THERMAL TREATMENT OF FOOD PRODUCTS

Abstract: Apparatus for imparting thermal energy to or removing thermal energy from a food product, said apparatus com­ prising intensive and semi-intensive thermal treatment sec­ tions and at least one equilibrating section.

Description: THERMAL TREATMENT OF FOOD PRODUCTS Technical Field This.invention relates to an improved apparatus and method for rapidly and effectively transferring thermal energy either into or out of food products. One aspect of the invention relates to an apparatus comprising a plurality of adjacent thermal treatment zones adapted to rapidly heat and/qr cool food products passing sequentially therethrough. A further aspect of the invention relates to an apparatus and method useful for substantially equilibrating the temperature throughout a food product undergoing thermal treatment. Background of the Invention It is well known that the texture, flavor, odor and appearance of many food'products are significantly affected by the temperatures at which such products are prepared, stored and served. it has also been appreciated that moisture content, another im,oortant factor in the overall desirability or accebility of food products, is greatly affected by the thermal treatment accorded to such products. Many complex chemical and physical changes in food products are brought about by the manner in which their temperature and moisture content are regu latest Because of these and other considerations, numerous different apparatus and methods for heat and cooling food products have been disclosed in the prior art. Thus, for example, direct fired ovens, hot air convection ovens, infrared ovens and microwave ovenshave all been utilized, either alone or in combination, to impart thermal energy to food products. Similarly, cooling has been accomplished by conventional refrigeration, flashfreezing, liquid freezant immersion, cryogenic freezing and the like. Particularly desirable and effective apparatus and methods for imparting thermal energy to food products have previously been disclosed in United States Patents 3,884,213 and 4,154,861. The apparatus and methods disclosed in the foregoing patents employ columnated jets of air or other gaseous fluid to create discrete areas of very high heat transfer on the surface of a food product. This high heat transfer accomplishes the advantageous effects of crisping, browning, searing, chilling, or freezing in those localized areas where the jets impinge against the surface of the product. When the jets are of proper size, spacing, temperature, velocity and direction, very desirable results are obtained. Furthermore, when the food products are passed beneath the jets at a selected rate, these effects are spread evenly over the surface. Calculations, measurements of heat transfer and evident results on products heated illustrate that the impingement of jets of air substantially perpendicularly to the surface of the product accom plish,es heat transfer rates of 2 to 10 times greater than beat transfer of the same volume of air moving parallel to the product surface. This relatively new, very rapid heat transfer is desirable to initiate rapid cooking, baking, cooling or freezing. However, because most food products and recipes or. procedures for theirk preparation are designed with the thought in mind of heating or cooling those products by conventional means, they may not be prepared satisfactorily if they are only subjected to intensive impingement heating or cooling as previously disclosed. Although impingement heating or cooling can very quickly bring the surface temperature of the food products to very near that of the impinging gas, interior portions of those products may not be satisfactorily prepared by intensive impingement heating or cooling alone. Apparatus and methods are therefore needed for thermally treating food products in such manner that both the surface and interior portions of those products are satisfactorily prepared. One method previously disclosed for heating both the surface and interior portions of food products is through use of microwave radiation in combination with impingement heating. When microwave energy is employed in combination with the columnated jets of'heated gas impinging on the surface of the food products, internal and external heating can be accomplished simultaneously. However, the use of microwave energy is not well suited for all situations. For example, when using microwave energy, particular care must be taken to seal -the enclosure in which the cooking is done in order to prevent the escape of potentially dangerous and harmful microwave radiation. Such difficulties become even more significant when dealing with conveyorized industrial or institutional sized ovens. Also, while microwave energy is effective for heating the interior portions of food products, there is no analogous apparatus or method that is similarly effective for cooling the interior portions of food products. Therefore, an apparatus and method are needed for rapidly and efficiently heating and/or cooling both the surface and interior portions of food products. An apparatus and method are also needed that can further reduce the time and energy required to sequentially heat and cool food products, as is required in the preparation of many precooked, chilled or frozen foods Summary of the Invention I have devised an improved apparatus and method for transferring thermal energy into or out of food products. The apparatus and method of the invention preferably employ at least one intensive or semi-intensive thermal treatment zone or section for supplying columnated jets of a gaseous fluid to the exterior surfaces of food products moving relative thereto in combination with at least one equilibrating zone or section for promoting heat transfer into or out of the interior portions of the food products. Through use of the disclosed apparatus and method, those working in the food preparation industries will now be able to either heat or cool many food products with minimal time and energy requirements while simultaneously achiev ing significantly improved thermal equilibrium throughout the food products, thereby improving overall product