JPH0372266B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to freezing of liquids. The term “liquid” refers to emulsions; suspensions; solutions; liquid phases of substances that are fixed at room temperature but melt at temperatures not much higher than room temperature; pastes; It is used to contain liquid foods; piure; egg white; egg white mixture; whole blood; fruit juice; and serum. It is essential that such liquids are not very viscous and therefore cannot be pumped or routed through distribution nozzles or distribution orifices.

The present invention is particularly effective when stored at room temperature for a long period of time.
For example, it relates to the freezing of liquids whose quality is likely to be impaired by chemical or microbial action. One example of such a liquid is a dairy product such as cream.
Most creams are manufactured in farms or factories located far from the final consumer. Therefore, a problem arises in that it is difficult to keep the cream fresh while it is distributed from the place of production to the place of sale. A particularly efficient distribution system is required, and creams are generally not transported long distances before being sold at retail outlets. It has therefore been proposed to freeze the cream and store the frozen cream in the refrigerator before selling it. This made it possible to export cream from one country to another. For example, it is known in the Republic of Ireland to freeze cream into slabs, break the slabs into more manageable blocks, package the blocks, and export the resulting product to England.

One drawback of such commercially practiced cream freezing methods is that the thawed cream is not as high quality as regular fresh cream. For example, when this thawed cream is added to a hot drink, such as coffee, the cream tends to break down and leave a layer of oil on the surface of the drink. For this reason, the inventor investigated a new method of freezing liquids.

British Patent Specification No. 1264439 relates to a frozen food product consisting of free-flowing discrete particles of eggs or semi-liquid dairy products (e.g. cream), each particle having a popcorn-like shape. . This food contains eggs or semi-liquid dairy products at -150
Produced by direct contact with a non-toxic liquefied gas refrigerant with a turbulent flow surface at temperatures below 0°C. This food substance gradually sinks. After sinking, this refrigerant material is collected and stored in a frozen state. This liquefied gas is liquid nitrogen.

The method described in GB 1264439 is believed to have two drawbacks. First, popcorn-shaped products have a hollow, thin-walled structure that makes them fragile and tend to generate unacceptably large amounts of dust when the products are transported to stores. Second, this method makes limited use of refrigeration obtained from liquefied gases such as liquid nitrogen. The reason for this will be explained below.

Another method of interest is described in British patent specification no.
Described in No. 1376972. According to this specification, this method is limited to the production of frozen foods from eggs. The eggs fall through at least one nozzle and come into direct contact with a non-toxic liquefied gas (e.g. liquefied nitrogen) at a temperature below -150°C. Egg flow rate from each nozzle is approximately 454-2268 g (1-5 lbs) per hour
The eggs enter the liquefied gas from the surface of the liquefied gas as loose particles and freeze in the liquefied gas to form pellets with a size of 3 mm to 7 mm. The pellets are collected at the bottom of the container containing the liquefied gas and removed from the container. The pellets are then stored in a suitable freezer.

Since the pellets produced by the method described in GB 1,376,972 are different from popcorn-like products, the first disadvantage associated with the production of frozen eggs as described in GB 1,274,439 is eliminated. However, as far as the second drawback is concerned, the British Patent Specification No.
The method described in No. 1376972 is described in British Patent Specification No. 1264439.
It is not intended to improve the method described in the above issue at all.

As described in our pending application 02416/1981, the reasons for the low utilization of liquid nitrogen in the method described in the above-mentioned British patent are as follows. That is, as the pellets sink (the specific gravity of frozen cream is greater than that of liquid nitrogen), the temperature of the pellets rapidly drops from about -10° to -20° to below -100°C. Accordingly, our pending patent application provides a method for producing frozen pellets for liquid use. This method involves lowering droplets into a non-toxic liquefied gas with a boiling point below -30°C, freezing the droplets to form buoyant pellets of frozen liquid, and before the pellets lose their buoyancy. The process includes separating the pellets from the liquefied gas. Typically, a flow of liquefied gas is set up to cause droplets to descend onto the surface of the liquefied gas, the droplets are then conveyed by the liquefied gas to a separator, and the separator separates the droplets from the liquefied gas; The contact and convection time between the liquid nitrogen and the pellets is such that the time is insufficient for the pellets to lose their buoyancy.

We have discovered that for a given liquid viscosity, there is an upper limit to the size of frozen liquid pellets or solids that can be produced by this method. This is because the evaporated liquefied gas (typically nitrogen) forms a cushion of gas beneath each droplet, counteracting the force of gravity. Therefore, the surface tension exerted by the liquefied gas tends to pull the droplets apart, and there is a limit to the maximum size of a droplet that can stably exist on the surface of liquid nitrogen. Additionally, there is a limit to the amount of frozen pellets that can be formed per unit time per nozzle through which droplets are dispensed. For example, it has been found that the maximum production rate for frozen double cream pellets is on the order of 10 cm ³ per nozzle per minute. It is desirable to greatly exceed such production speeds in commercial implementation without resorting to freezers with dozens of dispensing nozzles.

