Posted on 03/09/2013 12:22 PM
Joined: October 24, 2005
or fluid bed roaster, is a machine that uses fast streams of hot air to roast coffee beans. There are different types, or configurations, of air roasters, but all use hot air to convectively roast the beans and to help keep the beans moving. Most commercially available coffee is either air roasted or drum roasted.
Open-source electronic prototyping platform allowing to create interactive electronic objects.
Asymmetrical Roast Chamber
A fluid bed roast chamber utilizing a convection air entry point that is located to one side of the chamber creating an asymmetrical ?V? shape instead of being centered as in a conical roast chamber. Attributes of this design is the ability to fluidize the coffee bed using lower static pressure than with a centered convection air entry point and requires less energy input.
Batch roasters produce a fixed quantity (lbs per batch) of roasted beans at a time. In a batch roaster, the beans are removed before roasting the next batch. Continuous roasters produce roasted coffee at a fixed rate (lbs per hour).
A probe thermometer used to monitor bean temperature during the roasting process. Bean probes accurately measure the surface temperature of coffee beans during roasting. Modern roasting systems use either resistance thermal detector (RTD), or thermocouple (TC), bean probes, along with electronic temperature controllers, to monitor and control the roasting process.
Bean Mass Temperature
Bean Temperature - Roast degree is often defined by internal bean temperature, which cannot be measured directly, but can be approximated by the coffee bean surface temperature as measured by a bean probe (probe thermometer). Modern roasting systems monitor the surface temperature of roasting coffee beans, and can consistently recreate a roast by controlling the bean temperature vs. time profile. Final bean temperature, and time-temperature profiles, are now used in place of bean color monitoring for consistency in roasting. Internal bean temperatures are often cited along with bean probe temperatures when describing degree of roast, but actual internal bean temperature depends not only on the bean surface temperature, but also the time-temperature profile and type of roaster used.
One British Thermal Unit (BTU) is the amount of heat needed to raise the temperature of one pound of water by one degree Fahrenheit. One kilowatt is equal to 3412.142 BTU's.
The phase of coffee roasting (from around 300 F bean temp to the start of first crack) following the drying phase where browning from Maillard reactions and pyrolysis are taking place.
A type of fluid bed roaster utilizing a special variable density perforated plate allowing multiple spouting zones. Claimed attributes of this roaster is the ability to roast with lower temperatures resulting in less loss of volatiles compared to conventional fluid bed roasters.
Measure of air flow in cubic feet per minute.
The part of any roaster/roasting system designed to collect the chaff.
Environment Temperature within the drum or roast chamber when the beans are loaded into the roaster.
In relation to coffee roasting, the transfer of heat from roaster drum wall to beans via contact as well as from bean to bean contact.
Conical Roast Chamber
A fluid bed roast chamber having a cone shaped base.
As related to coffee roasting, the movement of heated air around and through the coffee for the purpose of roasting.
is used to separate particulates, such as chaff, from roaster exhaust. The exhaust from cyclone separator is typically passed through a thermal oxidizer (incinerator) to burn the smoke. Roasters equipped with both a cyclone separator and thermal oxidizer emit a clean, smoke and particle free, exhaust.
Equipment used to record the time and temperature data during the roast
Direct Flame Roaster
A coffee roaster in which heat is applied to the beans by a live flame in contact with the coffee. In a typical direct flame roaster, the coffee being tumbled via drum is never in contact with the flame full time but only in brief moments as the coffee recirculates back into the flames path.
?Direct flame? roasters were nearly universal in Europe and the United States in the years between WWI and WWII, but went out of style because of their low fuel efficiency and the extensive training needed to operate them properly ? not because their coffees didn?t taste good!
The direct fire method of roasting has many loyal customers and connoisseurs worldwide, but it does have one drawback: it is much more difficult than the mass commercial method of indirect fire to produce an evenly roasted coffee. As a result, it truly has taken us years to perfect our talent in roasting the coffee evenly without burning it. "Burning it" is meant literally, as when coffee oil is directly exposed to the fire during the roasting process, the chance of a fire that destroys the roaster itself is highly likely. This method of roasting is truly the most dangerous of all methods of roasting. If you can imagine what happens when oily meat catches fire on the grill, you can start to imagine what happens when oily coffee beans catch fire?only multiply it by a hundred times. However, when roasting coffee to the point of a Dark French roast, Italian roast, or other dark roast, the coffee has to be brought just to the point of catching fire without actually catching fire. It is the ability to judge the point at which the whole batch will start to flame, and the timing necessary to pull the batch out into the cooling drum that defines the perfected art of specialty extreme dark roasting.