quality in a manner that has not been possible prior to the present invention. A A primary object of the invention is to provide an apparatus and method for effectively and efficiently promoting the transfer of thermal energy into or out of a food product and for controlling the distribution of thermal energy throughout the interior of the food product. Another objectof the invention is to provide an apparatus and method for transferring thermal energy into or out of a food product through the use of at least one intensive or semi-intensive thermal treatment section in combination with at least one equilibrating section. Another object of the invention is to provide an apparatus and method for transferring thermal energy into or out of a food product through use of at least one intensive thermal treatment section in combination with at least one semi-intensive thermal treatment section. A further object of the invention is to provide a conveyorized cooking apparatus employing an intensive heating section with columnated jets of a relatively hotter gas for rapidly transferring thermal energy to a food product moving relative thereto in combination with an equilibrating section for promoting the penetration of thermal energy to the interior portions of the food product. A further object of the present invention is to provide a conveyorized apparatus for cooling food products that employs columnated jets of a relatively colder gas to cool a food product waving relative to said ets in combination with an equil ibrating section for promoting the transfer of thermal energy out of the interior portions of food products so as to reduce their overall level of thermal energy. ,Another object of the invention is tq provide an apparatus and method for promoting the transfer of thermal energy onto or out of a food product through the use of an intensive thermal treatment section, a semi-intensive thermal treatment section, and a separate equilibrating section. Another object*of the invention is to provide an apparatus comprising at least one intensive or semi-intensive thermal treatment section for impart ing thermal energy to or removing thermal energy from a food product moving relative thereto, in combination with at least one equilibrating section for bringing the interior and surface portions of the food product into substantial thermal equilibrium after the food product has exited the inten sive or semi-intensive thermal treatment section. A further object of the invention is to pro vide a cooking apparatus comprising an intensive cooking section and a semi-intensive cooking sec tion in combination with at least one eqtilibrat- ing section adjacent to the end of at least one of the cooking sections. A further -object of the invention is to pro vide an apparatus for cooling food products through use of one or more intensive or semi-intensive cooling sections in combination with at least one equilibrating section adjacent to the end of one of at least one of the cooling zones. A further object of the invention is to pro vide an apparatus useful for promoting substantial thermal equilibrium between the exterior surfaces and interior portions of a food product. Another object of the invention is to provide a method for imparting thermal energy to or removing thermal energy from a food product by subjecting the surface of the food product to columnated jets of a gaseous fluid having greater or lesser thermal energy, than the surface portions of the food product, and thereafter bringing the interior portions of the food product into substantial thermal equilibrium with the surface portions of the food product by maintaining the food product in a relatively less turbulent atmosphere having a thermal energy level with which the interior portions of the food product are desired to be brought into thermal equilibrium. A further object of the invention is to provide an apparatus and method that will reduce the time and energy required for the thermal treatment of certain precooked frozen foods In some cases the foregoing objects may be accomplished by adapting the apparatus of the invention with means to perform the desired functions within a single enclosure and by programming the apparatus to perform those functions in a desired sequence. Other and further objects of the invention will become apparent upon reading the detailed description of the invention in relation to the drawings annexed hereto and briefly described below. Brief Description of the Drawings The subject invention, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings in which: - Figure 1 is a perspective view of one preferred embodiment of the thermal treatment apparatus of the invention having an intensive heating section, a semi-intensive heating section, an equilibrating section, a semi-intensive cooling section, and an intensive cooling section combined in an adjacent ¯and contiguous, communicating-relationship; Figure 2 is a front elevation view, partially in section, of the intensive and semi-intensive heating sections of the apparatus of Figure 1; ; Figure 3 is a plan view, partially in section, of the intensive and semi-intensive heating sections - of Figures 1 and 2; Figure 4 is a side elevation view of the inten sive heating section of Figures 1-3; Figure 5 is a plan view, partially cut away, of a lower jet plate as shown in Figures 2-4; Figure 5A is sectional view taken along line A-A of Figure 5. Figure 6 is a front elevation view, partially in section, of the equilibrating section of Figure 1; Figure 7 is a plan view, partially in section, -of the equilibrating section of Figures 1 and 6; Figure 8 is a front elevation view, partially in section, of an alternate embodiment of the equi librating section of Figure 1; Figure 9 is a plan view, partially in section, of the equilibrating section of Figure 8; and Figure 10 is a front elevation view of the semi-intensive and intensive cooling sections of the apparatus shown of Figure 1. Numeral references are employed to designate like parts throughout the various figures of te drawing. Description of a Preferred Embodiment Referring to Figure 1, one preferred embodiment of thermal treating apparatus 10 of the invention