IE41617B1 - A method and device for treating curd for cheese manufacture - Google Patents

Abstract

Curds used for cheese prodn. are treated in drainage columns by allowing the level to reach a pre-determined level and then either stopping/reducing the ingress of milk and curds to the column or opening the valve at the base of the columns to allow a block of curds to exit or combining both processes with a suitable time delay between. This system ensures that (large) cheeses having increased homogeneity within themselves and with one another can be produced. The process may be automated.

Description

This invention relates to a method for treating curd for cheese manufacture in one or more draining columns in parallel discharging curd at their lower ends, and to a device for applying such a method.

Such a method is known in several different ways.

For continuous curd manufacture the use of draining columns is the only suitable method to obtain blocks of curd, but such columns are also applicable in cases in which the curd is manufactured in a discontinuous manner lo in a cheese vat. If desired such columns may operate entirely automatically, hut it is also possible to have part of the actions to be exerted done by personnel.

The use of such draining columns has several advantages, as known to the expert, but also disadvantages. In some known methods it is difficult to obtain cheeses with sufficient uniformity in weight and moisture content, in particular in the manufacture of larger cheeses. In other known systems it is possible to manufacture uniform cheeses one after the other in a single draining column, hut it is 2u difficult to obtaih uniform filling of a number of draining columns with curd if more columns are used in parallel, so that the cheeses made from several columns will thus not always be sufficiently uniform and homogeneous, and the -241617 cheeses made will easily have defects as to their structiire, e.g. because they have a too open texture with fine openings.

This invention aims at improving such known systems, methods and devices by providing means for obtaining that the column of curd will set always to the same extent, and that the curd will always remain submerged in the whey. The invention not only aims at obtaining uniformity in the curd blocks from the same column, but also in curd blocks resulting from different columns operating in parallel.

By taking care that the curd in the columns will always remain submerged in the whey, the inclusion of air is entirely avoided, and by the uniform setting the homogeneity of the cheese is highly promoted · According to the invention there is provided a method of manufacturing cheese in which a mixture of whey and curd is supplied to one or more parallel draining columns each periodically discharging curd from its lower end and in each of which a signal is derived from observing the curd at a certain level in said column, wherein when at least a certain predetermined quantity of curd is observed at said level, the supply of the mixture of whey and curd to the column is stopped or decreased and the observation of the curd at said level is continued during or repeated after a certain period of time, during which time said supply is stopped or decreased, and wherein the supply of the mixture of whey and curd to the column is restarted or increased if at the end of said period of time the quantity of curd present at said level is less than said predetermined quantity,the procedure of observing and - 3 41617 of starting or increasing the supply of the mixture to the column being repeated until said predetermined quantity of curd has been observed continuously or repeatedly at said level for a predetermined period of time whereupon 5 a block of curd is discharged from the column.

A time delay is desirable when opening the supply of whey and curd tq the column again in order to avoid unstable operation which could occur by switching on and off of the supply means such as a pump frequently. A time delay in closing the supply of whey and curd to the column or in opening the discharge of curd has the advantage that the curd is given sufficient time to settle and to set if the observing member for the curd already gives a signal when the curd has not sufficiently set e.g.· because it is difficult or impossible for this member to distinguish between set and non-set curd. If an observing member is used which is able to make this distinction, a time delay in using the signal therefrom is not always necessary.

According to a further aspect of the invention there is provided a device which includes one or more parallel draining cd I urns for curd, a curd observing member located at a level to which the curd in the settled and set condition has risen when sufficient curd has been accumulated to form a curd block for discharge, and means controlled by said curd observing member for starting the supply of the mixture of whey and curd to the column, for stopping or regulating said supply, if desired with a built-in time delay in the circuit between the curd observing member and the said means controlled thereby.

The invention, moreover, proposes to apply in a preferred embodiment one or more further observing members, such as and in particular an observing member for whey to be active near the highest level of the whey so as to close the whey and curd supply if whey is present at the level of said observing member.

Moreover, it is possible to apply together therewith an observing member for whey at a level lower than the said whey observing member at the highest level, to control a separate supply of whey or water.

Observing means for determining the presence of whey may he embodied in different manners as known to the expert and this does not give difficulties to the expert as they only have to compare whey to air. Thus it is possible to use for this purpose several usual types of observing members for observing the presence of any liquid or of an electrically conductive liquid. Much more difficult is the observing of the presence of curd of sufficient density. This may be done by determining the difference in electric conductivity of set curd in whey as compared with the conductivity of whey alone. As, however, said conductivity not only depends on the presence of more or less curd in the whey, but also on other variables, such as the temperature, the acidity, the presence of additional substances supplied such as water etc., it is preferable to compare a measurement by such a curd observing member to a measurement in the whey, and preferably in the whey from the same process, of the same type, acidity and temperature as the whey in the column. This is preferably embodied - 5 41617 in such a way that the member for measuring the whey to obtain the comparing signal is positioned in a space which is in liquid communication with the interior of the column and is separated therefrom by a sieve surface which allows whey to pass and which avoids curd from reaching said member, said member being present at the same height as the curd observing member.

