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An apparatus for pasteurizing a dry food product comprises an impingement chamber, a conveyor for conveying the dry food product through the impingement chamber; a heater and water supply assembly for generating heated, moist air, and a fan for circulating the heated, moist air through the impingeme

An apparatus for pasteurizing a dry food product comprises an impingement chamber, a conveyor for conveying the dry food product through the impingement chamber; a heater and water supply assembly for generating heated, moist air, and a fan for circulating the heated, moist air through the impingement chamber and onto the dry food product. In operation, the moisture in the heated, moist air condenses on the surface of the dry food product and produces a heat of condensation which heats the surface of the dry food product. Moreover, this heat of condensation is sufficient to kill a percentage of any pathogenic microorganisms which may be present on the surface of the dry food product.

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1. A pasteurizing apparatus for pasteurizing a dry food product based on the heat of condensation from a pasteurization medium without substantially cooking the dry food product, the apparatus comprising: (a) an impingement chamber comprising a plenum chamber and a pasteurization chamber, said plenu

1. A pasteurizing apparatus for pasteurizing a dry food product based on the heat of condensation from a pasteurization medium without substantially cooking the dry food product, the apparatus comprising: (a) an impingement chamber comprising a plenum chamber and a pasteurization chamber, said plenum chamber comprising a number of plenum fingers, each of which comprises an open base portion which communicates with the plenum chamber and a number of slots which communicate with the pasteurization chamber;(b) a conveyor extending through the pasteurization chamber for conveying the dry food product through the pasteurization chamber;(c) a pasteurization medium supply system in fluid flow communication with the plenum chamber, said pasteurization medium supply system generating a pasteurization medium comprising heated, moist air;(d) a circulation system for circulating the pasteurization medium from the plenum chamber through the base portion of the plenum fingers, through the slots, into and through the pasteurization chamber and onto the dry food product being carried by the conveyor; and(e) a temperature measurement system for determining an average surface temperature of the dry food product being carried by the conveyor, said temperature measurement system comprising a simulated food product positioned on the conveyor within the dry food product, said simulated food product constructed of a highly heat conductive material and configured to resemble the dry food product, and a temperature sensor which is attached to the simulated food product to sense the temperature of the dry food product on or near the surface of the simulated food product;(f) a measurement system for measuring the temperature and humidity within the pasteurization chamber; and(g) a control system for controlling the temperature and moisture content of the pasteurization medium supplied to the pasteurization chamber and for controlling the operation of the circulation system to generate a sufficient heat of condensation on the surface of the dry food product being conveyed through the pasteurization chamber, sufficient to kill a desired percentage of pathogenic microorganisms present on the surface of the dry food product, but without substantially cooking the dry food product, said control system: setting preselected temperature and humidity levels within the pasteurization chamber such that when the pasteurization medium condenses on the surface of the dry food product a heat of condensation is produced that is sufficient to kill a percentage of any pathogenic microorganisms which may be present on the surface of the dry food product without substantially cooking the dry food product; andsaid control system, if the measured temperature and/or humidity within the pasteurization chamber deviates sufficiently from the preselected temperature and/or humidity levels, altering the temperature and/or moisture content of the pasteurization medium to bring the temperature and/or humidity within the pasteurization chamber to within an acceptable deviation from the preselected temperature and/or humidity levels within the pasteurization chamber. 2. The pasteurizing apparatus of claim 1, wherein the slots are positioned so as to direct the heated, moist air toward the conveyor. 3. The pasteurizing apparatus of claim 2, wherein the number of plenum fingers comprises a number of upper plenum fingers which are located above the conveyor and a number of lower plenum fingers which are located below the conveyor. 4. The pasteurizing apparatus of claim 3, wherein the control system for selectively directs the pasteurization medium in the plenum chamber to either or both of the upper and lower plenum fingers. 5. The pasteurizing apparatus of claim 1, wherein the pasteurization medium supply system comprises a heater which includes a heat exchanger surface that is located in the impingement chamber. 6. The pasteurizing apparatus of claim 5, wherein the pasteurization medium supply system comprises a water supply assembly which is connected to a water supply and which sprays the water from the water supply into the impingement chamber. 7. The pasteurizing apparatus of claim 1, wherein the pasteurization medium supply system comprises a steam generator. 