preferably comprises intensive heating section: 12, semi-intensive heating section 14, .e'quilibrat- ing section 16, semi-intensive cooling section 18 and intensive cooling section 20. The various sections are preferably positioned in adjacent, contiguous and communicating relationship so as to permit a food product introduced into intensive heating section 12 of thermal treating apparatus 10 by conveyor means 22 to be transported longitud inally through each successive adjacent section, finally exiting from intensive cooling section 20. Although Figure 1 depicts a preferred embodiment useful for sequentially heating and cooling food produts, it is be understood that the thermal treatment section or sections and the equilibrating section or sections of the invention can be variously arranged and combined, depending upon the particular food product and method of preparation or storage involved. Thus, thermal treating apparatus 10 may comprise a plurality of intensive and semi-intensive heating sections in combination with one or more equilibrating sections, without any cooling section. Similarly, one or more cooling sections may be employed in combination with an equilibrating section without the need for any heating section. Also, it may be preferable for some applications to employ equilibrating sections between intensive and semi-intensive heating sections, between semi intensive or intensive cooling sect ions, or both. According to one preferred embodiment of the present invention, it is desirable that thermal treating - apparatus 10 comprise at least one intensive or semi-intensive thermal treatment section for supply ing,columnated jets of a gaseous fluid to the exterior surfaces of a food product moving relative thereto in combination with at least one equilibrat tempering,sction having a relatively less ¯turbulent atmosphere in which the surface and interior portions of the food product are desirably brought into substantial thermal equilibrium. According to another preferred embodiment of the invention, it is desirable that thermal treat ing apparatus 10 comprise at least one intensive thermal treatment section and at least one semi intensive thermal treatment section for supplying columnated jets of gas to impinge on the exterior surface of a food product in relative motion thereto. The structure and function of the different sections of thermal treating apparatus 10 of Figure 1 are separately described and explained below. It is understood, however, that thermal treating apparatus 10 can be fabricated and constructed either in separate modules or on a unitary frame work or supporting structure. When fabricated in separate modules, the various sections of thermal treating apparatus 10 can be fastened to each other, to the floor, or by some other method in order to maintain the correct positional alignment between them. Similarly, thermal treating apparatus 10 can be adapted in such manner that conveyor means 22 comprises a unit-ary carriage traversing a single closed loop extending longitudinally throughout thermal treating apparatus 10. Nevertheless1 it is also within the scope of the invention to employ a plurality of carriages in sequential relation to transport a food product longitudinally through thermal treating apparatus 10. By using a plural ity of shorter carriages, it may be possible to simplify fabrication, assembly, maintenance, and repair. Moreover, depending upon the particular food product, configuration and d application, it may be desirable - for different carriages of con veyor means 22 to advance at different speeds through the various section of thermal treating apparatus 10. Intensive heating section 12 and semi-intensive heating section 14 of Figure 1 are further described and explained with reference to Figures 2-5A, Inten sive heating section 12 and semi-intensive heating section 14 each comprise a cabinet having interior and exterior top walls 24, 26, bottom walls 28, 30; side walls 32, 34, back walls 56, 57 and front walls 59, 61, respectively, and are preferably constructed from a metallic material such as stain less steel, aluminized'steel, or the like Insulat ing material 36 is preferably disposed between the interior and exterior walls of intensive heating section 12 and semi-intensive heating section 14 in order to minimize heat loss to the surrounding air. Intensive heating section 12 and semi-inten sive heating section 14 further comprise support ing structure 38 for maintaining those sections in a desirable elevational and positional relation to the user, to each other and to other related equip ment. Conveyor means 22 transports food products 40 longitudinally through cooking chamber 42 defined by by interior top, bottom, side, back and front walls 24, 28, 32, 56, 59 respectively, of intensive heat ing section 12 and semi-intensive heating section 14. conveyor means 22 fuether comprises carriage 44 supported by rollers 46 rotatably secured to exterior sidewalls 34 for movement along tracks or guide surfaces that are secured to the interior back and front walls 56, 59, respectively, of inten sive heating section 12 and semi-intensive heating section 14. Carriage 44 is preferably mounted so that the elevation of food products 40 within cooking chamber 42 can be adjusted as desired. Conveyor means 22 is preferably driven by a variable speed motor that will permit the user to vary the speed at which food products 40 advance through cooking chamber 42. In other emodiments of the invention, alternate means (such as, for example, a carousel) an be satisfactorily employed to transport food products 40, depending on the physical configura tion of the particular apparatus utilized. Intensive heating section 12 and semi-intensive heating section 14 further comprise a plurality of jet fingers 48 communicating through plenum 50 with blower means 52 which is preferably secured to back wall 56,57. As shown in Figure 4, blower means 52 preferably comprises rotating shaft 58 having impeller means 60 secured thereto. Rotating shaft 58 is driven by motor 62 through belt 64 passing from pulley 66, mounted on the output shaft of motor 62 to pulley 68 mounted on rotating shaft 58. Although impeller means 60 