US 3486548 A
Abstract available in
Claims available in
Description (OCR text may contain errors)
Dec. 30, 1969 P. E. TODD METHOD AND APPARATUS FOR CONCENTRATING LIQUID-SOLIDS MIXTURES 4 Sheets-Sheet 1 Filed July 51, 1967 Light 53 Vacuum 53 Light 2 Discharge v INVENTOR PH/L /P E. TODD BY mug,
ATTORNEYS Dec. 30, 1969 P. E. Tom: 3,486,543
METHOD AND APPARATUS FOR CONCENTRATING LIQUID-SOLIDS MIXTURES Filed July 5 4 Shets-Sheet 2 PHIL/P 5. r000 BY JM, W/Vut,
ATTORNEYS Dec. 30, 1969 P, E. TODD 3,486,548
METHOD AND APPARATUS FOR CONCENTRATING LIQUID-SOLIDS MIXTURES Filed July 51. 1967 4 Sheets-Sheet 4.
CHOPPED FRUIT' v SYRUP IMIXING- z-coouwe PASTURIZING-3 INVENTOR. CANNlNG-4 PHIL/P E. 7000 BY #04, Mew 44x, m W
ATTORNEYS United States Patent O Int. Cl. B01d 1/22 U.S. Cl. 159-5 9 Claims ABSTRACT OF THE DISCLOSURE Concentrating method in which hydrous material containing liquid and solids (e.g., sugar syrup with pieces of fruit) is fed continuously to one end of a horizontal heated surface and moved continuously across the surface in the form of a thin layer section of regulated depth, with discharge of the concentrate at the other end thereof. During transit the material is subjected to a partial vacuum. Also apparatus for carrying out the foregoing method in which conveying means moves across a horizontal heated surface and serves to divide the material on the surface into successive layers. The material to be concentrated is fed to one end of the surface and removed as a concentrate from the other end. A cover or hood covers the surface and is evacuated for removal of vapors.
This invention relates generally to methods for the concentration of mixtures of liquids and solids, such as jams, preserves and marmalades, and to apparatus for carrying out such methods.
In the food processing industry it is frequently necessary to concentrate mixtures containing liquid and solids, to a relatively high consistency or viscosity. Particular reference can be made to the manufacture of so-called jams, preserves, and marmalades which contain sugar syrup and solids and are commonly classed as high solidshigh acid foods. The processing of such foods involves concentration by evaporation to a solids content which may be of the order of from 6070%. The conventional concentrating methods and equipment commonly employed for such mixtures are unsatisfactory for a number of reasons. Particularly, they tend to cause impairment of flavor due to overcooking and excessive localized heating. Also conventional equipment is not well-adapted to high capacity continuous plant operations. The difliculties experienced with conventional methods and equipment are accentuated when the material contains coarse pieces of fruit or like material, and it is desired to retain comparable pieces in the final product. Conventional methods and equipment tend to crush or pulp such solids and they may be subjected to heat injury and flavor impairment by localized overheating and loss of essences through prolonged evaporation periods.
In general it is an object of the present invention to provide an improved concentrating method and apparatus capable of effectively concentrating mixtures of the type referred to above and characterized by continuous operation.
Another object of the invention is to provide an improved concentrating method and apparatus capable of producing concentrated foods mixtures with superior flavor.
Another object of the invention is to provide an improved concentrating method and apparatus capable of handling and concentrating mixtures of the type having fruit or like solids in the form of relatively coarse pieces.
Additional objects and features of the invention will appear from the following description in which the preferred embodiment is set forth in detail in conjunction with the accompanying drawing.
