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Capabilities
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Whatever the end-product, the manufacture of speciality and European pressed cheese involves the following main process stages:
Milk treatmentPasteurisation |
Removal of spores
Sporogenous micro-organisms can cause problems with blowing and atypical eye formation with some cheese types.
The development of these spores can be reduced by the addition of nitrate, which is becoming more and more undesirable and may even be prohibited in some countries. Spores can be removed by special separators and by means of a APV microfiltration (MF). SPX's MF is highly recommendable because it efficiently solves the problems with spores without affecting the cheesemaking characteristics of the milk.
Fat and protein standardisation
Most of the milk for cheese making is fat standardised in order to achieve a specific ratio between fat and total solids content. The APV Compomaster System is designed for automatic in-line fat standardisation with high accuracy.
Protein standardisation of cheese milk by means of APV ultrafiltration (UF) is becoming more and more common in achieving a uniform protein content. The most important advantages are:
- More consistent and slightly higher cheese yield
- Easier control of weight accuracy
- Higher throughput in the cheese vat
- Lower rennet consumption.
Homogenisation
For certain types of cheese, milk is homogenised. When used - typically for Blue Mould cheese and Feta - the cheese will appear more pale and make the fat more susceptible to fat cleavage by means of lipase enzymes, which contribute to the characteristic flavour of these cheeses.
Starter cultures
Acidification of the cheese milk influences a number of conditions:
- Curdling
- Syneresis (release of whey from the curd)
- Texture of the cheese
- Preservation effect
- Maturation of the cheese
Equipment and systems for growing starter culture is also one of SPX's specialities. The amount of starter culture is approximately 0.5-2.0% of the milk volume, depending on the type of cheese. Alternatively, highly concentrated cultures can be used.
Mould
These cultures create special appearances but also have significant
effect on flavour and texture.
Rennet enzymes
Rennet is essential in cheese making since this is the enzyme that
makes the curd formation possible. Very few cheese are made without
the use of rennet. Typically 25-40 g rennet/100 l cheese milk is
used.
Other additives
Calcium chloride may be added to promote a firmer curd if curdling
is slow. Colour is added to some cheeses either to give them colour
or to make them white.
Nitrate may be added to prevent blowing, but in some countries, its use is prohibited and, as mentioned before, spores can be eliminated by means of MF.
Curdmaking
The purpose of the curdmaking process is to transform the cheese milk into quality cheese curd with the highest possible yield. This depends on a large number of factors relating to:
- Milk composition and its treatment
- Additives used
- Composition of the final cheese
- Cheesemaking systems and the cheesemaking process itself.
In general, the yield is approximately 1 kg cheese/10 kg milk for semihard types. For extra hard and soft types the yield may be 0.8 kg and 1.5 kg cheese to 10 kg milk, respectively.
The cheesemaking process takes place in several steps. The APV CurdMaster is a good example of a flexible cheese vat which has proved its ability to produce quality curd for hard and soft cheese types alike, and also provides a very high yield due to minimal loss of casein fines and fat in whey.
Vat filling and renneting
Pre-treated milk is led to the cheese vat at approximately
30°C and the starter culture is added.
When filled with milk and the desired pre-ripening level has been reached, rennet is added. Thorough distribution of the rennet is important in order to avoid marbling of the cheese. The CurdMaster ensures excellent mixing due to the design of the stirring tool and the double O-shape of the vat. Coagulation time is typically 20-40 min.
Cutting
It is important for the yield that the curd has the same firmness
each time cutting is started. A good cutting process is critical to
reducing loss of fat and fines in whey. Consequently, SPX
has given special consideration to the design of the cutting tool
of the APV CurdMaster. It has staggered knives made of thin special
steel, a fact which is known to reduce loss of fat and fines. The
stirrer blades are made of polypropylene allowing them to float
during cutting so that they do not break the curd
unintentionally.
Pre-stirring
When stirring before whey draining, it is important to handle the
curd gently as it is still soft, but at the same time it is
necessary to prevent the curd from sedimenting and clotting. The
APV CurdMaster offers optimum stirring effect even at low stirring
speeds. The effect is further increased by the large stirrer blade
on the agitator.
The APV CurdMaster is very versatile and able to produce high-quality hard and soft cheese curd, and even low-fat types.
