US3104977A - Method for freezing food - Google Patents

Description

Sept. 24, 1963 w. 1 MORRISON 3,104,977

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3,104,977 METHGD FOR FREEZING FOOD Willard L. Morrison, Lake Forest, Ill., assignor to Liquefreeze Company, inc., New York, NX., a corporation of New York Filed Jan. 14, 1960, Ser. No. 2,481 2 Claims. (Cl. 99-192) My invention relates to method and apparatus for freezing food and has for one object to provide a method and apparatus which will eliminate much of the delay and cost now necessary in connection with the preparation of frozen food for the market.

1l propose to pack the food in one pound or other suitabl-e sized packages for use and then pack the soft, unfrozen packages in a carton, seal the carton and then freeze the carton and its contents by immersing it in a bath of liquid nitrogen at atmospheric pressure and -320 degrees F. The soft, unfrozen package can easily be placed in the carton and has sufcient strength to maintain its shape under the very light loads involved. The carton is rigid and stiff and retains its shape and strength even when wet with liquid nitrogen. Thus when the loaded carton is immersed and it and its contents wet with nitrogen and frozen by heat exchange down to the desired point, depending on how long it remains immersed, the contents of each package on freezing expands and expands the package so as to properly fill the car-ton with, for example, a dozen rectangular one pound food packages.

This obviates the necessity of providing time and space to freeze the individual packages by Wind tunnel or cold plate and at the same time makes it unnecessary to handle and cartonize the frozen packages with resultant deterioration. The oartonizing is simple and easy and once cartonized, each individual package is protected during freezing and subsequent treatment.

lt is proposed to use the gas evaporated from the bath by heat exchange to provide initial cooling of the packages before they are cartonized. They will not be cooled down to the freezing point but to a point just above it where they begin to freeze, perhaps where the contents are mushy so that they can be easily placed in the carton.

Other objects will appear from time to time in the specification and claims.

The invention is illustrated diagrammatically in the accompanying drawings, wherein:

FIGURE l is a ilow sheet;

FIGURE 2 is a vertical section through part of the apparatus;

yFIGURE 3 is a plan view in part section of one end of the apparatus of FIGURE 2.

Like parts are indicated by like characters throughout the specification and drawings.

Referring to the flow sheet, the food-it might be peas for exampleis blanched in the usual way in the blanching station. yIt then llows through a cooling flume immersed .in water, the water being cooled by any suitable Water cooler. The blanched, cooled peas are then carried from the iiume through la gas cooled conveyor to a gas cooled packaging machine where in the usual way, perhaps beans or peas are packaged in preferably one pound or other suitable size packages. These packages are then cartonized 'at the cartonizing station and then fed through a liquid bath of liquid nitrogen, being kept in the hath for a suitable length of time depending upon the temperature to be desired. Thereafter the cartons without opening or without handling the individual packages ow to a warehouse or truck.

Meanwhile the gas evaporated in the liquid bath is conducted as gas no longer in liquid phase to and passes Yarent' 'ice through the package machine area, thence through the gas cooled conveyor area and back to the liquid source which, if desired may be a reliquefaction plant where nitrogen is reliqueiied. =It then ows as liquid from the liquid source back to the bath. lf the liquid source is not a reliqueiier, then the gas after leaving the gas cooled conveyor can be wasted. If it is' a reliquelier, the gas will be supplied thereto for reliquefaction.

Referring to 'FIGURES 2 and 3, the packaging charnher is illustrated diagrammatically at 1. One pound wrappers 4 are brought to it on a conveyor S. They are filled with food, for instance peas, the packaging mechanism forming no part of the present invention being not illustrated. The sealed packages 6 leave the packaging chamber 1 on the conveyor 7 and go to the cartonizing table `b where the one pound packages are packed in the carton as shown. The sealed carton 9 is then fed by a conveyor 10 to a chute 11 and falls by gravity into the liquid nitrogen bath A12 in the insulated housing 1-3. The force of gravity on the column of cartons forces each in succession downwardly beneath the conveyor '14. which travels around rollers 15 driven by the drive roller 16 from any suitable variable speed source of power not shown. The belt -14 is on its lower run below the level of the liquid in the bath so that the filled cartons which tend to float are held below the liquid level and are conveyed forwardly through the bath by the belt 14. As the cartons leave the bath, they are forced upwardly onto the discharge belt l17, passing around pulleys 18, driven by any suitable source of power by the pulley 19. Each packageras it rides up to the top of the belt 17 is received on the delivery belt 20 and fed into the shipper container 21. The liquid nitrogen is supplied to the bath E12 through a pipe 22 from a reliquefaction unit or liquid nitrogen source 23. The gas evaporated by the heat of the food in the bath passes out through a duct 24. Any suitable means 25 are provided at entrance and exit to minimize escape of the gas from the bath chamber. The duct 24 leads to the packing chamber and the gas then leads through -a duet 26 to the nitrogen cooled conveyor whence the duct 27 leads to the liqueer.

The cooling effect of the liquid nitrogen is of course much greater than that of the gaseous nitrogen even at the same temperature because liquid nitrogen when it boils expands some six hundred times. The liquid nitrogen must remain in the bath so that all the foodstuff as it passes through will be wet with it for a suliicient length of time to produce the desired low temperature. The bath is at rest. The food passes through it but with respect to the gas boiled off, the gas is flowing. The foodstuff is traveling also but its travel has nothing to do with the temperature desired. The desired temperature of the food before it is cartonized is controlled by controlling the rate at which the gaseous nitrogen flows past. Or to put it another way, by controlling the proportion of the gaseous nitrogen which passes around the `food in consonance with the proportion which can be returned directly for reliquefaction. Perhaps under some circumstances all the gaseous nitrogen will be passed around the unfrozen food. Perhaps under other circumstances only a part will be treated and the remainder with minimum rise in temperature will be returned for reliquefaction or wasted if reliquefaction is not used.