employed in the preferred embodiment of the invention is an axial flow, pitchedLblade fan, other impeller means such as, for example, radial-flow, squirrel cage fans can also be-successfully employed for use in some applications. Furthermore, although rotating shaft 58 is shown in Figure 4 as being belt-driven by motor 62, it is understood that impeller means 60 and motor 62 can also be constructed in a direct drive configuration. Heat source 54 is desirably located beneath blower means 52 or in some other position suitable forii.ntroducing a heated gas into cooking chamber 42, where it is combined and mixed with gas being recirculated from jet fingers 48 through blower - means,52. -8ecause of the relatively high velocity ¯ through cooking chamber 42, the entire volume of gas is recirculated about once each second, thereby assuring satisfactory distribution of the thermal energy input by heat source 54. Heat source 54 preferably comprises heat source blower means 70 and heat source air duct 72 commun icating through outlet 74 with cooking chamber 42. According to one embodiment of the invention, ambi ent air drawn through inlet 71 by heat source blower means 70 is passed across a heating means positioned in heat source air duct 72 and is thereafter dis charged through outlet 74 into cooking chamber 42. The heating elements which supply thermal energy to the air or other gaseous fluid passing through heat source air duct 72 can comprise, for example, electrical resistance heating elements, gas-fired burners, oil burners, or some other suitable source of thermal energy. According to one preferred embodiment of the invention, a thermostat sensor is positioned near inlet port 76 to plenum 50 to monitor the temperature of the gas being recirculated through cooking chamber 42 by blower means 52. Jet fingers 48 and plenum 50 are preferably constructed from a metallic sheet material such as stainless steel or aluminized steel and are posi tioned inside cooking chamber 42 and secured to the interior walls of intensive heating section 12 and semi-intensive' heating section 14 by suitable mounting brackets, or the like. Plenum 50 preferably surrounds impeller means 60 and communicates through inlet port 76 and out let ports 78 with cooking chamber 42 and jet fingers 48, respectively. According to one embodiment of the invention, dampers are positioned in each of outlet ports 78 to control the flow of heated air from plenum 50 into each of jet fingers 48. Accord ing to a preferred embodiment of the invention, rear walls 80 of plenum 50 are inwardly tapered as plenum 50 extends outwardly from impeller means 60 to assist in controlling the pressure and volume of heater gas that is delivered through the outer jet fingers 48 to food products 40 on carriage 44. Upper and lower jet fingers, 48 further comprise tapered ducts 82 and orifice plates 84 for direct ing columnated jets of heated gas against the upper and lower surfaces of food products 40 passing therebetween on carriage 44. According to the embodiment of the invention shown in Figures 2-3, upper and lower jet fingers 48 are positioned so that they are directly opposed. It is understood, however, that in some applications upper and lower jet fingers 48 are desirably offset, and the lateral spacing between successive upper or lower jet fin gers 48 can vary independently. Although the dimen sions and relative spacing of the jet fingers in relation to each other and to food products 40 on carriage 44 can vary, the dimensions and spacing are desirably such that the columnated jets of heated gas discharged through orifices 86 in orifice' plates 84 contact the entire upper and lower sur faces of food products 40 as the food products pass longitudinally through intensive heating sec tion 12 and semi-intensive heating section 14. Preferably, the lateral spacing between adjacent jet.fingers is sufficient to permit the gas dis-' charged through orifices 86 to be recirculated between 3"et' fingers 48 and behind plenum 50, where' impeller means 60. The vertical spacing between opposed jet fin gers 48 in intensive heating section 12 and semi intensive heating section 14 is preferably adequate to permit the unimpeded passage of food products 40 therebetween. The preferred vertical spacing between opposed jet fingers 48 will also depend on the diameter and relative spacing of orifices 86 in orifice plates 84. A plan view, partially in section, of a lower jet finger 48 suitable for use in the present inven 'tion is shown in Figure 5. Referring to Figure 5, jet finger 48 preferably comprises spaced apart orifices 86 inorifice plate 84 that communicate through tapered ducts 82 with plenum 50 as shown in Figure 4,. The spacing for return of impinged air between orifices 86 is preferably at least twice their diameter so that sufficient space is - provided between adjacent jets that the returning air does not impede the flow of the columnated jets of heated gas being discharged through orifices 86. Such spacing permits the flow of diffused gas resulting from impingement of columnated jets of heated gas against the surface of the food product through spaces between the jets through cooking chamber 42 to the inlet'ports 76 behind impeller means 60 at the rear of plenum 50. Such spacing also results in application of discrete areas of high and low gas pressure over the surface of the product, permitting the impinging gas to flow over the surface to an adjacent low pressure area. Referring to Figure 5A, jet fingers 48 prefer ably further comprise columnating plate 88 in spaced apart relation to orifice plate 84. Columnating plate 88 comprises orifices 90 concentrically aligned with orifices 86 in orifice plate 84, although columnating plate 88 lies in a substantially hori zontal plane, whereas orifice plate 84 is slightly inclined relative thereto to assist in diffusing the columnated jets of gas passing through orifices 86 of the surface of food products 40. In a par ticularly preferred embodiment, a common centerline passing through orifices 86 and 90 is desirably inclined about two and a half degrees from a verti cal line extending through the center 6f orifice 86. Columnating plate 88 is desirably employed in