It is an object of the present invention to provide a method and apparatus for producing generally spherical to elongated frozen liquids which makes it possible (at least in the cream embodiment) to overcome or alleviate the limitations associated with our pending application above. It is to provide.

According to the present invention, a method of freezing a liquid to form a substantially spherical (or substantially prolate) frozen liquid is provided. The method involves passing the liquid to be frozen through at least one nozzle having an exit orifice, delivering a substantially continuous pulsating stream of liquid into a stream of liquefied gas having a boiling point below -30°C flowing along a channel. , the velocity of the liquid through the exit orifice of the nozzle is large enough to form part of the liquid into discrete masses with a cross-sectional area larger than the orifice, and these masses are frozen at least at their periphery. The method includes the steps of maintaining these masses in contact with a liquefied gas for a sufficient period of time to cause the solids to liquefy and collect the resulting generally spherical or generally prolate frozen bodies of liquid.

The invention also provides an apparatus for freezing liquids. The apparatus comprises means for defining an exit orifice of at least one nozzle and at least one groove, the means for defining an orifice comprising:
It is arranged above the groove to distribute the liquid to be frozen into the groove, and is further adapted to receive a liquefied gas having a boiling point below -30°C and to direct this liquefied gas into the groove. a peristaltic pump for passing the liquid to be frozen through an orifice and creating a substantially continuous pulsating flow of liquid into the liquefied gas stream; and freezing of the liquid from the liquefied gas. a separator adjacent the downstream end of said groove, adapted to separate bodies, such that upon operation of the device, the liquid itself forms loose, generally spherical or generally prolate masses; and at least a portion of the mass has a cross-sectional area greater than the cross-sectional area of the orifice, such that the mass is maintained in contact with the liquefied gas for at least a sufficient period of time to freeze the surface of the mass. .

Preferably said groove has a downwardly sloping bottom along which larger chunks can be rolled by the liquefied gas. This slope is preferably relatively gentle, ie in the range of 1/10 to 1/60.

The liquefied gas is preferably non-toxic and need not have a greater specific gravity than the liquid to be frozen. In fact, we use liquid nitrogen as the liquefied gas. Even when the liquid to be frozen has a greater specific gravity than liquid nitrogen (as is typically used), the liquid is tends to float first on the surface of a liquid nitrogen stream.

The orifice is generally defined by a nozzle. The diameter of the orifice is selected according to the viscosity of the liquid to be frozen.

Generally, the preferred orifice diameter increases as the viscosity increases. When producing frozen double cream or whipped cream we used orifices with a diameter of 1 mm to 3 mm.

The liquid to be frozen is preferably passed through the orifice by a positive displacement pump. Such a pump can provide a continuous moving flow of liquid to be naturally frozen. However, by using a pump that provides a uniform, non-pulsating flow of liquid, and by providing a reciprocating member or other member downstream of the orifice that temporarily interrupts the flow at a constant frequency;
It is also possible to provide a pulsating but substantially continuous flow. A variety of positive displacement pumps can be used in the methods and apparatus of the present invention. For example, reciprocating piston pumps, diaphragm pumps or lobe pumps
can be used. We believe that the larger the pulsations, that is, the greater the difference in amplitude between the maximum and minimum widths of the pulsating liquid emerging from the orifice, the easier it will be to form relatively large lumps of liquid. ing. Furthermore, the formation of relatively large, approximately spherical or approximately elongate masses of liquid would be more effective than if substantially all of the cream were formed as particles having a cross-sectional area approximately equal to or less than the cross-sectional area of the orifice. We have also discovered that the rate of production of frozen liquids is generally large. To create a suitably pulsating flow of the liquid to be frozen we use a peristaltic pump. The advantage of using such a pump is that it facilitates the hygienic handling of liquid or semi-liquid foods such as creams. This is because there is no direct contact between the moving parts of the pump and the cream.

In use, the nozzle must be properly positioned relative to the flow of liquefied gas to create excessive turbulence, i.e., turbulence that would interfere with the formation of substantially spherical or substantially elongated masses of the liquid to be frozen. Make sure not to.

Therefore, when used, the exit orifice of the nozzle should be directly above (e.g. 1 cm or less) above the flow of liquefied gas, facing or facing the direction of flow of liquefied gas rather than against it, and aligned with the axis of the nozzle. is generally at an angle of 10° to 60° with respect to the flow of liquefied gas. It is also possible to arrange the outlet of the nozzle below the surface of the liquefied gas, but this is not so preferred. It is desirable to provide a substantially laminar flow of liquefied gas along the groove to avoid excessive turbulence.

The depth of the liquefied gas in the groove is between 0.5 and 1.5 times (and most preferably between 0.6 and 1.2 times) the maximum diameter of the largest spherical or prolate body produced, i.e. the diameter along the main axis in the case of spheres. ) is preferably maintained within the range. For example, this depth can be about 1 cm. It has been found that in this case large sized lumps are rolled along the bottom of the groove by the liquefied gas. Preferably, the bottom of the groove is shaped to facilitate such rotational movement.