8. A pasteurizing apparatus for pasteurizing a dry food product based on the heat of condensation from saturated steam and based on the heat of condensation from a pasteurization medium without substantially cooking the dry food product, the apparatus comprising: (a) a steam chamber;(b) a steam generating system for generating saturated steam and supplying the saturated steam to the steam chamber;(c) a pasteurization chamber physically separate from the steam chamber, said pasteurization chamber located immediately downstream of the steam chamber;(d) a pasteurization medium supply system for generating a pasteurization medium comprising heated, moist air and supplying the pasteurization medium to the pasteurization chamber, said pasteurization medium supply system structurally and functionally separate from the steam generating system;(e) an isolation system configured and positioned to isolate the steam chamber from the pasteurization chamber to retain the saturated steam in the steam chamber and to retain the pasteurization medium in the pasteurization chamber;(f) a conveyor for conveying the dry food product first through the steam chamber and then through the pasteurization chamber;(g) a measurement system for measuring the temperature and humidity levels within the steam chamber and the temperature and humidity levels within the pasteurization chamber;(h) a control system for controlling the temperature, pressure and volume of saturated steam supplied to the steam chamber to enable the steam to condense on the dry food product being conveyed through the steam chamber, to produce a heat of condensation on the dry food product which is sufficient to kill a first percentage of any pathogenic microorganisms present on the surface of the dry food product without substantially cooking the dry food product;(i) said control system also controlling the pasteurization medium temperature and moisture by volume of the pasteurization medium supplied to the pasteurization chamber so that as the dry food product is conveyed through the pasteurization chamber, the moisture in the pasteurization medium condenses on the surface of the dry food product and produces a heat of condensation which is sufficient to kill a second percentage of the pathogenic microorganisms, but without substantially cooking the dry food product;(j) said control system setting preselected temperature and humidity levels within the steam chamber such that when the steam condenses on the surface of the dry food product, a heat of condensation is produced that is sufficient to kill a percentage of any pathogenic microorganisms which may be present on the surface of the dry food product without substantially cooking the dry food product;(k) said control system setting preselected temperature and humidity levels within the pasteurization chamber such that when the pasteurization medium condenses on the surface of the dry food product, a heat of condensation is produced that is sufficient to kill a percentage of any pathogenic microorganisms which may be present on the surface of the dry food product without substantially cooking the dry food product; and(l) said control system operational so that if the measured temperature and/or humidity within the steam chamber and/or the pasteurization chamber deviates sufficiently from the preselected temperature and humidity levels, the control system alters the temperature and/or pressure and/or volume of the saturated steam supplied to the steam chamber and/or alters the temperature and/or moisture content of the pasteurization medium supplied to the pasteurization chamber to bring the temperature and/or humidity within the steam chamber and/or pasteurization chamber to within an acceptable deviation from the preselected temperature and/or humidity levels within the steam chamber and/or pasteurization chamber. 9. The pasteurization apparatus of claim 8, wherein the control system controls the operation of the pasteurization medium supply system to produce air at a temperature above about 212° F. at a humidity level between about 72% MV and 88% MV, and said control system controls the operation of the steam generating system to produce saturated steam at a temperature equal to or below about 212° F. at a humidity level between about 90% MV and 100% MV. 10. The pasteurization apparatus of claim 8, wherein the control system controls the operation of the pasteurization medium supply system to produce air at a temperature between about 220° F. and 450° F. at a humidity level between about 60% MV and 90% MV, and the said control system controls the operation of the steam generating system to produce saturated steam at a temperature between about 200° F. and 212° F. 11. The pasteurization apparatus of claim 8, wherein the control system controls the operation of the pasteurization medium supply system to produce air at a temperature between about 385° F. and 395° F. at a humidity level between about 75% MV and 85% MV, and said control system controls the operation of the steam generating system to produce saturated steam at a temperature between about 204° F. and 212° F. 12. The pasteurization apparatus of claim 8, wherein the isolation system comprises a number of steam knives. 13. The pasteurization apparatus of claim 12, wherein the isolation system comprises at least one steam knife which is positioned at an interface between the steam chamber and the pasteurization chamber. 