Fluidized bed coffee roaster
A fluidized bed coffee roaster controls air flow and/or temperature to maintain a desired time-temperature roast profile. The roaster may also provide a two stage quenching cycle for rapidly cooling roasted coffee beans to ambient temperature. In a first stage of the quenching cycle unheated air is passed through the roasted beans while they are still in the roasting chamber of the fluidized bed roaster. In a second stage of the quenching cycle which is carried out outside of the roasting chamber, in a fluidized bed quenching station, unheated air is flowed through, and fluidizes, the roasted coffee beans cooling them to ambient temperature.
1. A fluidized bed coffee roaster providing a controlled roast profile, said roaster comprising:
a roasting chamber including an air-permeable member which is supported in said chamber and which is operable to support a volume of coffee beans thereupon;
an air inlet disposed so as to introduce a stream of air into said chamber through said air-permeable member so as to pass through and fluidize said volume of coffee beans;
an air outlet disposed so as to direct said stream of air out of the chamber after said stream of air has passed through the volume of coffee beans;
a blower operable to provide said stream of air;
an air duct operatively connecting said blower with the air inlet of the chamber so as to direct the stream of air from the blower to the inlet;
a heater associated with the air duct at a point downstream of the blower and upstream of the roasting chamber, said heater, when activated, being operable to heat the stream of air;
a roast temperature sensor disposed downstream of said heater, and operable so as to sense the temperature of the stream of air and generate a roast control signal corresponding thereto; and
a controller which is in operative communication with the roast temperature sensor, the blower, and the heater, said controller being operable to selectably independently activate and deactivate the heater and/or blower, said controller having a roast profile electronically stored therein, said roast profile comprising a plurality of data points defining said roast profile, each point corresponding to a particular time and temperature, wherein said roast profile is a step profile which includes: a first time interval during which the temperature of said volume of coffee beans is increased from a first temperature value to a second temperature value, a second time interval during which said volume of coffee beans is maintained at said second temperature value, and a third time interval during which the temperature of said volume of coffee beans is increased from said second temperature value to a third temperature value;
said controller being further operative, on a periodic, cyclic basis to:
read a roast control signal value;
correlate said roast control signal value with said roast profile; and
control the operation of said blower and/or heater so as to maintain the temperature of said volume of coffee beans in accord with said roast profile.
2. The fluidized bed coffee roaster of claim 1 , wherein said periodic, cyclic basis constitutes a plurality of periods each in the range of 5% to 30% of the roast profile.
3. The fluidized bed coffee roaster of claim 1 , wherein said periodic, cyclic basis constitutes a plurality of periods each in the range of 60 to 180 seconds.
4. The fluidized bed coffee roaster of claim 1 , wherein said roast temperature sensor is disposed either in the roasting chamber, or immediately at the exit of the roasting chamber and is operable so as to sense the temperature of the stream of air in said roasting chamber.
5. The fluidized bed coffee roaster of claim 1 , wherein said roast temperature sensor is disposed and operable so as to sense the temperature of the stream of air upstream of said roasting chamber.
6. The fluidized bed coffee roaster of claim 1 , wherein said roast temperature sensor is disposed and operable so as to sense the temperature of the stream of air at a point downstream of said roasting chamber.
7. The fluidized bed coffee roaster of claim 1 , further including:
a discharge outlet which is operable to discharge the volume of coffee beans from said roasting chamber; and
a fluidized bed quenching station in communication with said controller, said fluidized bed quenching station comprising: a container configured and operable to receive and retain the volume of coffee beans from said discharge outlet, said container having a bottom surface which is air-permeable; and a quenchant air supply system disposed and operative, when activated by said controller, to deliver a stream of quenchant air through the bottom surface of said container, so as to fluidize and cool said volume of coffee beans.