The flow rate of the liquid through the orifice is such that according to the invention a relatively large frozen liquid is obtained.
That is, they are selected to provide approximately spherical or approximately spheroidal masses with a diameter (along the major axis in the case of spheroidal particles) that is much larger than the diameter of the orifice (typically circular). Double cream is continuously pumped using a peristaltic pump through a suitably placed nozzle with an outlet orifice of 2-3 mm diameter onto the surface of a stream of liquid nitrogen 0.5-1 cm deep flowing along a slightly inclined groove. Upon passing, it was found that there were three different working phases depending on the flow rate of the cream.

By operation of a peristaltic pump, the liquid to be frozen, e.g. cream, is advanced onto the liquefied gas, forming a "tadpole" or comb having a head with the largest diameter and a tail with the smallest diameter. ” Discrete masses are formed. Because the largest diameter portion of each mass tends to advance more slowly than the smallest diameter portion, the difference in velocity causes the tail to enter the head, resulting in the formation of a mass with a larger diameter than the orifice.

At the lowest flow rates, virtually no frozen spheroidal or spheroidal cream with a diameter greater than the diameter of the orifice (or diameter along the major axis in the case of spheroidal particles) was formed. It has been discovered that at intermediate flow rates the cream does not break apart to form spherical or spheroidal particles on the surface of the liquid nitrogen. However, surprisingly, as the flow rate of the cream from the nozzle is increased, it is again possible to form a frozen cream having an almost long spheroidal shape; however, in this case, it is 0.6 to 0.8
It was discovered that particles with a diameter (along the major axis) of mm can be produced in large quantities. In general, such particles can be produced at cream flow rates of 200 cm ³ per nozzle per minute, depending on nozzle size, liquid nitrogen velocity, cream viscosity, among other parameters.

Thus, the liquid flow rate necessary for the present invention can be determined by simple experiments.

We have also found that in forming relatively large spherical or spheroidal frozen creams according to the present invention, smaller particles are formed as well. This is not a drawback. This is because when the frozen cream produced by the method of the present invention is placed in a container, if there is a size distribution, high-density packing can be easily achieved.

The speed at which the liquid nitrogen is flowed along the groove and the flow of the groove are preferably selected to prevent freezing of the entire larger particles of liquid that are formed. The downstream end of the groove is therefore preferably located above the inlet of the separator. The separator separates the frozen particles from the liquefied gas and allows the material to contact the liquefied gas and/or its cold vapor for a sufficient period of time to complete its freezing. Typically in this separator, the frozen particles are directed towards an outlet in a direction generally opposite to the direction in which the liquefied gas travels as it flows along the channels. The separator can thus be arranged generally below the groove,
This allows the device of the invention to be housed in a relatively compact housing.

Generally, the residence time of the liquid in the groove can be selected within the range of 3 to 15 seconds on the premise that at least the surface of the liquid particles is frozen. Typically the length of each groove is 1 m to 2 m and the velocity of the liquefied gas is in the range 0.14 to 0.66 m per second (in the case of double cream we use a velocity in the range 0.2 to 0.4 m per second). did). The appropriate liquefied gas flow rate can be found by simple experimentation for a given depth of liquefied gas and a given rate of dispensing the liquid to be frozen, among other parameters. We have found that the depth of the liquefied gas within the groove is an important parameter related to the flow rate of the liquefied gas as well as the rate of dispensing the liquid to be frozen. Therefore, holding all other parameters constant, if the liquefied gas in the groove is too shallow, the liquid to be frozen will concentrate at the upstream end, where it will form relatively long strands or elongated particles rather than spherical or elongated particles. Frozen or partially frozen liquid particles are formed. On the other hand, if the liquefied gas in the groove is too deep, it tends to concentrate at the downstream end, and the frozen particles enter the separator (particularly the preferred type of separator mentioned above), eventually forming relatively long frozen cream particles. Moreover, it is not always possible to completely control the excess depth by reducing the velocity of the liquefied gas flow. This is because lowering the flow rate of the liquefied gas may cause the spherical or elongated cream to agglomerate as it flows along the grooves. In general, however, we believe that as long as the above relationship between depth and diameter of the largest spherical or prolate particles is maintained, the apparatus of the present invention can be operated satisfactorily.

Preferably, the separator comprises a perforated rotating drum. In operation, this perforated rotating drum allows the liquefied gas to fall into the reservoir by gravity and is tilted so that its inlet end is at the top, directing the frozen particles of liquid towards the rotating screw. pushes the particles toward the exit, where they can be collected. Preferably, the rotating screw forces the frozen particles over an inclined surface that is in contact with cold vapor evaporated from the liquefied gas. This arrangement facilitates substantially complete freezing of the spherical or oblong particles.

The liquefied gas separated from the frozen particles is generally collected in a sump and dropped into a reservoir. This reservoir supplies liquefied gas to each groove by means of a pump.
Lifting pumps include, for example, bucket arrays or Archimedean screws that move along a path extending from sump to reservoir. The buckets are arranged to draw the liquefied gas from the sump and into the reservoir.