combination with orifice plate 84 in order to pro duce the columnated jets of heated gas that impinge on the upper and lower surfaces of food products 40. Without the use of a columnating means such as columnating plate 88, the heated gas passing from tapered ducts 82 through orifices 86 would diffuse too rapidly before impinging against the surface of food products 40 in cooking chamber 42. Furthermore, while it is understood that a jet finger 48 comprising columnating plate 88 in combi nation with orifice plate 84 is a preferred appa ratus for producing the columnated jets of heated gas, other means for producing the jets can also be employed within the scope of the invention. Thus, for example, vertical tubes having an outlet diameter equivalent to that of orifices 86 in ori- fice plate 84. can be secured to orifice plates 84 so as to produce the columnated jets as desired. The use of such tubes is illustrated, for example, in U.S. 4,154,861. The principle difference between intensive heating section 12 and semi-intensive heating sec tion 14 resides in the relative rate at which thermal energy is imparted to the surface of food products 40 by the gas jets impining thereon. One method of controlling the rate is by changing the relative lateral spacing of jet fingers 48. Other methods include, for example, varying the orifice size of spacing, employing dampers to restrict the flow of gas to different jet fingers, blocking off certain orifices within a single jet finger, and the like. According to one embodiment, as shown in Figures 1-3, jet fingers 48 in semi- intensive heating section 14 are laterally spaced approximately twice as far apart as in intesive heating section 12. The number of jet fingers 48 in intensive'heating section 12 and semi-intensive heating section 14 is the same although the lineal distance traversed by food products 40 on carriage 44 while passing through intensive heating section 12 is only half of the distance traversed while passing through semi-intensive heating section 14. In other words, the number of columnated jets of heated gas to which food products 40 are subjected for each foot of travel through intensive heating section 12 is - approximately twice as great as the number of colum-, nated jets to which food products 40 are subjected per foot of travel through semi- intensive heating section 14. , Typically, food products 40 enter thermal treating apparatus 10 with a high moisture content and at room temperature, or in any event, at a temperature less than that desirable for cook ing the food products. A major portion of the desired total thermal energy to be supplied to food products 40 during cooking is applied to food products 40 in intensive heating section 12. In this manner, the surfaces of food products 40 are quickly raised to cooking temperatures, and excess moisture is simultaneously removed. According to - > rred embodiment of the invention more than about two-thirds of the overall thermal energy to be applied to food products 40 during the cooking stage is applied in intensive heating section 12 of thermal treating apparatus 10 Once the moisture content of the surface of food products 40 is reduced and the surface temperature is elevated to an appro priate cooking temperature, food products 40 are preferably transported into and through semi-intensive heating section 14. In semi-intensive heating section 14, thermal energy us applied to food products at a less intensive rate. The rate at which thermal energy is applied to food products 40 in semi-intensive heating section 14 is desirably reduced in order to permit the thermal energy to penetrate to the interior portions of food products 40 and to permit excess moisture to migrate from the interior por tions of food products 40 to the surface. In th,s manner it is possible to continue cooking food products 40 without burning or excessively drying the food surfaces. According to a preferred embod iment 6f the invention, less than half and most preferably, less than about one-third, of the over all thermal energy to be applied to food products 40 during the cooking stage is applied while food products 40 are passing through semi-intensive heating section 14 of thermal treating apparatus 10. While it is believed that tbe general consid erations described above will apply to most food products, it is understood that the various param eters discussed in connection with the preferred embodiments of intensive heating section 12 and semi-intensive heating section 14 can vary acoording to the particular food product for which thermal treatment is desired. Thus, for example, the com position, temperature, pressure, velocity, and width of the columnated jets of heated gas, the dimensions, number and relative spacing of jet fingers 48, and the configuration, elevation and speed of advance of conveyor means 22 can all be varied so as to achieve the optimum temperature, moisture content, and associated rate of cooking that is desired for a particular product. While in the preffered embodiment, intensive heating section 12 and semi-intensive heating sec tion 14 are each shown as having a single plenum through which heated das is forced by a single impeller means, it is understood that other config urations emplying different combinations of plenums and blower means can be similarly employed within the scope of the invention. According to a preferred embodiment of the invention, food produ'cts 40 being discharged from semi-intensive heating section 14 are next trans- ported into equilibrating section as shown in Figures 6-9. Equilibrating section 16 comprises equilibrating chamber 94 having a carriage 44A disposed therein that is preferably aligned so as to cooperate with carriage 44 of semi-intensive h'eat'ing section 14 of thermal heating apparatus 10. Equilibrating section 16 comprises a cabinet consisting of interior and exterior top walls 96, 98, side walls 102, 104, interior land exterior 106, 108, front walls 110, 112, respectively, and bottom surface 100, and is elevated to a desired height by supporting structure 114. The cabinet portion of equilibrating section 16 is preferably constructed from metallic materials, and the respective inferior