Dry food pasteurization apparatus and method

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.

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;
• and
• adjusting 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.

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.

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.

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.