GB2105166A - A method and apparatus for the production of cheese - Google Patents

Abstract

In a method for the production of cheese on the basis of milk which is concentrated by ultrafiltration optionally combined with diafiltration, texture and coherence of the cheese are obtained by breaking the curd to cheese grains in the form of irregular small pieces before they are assembled to cheese. An apparatus for carrying out the method has a number of preferably vertical containers, means for transportation of the containers in the closed circuit, a feeding device, an emptying device and means for breaking the curd, e.g. - a mill or spiked rollers.

Description

SPECIFICATION A method and an apparatus for the production of cheese In the traditional method for the production of cheese the milk is caused to curdle by the addition of rennet combined with a starter. The coagulum is then cut into cubes and the curd gives off some whey and forms cheese grains. The liberation of whey can be facilitated by stirring the mixture of whey and cheese grains, optionally while heating. Cheese grains and whey are then separated and the cheese grains are transferred to moulds. The whey is a waste product which is used for instance as fodder.

When cheese is formed in this manner from cheese grains which are first separated and subsequently compressed into an aggregate mass the cheese obtains a characteristic "structure" or "texture" which depends on the curdling technique used for the individual types of cheese. It is to be understood that the so-called structure or texture appears when the cheese is cut through or cut into slices seeing that in the cut there will still be traces of the boundary surfaces of the cheese grains, and there will be a certain porosity.

It is well known that the yield of cheese production can be increased by 16-18% when the milk is concentrated by ultrafiltration and the retentate is used for the production of cheese (French patent No.

2,052,121).

In a known method forthe production of cheese on the basis of the retentate from ultrafiltration of milk, the retentate is inoculated with a bacteria culture and rennet is added whereafter the retentate is curdled to individual cheeses each in its own mould. It has been possible in this way to produce feta cheese.

By this method one has succeeded in producing cheese which from a taste point of view was hardly distinguishable from cheese produced by the traditional method, but the cheese lacked structure ortexture because when cutting through or slicing the cheese the cut appeared as a homogeneous surface without porosity or pattern and for that reason the cheese was not always accepted by the consumers.

Attemps have been made to produce cheese on the basis of retentate which cheese not only with regard to taste but also in texture was like traditionally pro duced cheese, viz. by dividing the curdled retentate into cubes, separating them and compressing them in moulds. However, itturned outto be impossibleto make the thus prepared cheese grains stick together, and the cheese produced were inclined to break with fractured surfaces where sticking together had not taken place.

It is the object of the invention to provide a method to impart structure or texture to cheese when the cheese is produced on the basis of milk concentrated by ultrafiltration, curdled, cut up and collected, in such manner that coherent and stable cheese are obtained which are identical to traditionally produced cheese not only with regard to taste but also with regard to appearance.

In the method according to the invention milk is concentrated by ultrafiltration, optionally combined with diafiltration, the retentate inoculated with lactic acid bacteria and curdled by the addition of rennet and/or acid, the curd divided into small pieces which are then assembled to cheeses, and the novel feature of the invention is that the division of the curd into small pieces takes place by breaking the curd to cheese grains in the form of irregular small pieces.

Surprisingly it has been found that whereas regulardly cut cubical pieces of curd cannot be compressed into stable coherent cheeses having the desired structure or texture cheese grains in the form of irregular small pieces from the broken curd can be compressed or consolidate and be shaped into cheese which have the desired texture and are not inclined to disintegrate or fall apart. It should be understood that the breaking of the curd takes place in such manner that the cheese grains formed as irregular small pieces have approximately the same size as the cheese grains formed during the traditional production of cheese, but a wider tolerance can be allowed.

In a suitable embodiment of the method according to the invention, the curd is cut into rod-shaped pieces which are then broken into irregular small pieces to form cheese grains, or the retentate is curdled in relatively tall cylindrical or prismatic containers whereafter the thus formed rod-shaped pieces of curd are broken into cheese grains.

The rod-shaped pieces of coagulum or curd are especially suited for the subsequent breaking in a special apparatusforthis purpose. As an experiment curd was cut into rods having a square cross section of 5 x 5 cm and a length of 15 cm, and the rods were broken by letting them pass a rotary pump with two tridentate rotors, and hereby a satisfactory result was obtained.

According to the invention the retentate after dosage of starter and rennet can be curdled continuously while flowing through a tubular curdling chamber in the way that the retentate after the inoculation is pumped into one end of the curdling chamber and passes the latter at such rate that it is ready curdled at the exit end of the chamber where it may optionally be extruded into one or more rods which are then broken into cheese grains. Hereby it is possible to establish a closed process line for carrying out the method according to the invention in which milk is supplied to a pasteurization and standardization plant and from these through the ultrafiltration plant is passed on to the curdling chamber and then is shaped and compressed to cheeses.

The cheese grains produced according to the invention may be transferred to moulds to form final cheese or they may be transferred to relatively large moulds and after compression be divided into several smaller cheeses. Finally, the cheese grains may be transferred to relatively tall moulds in which they consolidate by gravity.

