important for a complete emulsification of the processed cheese. The temperature and duration of the process depends on the type of processed cheese aimed for and the nature of the raw cheese (BAT for Food, Drink and Milk Industries, June 2005).
- 4. Temperature ranges and other parameters
- (Dairy science and Technology, University of Guelph, http://www.foodsci.uoguelph.ca/dairyedu/home.html).
- 5. Benchmark data
II. NEW TECHNOLOGIES:
- a) Changes in the process
- Using ultrafiltration (UF) for protein standardization of cheese milk
- (BAT for Food, Drink and Milk Industries, June 2005) (see also Membrane processes in the food industry).
- a) Description of the technology:
- Ultrafiltration can be used for protein standardization of cheese milk. The milk flows under pressure over a membrane that withholds the protein molecules, thus increasing the protein content of the retentate. The membrane pore size ranges from about 10-100nm.
- As using UF leads to an increase in the cheese yield per processed milk unit, the generated quantity of whey is smaller compared to traditional standardization. Furthermore, even when UF requires additional electrical power, thermal energy and water compared to traditional standardization, in large scale production, the increase in cheese yield compensates for the increased consumption of energy and water.
- The permeate from the UF unit is further treated by reverse osmosis (RO). The RO water, which is of drinking water quality, can be used for cleaning purposes.
- UF can be applied to both skimmed milk and whey. UF units can be installed in new and existing installations because of their low space requirements.
- This process results in reduced energy and water consumption, whey and waste water in comparison with traditional standardization. Membranes have to be cleaned regularly, therefore water is consumed and the investment cost is high. Still, cheese of homogenous quality can be produced using this technique. This technique also offers a larger flexibility for making different types of cheese.
- The estimated savings in water and energy consumption in a dairy using UF for protein standardization are presented below (calculations made for 25000t/yr yellow cheese production):
- b) Description of suitable energy supply systems:
- Membrane processes may result in reduced heat consumption, but electrical power is required to pump liquid through a semi-permeable membrane.
- c) Possible energy savings reachable by those measures:
- No information available.
- d) Economic evaluations:
- No information available.
- High temperature cheese ripening with later humidification and ionization of ventilation air
- (BAT for Food, Drink and Milk Industries, June 2005)
- a) Description of the technology:
- In cheese manufacturing, the temperature of the air is increased to shorten ripening times. This leads to a reduction in the demand of storage facilities, cooling power and ventilation energy. As a higher temperature increases the risk of dehydrating the cheese and of contamination by mould, the ventilation air is humidified and cleaned by a discharge tube which ionizes the air, which is passed through ventilation ducts. As ions in the ventilation air react with dust particles, microorganisms and viruses the air is effectively cleared of these sources of contamination.
- This process results in reduced energy consumption. It is applicable in cheese manufacturing installations, but its use can be limited due to the desired taste, product quality and stability.
- b) Description of suitable energy supply systems:
- Air humidification and ionization require electricity consumption for operating pumps.
- c) Possible energy savings reachable by those measures:
- In an example dairy, energy savings amounting to 272000 kWh/yr, or 85000 m3/yr of natural gas, were reported. A shortening of the ripening time by 50%, an improvement in the product quality and a reduction of the consumption of plastics and fungicidal agents were also reported.
- d) Economic evaluations:
- No information available.
- b) Changes in the energy distribution system
- Utilization of heat from warm whey for pre-heating cheese milk
- (BAT for Food, Drink and Milk Industries, June 2005)
- a) Description of the technology:
- The incoming milk is pre-heated with warm whey, which is simultaneously strained off from another vat. Heat exchangers and tanks are needed for circulating the water. Savings in energy for heating the incoming milk and cooling energy for the processed whey are achieved.
- This process is applicable in new and existing installations. In existing installations the lack of sufficient space can be a constraint.
- b) Description of suitable energy supply systems:
- A circuit of heat exchangers and tanks is needed to achieve the heat transfer. Electrical energy will be consumed to operate the pumps of the circuit.
- c) Possible energy savings reachable by those measures:
- The savings in energy and water consumption in a dairy using the mentioned process are presented below (calculations made for 250 million t/yr whey production):
- d) Economic evaluations:
- No information available.
- c) Changes in the heat supply system
No information is available.
III. SOLAR SYSTEMS INTEGRATION:
The temperature levels for thermal treatment, ripening and melting during cheese production can be easily reached by solar systems (the temperature level of melting differs for different types of cheese but it shouldn’t exceed the level of 100°C). Due to the fact that large amounts of hot water or steam may be required, auxiliary boilers can be used additionally to solar collectors (Joanneum Research).
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