It is standard practice to freeze one pound or use size food packages in wind tunnels or between plates. When they are frozen in wind tunnels, they are hard to pack in cartons because they ydo not tit, because they expand and change their shape slightly.

The vpresent invention makes separate package freezing unnecessary. The food may be packed in the usual way under convenient, well known, temperature conditions in separate packages. These packages may then be packed in the carton unfrozen, even at room temperature. I prefer to cool them slightly down toward but still above freezing because I have by my method, liquid nitrogen available which can be used easily and effectively to cool down toward freezing. The optimum would be to freeze the yfood down to the point at which it just begins to be a little mushy, then each separate one pound package is placed in a carton and the carton is sealed. Flimsy one pound packages expand and tend to go round or change their shape When they are cooled in the wind tunnel or between cold plates so that is why so much care must be taken but the carton if strong enough to stand shipment is strong enough to act as a form so that when the llimsy packages expand as they freeze, all twelve of them come in contact with one another and snugly ll the carton and each of them is rectangular and of proper shape.

lt is of the utmost importance that each carton remain in the path the desired length of time to insure the desired temperature drop. This merely means that the rate of speed of all the conveyors Will be coordinated as is common in such industry to insure that each carton stays in the bath the desired length of time.

An important advantage is that when the carton with its frozen contents leaves the bath chamber on its Way to storage or shipper container, the carton containing as it does, if not any unevaporated liquid nitrogen, at least cold gaseous nitrogen lilling the pores of the carton, provides a protective envelope about the assembled packages to prevent contact of ambient air with them for a length of time suicient to get them into cold storage or into the shipper container or into some area where ambient air will not deteriorate the package. This is in sharp contrast with the situation prevailing where the individual packages at zero or less degrees F. must be separately handled and packed in cartons after freezing and special means must be taken to protect those individual packages before being cartonized against contact With the ambient air. Y

The carton serves as the shape or form so no special shaping and no special control of the shape or dimensions of the lled package is necessary.

The packages, Wrappers or containers may be of paper waxed or unwaxed, thin cardboard or plastic Vbut in each case they are soft, ilexible and disposable. The carton is preferably of paper board, corrugated boxboard, plastic or even wood as the case may be and While it is :disposai le, it is stili and rigid compared to the material of which the package wrappers themselves are made and this rela- Y lends itself well to treatment according to my tionship is essential in that the fhmsy wrappers must be selves to the freezing of the food in the usual Way but they must be adequately resisted by the strength of the carton so that when they have made their expansion and change shape, they will all be locked in place in contact with one another to till the carton solidly to avoid loose handling and deterioration. v

T he foods Which are packed may take the form of raw or uncooked vegetables-blanching is not cookingwhich till the small disposable containers or may take the -form of cooked food, Stews and the like. Either type of food invention.

I claim:

l. The method of freezing -food which consists in packing it in 1a plurality of separate, generally rectangular ilexible walled, disposable containers, cooling the separate packages down to a point just above freezing where their contents becomes mushy, illing a rectangular generally rigid Walled carton with said containers in Contact with `one another, closing and sealing the carlton and exposing the filled carton to a bath lof liquid nitrogen at atmospheric pressure until the temperature of -the food is below zero degrees F.

2. The method 'of freezing yfood which consists in packaging cooked food in flowable condi-tion in a plurality of separate, generally rectangular, flexible Walled, disposable containers, cooling the separate packages down to a point just above Ifreezing Where their Vcontents 4becomes mushy,

illing a rectangular, generally rigid, Walled carton withy said containers in contact with one another, clos-ing and sealing the carlton and exposing the illed carton to a bath of liquid nitrogen yat atmospheric pressure until the temperature lof the `food is below zero degrees F.

References Cited in the file of this patent UNITED STATES PATENTS 1,907,649 Marx May 9, 1933 2,364,049' Bensel Dec. 5, 1944 2,424,870 Welling et al. July 29, 1947 2,484,297 Klein Oct. 11, 1949 2,785,075 Malecki Mar. 12, 1957 2,920,462 Roser et al. Jan. 12, 1960 2,942,428 Morrison June 28, 1960 2,969,649 MorrisonV Jan. 31, 1961 OTHER REFERENCES The Freezing Preservation of Foods, 1943 by D. K. Tressler et al., published -by The Avi Publishing Co., Inc., New York, pages 225, 226, .and 227.

Claims (1)

1. THE METHOD OF FREEZING FOOD WHICH CONSISTS IN PACKING IT IN A PLURALITY OF SEPARATE, GENERALLY RECTAMGULAR FLEXIBLE WALLED DISPOSABLE CONTAINERS, COOLING THE SEPARATE PACKAGES DOWN TO A POINT JUST ABOVE FREEZING WHERE THEIR COSTENTS BECOMES MUSHY, FILLING A RECTANGULAR GENERALLY RIGID WALLED CARTON WITH SAID CONTAINERS IN CONTACT WITH ONE ANOTHER, CLOSING AND SEALING THE CARTON AND EXPOSING THE FILLER CARTON TO A BATH OF LIQUID NITROGEN AT ATMOSPHERIC PRESSURE UNTIL THE TEMPERATURE OF THE FOOD IS BELOW ZERO DEGREES F.

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