It is not necessary to completely separate the liquefied gas from the partially or completely frozen liquid material. In practice, it is preferred that the drum be provided with perforations or other openings sized to permit the passage of the smallest particles of frozen liquid material. For example, in the case of freezing cream, the openings are large enough to allow particles whose largest dimension is 1 mm or less to pass through, allowing them to collect together with the liquefied gas. Such particles are therefore returned to the groove and in fact some of them combine with larger cream masses to form even larger masses.

If the viscosity of the liquid to be frozen changes significantly with temperature, it is desirable to control the temperature at which the liquid is transported through the orifice by means of a pump or other means. Generally, it is desirable to select a temperature on the lower viscosity side in this temperature range. For example, when freezing double cream, it is preferable to feed the cream to a pump kept at a constant temperature in the range of 13° to 25°C. At this temperature the viscosity of the cream is 1° where cream is commonly supplied.
Significantly lower than in the ~10°C range.

It is desirable to pre-cool the liquid to be frozen by passing the liquefied gas through the device before dispensing it into the liquefied gas stream. In particular, it is desirable to maintain the temperature at the bottom of each groove not higher than the boiling point of the liquefied gas. When bubbles collect on such surfaces, they can interfere with the formation of relatively large spherical or elongated particles of the liquid to be frozen.

Generally, commercial embodiments of the apparatus of the present invention have at least three grooves extending parallel to each other, each groove having its own orifice associated with it.

The method and device of the invention will now be explained by way of example with reference to the accompanying drawings.

First, FIG. 1 will be explained. The peristaltic pump 2 uses four flexible tubes 4. The flexible tube 4 has a header 6 whose inlet end is attached to the outlet 8 of the pasteurizer 10.
The outlet end is connected to four cream dispensing nozzles 12 which cooperate with the cream freezer. The cream freezer is shown in more detail in Figures 2-7.

Next, FIG. 2 will be explained. The cream freezer 14 includes a heat insulating housing 16. When the device is in use, a nozzle extends from the top of this insulated housing. Generally, the housing 16 includes inner and outer stainless steel plates with a suitable insulating material (eg, perlite) therebetween. The purpose of insulation is to reduce the amount of heat absorbed by freezer 14.

The housing 16 is provided with a reservoir 18 on its left hand side (as shown). Reservoir 18 has an outlet in a dam or baffle 20 adapted to supply liquid nitrogen to the upstream end of trough 22. The trough 22 has four grooves 24 through which liquid nitrogen flows. (The arrangement of reservoir 18 and dam 20 is described in more detail below with reference to FIG. 6). The grooves 24 extend substantially parallel to each other and extend from their respective upstream ends into the housing 1.
It slopes generally downward to the downstream end on the right hand side of 6. Its slope is about 1/35. trough 24
A guide plate 26 extends beyond the downstream end of. The guide plate 26 terminates inside the first rotating drum 28 and near its inlet. The guide plate 26 has a substantially vertical upper portion extending directly above the tip of the trough and the drum 2.
It has an inner lower portion that slopes downwardly toward 8. During operation, liquid nitrogen falling from the downstream end of trough 22 is guided by guide plate 26 and enters rotating drum 28 . The rotating drum 28 is generally frustoconical in shape with its inlet end being narrower than its outlet end and its longitudinal axis being horizontal. This gentle slope allows lumps of cream to roll down when the cream freezer is in operation. A narrow slot 30 is formed through the drum 28 at its lower or outlet end. This allows the liquid nitrogen to fall by gravity from the slot 30 during operation, but retains the partially or completely frozen spherical or oblong cream mass. In this way cream can be separated from liquid nitrogen. A downwardly inclined guide plate 32 is provided below the slotted end of the drum 28. This guide plate 32 is adapted to collect liquid nitrogen that falls from the slot 30 during operation of the apparatus.
The guide plate 32 is arranged to be inclined towards the reservoir 34 and collect liquid nitrogen.

The outlet end of rotating drum 28 is connected to a second rotating drum 38 by a flange 36. Second
A narrow slot 40 is provided in the rotating drum 38 to separate residual liquid nitrogen from the frozen spherical or spheroidal cream and to allow nitrogen vapor emanating from the reservoir 34 to be directed into the interior of the drum 38. . A guide plate 42 slopes downwardly from the outlet end of drum 38 to sump 34 to collect liquid nitrogen and guide it to sump 34 during operation of the apparatus. The drum 38 has a generally frustoconical shape and its longitudinal axis is arranged horizontally. There is thus an upward slope along which the frozen cream mass is advanced during operation of the cream freezer. The inlet end of the drum 38 (the right-hand end in FIG. 2) is connected to the drum 2 by a flange 36.
connected to the outlet end of 8.

A shaft 44 extends inside the drum 38, and a screw 46 is attached to or formed integrally with the shaft 44. The screw 46 is adapted to advance the frozen spherical or oblong cream mass upwardly along the surface of the drum 38 to an outlet 48. The cream mass is directed downwardly through the outlet 48 and into a collecting tray 50. A collection tray 50 extends through the insulated housing 16 and into the interior of the freezer 14 at a lower portion of the outlet 48.