Instead of the electric conductivity it is also possible to use the light transparency as the measured parameter. There are also other possibilities, such as the difference in reflection between whey and curd, but these seem to be less preferable. In many cases a system is advantageous in which a known hopper level observer or the like is used, consisting of a moving, e.g. rotating or reciprocating body, which in somewhat settled curd is subjected to much more resistance than in whey alone, which member observes this resistance to convert it into for instance a corresponding electrical signal if in the area where it is active there is rather much curd, or which member is stopped by said resistance and converts this stopping into a signal for controlling the supply or the discharge or both.

In the system according to the invention the curd observing member may be embodied or adjusted in such a way that at a certain moment it observes the presence of sufficient curd to stop the supply of the mixture of whey and curd, but in further settling and setting of the curd its level in the column drops so that it may reach a level, which is below the desired level, necessary for having a sufficient quantity of curd in the column to allow discharge of a curd block of sufficient volume or to be able to keep the supply to the column closed. This problem may he solved by again opening the closed supply of the mixture to the column with a certain time delay until the supply is closed again because the curd observing member again observes a considerablequantity of -641617 curd in its presence. The whey, flowing substantially downwardly in the colunn, aids in settling and setting of the curd and this whey is preferably discharged at least in part by a perforated wall part of the colunn at or near the lower end thereof. I'hus it is possible to alternately open and olose the supply of the mixture to the colunn, e.g. several times before the final level of the setting curd parts does no more drop below the fixed and chosen level of the curd observing member, after which-the discharge may be opened and a curd block may be cut off. This discharge may be controlled by the curd observing member itself or been adjusted at a fixed frequency rate adapted to the frequency rate of processing of the cheeses or to the average frequency rate with which it is desired to bring the curd from the cheese vat or the like into the column or columns, and, anyhow, chosen so that there is always sufficient time to assemble a sufficient quantity of curd in settled and set condition in the column or columns before discharging it from the column(s).

It is possible to compare measurements in whey and in curd in known manner, e.g. by applying a Wheatstone bridge, if electric signals are used.

In many canes it is possible that the observing member may be contaminated by curd . The bridge resistances in both branches of the Wheatstone bridge used may then becomo unequal, even if the observing members are present in exactly the same type of fluid, e.g. in pure whey. However, when apolying the invention, the level, of the curd will drop each time a curd block is cut off, so that each time said observing member for curd is present in pure v/hey, as is the comparing whey observing member. This gives the possibility to apply -741617 an automatic compensation of the Wheatstone bridge in the time interval between cutting off of a curd block and opening of the supply of tho mixture of whey and curd to the column, until the bridge is balanced. By doing this the influence of a possible contamination of electrodes for following measurements is done away with. This may be done if there is sufficient built in delay between the switching off and the switching on of the supply of the mixture to give time for said compensation without the possibility that curd will disturb the compensation. This is easily obtained because only two or three seconds are needed for said compensation, and the real time delay in the system may well he longer.

The invention will now he explained in more detail with reference to the enclosed drawing giving a preferred embodiment of the system of the invention, partly diagrammatic and in vertical section, showing a draining column with observing and control means.

This drawing shows' a draining column 1 for curd, having an upwardly conically flaring part at its top indicated hy 2, with a whey discharge 3. Λ perforated cylindrical surface A separates the interior of the column from the diverging space within part 2. At the lower end this column has a perforated wall, consisting of one or more parts 5, 6 one above the other, around each of which there is a whey receiving box 7, 8 respectively, with a whey discharge 9, 10 respectively. The column is closed at its lower end by a slide valve 11, which may he 3lid hack and fro horizontally to close or open the column and which may' in a manner known as such have a cutting edge in order to cut off a piece of curd during its closing movement. -8J When this member 11 is in open position, the curd may leave the column at its lower end by its own weight and by the pressure of curd and whey above it and it may then be taken up by suitable means, such as a cheese mold, indicated diagrammatically by 12, present on a table 13» over which this mold may be moved, e.g. by subsequent cheese molds being fed to the lower end of the column from the side and pushing the cheese mold 12 just filled away from the lower end of the column.