According to the invention it is suitable that the cheese grains are at a temperature of above 30"C when they are transferred to moulds and that they are kept at this temperature until they are cemented together.

The breaking of the coagulum or curd can take place in many different ways. One need not necessar ily divide the curd into or prepare it in rod-shape.

Blocks or coagulum or curd may for instance be broken in an apparatus suited for this purpose, e.g. by passing rollers with spikes or similar tearing mem bers. It is important that the whole curd, i.e. also fines formed during the breaking, is included in the moulds. This is both in order to avoid waste of curd and because the fines can play an important part as a binder between the cheese grains.

Aftertransfer of the cheese grains to the mouldsthe cheeses are further treated substantially in the traditional manner with pressing and/orturning and salting.

When shaping has taken place at above 30"C the cheeses are slowly cooled to about 22"C so that an after souring ofthe cheese can take place. The cooling is preferably commenced 4-6 hours afterthe addition of starter, and the cheeses are after soured till next day. Salting is carried out when it is suitable for the type of cheese in question.

The invention also relates to an apparatus for carrying out the method according to the invention in which the retentate is curdled in relatively tall cylindrical or prismatic containers, and the novel features of the apparatus are a number of preferably vertical containers, means for transportation of the containers in a closed circuit, a feeding device, an emptying device, and a mill for breaking ofthe retentate curdled in the containers. The apparatus according to the invention preferably consists of a conveyor or a chain conveyor the drive roller and guide roller of which have vertical shafts, the curdling containers being firmly mounted on the conveyor or chain conveyor.

By means ofthe apparatus according to the invention it is possible to obtain a continuous progress of the method when, as preferably, the individual containers contain an amount of retentate corresponding to one cheese or a number of cheeses which are to be packed in one package. The rod of curd formed by the curdling is pushed directly into a mill or other apparatus suitable for breaking the curd into cheese grains, and the cheese grains are passed directly into a mould. Cheese moulds with cheese can hereby pass from curdling apparatus in a continuous stream.

According to the invention the containers can suitably have hinge bearings and be direct links of two chains which stretch between two rotors provided with notches which are engaged by the containers during the travel of the chains. Hereby a simple and sturdy construction and a reliable steering of the vertical position of the containers are obtained.

In the apparatus according to the invention each container has a bottom cover which is kept closed by resting against a track which serves the purpose of supporting the containers, but in such manner that the track has an interruption at the point where curdled retentate is to be pushed out so that the bottom cover can be opened.

The bottom covers suitably have springs which rest on the track in order to make sure that the covers are tightly closed even if there are minor inaccuracies in the passage of the chains along the track.

According to the invention the driving mechanism which moves the containers is adapted to move the containers stepwise so that they are consecutively moved forward to the feeding device and the empty ing device, respectively. It will of course be possible to arrange the apparatus according to the invention with uninterrupted movement ofthe driving mechanism, but it will be complicated to arrange the feeding device and the emptying device so that they follow the movement of the containers during filling and emptying.

The apparatus according to the invention is further explained with reference to the embodiment shown in the drawing where Figure 1 shows a perspective diagram of one end of the apparatus, and Figure 2 on a larger scale shows a section of a double chain conveyor at the emptying phase.

In the drawing 1 is a vertical cylindrical container.

As indicated in broken lines in Figure 1 and in greater detail in Figure 2 the containers 1 are connected with connecting links 2 which by means of pins 3 are connected with hinge bearings 4 on the containers 1. As shown in Figure 2 the containers 1 have bottom covers 5 and are open atthetop. The bottom covers 5 are hinged to the containers by a bearing 6 and are kept closed by means of a flat spring 7 which rests against a track 8. When a container 1 is in the emptying position the track 8 is interrupted so that the bottom cover 5 opens and a ready curdled rod 10 can be pushed down into an underlying breaking device or mill 9.

The track 8 has an inclined surface 11 which catches the flat spring 7 and closes the bottom cover 5 when the container is moved away from the emptying position above the mill 9.

The chain conveyor formed by the containers 1 and the connecting links 2 has two rotors 12. Figure 1 shows one end ofthe conveyor with a rotor 12 having a vertical shaft 14. The rotor 12 has notches 13, and some of the containers still engage notches 13. The other end of the chain conveyor is identical to that shown in Figure 1 except for the interruption of the track at the emptying station. The rotor 12 in one end of the conveyor is connected to a driving mechanism (not shown), and one rotor shaft 14 is provided with means for tightening the chains.

In Figure 1 is outlined a feeding device 15 from which the retentate is portioned to the containers.

Emptying ofthe ready curdled retentatetakes place at the mill 9. As outlined in Figure 2 the emptying device can consist of a piston 16 with a piston rod 17. The piston 16may either be moved down to the bottom of the container 1 and thereby press the rod of curd 10 down into the mill 9, orthe piston 16 may be lowered only a short distance into the container 1, and the rod of curd be expelled by means of compressed air introduced through a hollow space in the piston rod 17.

