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US 5,020,237 AGranted
Method and apparatus for dehydrating fruit
AssigneeThe J. M. Smucker Company
InventorsDavid R. Gross, Robert J. Valenzky
Life of this patent
Estimating the term…
Abstract
A method and apparatus for vacuum dehydrating fruit to a moisture content below about 15% but preferably below about 5%, using combined infrared energy and microwave energy simultaneously.
Claims40
A vacuum dryer for removing moisture from a food product comprising:
- chamber means defining an elongated cavity having an inlet end and an outlet end;
- means for evacuating said cavity to a vacuum;
- inlet means communicating with said inlet end for presenting said food product into said cavity;
- outlet means associated with said outlet end for removing said food product from said cavity;
- conveyor means in said cavity for moving said food product from said inlet end to said outlet end through first and second heating zones on a preselected path;
- first infrared energy means and first microwave energy means operative simultaneously in said first heating zone for simultaneously heating the exterior and interior of said food product moving on said conveyor means along said path and through said first heating zone;
- second infrared energy means and second microwave energy means operatively associated with said cavity for simultaneously heating the interior and exterior of said food product moving on the conveyor means along said path and through said second heating zone;
- first control means for controlling the energy of said first infrared energy means to provide a predetermined surface temperature for said food product moving through said first zone;
- second control means for controlling the energy level of said first microwave energy means to provide predetermined internal heating of said food product in said first zone, said first control means and said second control means being effective to establish a moisture gradient toward the outer surface of said food product in said first zone and a surface temperature at said vacuum effective for evaporating substantially all of the moisture exiting from said food product;
- and, cooling means operatively associated with said outlet means for receiving said food product from said conveyor means and effective to cool said food product and discharge said food product at atmospheric pressure exterior of said chamber means.
7 more elements
A vacuum drying method for removing moisture from fruit to a predetermined level comprising the steps of:
- (a) placing the fruit in an enclosure under an applied vacuum;
- (b) subjecting the surface of the fruit to radiant heating with infrared energy;
- (c) controlling the radiant heating to maintain the surface at an elevated temperature without causing browning of the surface of the fruit or rupturing the cell walls;
- (d) maintaining the radiant heating until a predetermined amount of moisture has been removed from the fruit;
- and
- (e) rapidly cooling the fruit under progressively decreasing vacuum thereby producing dried fruit having a low level of hygroscopicity with long flavor retention.
3 more elements
A method for drying a moisture containing food product, comprising the step of:
- simultaneously, and under vacuum, heating the interior of said food product with microwave energy sufficient to effect outward migration of moisture to the outer surface of the article while radiantly heating the outer surface of the article with infrared energy to a temperature sufficient to vaporize substantially all moisture arriving at said outer surface at said temperature and vacuum.
A method for dehydrating fruit to a moisture content of below about 5% so as to retain a high degree of color, and texture quality and organic fragrance compounds comprising the steps of:
- (a) evacuating a cavity to a predetermined vacuum;
- (b) conveying the fruit in a path through the cavity;
- (c) internally heating with microwave energy the fruit to effect a moisture gradient toward the surface of the fruit;
- (d) externally heating the fruit with infrared energy to effect evaporation of substantially all the moisture arriving at said surface of the fruit at said predetermined vacuum simultaneously with said internal heating;
- (e) discharging said fruit in a dehydrated form into a cooling chamber;
- (f) closing said cooling chamber after said dehydrated fruit is received;
- (g) introducing a cooling medium into the cooling chamber to cool said dehydrated fruit;
- and
- (h) removing the cooled dehydrated fruit from said cooling chamber.
6 more elements
In a method of drying fruit under vacuum using microwave energy to internally heat the fruit to effect outward migration of interior moisture to the outer surface of the fruit at an evaporation rate limited by the prevailing temperature and vacuum, the improvement comprising:
- (a) augmenting the microwave energy with infrared energy to raise the surface temperature sufficient to effect an evaporation balanced with the migration of interior moisture for said vacuum while maintaining the surface temperature below the browning temperature of the fruit pieces.
In a drying apparatus for removing moisture from a food product, said apparatus comprising:
- a vacuum chamber having a feed zone, a first heating zone, a second heating zone and a discharge zone, a conveyor means for moving said food product along a selected path in succession through said zones, first microwave means for directing microwave energy to said food product in said first heating zone, second microwave means for directing microwave energy to said food product in said second heating zone;
- the improvement comprising:
- a radiant heating device extending along said selected path in at least said first heating zone whereby said product is heated simultaneously by said first microwave means and said radiant heating device in said first heating zone.
An apparatus for dehydrating fruit to a moisture content of below about 5% so as to retain a high degree of color, flavor and texture quality and aromatic compounds, said apparatus comprising:
- a housing defining an elongated cavity;
- means for evacuating the cavity to a predetermined vacuum;
- conveyor means moving along a path extending longitudinal in the direction of the length of the cavity;
- microwave impermeable means transversely disposed in said cavity with openings surrounding the conveyor means and defining a longitudinal series of chambers or zones through which said conveyor means moves the fruit sequentially;
- inlet means for feeding fruit into the first of said chambers;
- wherein said fruit has an entering residual moisture content and a temperature dependent plastic range between which the cell walls of the fruit lack rigidity, but are not ruptured;
- first infrared radiation heating means in the second of said chambers adjacent the conveyor means for radiantly heating the surface of fruit moving through said second chamber;
- first microwave heating means in said second chamber adjacent said conveyor means for internally heating the fruit;
- control means for energizing said first infrared means to a high energy level to heat the surface of the fruit;
- control means for energizing said first microwave means to a predetermined fruit mass dependent level sufficient to remove the moisture content of the fruit to in the general range of about 25% to 30% through surface evaporation at the temperature of the surface of the fruit and the vacuum;
- second infrared radiation heating means in a third chamber adjacent said conveyor means;
- second microwave heating means in the third chamber adjacent the conveyor means;
- control means for operating said second microwave heating means at a lower power level less than said first microwave heating means for internally heating the fruit to promote outward migration of residual moisture to effect evaporation at the prevailing surface temperature of the fruit to under about 5%;
- means for cooling said dehydrated fruit;
- and means for discharging the cooled dehydrated fruit from said apparatus.
12 more elements
Dependencies are inferred from the claim text.