Whey draining
The CurdMaster is equipped with an automatic whey strainer: a
continuous whey draining device with continuous whey suction.
Alternatively whey draining can take place through valves in the
vat wall.
Heating
Usually, the whey is diluted with hot water in order to wash out
the lactose content and promote syneresis for reduction and
adjustment of the moisture content in the cheese grains.
Consequently, heating is a necessary curdmaking factor for all the
hard cheese types such as Emmental and Gouda. For most cheese
types, a final stirring period is important to adjust the firmness
of the cheese grains. The curd and remaining whey are then pumped
from the cheese vat to further processing.
The curd and remaining whey is pumped gently to the OPD PrePress System by means of an APV lobe rotary pump. Here, the curd is distributed using an automatic curd distributor. For round-eyed cheese the curd distribution takes place under whey (wet distribution), and for granular types, the whey is drained from the curd before it is distributed (dry distribution). The curd is then prepressed and the whey is drained off. The cheese blocks are then conveyed to the APV SaniPress for final pressing in APV Perfora cheese moulds. Finally, they are transferred to brining and ripening.
Cheese pressing systems
The OPD PrePress System and the SaniPress System for final pressing
are part of a new generation of equipment, providing high sanitary
standards and flexibility of size, composition and type of cheese.
The OPD PrePress is supplied with a polypropylene belt ensuring low
loss of fines and easy cleaning.
The system is designed to exclude air in the whey. An optional feature is the use of laser measuring of the length and height of the curd mat in order to ensure high weight accuracy of the individual cheese blocks.
The SaniPress System has been designed around the idea of pressing the cheese in a closed pressing tunnel by means of a diaphragm instead of cylinders. The system applies an even pressure on the entire surface of the mould lid. Typically, low pressure at approximately 0.3-0.4 bar is used.
The pressing principle permits the pressing of several cheeses in multimoulds without the use of spring-loaded lids.
Brining Systems
The DeepBrine System
The APV DeepBrine fulfills the requirements of a modern
brining system. The system consists of a number of stainless steel
cages divided by shelves. The cages are placed in large concrete
basins coated with plastic. The cheeses are led to and from the
cages through concrete channels in which flow is created by means
of propellers. The cages can be lifted up and down so that the
cheeses can float in and out of the individual shelves. The system
is usually configured for the "first in - first out" principle.
The RackBrine
The APV RackBrine System is very flexible and suited for both water
cooling and brining.
The system consists of:
- Brining racks
- Loading system
- Cooling/brining vat
- Unloading system
- Rack conveying and washing system
- Overhead crane for transport of racks
- Brine buffer/cooling system
The loading system can be supplied as a dry loading unit or as a wet loading unit where the cheeses are gently pushed onto the shelf under water/brine level.
The TrayBrine System
For medium-sized production, SPX Systems offers a very flexible and
hygienic cheese brining system consisting of plastic trays. The
cheeses are placed manually in the trays which are stacked and
transported to the brining room. Here the stack is connected to the
brine flow system. The design of the trays ensures an efficient
internal flow and thereby optimum brining. Once the brining period
has ended, a timer stops the flow and the brine flows from the
trays to a collection tank. The cheeses can the rest in the trays
until the store personnel are ready to empty them. Then the trays
can be cleaned automatically before they are refilled.
Pack Salt
The brine treatment, either by means of pasteurisation or
micro-filtration, involves a need for investment in equipment, but
also a quite substantial daily operation cost. A lot of effort has
therefore been put into finding a method to substitute the brine
salting method. SPX has developed and patented a method for
dry salting of final pressed cheese known as the APV PackSalt
method.
The APV PackSalt method takes place in connection with the packing of the cheese into a deep-draw foil. This salting/packing takes place just after the block has been blown out of the mould.
The deep-draw packing machine has been equipped with a salt dosing unit for dosage of dry salt in both the bottom of the foil and on the upper surface of the cheese.
The cheese which has just been blown out of the mould is led to the packing machine via a weighing/filling line, in which it is continuously weighed just before a robot arm places it in the packing. The actual weight of the cheese is transmitted to the salt dosing unit, which, on the basis of the weighing figures, adjusts the salt quantity to be dosed in the foil. This ensures a uniform salt content in the cheese irrespective of weight deviations.