Summary of the invention A method for the concentration of hydrous mixtures containing liquid and solids. The mixture is supplied continuously to one end of a horizontal heated surface to form a layer of the material. Successive layer sections are moved continuously from the feed end of the horizontal surface to the other discharge end. During transit the layer sections are subjected to a partial vacuum whereby progressive evaporation of moisture occurs. At the other discharge end of the heated surface the concentrated material is continuously discharged. The apparatus for carrying out the method consists of a metal wall or plate which is disposed horizontally and which forms the substantially horizontal surface. Means is provided for continuously supplying heat to this wall. A hood or enclosure is disposed over the upper surface of the wall and is adapted to be evacuated. Means are provided for continuously supplying the mixture to be concentrated to one end of the horizontal plate, whereby the mixture spreads as a layer over the upper surface of the plate. Also conveyer means is provided for isolating successive sections of the mixture and for moving the same over the upper surface of the plate, toward the other discharge end of the same. In addition means is provided for continuously removing the concentrated material from the other discharge end of the wall.
Referring to the drawing:
FIGURE 1 is a side elevational view illustrating concentrating apparatus incorporating the present invention;
FIGURE 2 is an end view of the apparatus shown in FIGURE 1, looking toward the right hand end of FIG- URE 1;
FIGURE 3 is an end view looking toward the left hand end of FIGURE 1, and partly in section;
FIGURE 4 is an enlarged section showing the feed end of the apparatus;
FIGURE 5 is a detail in section illustrating the discharge end of the apparatus;
FIGURE 6 is a side view in section showing the heating jacket and associated parts;
FIGURE 7 is a plan view of FIGURE 6;
FIGURE 8 illustrates equipment that may be employed with the apparatus of FIGURES I7; and
FIGURE 9 is a schematic view illustrating my method employed for the manufacture of fruit preserves.
DESCRIPTION OF PREFERRED EMBODIMENTS My method can best be described and understood after a description of the apparatus shown in FIGURES 16 inclusive. It consists of a supporting frame 10 carried by the standards 11. The frame 10 may include the side structural channels 12 secured to suitable laterally extending members (not shown). This frame serves to support an assembly 13 (FIGURES 5 and 6) which includes a flat horizontal heat transfer plate 14 made of suitable material such as stainless steel. The underside of the plate 14 is provided with a steamheated jacket 16. At one end of the apparatus the jacket connects with a steam inlet pipe 19, and at the other end there is a connection with the condensate pipe 20. Spacers 22 are shown inserted between the plate 14 and the wall 17 of the steam jacket. They serve to stiffen the plate 14 and to provide a zigzag passage for flow of steam.
Overlying the horizontal plate 14 (FIGURE 1) there is a conveyer 32 of the endless chain type. At the feed end of the apparatus the conveyer consists of the shaft 33 which is carried by bearings 34 and which is provided with the chain sprockets 36. At the discharge end of the apparatus there is a similar shaft 37 carried by bearings (not shown) and provided with sprockets 39. The endless chains 44 engage the sprockets 36 and 39, and serve to carry the spaced flights 45. These flights are in the form of slats which extend substantially the full width of the wall 14, and are adapted to ride upon and wipe over the upper surface of the plate 14. They can be made of suitable material such as Teflon, Kel-F, or nylon. Preferably they have suflicient flexibility to ensure good wiping contact over their entire length with the upper surface of plate 14.
The upper run of the endless chains 44 are shown supported by a plurality of idler sprockets 46 which in turn are carried by the idler shafts 47. These shafts are suitably journalled at their ends by bearings (not shown). The conveyer chains are driven by suitable means, such as an exterior drive sprocket 48 which is shown mounted upon one end of the shaft 33. Preferably the drive is variable whereby the speed of operation of flights 45 can be adjusted for optimum operation under given operating conditions.
A sealed hood or cover 49 encloses the space over the heat transfer plate 14. The side walls of the hood are shown with margins 50 that are adjacent the inner faces of the channels 12, and secured to the side edges of the heat transfer plate 14. This hood is shown provided with ducts 51 which can be connected by conduits (not shown) to a suitable evacuating system. The evacuating system may for example consist of a vapor condenser and a vacuum pump. Also the hood can be provided with glass covered inspection openings 52 and light fittings 53. One end wall of the hood is provided with a quick opening closure 54 and the other end wall 55 has a gasket sealed clamping 55a to the corresponding end margin of plate 14.