14. A pasteurization method for pasteurizing a dry food product based on the heat of condensation from saturated steam and based on the heat of condensation from a pasteurization medium, and without substantially cooking the dry food product, the method comprising: providing a steam zone which comprises saturated steam at a temperature set point equal to or below about 212° F. and at a humidity set point level of between about 90% MV and 100% MV;providing a pasteurization zone adjacent the steam zone which comprises a pasteurization medium composed of air at a temperature set point above about 212° F. and at a humidity set point level of between about 72% MV and 88% MV;isolating the steam zone from the pasteurization zone to retain the saturated steam in the steam zone and to retain the pasteurization medium within the pasteurization zone;conveying the dry food product through the steam zone and then through the impingement zone at a selected speed;measuring the temperature and humidity levels in the steam zone and in the pasteurization zone;controlling the supply of saturated steam in the steam zone so that as the dry food product is being conveyed through the steam zone, the saturated steam condenses on the surface of the dry food product in sufficient quantity to produce a heat of condensation which is sufficient to kill a first percentage of any pathogenic microorganisms present thereon;controlling the pasteurization medium in the pasteurization zone so that as the dry food product is being conveyed through the pasteurization zone, the moisture of the pasteurization medium condenses on the surface of the dry food product in sufficient quantity to produce a heat of condensation which is sufficient to kill a second percentage of the pathogenic microorganisms;adjusting the temperature and/or the humidity of a steam supply to the steam zone if the measured temperature and/or humidity levels deviate by a predetermined variance from the temperature and/or humidity set points in the steam zone; andadjusting the temperature and/or the humidity levels of a pasteurization medium supply to the pasteurization zone if the measured temperature and/or humidity levels deviate by a predetermined variance from the temperature and/or humidity set points in the pasteurization zone. 15. The pasteurization apparatus of claim 13, wherein the isolation system is configured and positioned to isolate the saturated steam in the steam chamber from a location upstream of the steam chamber. 16. The pasteurization apparatus of claim 15, wherein the isolation system comprises at least one of a steam knife and a vent stack which is positioned at an interface between the steam chamber and the location upstream of the steam chamber. 17. A pasteurization apparatus for pasteurizing a dry food product based on the heat of condensation from a pasteurization medium and without substantially cooking the dry food product, the apparatus comprising: (a) a pasteurization chamber;(b) a conveyor extending through the pasteurization chamber for conveying the dry food product through the pasteurization chamber;(c) a pasteurization medium generator in fluid flow communication with the pasteurization chamber, said pasteurization medium generator generating a pasteurization medium comprising heated, moist air for the pasteurization chamber;(d) a circulation system for directing the pasteurization medium onto the dry food product in a first zone within the pasteurization chamber and in a second zone within the pasteurization chamber;(e) a measurement system for measuring the temperature and humidity within the pasteurization chamber;(f) a control system for setting preselected temperature and humidity levels of the pasteurization medium in the first zone in the pasteurization chamber such that the surface temperature of the dry food product is below the dew point temperature of the pasteurization medium, and such that heated, moist air of the pasteurization medium condenses on the surface of the dry food product and produces a heat of condensation which is sufficient to kill a percentage of any pathogenic microorganisms which may be present thereon without substantially cooking the dry food product; and(g) said control system setting preselected temperature and humidity levels of the pasteurization medium in the second zone in the pasteurization chamber such that the surface temperature of the dry food product is approximately the same as or greater than the dew point temperature of the pasteurization medium, and such that the pasteurization medium causes the moisture to evaporate from the surface of the dry food product; and(h) said control system if the measured temperature and/or humidity within the first and/or second zone in the pasteurization chamber deviates sufficiently from the preselected temperature and/or humidity levels, controlling the pasteurization medium generator to alter the temperature and/or moisture content of the pasteurization medium to bring the temperature and/or humidity levels within the pasteurization chamber to within an acceptable deviation from the preselected temperature and/or humidity levels within the pasteurization chamber. 18. A pasteurization method for pasteurizing a dry food product based on the heat of condensation from a pasteurization medium, and without substantially cooking the dry food product, the method comprising: (a) generating a pasteurization medium comprising heated, moist air with a dew point temperature greater than an initial surface temperature of the dry food product;(b) conveying the dry food product through the pasteurization medium;(c) measuring the temperature of the dry food product prior to conveying the dry food product through the pasteurization medium;(d) condensing a sufficient quantity of the pasteurization medium on the surface of the dry food product to thereby produce a heat of condensation which is sufficient to kill a percentage of any pathogenic microorganisms which may be present thereon without substantially cooking the dry food product;(e) heating the dry food product with the pasteurization medium until the surface temperature of the dry food product is approximately the same as or greater than the dew point temperature of the pasteurization medium;(f) evaporating the condensation from the surface of the dry food product using the pasteurization medium;(g) measuring the temperature and humidity of the pasteurization medium; and(h) if the dew point temperature of the pasteurization medium is not greater than the initial surface temperature of the dry food product, adjusting the dew point temperature of the pasteurization medium to be greater than the initial temperature of the dry food product. 