and exterior walls are perfer ably constructed from a metallic sheet material such as, for example, stainless steel, aluminized steel, or the like. Insulating material 116 can be utilized between the respective interior and exterior walls of the cabinet portion of equilib rating section 16. However, where sheets of seain- less steel are employed in making the respective walls, the use of insulating material 116 may not be required. Food products 40 are transported through equilibrating section 16 on carriage 44A. Carriage 44A is understood to be a part of conveyor means 22 of thermal treating apparatus 10 and may be - part of a unitary conveyor means extending from ¯intensive heating section 12 and semi-intensive heating section 14 into equilibrating section 16, or may be an independently controlled portion of conveyor means 22 that is posftioned in cooperating alignment with carriage 44A of intensive heating section 12 and semi-intensive heating section 14 as set forth above. Equilibrating section 16 is adapted to discharge heated gays into equilibrating chamber 94 through inlet duch 116, which extends transversely through interior and exterior side walls 102, 104 of equilib rating section 16 and outside wall 34 of semi--intensive heating section 14 from plenum 50 as shown in Figure 3. Thus, equilibrating chamber 94 of equilibrat ing section 16 communicates with plenum 50 of semiintensive heating section 14 and a minor portion of the heated gas discharged by blower means 52 of semi-intensive heating section 14 is controllably introduced into equilibrating section 16. The flow of heated gas through inlet duch 116 into equilibrating chamber 94 of equilibrating section 16 is preferably controlled by damper 118 or a functional equivalent thereof. According to a particularly preferred embodiment of the invention, the amount of heated das discharged through inlet duch 116 into equilibrating chamber 94 of equilib rating section 16 is less than about 10 percent of the total amount of heated gas discharged into plenum 50 by blower means 52 of semi-intensive heating section 14. According to the embodiment of equilibrating section 16 shown in Figures 6-7, curved baffle 120 extends downward from interior top wall 96 and is positioned transversely across equilibrating section 16 over, carriage 44A on which food products 40 are transported. Curved baffle 120 is desirably positioned near the point where food products 40 exit from equilibrating section 16 on carriage 44A. and deflects a major portion of the heated gas introduced through inlet duct 116 back through equilibrating chamber 94 toward the entrance of equilibrating section 16. Referring also to Figure 2, it is seen that some heated gas designating by arrows,122 enters equilibrating chamber 94 of equilibrating section 16 from equilibrating chamber 42 of semi-intensive heating section 14. This flow arises from the "splshing" effect of the opposed columnated jets of air converging on each other or impinging on product from the outermost upper and lower jet fingers 48 of semi-intensive heating section 14. In this embodiment, the heated gas designated by arrows 122 combines with the heated gas entering through inlet duct 116 to recirculate air deflected by curved baffle 120 throughout equilibrating chamber 94 of equilibrating section 16. A minor portion of the heated air impinging on curved baffle 120 is deflected down wardly, underneath said baffle, and exits equilib- - rating chamber 94 of equilibrating section 16 through vent pipe 24 transversing interior and exterior top walls 96, 98. As heated gas passes under curved baffle 120 and upward -through vent pipe 124, a minor amount of outside air is also drawn in under interior and exterior side walls 102, 104 as designated by arrows 126 in Figures 6-9. According to a particularly preferred embod -iment of the invention, interior and exterior side walls 102, 104 desirably extend downward to a point that is just high enough to permit food products 40 to exit equilibrating section 16 on carriage 44A. The bottom of curved baffle 120 is preferably higher than the bottom of interior and exterior side walls 102, 104 to promote the flow of air or other gas as described above. The vertical distance between the bottom of curved baffle 120 and side walls 102, 104 is shown as the distance "d" in Figure 6, and is preferably about one inch. Also, 'the vertical distance between the bottom of curved baffle 120 and the tope of carriage 44A is preferably less than the vertical dimension of curved baffle 120. An alternate embodiment for equilibrating section 16 of thermal treating apparatus of the invention is depicted in Figures 8-9. In Figures 8-9, inlet duct 116 introduces heated gas into equilibrating jet finger 128 which is secured thereto in such manner that columnated jets of heated gas are discharged into equilibrating chamber 94 of equilibrating section 16 in a longitudinal direction parallel to the direction Of travel of fo,,,o,d,;,,j;,t,S food products carriage 44A. Equilibrating jet finger 128 is constructed in the manner previously described for jet fingers 48 of intensive heating section 12 and semi-intensive heating section 14 of thermal treating apparatus 10, and thus comprises tapered duct 130, orifice plate 132 having orifices 134 positioned therein that are concentrically aligned with cooperating orifices in a spaced apart columnating jet plate (not shown). In the embodiment shown in Figures 8 and 9, jets of heated gas discharged from orifices 134 in equilibrating"jet', finger 128 impinge against curved baffle 136, and amajor portion of the heated gas impinging on curved baffle 136 is deflected back toward equilibrating jet finger 128, thereby setting up a recirculating air flow within equilib rating chamber 94 of equilibrating section 16. As previously described in regard to Figures 6 and 7, vent pipe 124 is positioned behind curved baffle 136 to vent gas passing underneath the baffle The relative elevation between the bottom of curved baffle 136 and the bottom of interior and exterior side walls 102, 104 is preferably the same as has previously been described in relation to Figure 6. Although the embodiments shown in Figures 6-9 only