A spray header 52 is provided above the reservoir 34. The spray header 52 is a pipe 54
is connected to a liquid nitrogen source 59 (typically a vacuum insulated container suitable for supplying liquid nitrogen). The pipe 54 is provided with a flow rate control valve 56 . Reservoir 34 is provided with upper and lower liquid level detection elements 58 . Lower liquid level detection element 58
The valve 56 is arranged to automatically open to inject liquid nitrogen into the reservoir 34 when the liquid nitrogen is exposed and to automatically close again when the upper liquid level detection element is covered. In this way, liquid nitrogen is supplied to the reservoir 34 intermittently. Generally, to do this, an electrical signal is relayed from the sensing element 58 to a regulator 60 mounted on the drum. Regulator 60 is adapted to issue signals to open and close valve 56 in response to the sensing element. For example, the regulator 60 may generate an electrical signal and the valve 56 may be a solenoid valve which opens or closes the solenoid valve. By such means it is possible to maintain the liquid level in the reservoir 34 between a selected minimum and maximum value.

Rotating drums 28 and 38 are driven by electric motor 62. Belt and pulley drive mechanism 64
, which transmits power from the motor 62 to the rotating drums 28 and 38. This motor is typically mounted on the outside of housing 16.

Inside the rotating drum 38 and at its outlet end there is a gas outlet 51. The gas outlet 51 communicates with a fan 53 located outside the housing 16. Turning the fan creates a flow of nitrogen vapor along the inside of the rotating drums 28 and 38 in the direction of the passage of the cream mass, thereby facilitating complete freezing of the cream.

At the bottom of the reservoir 34 is a drain pipe 66 with a tap 68. The pipe 66 generally extends through the bottom of the housing 16, and the tap 68 is located at a predetermined location on the outside of the housing 16 for manual operation.

As shown in FIGS. 2, 3 and 3a, a lift pump is installed to pump liquid nitrogen from sump 34 to reservoir 18. This pump includes eight buckets 70 arranged substantially radially at equal intervals. Each bucket 70 is pivotally supported by a rod 73. The rod 73 extends from corner to corner diagonally opposite the opening of the bucket 70. Each rod 73 extends substantially horizontally from an elbow piece 74. The elbow piece 74 is fixed to the flange 36 by welding or other methods. One end face 77 of each bucket 70 is provided with a relatively low wall portion 72. This portion 72 is located at the unpivoted corner and is partially surrounded by a side wall 76. Side wall 76 has an integral weight balancing baffle 78 of generally triangular shape. This baffle 78 facilitates the delivery of liquid nitrogen from the lower wall portion or groove 72 when the bucket is tilted during operation. The bucket 70 is positioned so that it will not tip over and spill wall nitrogen when filled with liquid. In operation, the bucket passes through the sump 34 at its lowest point and rotates along a path such that the bucket can pump liquid nitrogen from the sump and reaches above the reservoir 18 at its top. The end face 77 of each bucket has an external lug 7 projecting therefrom for emptying the bucket.
5 is provided. The lug 75 supports a small cylindrical cam follower 81 which engages the cam surface 80 at the top of the circular path as the bucket rotates.
(Omitted from Figure 2 for clarity)
(See Figures 3 and 3a). The cam surface 80 applies a moment to each bucket 70 as it travels over the reservoir 18, causing it to rotate around the rod 73.
Liquid nitrogen is configured to naturally fall from the groove 72 into the reservoir 18 . If desired, an overflow pipe 82 may be provided in the reservoir 18 to return excess liquid nitrogen to the reservoir 34. Overflow pipe 8 if desired
2 to the bottom of the reservoir 18 in a liquid-tight manner when the reservoir contains liquid.
The liquid may drip into the reservoir 34 little by little. Such an arrangement facilitates cleaning of the device after use. This is because water can move directly from reservoir 18 to sump 34, thereby allowing liquid to be withdrawn from the reservoir. The construction of such a reservoir is shown in more detail in FIG.

As shown in FIG. 6, the bottom of reservoir 18 slopes toward the upstream end of trough 22. As shown in FIG. The dam or baffle 20 is a plate having a row of generally rectangular slots 101 at its end (see Figure 6a). Slot 101 cooperates with the bottom of groove 24 to create a laminar flow of liquid nitrogen from the reservoir along groove 24. Overflow pipe 82 is positioned so that liquid nitrogen does not flow over the top of dam or baffle 20 during operation. Baffle or dam 20 is typically curved to provide a generally concave cross-section toward trough 22.

A perforated plate 103 is provided at the bottom of the reservoir 18 to facilitate providing a laminar flow of liquid nitrogen from the reservoir 18 to the trough 22. perforated plate 10
3 has a number of openings approximately 1/2 inch (1.27 cm) in diameter. Perforated plate 103 extends generally parallel to the bottom of reservoir 18 and is typically positioned about 1 cm above the bottom. In operation, perforated plate 103 acts to dampen turbulence such as that caused by liquid nitrogen pouring from bucket 70 into reservoir 18.