From a curd processor or the like a mixture of whey and curd may be supplied through a pipe 14 to the column. Preferably a pump 26 is provided in this pipe. When applying more than one column the pipe 14 nay be branched into two pipes 13 and 16 or into more pipes corresponding to the number of draining columns. Each of said pipes extends above the column to the center thereof and then downwardly into the column as indicated at 171 and below the opening at the lower end of said pipe there is a deflecting plate 18 to introduce the mixture of whey and curd into the column in a way which gives sufficient distribution all around and which does not give a downwardly penetrating jet which would disturb the settling and setting curd in the lower end of the column.

To each pipe 15» 16 a supply duct 19 may feed whey, preferably from the same process or processor, or water, and this supply is controlled by a valve 20.

In the column at the desired level there is a curd observing member 21. 'When the indication thereof for obtaining a good observation has to be compared with an observation in whey alone, it is possible to apply a whey observing member 22 at the same level at another position in the column, where curd cannot come into contact with -941617 this member, and this may be obtained by mounting a perforated, hood 25 in the column, so that only whey is able to contact member 22.

In the upper end of the column there is a whey observing 5 member 24-. Between observing members 21, 22 on the one hand and 24 on the other hand there may he a number of whey observing members 25 at different heights in the column.

In the supply pipes 15, 16, for the mixture there are adjustable valves 27.

Assuming that the observing members for whey and curd are electrodes, which e.g. determine the electric conductivity in order to derive an indication therefrom whether there is whey or curd or a mixture with' more or less curd in contact therewith, the draining column may be connected to earth electrically. A comparing member 29, for instance consisting of a Wheatstone bridge, compares the values measured by the observing members 21 and 22, with lead 28 giving the comparison for the column with earth connection. If at 21 there is only whey, this electrode will give the sane signal as observing member 22 for whey alone and in that case the Wheatstone bridge 29 is balanced and there is no resulting signal which has to be transmitted. If sufficient curd is present at electrode 21, the signals supplied by electrodes 21 and 22 will no longer be equal and a difference signal is generated in the Wheatstone bridge 29 which 13 fed to amplifier 50, whioh gives a signal of sufficient strength to a tine delay member 51· From member 51 a signal conductor leads to a time delay member 55, which, however, only operates when closing valve 27 by operating member 56 and not when opening this valve. -1041611 When member 31 transmits a signal for closing valve 27 in one or more columns the AND-gate 33 takes care of switching off pump 26 or of decreasing its delivery. Time delay member 34 is not active in this switching off, but only gives a time delay when said pump is switched on, e.g. a time delay of six seconds. The time delay of member 35 for closing the valve 27 may also be six seconds. In this way it is obtained that all the valves 27 are certainly not yet closed when the pump possibly does not come to an immediate stop but continues to rotate during a short period after switching off, Each column in essence has the same electric circuit as shown for one column, but this has not been indicated in more detail, apart from time delay member 32 for another column having the same function as member 31 for the column shown in the drawing.

From each of the whey observing members 25 a conductor leads to a contact 37 and with selection switch it is possible to select one of said contacts to connect the desired whey observing member 25 to a signal amplifier transmitting a signal for closing valve 20 if at the member 25 concerned whey is present. Whey observing member 24 is connected to the conductor which extends from curd observing member 21 to comparing member or Wheatstone bridge 29.

In the case as shown in the drawing it has been assumed that the closure slide valve 11 at the lower end of the column is operated by means not shown, which open and close this slide with a fixed frequency rate, e.g. after each 60 seconds. However, the invention also includes the possibility that the curd observing member 21 controls this valve 11 to open it when a sufficient quantity of curd in sufficiently settled and set condition had reached Phis observing member. This may then take place together with the opening and closing of the supply of the mixture of whey and curd to the column as shown and described.

If the curd observing member is not only able to react on the presence of a sufficient quantity of curd but is also adapted to distinguish sufficiently accurately between a larger and a smaller quantity of curd at the same level or between more or less settled and set curd, no time delay means need be used in the conductor for interrupting the supply to or opening the discharge from the column. In that case the time delay member 31 may be omitted, but it will be clear that in that case there will still he the need for time delays e.g. when the supply of the mixture of whey and curd to the column is opened again for avoiding an instable action of the pump.

The signal leads from the observing members 21 and 24 are connected to each other and thereby it is ascertained that the supply of the mixture of whey and curd to the column is only opened if both observing members make this desirable. To this end this part of the system is embodied, in such a way that each of the observing members 21, 24 is adapted to interrupt the supply of the mixture to the column independently of the other observing member, but that this supply can only he opened if this is considered desirable by both observing members in viev/ of the absence of sufficient curd at observing member 21 and the absence of whey at observing member 24. This can he done for instance hy insertin' suitable Oil-gates and AHD-gates in the signal conductors from electrodes 21 and 28 to the Wheatstone bridge 29· -1241617 Observing member 25 warrants that the curd is always sufficiently submerged in the whey and that the mixture of whey and curd is supplied to the column below the liquid level and not in contact with air.