provide for the introduction of heated gas into equilibrating chamber 94 of equilibrating section 16 at a position above food products 40 being transported on carriage 44A, it is understood that it may'be preferable for'some applications to construct equilibrating section 16 in such manner that heated gas is introduced into equilibrating section 94 both above and below food products 40 through a plurality of ducts communicating with plenum 50 of the preceding heating section. Further more, while equilibrating section 16 has discharged described herein as receiving heated gas discharged from semi-intensive section 14, it is understood from the earlier explanation in regard to Figure 1 that where equilibreting section 16 is positioned adjacent to an intensive heating section, heated gas from the intensive heating section can be sim ilarly discharged into equilibrating section 16. In equilibrating section 16, the interior portions of food products 40 are desirably brought into thermal equilibrium with their outside sur faces. In other words, equilibrating chamber 94 of equilibrating section 16 is maintained by means of the apparatus disclosed herein as an environment in which thermal energy is able to penetrate to the inner portions of food products 40 without causing unwanted burning, scorching, blistering or excessive drying on the outside surfaces of those products. Through use of equilibrating section 16, the atmosphere surrounding food products 40 is maintained at a temperature substantially equiva- lent to that of the columnated jets of heated gas that impinged directly upon the food surface in the intensive and semi-intensive heating sections. In equilibrating section 16, the rate at which thermal energy is supplied to food products 40 is generally nuch less that in intensive heating sec tion 12 and semi-intensive heating section 14. This can be attributed largely to the lower flow '",\'ates and velocities of the heated gas in equilib rating' section 16, and also to the difference in the angle at which the gas contacts the food sur face. It should be understood, however, that the introduction of gas from an intensive or semi intensive section is not always required for suc cessful operation of the equilibrating section. According to another preferred embodiment of the invention, equilibrating section 16 is employed in combination with another heating section into which food products pass after exiting equilibrat ing section 16. In equilibrating section 16, the surface portions of food products 40 may be some what cooled by the evaporation of moisture that ¯ migrates toward the surface as thermal energy pene trates into the interior portions of those food products. By subjecting food products 40 to a subsequent heating section in whidh columnatedw jets of air impinge directly on the food surfaces, it it is possible to drive off any r.emaining excess moisture and once again raise the surface tempera- ¯ ture to the desired level. When a thermal treating apparatus having this configuration is utilized, it may be desirable to slightly undercook the sur face of food products 40 in the heating section or sections so that the columnated jets of heated gas in the beating section following the equilibrating section can be utilized to bring the surface of food products 40 to the optimum desired temperature and degree of doneness. One satisfactory method for achieving desirable results with some food products is to position an equilibrating section following an intensive heating section and in advance of a semi-intensive heating section. food products 40 cooked by means of the apparatus and methods disclosed heroin are desired to be cooled or frozen for shipment and/or storage, semi-intensive and intensive cooling equipment employing jet fingers similar to those previously dicolaced for the intensive and semi-intensive disclosed for the intensive and semi-intensive heating section can be utilized in thermal heating apparatus 10 of the invention. Figure 10 illustrat a front elevation view. 'partially in section, of semi-intensive 'c'ooli'ng" section 18 and intensive cooling section gas shown in Figure 1. Semi intensive cooling section 18 and intensive cooling section 20 comprise cabinets 138 having interior and exterior top, bottom, front back and side walls, which are preferably insulated, at least in intensive cooling section 20, to minimize refrige ration requirements. Disposed within cabinet 138 of each cooling section is a plenum 140 communicat ing with a plurality of jet fingers 142 which are further disposed above and below a carriage 44B in cooling chamber 144 for transporting food products 40 therebetween through cooling section. A gas that is relatively cooler than food products 40 is discharged through plenums 140 and jet fin gers 142 so as to impinge on the surface of food products 40 moving through semi-intensive cooling section 18 and intensive cooling section 20 on carriage 44B. According to one preferred embodiment of the invention, the relatively cool utilized in semi-intensive cooling section 18 is einer room temperature air or ambient outside air supplied to cooling section blower means 146 of semi-intensive cooling section 18 through cooling gas inlet duct 148. when food products 40 enter semi-intensive cooling section 18 at a temperature considerably in excess of room temperature or ambient outside temperature, cooling can be achieved through use of the relatively cooler air without the need for': expensive refrigeration. As food products 40 progress through semi-intensive cooling section 18, the temperature differential between the sur face of food products 40 und the cooling gas sup plied through jet fingers 142 decreases rapidly. Desirably, the surface temperatures of food products 40 exiting semi-intensive cooling section 18 are at or slightly above room temperature. According to the embodiment of the invention shown in Figures 1 and 10, food products 40 pass from semi-intensive cooling section 18 into inten sive cooling section 20. In intensive cooling section 20, refrigerated air is supplied from refrigeration unit 150 through cooling gas inlet duch 152 to the inlet of coolin section blower means 146. Cooling section