19. A pasteurization apparatus for pasteurizing a dry food product based on the heat of condensation from saturated steam and based on the heat of condensation from a pasteurization medium without substantially cooking the dry food product, the apparatus comprising: (a) a steam chamber;(b) a pasteurization chamber which is located downstream of the steam chamber;(c) a conveyor conveying the dry food product through the steam chamber and the pasteurization chamber from a first location immediately upstream of the steam chamber to a second location immediately downstream of the pasteurization chamber;(d) a steam supply system for generating saturated steam and supplying the saturated steam to the steam chamber at a set point temperature equal to or below about 212° F. and/or a set point humidity level between about 90% MV and 100% MV;(e) a pasteurization medium supply system for generating heated, moist air and supplying the pasteurization medium to the pasteurization chamber at a set point temperature above about 212° F. and a humidity set point level of between about 72% MV and 88% MV;(f) an isolation system configured and positioned to isolate the saturated steam in the steam chamber from the pasteurization medium in the pasteurization chamber;(g) a measurement system for measuring the temperature and humidity levels within the steam chamber and within the pasteurization chamber;(h) a control system for controlling the temperature and moisture content of the saturated steam in the steam chamber so that as the dry food product is conveyed through the steam chamber, the saturated steam condenses in sufficient quantity on the surface of the dry food product to produce a heat of condensation which is sufficient to kill a first percentage of any pathogenic microorganisms present thereon without substantially cooking the dry food product;(i) said control system controlling the temperature and moisture content of the pasteurization medium in the pasteurization chamber such that as the dry food product is conveyed through the pasteurization chamber, the moisture in the pasteurization medium condenses in sufficient quantity on the surface of the dry food product to produce a heat of condensation which is sufficient to kill a second percentage of the pathogenic microorganisms without substantially cooking the dry food product;(j) said control system setting preselected temperature and humidity levels within the steam chamber such that when the steam condenses on the surface of the dry food product, a heat of condensation is produced that is sufficient to kill a percentage of any pathogenic microorganisms which may be present on the surface of the dry food product without substantially cooking the dry food product;(k) said control system setting preselected temperature and humidity levels within the pasteurization chamber such that when the pasteurization medium condenses on the surface of the dry food product, a heat of condensation is produced that is sufficient to kill a percentage of any pathogenic microorganisms which may be present on the surface of the dry food product without substantially cooking the dry food product; and(l) said control system operational so that if the measured temperature and/or humidity within the steam chamber and/or the pasteurization chamber deviates sufficiently from the preselected temperature and humidity levels, the control system controls the steam supply system to alter the temperature and/or moisture content within the steam chamber and/or controls the pasteurization medium supply system to alter the temperature and/or moisture content of the pasteurization medium to bring the temperature and/or humidity within the steam chamber and/or pasteurization chamber to within an acceptable deviation from the preselected temperature and/or humidity levels within the steam chamber and/or pasteurization chamber. 20. The pasteurization apparatus of claim 19, wherein the isolation system comprises at least one of a steam knife and a vent stack which is positioned at an interface between the steam chamber and the pasteurization chamber. 21. The pasteurization apparatus of claim 13, wherein the isolation system further comprises a vent stack which is positioned at the interface between the steam chamber and the pasteurization chamber. 22. The pasteurization method of claim 14, wherein isolating the steam zone from the pasteurization zone comprises operating a steam knife between the steam zone and the pasteurization zone. 23. The pasteurization method of claim 14, further comprising: determining an average surface temperature of the dry food product in at least one of the steam zone and the pasteurization zone; andcontrolling the quantity of the dry food product being conveyed through the steam zone and pasteurization zone based on the measured average surface temperature of the dry food product. 24. The pasteurization method of claim 23, wherein the temperature determining step comprises determining the temperature of a simulated dry food product which is conveyed within the dry food product through the at least one of the steam zone and the pasteurization zone, the simulated food product being configured to generally resemble the dry food product and being made of a heat conductive material. 