As shown particularly in FIGURE 4, at the feed end of the apparatus there is a feed duct 56 which is divergent or fan-shaped as shown in FIGURE 2. The lower apex end of this duct is connected with the feed supply pipe 57 and may also be provided with a normally closed drain 58. The plate 14 is provided with a slot 59 extending over substantially its entire width and which is in free communication with the upper open end of the duct 56. The feed material pumped through pipe 57 spreads or flows laterally over the adjacent upper surface of the plate 14 in the vicinity of the slot 59, and successive layer sections or portions are isolated between the travelling flights 45 and caused to be moved continuously over the upper surface of plate 14. The depth of the layer portions between each set of adjacent flights 45 is regulated or controlled by the rate of feed through the pipe 57 and the speed of movement of the flights 45. For a given feed mix and set of operating conditions the depth of the layer remains substantially constant at the feed end of plate 14. In general this layer can be relatively thin and of such depth as to insure substantially complete coverage of plate 14 between the flights, for the entire length of the. apparatus. This depth may vary somewhat in different runs depending on such factors as the consistency or viscosity of the feed mix and the amount of moisture to be removed.
At the discharge end of the apparatus (FIGURE there is a somewhat similar arrangement for removing concentrate. Thus a fan-shaped duct 60 has its upper end communicating with the space above the plate 14 through the transverse slot 61. The apex end of duct 60 connects with the discharge pipe 62, which may be connected with means such as a pump or a barometric leg, to maintain a vacuum seal. The material being moved along by the flights 45 is delivered to the region of the slot 61, whereby it flows down by gravity through the duct 60 and pipe 62.
FIGURE 8 schematically illustrates equipment which can be used with the apparatus shown in FIGURES l-4. The concentrating apparatus is indicated at 66 and is shown with its hood connected by conduit 67 with the vapor condenser 68. This condenser may be of the water jet type and is shown connected to the evacuating pump 69. A mixing tank 70 is shown for receiving the ingredients of the mix, and is connected by pump 71 with the heat exchanger or cooler 72. Water connections 73 and 74 are shown for circulating cold water through the cooler. From the heat exchanger 72 the mixture is introduced into the concentrator 66 by way of pipe 57 at a controlled temperature level which is above the vaporization point at the partial vacuum maintained within the concentrator. For example, where the partial vacuum maintained is of the order of 28 inches mercury column, the temperature of the mix in a typical instance may be of the order of to F. Concentrate is continuously removed from the discharge end of the apparatus 66 through pipe 62. Pump 63 serves to pass this concentrate through the heater 64 which serves to elevate the temperature to a suitable level for pasteurization, such as 200 F. The concentrate can then be delivered to a holding tank where it is held for a sufficient period to ensure pasteurization, after which it is introduced into containers for marketing.
It is desirable to provide the system of FIGURE 8 with automatic controls such as schematically indicated. Thus a valve 76 is shown for controlling the steam supplied to the jacket 70a of the mixer 70. This valve is connected for automatic control to the temperature controller 77, whereby when the temperature level of the mix reaches a desired level (e.g., 200 F.), the steam supply is automatically reduced to provide only sufficient heat to maintain the temperature at that level. The cold water supply to heat exchanger 72 is shown controlled by valve 78, which in turn is connected to temperature controller 79 and recorder 80, whereby the water supply is regulated to maintain the temperature of the mix leaving the heat exchanger at a desired constant value. The steam supply to the concentrator heating jacket 16 is shown controlled by valve 81, which in turn has a control connection to the pressure responsive device 82, whereby a constant steam pressure is maintained in the jacket.
A suitable density responsive device 83 (e.g., a device of the gamma ray type) is inserted in the discharge line 62 to the pump 63. Density variations are translated into control values (e.g., electrical voltages, pneumatic pressure, etc.) by associated device 84, whereby correlated control signals are derived and applied by the indicated control connections 86 and 87 to the variable driving motor 88 of the concentrator, and the variable motor drive 89 of the feed pump 71. The arrangement is such that as the density increases above a desired value, the drive speed of pump 71 is increased to increase the rate of supply of the mix, and simultaneously the rake conveyor 32 of the concentrator is driven at an increased speed to provide a reduced holding time on the plate 14.