Next, FIGS. 4 and 5 will be explained. Trough 22 is provided with four similar grooves 24. Each groove 24 has a curved bottom 86 having a generally arcuate cross-section with integral generally rectangular sloped sides that are at an angle of approximately 45 degrees with the horizontal. The depth of the arcuate portion 86 of each groove is generally on the order of 1/2 cm. The length of the longest string is generally about 1 cm.

The top of the groove 24 is open so that during operation there is an interface between the liquid nitrogen flowing along the groove 24 and the gas space above it. Nozzle 12 depends from a support arm 88 that extends through a slot 90 in housing 16. The support arm 88 is attached to a hydraulic or pneumatic cylinder 94 that allows the nozzle 12 to be raised and lowered (see FIG. 4). At its lowest part, the nozzle 12 has each groove 2
4 so that its outlet 96 is approximately 1/2 cm above the level of liquid nitrogen flowing along the groove 24. However, the nozzle 12 is in the cylinder 94
(which is typically adapted to operate in conjunction with regulator 60) allows it to be retracted from this position, for example for cleaning.

The axis of the outlet 96 of the nozzle 12 typically extends through the groove 24.
towards the downstream end of the groove, making an angle of approximately 20° with the plane of the liquid nitrogen in the groove. Furthermore, the axis of the nozzle is preferably coplanar with the vertical plane bisecting each groove at its exit.

Spray orifice 100 over almost its entire length
A spray tube 98 having a spray tube 98 extending from the exterior of the housing 16 into the interior of the drums 28 and 38. The spray tube 98 can be connected to a source of water or other cleaning fluid to clean the drum after use.

Regulator 60 includes pneumatic, hydraulic, electrical, or electronic control circuitry well known in the refrigeration art such that it can operate as follows. Operation of a manual switch or pushbutton (not shown) on the regulator starts motor 62 to remove drum 28 and bucket 70.
Start the rotation. Valve 56 is opened to drain water from the spray header to sump 34 and thus reservoir 1.
At 8, start supplying liquid nitrogen. Fan 53 is activated simultaneously to create a stream of cold nitrogen vapor along drums 28 and 38 as described above. Liquid nitrogen flows from reservoir 18 through dam 20 and along trough 22 . The liquid nitrogen then enters the separator and falls through the slot in drum 28. Liquid nitrogen falls from the slot in drum 28 and collects in reservoir 34. Level sensing element 58 sends a signal to regulator 60 to appropriately open and close valve 56, thereby increasing reservoir 34.
to maintain the level of liquid nitrogen within a selected range. When the apparatus is initially at room temperature, most of the liquid nitrogen initially supplied to reservoir 34 as well as other parts of cream freezer 14 will evaporate. As the temperature of the cream freezer decreases, the evaporation rate gradually decreases. A few minutes after starting operation, the temperature at the bottom 86 of the groove 24 drops to the boiling point of liquid nitrogen (-196°C). This takes, for example, 5 minutes. Therefore, there is typically a timer circuit within regulator 60. After a predetermined period of time has elapsed since starting the motor 62, the hydraulic cylinder 94 lowers the nozzle 12 so that the lowermost part of the nozzle 12 is directly above the surface of the liquid nitrogen at the upstream end of the groove 24. The timer circuit also simultaneously starts the peristaltic pump 2 to pump cream from the pasteurizer 10 to the nozzle 12.

Peristaltic pump 2 is configured to provide relatively high flow rates. Generally the exit diameter is 2-3mm
For nozzles, the flow rate is at least 150 cm ³ per minute per nozzle. This is compared to the fact that the flow velocity of liquid nitrogen along the groove 24 is approximately 0.2 to 0.6 m/s, and the depth of liquid nitrogen (measured from the bottom of the groove) is 1 cm (the length of the groove is approximately 2 m, so the flow rate of liquid nitrogen is approximately 1 per minute per groove).

Next, FIG. 8 will be explained. The cream emerges from the exit orifice of each nozzle 12 as a continuous pulsating stream with a generally circular cross section. The pulsation is determined by the diameter of the smallest continuous cream cross section at each nozzle.
The diameter of the exit orifice 96 in FIG.

The pulsating flow emerging from the nozzle tends to float on the surface of the liquid nitrogen flowing through the channels 24 as a result of gas bubbles collecting on the underside of the cream. It is believed that at the surface of the liquid nitrogen stream, the portion of the largest cross-sectional area of the cream stream advances toward the downstream end of the groove 24 at a different speed than the portion of the smallest cross-sectional area of the cream stream. This velocity difference tends to further increase the difference between the maximum and minimum cross-sectional areas, resulting in an apparent head of larger cross-sectional area than the exit orifice 96 of each nozzle and a predetermined upstream A length of cream is formed having a relatively thin tail connecting the length of cream. The difference between the maximum and minimum thickness of the cream stream is then less pronounced. This tail is then separated from the head to form a separate length of head-tail cream. The cream itself soon becomes a relatively large mass. This large lump is in each groove 2
4 and is large enough to touch the bottom of groove 24 and roll along the bottom of groove 24 by the flow of liquid nitrogen. The head may contact the bottom of the groove before separation of the tail from the head occurs.