25. The pasteurization method of claim 14, further comprising controlling the delivery of the pasteurization medium within the pasteurization zone so that, after the step of condensing the moisture in the heated, moist air onto the dry food product, the moisture from the surface of the dry food product is evaporated as the dry food product is further conveyed through the pasteurization zone. 26. The pasteurization method of claim 25, further comprising controlling the pasteurization medium within the pasteurization zone to repeat the condensing and evaporating steps in turn while the dry food product is being conveyed through the pasteurization zone to achieve a desired kill percentage of the pathogenic microorganisms. 27. The pasteurization method of claim 18, wherein: the evaporating step lowers the surface temperature of the dry food product to below the dew point temperature of the pasteurization medium, andthe pasteurization method further comprises repeating the condensing, heating and evaporating steps in turn. 28. The pasteurization method of claim 18, further comprising, prior to the step of conveying the dry food product through the pasteurization medium: generating saturated steam;conveying the dry food product through the saturated steam; andcondensing a sufficient quantity of steam on the surface of the dry food product to thereby produce a heat of condensation which is sufficient to kill a percentage of any pathogenic microorganisms which may be present thereon without substantially cooking the dry food product. 29. The pasteurizing apparatus of claim 1, wherein the control system controls the operation of the pasteurization medium supply system to produce heated, moist air at a temperature between about 220° F. and 450° F. at a humidity level between about 60% MV and 90% MV. 30. The pasteurization apparatus of claim 1, wherein the control system controls the loading level of the dry food product on the conveyor, and adjusts the loading level of the dry food product on the conveyor based on the measured average surface temperature of the dry food product. 31. The pasteurization apparatus according to claim 30, wherein the control system controls the loading level of the dry food product on the conveyor also based on the temperature and humidity levels within the pasteurization chamber. 32. The pasteurization apparatus according to claim 1, wherein if the measurement system for measuring the temperature and humidity levels within the pasteurization chamber measures a deviation of the temperature and/or humidity within the pasteurization chamber from the preselected temperature and/or humidity levels within the pasteurization chamber, the control system determines whether or not the pasteurization medium contained a heated condensation which was sufficient to kill a desired percentage of the pathogenic microorganisms which may be present on the surface of the dry food product, and based on this determination, decides the disposition of the dry food product. 33. The pasteurization apparatus according to claim 8, wherein: said measurement system further comprising a subsystem for determining an average surface temperature of the dry food product being carried by the conveyor, the temperature measurement subsystem comprising a simulated food product positioned on the conveyor within the dry food product which is constructed of a highly heat-conductive material and is configured to resemble the dry food product, and a temperature sensor which is attached to the simulated food product on or near the surface of the simulated food product; andthe control system controls the loading of the dry food product on the conveyor, and adjusts the loading of the dry food product on the conveyor based on the measured average surface temperature of the dry food product. 34. The measurement system according to claim 8, further comprising: a circulation system for circulating the pasteurization medium through the pasteurization temperature and on to the dry food product being carried by the conveyor;said control system setting a preselected velocity for the pasteurization medium being circulated through the pasteurization chamber by the circulation system;said control system controlling the velocity of the pasteurization medium circulated through the pasteurization chamber by the circulation system and adjusting of the measured velocity of the pasteurization medium circulated through the pasteurization chamber deviates sufficiently from the preselected velocity, the control system altering the velocity of the pasteurization medium flowing through the pasteurization chamber to be within an accepted deviation of preset velocity; anda measurement system measuring the velocity of the pasteurization medium being circulated by the circulation system. 35. The pasteurization apparatus according to claim 34, wherein the control system based on the measurements by the measurement system determines whether the temperature and humidity of the steam within the steam chamber and the temperature and humidity within the pasteurization chamber were sufficient to kill a desired percentage of the pathogenic microorganisms present on the surface of the dry food product, and if not, the control system adjusts the velocity of the pasteurization medium circulated through the pasteurization chamber by the circulation system. 36. The pasteurization method of claim 23, wherein controlling the quantity of the dry food product being conveyed through the steam and pasteurization zones is also based on the measured temperature and humidity of the steam zone and/or the pasteurization zone.