The interior of the concentrator hood 49 is shown connected to a vacuum responsive device 72'. This device connects with the device 73 which derives control signals applied by connections 74' and 75 to vent valve 76 and variable pump drive 89. This arrangement is such that pump drive 89 is inoperative unless a predetermined vacuum exists in the hood of the concentrator. Also if the vacuum should become excessive, vent 76 is opened to break the vacuum.
The steam input to the heater 64 is shown provided with a control valve 91 that is controlled by the temperature responsive device 92. Thus the output from this heater is maintained at a desired constant temperature level (e.g., 200 F.).
The controls described above operate as follows. After introducing the desired mix into the mixer 70, steam is supplied at a rate suflicient to elevate the mix temperature to a desired level, after which the steam supply is automatically reduced to a value sufiicient to maintain the desired temperature. The pump 71 cannot operate until a desired minimum vacuum has been provided in the concentrator by vacuum pump 69. As the mix is being pumped through the cooler the cold water supply is controlled to provide a constant temperature level (e.g., 108 F.) for the output being supplied to the concentrator. The conveyer of the concentrator and also the rate of feed of the mix are controlled by the density of the output of the concentrate, whereby the density is maintained at a desired constant value. The heater 64 is controlled whereby its output is maintained at a desired level.
FIGURE 9 schematically illustrates the concentrating apparatus described above, together with steps in flow sheet form for the manufacture of a fruit preserve or like product. By fruit I have reference to the various fruits and berries such as are used in the manufacture of jams, preserves and marmalades, including citrus, pineapple, peaches, cherries, apricots, figs, plums and the various berries, including strawberries, blackberries, cranberries, blueberries and the like. The source fruit may be fresh or may have been frozen or thawed. It is prepared by various conventional methods, such as cleaning and removing of peels, seeds and the like. The fruit may be whole (e.g., strawberries) or may be chopped or sliced to a desired size and shape. In some instances the pieces may be coarse cube-like chunks, and in other instances they may be slices or strips of substantial length. Step 1 represents the mixing in mixer 70 of such chopped fruit with a suitable sugar syrup, or with the requisite amounts of sugar and water to make the syrup. Generally it is desirable to carry out this mixing step at an elevated temperature such as from 160 to 212 F. Thereafter this mixture, which may have a solids content of from 50 to 60%, is cooled by exchanger 64 in step 2 to a predetermined lower temperature level, such as for example a temperature of the order of 105 to 115 F. This mixture is then pumped at a continuous rate through pipe 57 of the concentrating apparatus 66. As the mixture passes upwardly through the divergent duct 56, and through the slot 59, it spreads or flows laterally to form a relatively thin layer extending over the adjacent area of the plate 14, and successive layer portions or sections are isolated between adjacent slats or flights 45. These isolated layer portions or sections are moved continuously toward the left as viewed in FIGURE 6, and during such movement heat is supplied through the plate 14 from the jacket 16, and the mixture is subjected to a partial vacuum. The partial vacuum is such as to cause effective evaporation of moisture without causing violent boiling. In practice partial vacuums corresponding to from 26 to 28 inches mercury column have been used. The heat supplied by steam in the jacket 16 can be such as to transfer heat through the plate 14 at a rate sufficient to maintain the temperature of the mixture at or about a suitable level for effective heat transfer. Each isolated portion or section of the mixture becomes gradually concentrated by evaporation as it moves over the plate 14 until the final concentration desired is attained as the material is delivered to the space adjacent the slot 58. The concentrate then flows through the conduit 57, after which it is subjected to pasteurizing 3, and introduced into containers in step 4. The holding time within the concentrator is controlled by the speed of the conveyer and may vary somewhat depending upon the character of the feed mix and the amount of water vapor removed. In practice, holding times ranging from to 25 seconds have been used with good results.