The coffee roasting community seems to be equally divided in the use of this term. Some use the term to describe the drum or roast chamber temperature when "dropping" the green coffee from hopper into the roaster and others use the term to describe the bean temperature when "dropping" the finished roast from the roaster into the cooling tray.
Willem Boot on the other hand uses the term "Charging Temperature" or "Charge Temperature" to describe drum temperature when loading the roaster most likely to ensure a distinction exists between loading and dumping the roaster. The use of "charge/charging" and "dump" would most likely lessen the potential for confusion.
Drum roasters employ simple technology that hasn?t really changed a whole lot over the years. In a basic sense, the typical drum roaster is just a cylinder rotating on a horizontal axis. Flights, vanes or paddles mix the beans, and heated air moves through the drum and removes the roasting byproduct. There are two types of drum roasters: solid drum and perforated drum roasters. The perforated design allows for more convective heat transfer ? or heat transfer through air ? than the solid drum.
Flights, vanes or paddles mix the beans, and heated air moves through the drum and removes the roasting byproduct.
First phase of the roast (from start of roast to around 300 F bean temp) typically requiring from 4 to 6 minutes for effective drying, where free moisture is being removed from the beans in preparation for the browning phase. A visual indicator for determining the coffee has reached this temperature is the change from green to yellow.
Discharging the coffee from the roaster at the end of a roast.
Bean temperature at the time of discharging from the roaster.
As related to coffee roasting, stages during the roast where the coffee is absorbing heat energy from its surroundings. The first stage is endothermic. The green beans are slowly dried to become a yellow color and the beans begin to smell like toast or popcorn.
As related to coffee roasting, stages during the roast where the coffee is releasing heat energy into its surroundings. The second step is followed by a short endothermic period which is followed by another exothermic step called the second crack. This second pyrolysis occurs between 225-230?C, and the roast color is defined as medium-dark brown (Agtron #50-45) (Davids, 68-69). The second pop is much quicker sounding and the beans take on an oily sheen.
Bean temperature at the end of a roast.
The first of two distinctly different periods of cracking sounds during a roast, when the coffee beans are giving off their own heat and expanding suddenly. "first crack" begins at bean probe temperatures around 400 degrees Fahrenheit, making a sound similar to popcorn, and then diminishes, and sometimes stops momentarily, before the start of "second crack". "Second crack" begins at bean probe temperatures around 440 to 450 degrees Fahrenheit. The darkest of palatable roasts (Dark French) is attained at the peak of "second crack". If the roast is allowed to continue to completion of "second crack", the coffee will be burnt and may catch fire.
Coffee roaster utilizing hot air to lift, circulate and convey heat to the beans. Beans are loaded into a stationary roasting chamber. Hot air is forced up through the coffee from a combustion chamber located either at the bottom or side, by a blower. This causes the coffee to tumble in the air stream and reducing contact with surfaces that may cause scorching. Most fluid bed roasters create a spouting effect (spouting bed) where the beans flow upward and out of the coffee bed in a fountain-like flow rather than a fully fluidized coffee bed. These systems do not re-circulate air as most drum roasters do. It is thought that because the air does not pass back through the burner large particles do not get processed further into smoke. Many people feel that because of this the finished cup tends to be cleaner.
Heat Gun - Bread machine
Heatgun - Dog Bowl
A roaster utilizing infrared radiant heating elements as a heat source to the beans.
Kilowatt which is an electrical unit of power representing 1000 watts and equivalent to 3412.142 BTU's.
Maximum Environment Temperature where the environment temperature (ET) is the surrounding air environment of the coffee within a roaster. MET is simply a suggested maximum ET for avoiding damage to the bean from excessive heat. Carl Staub popularized this term and the temperature limit he recommends (536 F) is primarily intended for conventional drum roasters and not fluid bed and other similar roasters where the beans experience a wider ratio of ?on the heat? and ?off the heat? cycling.
The Maillard reaction is a form of nonenzymatic browning. It results from a chemical reaction between an amino acid and a reducing sugar, usually requiring heat. Vitally important in the preparation or presentation of many types of food, it is named after chemist Louis-Camille Maillard, who first described it in 1912 while attempting to reproduce biological protein synthesis. The reactive carbonyl group of the sugar reacts with the nucleophilic amino group of the amino acid, and forms a complex mixture of poorly characterized molecules responsible for a range of odors and flavors. This process is accelerated in an alkaline environment (e.g., lye applied to darken pretzels), as the amino groups are deprotonated and, hence, have an increased nucleophilicity. The type of the amino acid determines the resulting flavor. This reaction is the basis of the flavoring industry. At high temperatures, acrylamide can be formed. In the process, hundreds of different flavor compounds are created. These compounds, in turn, break down to form yet more new flavor compounds, and so on. Each type of food has a very distinctive set of flavor compounds that are formed during the Maillard reaction. It is these same compounds flavor scientists have used over the years to make reaction flavors. http://en.wikiped...d_reaction
(PID temperature controller) PID stands for proportional, integral, derivative. Proportional means changing a variable in proportion to its difference from the set-point. Integral rectifies any small difference in the variable and the set-point. Derivative reduces the other oscillations. Also?a term commonly mis-used in place of temperature controller.