When the rotor 12 (Figure 1) rotates stepwise in the direction of the arrow an empty container 1 is passed under the feeding device 15 where it is filled with retentate mixed with rennet in the dosage device or rennet and retentate are simultaneously fed to the container. If desired there may at the first position of the container after filling be a stirrer which is lowered into the retentate and mixes retentate and rennet.

About 30 minutes after filling a container will reach the emptying station above the mill Swherethe ready curdled retentate is pressed out of the container down into the mill 9.

As indicated in Figure 2 the mill 9 consists of a housing 18 with an inlet spout 19 and a rotor 20 on a shaft 21.The rotor 20 has breaking members 22 which may consist of knifves or spikes which during rotation ofthe rotor will breakthe rod of curd 10 into irregular cheese grains and carry them to an outlet spout 23 (Figure 1) diametrically opposite the spout 19.

As indicated in Figure 1 the cheese grains fall from the outlet spout 23 down into cheese moulds 24 which are moved forward stepwise in time with the containers 1.

Between the emptying station at the mill 9 and the feeding device 15 there may be a cleaning station where the containers are washed so that curd residues, if any, are removed before the container is filled again.

The method according to the invention is illustrated by an example of production of feta cheese with reference to a block diagram showing the consecutive steps of the method.

1000 kilos offull milk holding 3.4% protein, 3.4% fat and 12.2% total solids is pasteurized at 72"C for 15 seconds and then subjected to ultrafiltration which yields 708.5 kilos of permeate with 4.9% solids and 291.5 kilos of retentate with 30.05% solids. The ultrafiltration takes place at an average pressure of 4.0 bars using a DDS membrane type GRG 1 P. The retentate is pasteurized at 90"C for 1 minute and homogenized with a pressure of 50 bars and is then inoculated with 1-2% starter of the cheddar type and optionally youghurt culture.After the inoculation there is an initial souring at 30"C for 60 minutes and then a mxing at which stage there may optionally be added bleaching agent ( < 1ml/kilo) and lipase composition ( < 0.15 g/kilo). The mixture is then heated to 39"C and curdling is effected for 30 minutes after addition of 0.3ml/kilo rennet, e.g. Chr. Hansen's standard rennet. The curd ia is then broken and the cheese grains transferred to moulds where the cheeses are shaped. The cheeses which are at a temperature of 30"C are turned 5 times at intervals of 10-30 minutes and in this process a certain draining of whey takes place.Thereafter the moulds are removed and the cheeses put in cans where 25 kilos of permeate are added. 20 hours of after-souring at about22"Cfollows whereby some whey is given off resulting in 187.4 kilos of fresh unsalted feta cheese with 42% solids.

The fresh cheeses are then salted by the addition of 8.2 kilos of salt and cooled at 4"C for 14 days whereafterthe final product is 200.2 kilos of salted feta cheese with 43% solids, 3.5% salt and about 40% fat in the solids.

The method according to the invention is especially suited forthe production of cheese with a structure as Tilsit, Feta, Blue Cheese and Camembert which are the varieties of cheese that can be made from milk concentrated by ultrafiltration. However, the invention is not restricted to the production of the said cheese type seeing that it will undoubtedly be possible to prepare other types of cheese on the basis of retentate using the technique according to the invention.

In the foregoing example of production of feta cheese the method is described on the basis of full milk as the starting material but it will be equally possible to practise the method according to the invention by ultrafiltration of skimmed milk and subsequent addition of fat to the retentate.

Claims (9)

1. A method for the production of cheese on the basis of milk which is concentrated by ultrafiltration, optionally combined with diafiltration, in which the retentate is inoculated with lactic acid bacteria and curdled by the addition of rennet and/or acid, the curd divided into small pieces which are then assembled into cheese, characterised in that the division of the curd into small pieces takes place by breaking the curd to cheese grains in the form of irregular small pieces.

2. A method as claimed in claim 1, characterised in that the curd is cut into rod-shaped pieces which are then broken into irregular small pieces to form cheese grains.

3. A method as claimed in claim 1, characterised in that the retentate is curdled in relatively tall cylindrical or prismatic containers.

4. A method as claimed in claim 1, characterised in that after dosage of rennet the retentate is curdled continuously while flowing through a tubular curdling chamber.

5. A method as claimed in claim 1, characterised in that the cheese grains are at a temperature above 30"C when they are assembled to cheeses and are left to stand at this temperature

6. An apparatus for carrying out the method according to claims 1 and 3, characterised by a number of preferably vertical containers (1), means fortransportation of the containers in a closed circuit, a feeding device (15), an emptying device (16,17) and means (9) for breaking the curd.

7. An apparatus as claimed in claim 6, characterised in that the means for transportation of the containers (1) consist of a conveyor or a chain conveyor the drive roller and guide roller of which have vertical shafts, the curdling containers (1) being firmly mounted on the conveyor or chain conveyor.

8. An apparatus as claimed in claims 6 and 7, characterised in that the curdling containers (1) have hinge bearings (4) and are direct links of two chains which stretch between two rotors (12) provided with notches (13) which are engaged by the containers during the travel of the chains. A method substantially as described above and disclosed in the specification.

9. An apparatus substantially as described above with reference to the accompanying drawing.