As an isolated layer portion or section is being moved along the upper surface of plate 14, some agitation takes place within the layer of material, due to the tendency of material immediately in contact with the plate 14 to remain stationary. Thus circulation takes place within the layer which is conducive to good heat transfer and effective evaporation of moisture.
The speed of movement of the conveyer flights 45 should be such that for the mixture being processed, the material does not tend to pile up as a thick mass immediately in advance of the flights. It has been found that with conveyer flight speeds of the order of from 1.5 to 2.5 feet per second, and with the apparatus being used on materials such as jams, preserves and marmalades, no serious pile up tends to occur in advance of the flights, but on the contrary the fluidity of the material undergoing evaporation is sufficient to maintain a layer extending completely between adjacent flights and over the entire width of plate 14.
It has been found that my method and apparatus can be used successfully in the concentration of mixtures containing solids of considerable size, as for example, whole berries, cubes or chunks which may be of the order of from A to A" in diameter, or slices which may be of the order of from V to /s" thick, to /2" wide, and /2 to 1 /2" in length. The presence of such solids does not interfere with effective concentration of the over-all mass of material. Heat is transferred to such solids not only by direct contact with the plate 14, but also by contact with surrounding heated liquid. The d1- mensions of the solids may be such that portions extend above the adjacent liquid level in the layer sections moving over the plate 14. It has been found that when such coarse pieces are present, they are not pulped or seriously reduced in size during transit through the concentrating apparatus.
In general it has been found that jams, preserves and marmalades concentrated by use of my method and apparatus have superior flavor characteristics. The flavor more nearly approximates the flavor of the fruit from which the mixture is made. This advantage is attributed to the conditions existing in the concentrating apparatus which are such as to avoid injury to heat-sensitive flavor constituents. Extended retention of material within the concentrator, with resulting over-heating, is avoided. Also localized over-heating is avoided due to the fact that the mixture is always under motion while it is in contact with the heated plate 14. The rapid rate of product throughput and the high evaporation rates result in retention of essences that would otherwise be lost in conventional methods and apparatus, and also serves to prevent or minimize detrimental product breakdown.
An example of my invention is as follows: The heated plate 14 had an effective length of about 8 ft. and an effective heat transfer area of 16 sq. ft. The drive to the conveyer was such that the conveyer flights 45 moved at a speed sufricient to provide a holding time of 20 seconds. The flights were located about 12 inches apart on the chains 44. The mixture prepared in step 1 comprised fresh strawberries averaging about 1 inch in diameter, together with sugar and water. The proportions were lbs. of whole strawberries to lbs. of canning sugar and 10 lbs. of water. This mixture was heated to a temperature of about 147 F. for a period of about 5 minutes, after which it was held for about 5 minutes and then pumped continuously through the cooler 68 to cool the mixture to about 106 F. This mixture was fed continuously to the concentrating apparatus at a rate of about 100 lbs. per minute (60 Brix). A partial vacuum was maintained corresponding to 26.5 inches mercury column. The concentrate was delivered from the concentrator at the rate of 80 lbs. per minute (68 Brix) and contained about 70.3% solids. It was pumped continuously through the heater 59 to elevate its temperature to 200 F. and then held in a tank for a period of about 5 minutes for pasteurization. Preserves made in this fashion were characterized by excellent flavor and keeping characteristics. The whole strawberries were clearly visible in the final product.
While I have described my method and apparatus as being particularly adapted for the manufacture of jams, preserves and marmalades it should be understood that it can be applied to a wide variety of mixtures including those that are somewhat difficult to concentrate by conventional apparatus. Particular reference can be made to the concentration of vegetable and fruit purees, fruit juices, meat slurries and the like.
In some instances it may be desirable to effect pasteurization before concentrating, in which event pasteuriziug temperatures and holding times are applied in conjunction with mixing.