Programmable logic controller
In relation to fluid bed coffee roasters, a sheet metal plate with multiple holes, located at the lowest part of the roast chamber where hot air emerges lifting the coffee beans into a fountain like re-circulating spout.
A popcorn popper will provide the even air flow and high temperatures needed for a nice clean roast. And it?s fairly simple, merely tossing your green coffee beans into a popcorn popper and keeping a close eye on them. Because this technique uses air to roast, the chaff (outer skin of coffee bean) will come flying out of the popper. You may want to roast outside, if possible.
Performing a roast following a predetermined time-temperature curve.
A trademark from a company producing borosilicate glass and glassware with a higher resistance to heat than common glass.
The chemical breakdown of fats and carbohydrates into delicate oils that provide the aroma and some of the flavor of coffee.
Industry term to describe under-ripe, underdeveloped coffee seeds that fail to roast properly.
A roaster utilizing infrared radiant heating elements as a heat source to the beans.
Ramp Soak Controller
Electronic temperature controller capable of running multiple programmed time and temperature segments allowing the heating or cooling of a substance at a controlled rate of change in degrees per unit of time. Typical ramp soak controllers are equipped with PID control capability.
Rate of Rise Meter
As related to coffee roasting, an electronic meter capable of displaying the increasing or decreasing of bean temperature (BT) or environmental temperature (ET) in degrees per minute. For an example of an affordable rate of rise meter see the TC4 and TC4C covered in ?Data loggers/Controllers/Rate of rise meters?.
Rate of change
Rate of rise
Router Speed Controller
An electronic control used for varying the rpm of a wood working router. Common router speed controllers consist of a small plastic case with a rotary adjustment knob on the front and female electrical receptacle on its side. These controllers have come into popular use as a means to adjust power levels to coffee roasting heating elements and fan motors.
Stir crazy turbo oven
The stage in roasting where the beans become brittle due to dehydration. As a result, the beans crack and begin to carbonize, producing the burnt characteristics of extremely dark roasts.
As related to coffee roasting, the typical form of recirculating bean path found in a fluid bed coffee roaster.
The TC4 system is a family of open-source temperature logger/controllers hardware and software. The basic TC4 device is a shield that is designed to fit atop an Arduino board. Each TC4 device can read up to 4 thermocouples and has outputs suitable for roaster heat and fan control when paired with an appropriate software application.
The TC4C is a standalone version of the TC4 shield. The TC4C does not require an Arduino board. Instead, circuitry equivalent to an Arduino board is combined with the TC4 system on a single board. The TC4C is software-compatible with Arduino Uno.
Temperature-measuring sensor consisting of two wires of different metals joined at each end. One junction (welded or fused bead) is placed where the temperature is to be measured, and the other is kept at a constant lower (reference) temperature. The two dissimilar metals create a voltage potential in millivolts which is read by a meter and displayed as a temperature.
A special pointed device for removing a sample of green coffee beans through the bag wall without opening the bag. Also, as part of a roasting machine, a metal scoop that is used to catch small samples of roasting coffee for examination during the roasting process.
Turbo Oven Roaster
Hot air convection style roaster utilizing a domestic cooking appliance ?turbo oven? convection head coupled to a stationary vertical roast chamber with motorized stirring paddles for bean agitation.
The Turbo Oven Roaster most closely resembles a ?packed bed? style of coffee roaster. Heating can be from single or dual heat modes with the second source typically being infrared halogen lamps built into the turbo oven or heat applied to the bottom of the roast chamber. Typical capacity up to 1 kg +
The point after initially charging a roaster with green coffee when the bean temperature (BT) reading stops falling and begins climbing.
Blower used in vacuum cleaners.
Trademark name for an adjustable-ratio rotary transformer for test and calibration work. In home roasting is typically used as a variable voltage source for powering fans and heating elements in home roasters.
Blower used in vacuum cleaners.
Edited by ginny on 03/14/2013 8:31 PM
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