By operation of a peristaltic pump, the liquid to be frozen, e.g. cream, is advanced onto the liquefied gas, and a "tadpole or comb" shaped piece is formed having a head with the largest diameter and a tail with the smallest diameter. A lump forms. Because the largest diameter portion of each mass tends to advance more slowly than the smallest diameter portion, the velocity difference causes the tail to enter the head, resulting in the formation of a mass larger in diameter than the orifice.

However, it should be understood that the above description of how relatively large spheroidal creams are formed is a simplification of a complex hydrodynamic process and is not intended to limit the scope of the invention in any way. I need to emphasize this. We believe that when the tail is broken, relatively small cream particles are formed, typically less than 1 mm in diameter. Such small particles float on the surface of the liquid nitrogen and are carried by the liquid nitrogen toward the downstream end of the groove 24. The cream mass that is rolled down the surface of the groove 24 by the liquid nitrogen moves more slowly than the cream mass that is carried by the surface of the liquid nitrogen.

The velocity of the liquid nitrogen flow along the groove 24 is such that by the time the cream mass reaches the downstream end of the groove 24, the cream mass is in sufficient contact with the liquid nitrogen that its surface is frozen and its interior is liquid. Adjusted so that it remains the same.

Typically, this convection time is chosen to be on the order of 5-10 seconds. The partially frozen spheroidal cream mass is carried by the flow of liquid nitrogen together with small masses, some of which are partially frozen, over the outlet end of the groove 24 and into the guide plate. 26
and from there it reaches the rotating drum 28. At least the main portion of the drum 28 has a slot 30 through which liquid nitrogen can pass. This allows the liquid nitrogen to be separated from the cream mass.
The liquid nitrogen collects on the guide plate 32 and flows down into the reservoir 34 by gravity. The size of the slot 30 is such that some of the smallest particles of cream fall through the slot along with the liquid nitrogen.

It should be recognized that cooling does not stop once the cream mass is separated from the liquid nitrogen. A significant amount of cold nitrogen vapor is present in drum 28 as the liquid nitrogen evaporates. As the drum 28 rotates, this cold nitrogen vapor comes into intimate contact with the cream mass. More fan 5
When turning 3, nitrogen vapor flows from drum 28 to drum 3.
8, and the cream mass flows into drum 2.
Cooling by the gas continues in drum 38 as it enters drum 38 from 8. The screw 46 then advances the cream mass towards the outlet 48 from which it falls by gravity and is collected in the accumulator 50. Small particles of remaining liquid nitrogen or cream fall by gravity from slot 40 and collect in reservoir 34.
The residence time of the cream mass in the portion of the freezer 14 between the end of the groove 24 and the outlet 48 is about 10 to 20 seconds. This convection time is generally sufficient to freeze even the center of the largest cream clumps, while overfreezing (i.e., cooling below approximately -30°C, in which case almost all of the largest cream clumps are frozen). (There is a tendency for cracks to form.) Nothing to do. The advantage of the device of the invention is that the cream is under-frozen (indicated by incomplete freezing of the largest cream lumps) and over-freezing (almost all of the largest cream lumps are cracked). This means that it is possible to drive in a manner that avoids the following: Cracking of cream masses, which are generally the largest in the form of long spherules, may occur in cases where these masses are relatively dimensionally unstable.

Operate the pump to pump liquid nitrogen into reservoir 3 along with the small particles of frozen cream that have collected in the reservoir.
4 and return to reservoir 18. The bucket pumps shown in Figures 2, 3 and 3a have been found to be particularly useful. This is because this pump does not use any valves, so there is no valve failure, as occurs when the valves come into contact with particles or small lumps of frozen cream, and cleaning is relatively easy. . The cream particles returned to the reservoir 18 are carried along with the liquid nitrogen below the dam 20 and into the liquid nitrogen flowing through the groove 24. There, at least a portion of the particles combine with the cream newly introduced into the flowing stream of liquid nitrogen from the nozzle 12. This phenomenon readily provides a wide range of particle sizes ranging from the smallest typically 1 mm (depending on the size of slot 20) to 8-9 mm. This distribution of the sizes of the spheroidal masses formed improves the packaging density of the resulting frozen cream.

Virtually all creams are formed into spherical masses. Typically at least 25% of the cream mass formed and generally at least 50
% has a diameter along its major axis that is at least twice the diameter of the outlet 96 of the nozzle 12. We have discovered that it is possible to assemble such frozen cream products containing at least 85% by weight of cream in relatively large chunks. We have also found that it is possible to collect frozen cream products containing at least 90% by weight of cream mass whose diameter along the major axis (i.e., length) is at least three times the diameter of the nozzle.

The collected frozen mass of cream can generally be packaged (eg, in a suitable plastic bag or container) and stored in a freezer for use. We have found that when this frozen cream is allowed to thaw, there is virtually no loss in quality, especially when it is used in hot beverages, and no fat separates from the cream.

As used herein, the term "substantially spherical mass or generally spheroidal mass" refers to a mass having a curved surface or curved edges. Includes regular spherical or oblate masses as well as disc-shaped or egg-shaped masses. Furthermore, this mass does not have to have a geometrically regular shape. We have found that typically the resulting masses are irregularly spheroidal, and that the degree of curvature of these masses is less pronounced than that of regular spheroids.