The time delay of member 31 is e.g. three seconds.

In the embodiment shown this member delays both upon opening and closing ofthe supply.

Claims (13)

CLAIMS:

1. A method of manufacturing cheese in which a mixture of whey and curd is supplied to one or mote parallel draining columns each periodically discharging curd from 5 its lower end and in each of which a signal is derived from observing the curd at a certain level in said column, wherein when at least a certain predetermined quantity of curd is observed at said level, the supply of the mixture of whey and curd to the column is stopped or decreased and 1° the observation of the curd at said level is continued during or repeated after a certain period of time, during which time said supply is stopped or decreased, and wherein the supply of the mixture of whey and curd to the column is restarted or increased if at the end of said period 15 of time the quantity of curd present at said level is less than saidpredetermined quantity^ the procedure of observing and of starting or increasing the supply of the mixture to the column being repeated until said predetermined quantity of curd has been observed continuously or repeatedly at said 20 level for a predetermined period of time whereupon a block of curd is discharged from the column.

2. A method according to claim 1, wherein the supply of the mixture of whey and curd after each interruption is started with a certain time delay from the moment when the 25 quantity of curd at said level becomes less than said predetermined quantity.

3. A method according to claim 2, wherein the supply of the mixture of whey and curd is also stopped or decreased when it is determined that a higher level above the observing 30 level for the curd,whey is present, while said supply is only started or increased again when at the said observing level for the cur,d the quantity of curd becomes less than said predetermined quantity.

4. A method according to claim 3, wherein a separate supply of water or whey to the column is started when the whey level drops below a level which is below the said higher level where the presence of whey is observed, and which is above the observing level for the curd.

5. A device suitable for applying a method according to any preceding claim, which includes one or more parallel draining columns for curd, a curd observing member located at a level to which the curd in the settled and set condition has risen when sufficient curd has been accumulated to form a curd block for discharge, and means controlled by said curd observing member for starting the supply of the mixture of whey and curd to the column and for stopping or regulating said supply, if desired with a builtin time delay in the circuit between the curd observing member and the said means controlled thereby.

6. A device according to claim 5, wherein a whey observing member is mounted at a level in the column higher than the level of the curd observing member, said whey observing member being connected to means for stopping or decreasing the supply of the mixture of whey and curd when whey reaches said whey observing member, and to means which, at a signal from said whey observing member to restart said supply when the whey level has dropped below the ί level of said whey observing member, only starts said supply if the curd observing member also gives-.a signal for starting this supply.

7. A device according to claim 5 or claim 6, wherein a further whey observing member for measuring a parameter of the whey has been provided and that means are provided to compare the measurement thereof to the measurement of the curd observing member for determining a difference signal which, if of sufficient magnitude, indicates the presence of a sufficiently dense curd mass at the curd observing member. - 15 41617

8. A device according to claim 7, wherein said further whey observing member is provided in a chamber in liquid connection with the interior of the draining column and separated therefrom by a perforated surface, said perforated surface allowing, whey to pass and keeping curd out.

9. A device according to claim 7 or claim 8, wherein the presence of curd is observed by measuring the difference in electric conductivity or light absorption in curd and in whey.

10. A device according to claim 5 or claim 6, wherein the curd observing member is a hopper level ihdicator or similar moving member, whioh in curd meets with so much more resistance to its movement than in whey, that thereby it gives a signal for influencing the supply of whey and curd.

11. A device according to any of claims 5-9 inclusive, wherein means are provided to correct the measurement of the curd observing member in the period in which said member is in contact with whey only and in which the supply of the whey and curd mixture is stopped or decreased, which correction as to a deviation caused by contamination of said member takes place by compensation with respect to the measured value of a whey observing member which is continuously in contact with whey.

12. A device according to claim 11 with an electric bridge circuit for comparing the measurement in whey and in curd, wherein the said compensating means are embodied ln such a way that they cause the electric current through the bridge caused by contamination of the curd observing member to hecome zero by changing one or more other resistances in the bridge. - 16 41617

13. A device according to any of claims 5-12 inclusive, wherein below the highest possible level for the whey in the column above the curd observing member one or more other whey observing members are provided, which in the absence of 5 whey at their position start a separate supply of whey or water to the column by connection with a control member therefor.