blower means 146 dis charges the refrigerated cooling gas through plenum 140 and jet fingers 142 so as to impinge on the surface of food products 40 passing therebetween on carriage 44B. Cooling gas discharged through jet fingers 142 is returned behind plenum 140 and recirculated through refrigeration means 150. In intensive cooling section 20, the tenperature of food'products,40 is desirably reduced very quickly to a temperature that is, satisfactory for shipment or storage of that particular product. Because direct impingement of the columnated jets of relatively cool gas will cool the surface portions of food products 40 more quickly than the interior portions of those products, thermal energy will continue to move - ' along the gradient between the interior and surface portions until a thermal equilibrium is reached. For this reason, it may be desirable to interpose at least one equilibrat ing section between semi-intensive cooling section 18 and intensive cooling section 20 of thermal treating apparatus 10. Acoording to this embodiment, a minor portion such as, forexample, less than about 10 percent of the relatively cooler das from semi-intensive cooling section 18 is introduced from the end of plenum 140 of semi-intensive cool ing section 18 into the cooling chamber of the equilibrating section. Structurally, an equilibrat ing section suitable for use with the cooling sec tions disclosed herein is substantially the same as that as previously described for use with the heating section of the invention. the lateral spacing desired for jet fingers 142 in semi-intensive cooling means 18 and inten sive cooling means 20 can vary, for example, acoord ing to the ,te,mperatur'e differential between incom- ing food products 40 and the cooling gas discharged through jet fingers 142, the physical dimensions, configuration, and spacing of food products 40, the rate of advance of carriage 44B, and the like. Thus, for food products 40 having large surface area to volumen rations, jet fingers 142 may be spaced relatively closely. On the other hand, for food products 40 having small surface area to volume ratios, additional time is required to equilibrate the thermal energy gradient that exists between the inetrior and surface portions, and wider lateral spacing between jet fingers 142 may be desirable in order to permit the thermal energy to move from the interior to the surface. While the present invention has been described in relation to its preferred embodiments, other ' alterations and modifications will become apparent to those of ordinary skill in the art opon reading this disclosure, and it is therefore intended that the present invention be limited only by the scope of the appended claims.

Claims: I claim: 1. Apparatus for imparting thermal energy to or removing thermal energy from a food product, said apparatus comprising at least one intensive thermal treatmens section furtther comprising means for directing a plurality of columnated jets of gas so as to impinge against the exterior surface of said food product while said food product is in motion relative to said columnated jets of gas, thereby imparting to or removing from said food "product a major portion of the thermal energy that, is desired to be imparted to or removed from said food product, and at least one semi-intensive thermal treatment section further comprising means for directing a plurality of columnated jets of gas so as to impinge against the exterior surface of a food product 'moving'relative to said columnated jets 9f gas, thereby imparting to or removing from the surface of said product a minor portion of the thermal energy that is desired to be imparted o or removed from said food product. 2. Apparatus comprising at least one thermal treatment section for imparting thermal energy to or removing thermal energy from a food product, : said thermal treatment saction further comprising means for directing a plurality of columnated jets of gas so as to impinge against the exterior surface of said food product while said food product is in motion relative to said columnated jets of gas, and at least one equilibrating section comprising means for establishing a substantial thermal equi librium between the surface and inetrior portions of said food product. 3. A method for imparting thermal energy to or removing thermal energy from a food product comprising the steps of: a. Introducing said food product into an apparatus comprising at least one thermal treatment section further comprising mewans for directing a plurality of columnated jets of gas so as to impinge against the exterior surface of said food product while said food product is in relative motion to said columnated jets of gas, thereby imparting thermal energy to oS removing thermal energy from said food product; and b. Thereafter subjecting said food product to an equilibrating section wherein the surface and interior portions of said food product are brought into substantial thermal equilibrium. 4. A method for imparting thermal energy to or removing thermal energy from a food product comprising the steps of: , a. Introducing said food product into at least one intensive thermal treatment section com prising means for directing a plurality of colum nated jets of gas so as to impinge against the surface of the food product, said food product being in relative motion to said columnated jets ','of gas, thereby imparting to or removing from food product a major portion of the thermal energy that is desired to be' imparted to or removed from said food product; and b. Thereafter introducing said food product into at least one semi-intensive thermal treatment section comprising means for directing a plurality of, columnated jets of gas so as to impinge against the exterior surface of the food product, said food product being in relative motion to said columnated jets of gas, thereby imparting to or removing from said food product a minor portion of the thermal energy that is desired to be imparted to or removed from said food product.

Inventors: SMITH, DONALD PAUL
Applicants: PATENTSMITH II, INC.
Application year: 1983
Main classification: A23L1
IPC codes: A23L3, F25D13, A23L1, A47J37, A47J39, F24C15, A21B1