The following examples further illustrate the method of the invention.

EXAMPLE A frozen mass of double cream was produced using an apparatus substantially as shown in FIGS. 2-7. The device comprises four nozzles 12, each cooperating with its own groove 24. Groove 24
are each 1m70cm, slope downward, and the slope is 1/35. Each nozzle 12 has an outlet with an inner diameter of 2 mm.

First, liquid nitrogen was flowed through the device to cool it. Bucket 70 and drums 28 and 38 were rotated at 7 revolutions per minute. Once the device was cooled, the nozzle was lowered to a dispensing position directly above (approximately 0.5 mm above) the level of liquid nitrogen in the groove. The axis of nozzle 12 is trough 2
It formed an angle of about 25° with 2. Pasteurized double cream was fed to nozzle 12 by a Watson-Marraux 301 four-roller peristaltic pump. The pump was operated at 1416 revolutions per minute to create four continuous pulsating streams of cream. So each flow is 354 per minute
It was created with the pulsation of The tube used in conjunction with the peristaltic pump was silicone rubber with an inner diameter of 4.8 mm and a wall thickness of 1.6 mm.

The cream was dispensed as a continuous pulsating stream from each nozzle at a rate of 190 cm ³ per minute. The velocity of liquid nitrogen flowing along each groove was 0.4 m/s. The depth of liquid nitrogen in each groove was 7 mm in normal operation (i.e. when the cream was dispensed at the above speed).

Collected frozen “almost spheroidal” chunks of cream.

The size distribution of the lumps of this cream was evaluated. According to this rating, about 95% of the cream mass
Weight% is 7-9mm in length, about 3% by weight is 5-7mm, about 1% by weight is 1-5mm, and 1% or less is 1% by weight.
It was shorter than mm. The above lengths are measured along the longest dimension of each mass.

It is not necessary to use fan 53 to create a flow of nitrogen vapor along the inside of drums 28 and 38. Even if fan 53 is omitted, such flow is likely to occur and the nitrogen vapor will be exhausted through outlet 51. However, if desired, a fan can be used to extract nitrogen vapor from inside the housing near the tray 50.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing means for supplying cream to the nozzle of the cream freezer of the present invention.
FIG. 2 is a partially sectional schematic side elevational view of the cream freezer of the present invention. FIG. 3 is a sectional view taken along the line - of FIG. 2; FIG. 3a is a perspective view of the bucket shown in FIG. 3 when viewed from the upper side in a tilted state. 4 is a schematic end view showing the arrangement of the dispensing nozzle and trough forming part of the cream freezer shown in FIGS. 2 and 3; FIG. FIG. 5 is a schematic side view showing the distribution nozzle and trough arrangement forming part of the cream freezer shown in FIGS. 2 and 3; FIG. 6 is a schematic diagram illustrating the reservoir shown in FIGS. 2 and 3. Chapter 6a
The figure is a partial side elevational view of the reservoir shown in FIG. 6. FIG. 7 is a schematic diagram illustrating the reservoir shown in FIGS. 2 and 3. FIG. 8 is a perspective view prepared from a photograph showing the formation of a cream mass according to the present invention. Explanation of drawing numbers, 2... Peristaltic pump, 4... Flexible tube, 6... Header, 12...
Cream distribution nozzle, 14...Cream freezer, 16...Insulated housing, 18...Reservoir, 20...Dam, 22...Trough, 24...
Groove, 26... Guide plate, 28... Rotating drum, 30
...Slot, 32...Guidance board, 34...Tame, 3
8...Rotating drum, 40...Slot, 42...
Information board, 45... Screw, 48... Exit, 5
0... Accumulation tray, 52... Spray header,
60...Adjuster, 62...Electric motor, 70...
Bucket, 78...cam follower, 80...cam face.

Claims (1)

[Claims] 1. A method of freezing a liquid to form a substantially spherical or substantially elongate frozen body of liquid, comprising: passing the liquid through at least one nozzle with an exit orifice and causing the liquid to flow along a groove. Introducing a substantially continuous pulsating flow of liquid into a liquefied gas stream having a boiling point below °C, the rate of passage of the liquid through the nozzle orifice is such that a portion of the liquid passes through a cross-sectional area larger than the nozzle orifice. the mass is of sufficient size to form into discrete masses, and these masses are maintained in contact with the liquefied gas for a sufficient period of time to cause at least the surface of these masses to freeze; A method for freezing a liquid, characterized by collecting frozen bodies of liquid that are approximately spherical or approximately spheroidal. 2. A device for freezing a liquid, comprising means for defining an outlet orifice of at least one nozzle and at least one groove, said orifice defining means for distributing the liquid to be frozen into said groove;
It is arranged above the groove, and is adapted to receive liquefied gas having a boiling point lower than -30°C, and is capable of flowing the liquefied gas outward along the groove by gravity. A device for freezing a liquid, comprising a reservoir, a peristaltic pump, and a separator adjacent the downstream end of the groove adapted to separate frozen liquid from liquefied gas.