1. A method for the concentration of hydrous mixtures containing liquids and solids comprising continuously supplying a quantity of the mixture to be concentrated to the feed end of a substantially horizontal heated surface, introducing said mixture as a continuous layer from below and through said surface onto one feed end thereof, as said mixture is introduced onto said surface, sequentially isolating successive portions or sections of said mixture layer and continuously moving successive layer sections one after the other over said surface from the feed end to the opposite discharge end of said surface, maintaining a partial vacuum above said surface during movement of said layer sections thereover, the layer sections being progressively concentrated by evaporation during movement over said surface, and continuously removing the concentrated mixture sections down through said discharge end of said surface.
2. A method as in claim 1 in which the hydrous mixture consists of sugar syrup together with fruit solids in the form of coarse pieces.
3. A method as in claim 1 in which the speed of movement over said surface and the rate with which the mixture is supplied are varied in response to variations in the density of the concentrated mixture sections removed from said discharge end of said surface.
4. A method as in claim 1 in which the hydrous mixture is introduced onto said feed end of said surface as a layer of generally uniform thickness which extends across substantially the full width of said surface so that subsequent spreading of said mixture over said surface is obviated.
5'. A method as in claim 1 in which said layer sections are agitated during movement thereof over said surface.
6. Apparatus for the concentration of hydrous mixtures comprising a fixed metal heat transfer plate forming a substantially horizontal surface, means for heating the underside of said plate, an enclosure disposed over and surrounding the surface and defining an evacuated space thereabove, means for continuously supplying a hydrous mixture to be concentrated as a generally uniform layer up through and upon one end of the horizontal surface whereby the mixture may be caused to flow over the surface, means for isolating said mixture into successive portions or sections and for continuously moving such successive layer portions or sections over said surface and toward the other discharge end of the same, and means for continuously removing concentrated mixture layer portions or sections down through the other discharge end of the surface.
7. Apparatus as in claim 6 in which the means for isolating and continuously moving successive layer portions or sections over said surface consists of a conveyer overlying said surface, said conveyer having spaced flights mounted thereon and extending laterally across said surface and in contact therewith, said flights being moved continuously from one end of the plate to the other discharge end thereof.
8. Apparatus as in claim 7 in which the means for supplying the material to be concentrated to one end of the horizontal surface consists of an upwardly extending duct having its upper open end communicating with a slot extending across said surface, and in which the means for continuously removing concentrated material consists of a downwardly extending duct having its upper open end communicating with another slot likewise extending across said surface adjacent the other end thereof.
9. Apparatus for the concentration of hydrous mixtures comprising a metal heat transfer plate forming a fixed substantially horizontal surface means for heating said plate, an enclosure disposed over said surface and enclosing said plate and defining a space above said surface which is, means for continuously supplying a hydrous mixture to be concentrated to one end of said surface whereby said mixture is positioned to be flowed over said surface in the form of a layer, means movable within said space for isolating and continuously moving successive layer portions or sections over said surface from said one to the other discharge end of the same, and means for continuously removing a concentrated mixture from said other discharge end of said surface; said means for moving said mixture over said surface consisting of a conveyor overlying said surface, said conveyer having spaced flights mounted thereon and extending transversely thereof and laterally across said surface in contact therewith, said flights being moved continuously from said one end of said surface to said discharge end thereof to move said layer sections along said surface toward said discharge end; said means for supplying said mixture to said one end of said surface consisting of an upwardly extending duct having its upper open end communicating with a slot extending across said surface; said means for continuously removing said concentrated mixture from said discharge end of said surface consisting of a downwardly extending duct having its upper open end communicating with another slot likewise extending across said surface adjacent said discharge end thereof.
References Cited UNITED STATES PATENTS 288,503 11/1883 Sheets 34-206 389,048 9/1888 Black 34206 880,917 3/1908 Raynor 34206 1,361,238 12/1920 Fleming. 2,081,512 5/1937 Smith 24165 X 2,452,983 11/1948 Birdsey 3413 X 2,636,555 4/1953 Klepetko et a1. 1594 2,846,319 8/1958 Kelly 159-49 1,191,921 7/1916 Macklind 159-5 1,154,190 9/1915 Macklind 1595 NORMAN YUDKOFF, Primary Examiner J. SOFER, Assistant Examiner US. Cl. X.R.