It is time to refresh the blog but the subject matter is not "gelling". We are working on upgrades but it would be premature to discuss a modification before it is introduced. I am open to re-examining a blog or even attempting a new topic. We are also considering a coffee related forum but it should be outside of the crowded topic of sensory and subjective appreciation for the brew. Our preference is to measure rather than just opine.
Send us an email about a topic.
Sunday, 23 February 2014
Tuesday, 26 November 2013
Improving the Roasting Efficiency.
There are several aspects to be considered before a process can be implemented to improve a design. Often it is possible to identify, let's say for the sake of discussion, 10 variables that will affect the process. What is usually impossible to predict is the rank or the level of dominance of each variable unless you are really really really a gifted analyzer or clairvoyant. Personally I resort to testing a few variables at a time to better understand their effect. There will undoubtedly be surprises and inconsistencies when various variables are tested together but it is simpler to test in parts than in whole.
The testing results are unlikely to produce a clear graph such are joys of solving problems with multiple unknowns. The results will give a better idea about the trade-offs that are required before a process can be adopted. We maintained that coffee beans should be uniformly heated so that the chemical reactions that occur within the beans progress evenly. It was also deemed important that the beans not be thermally overloaded. To clarify; the bean has a certain capacity to transmit heat to its interior, if the heat applied is greater than what can be evenly distributed the exterior surface becomes much hotter and creates a risk of scorching. It is also for this reason that we roast at a relatively lower temperatures of 240°C to 250°C instead of ... In "Espresso Coffee" R. Eggers writes the typical gas temperature of a drum roaster is 400° - 550°C. The high temperature cooking analogy for beans hit by the super hot air is frying eggs while using the stoves highest heat setting. Yet this fluidized bed roaster has a cycle time of less than 12 minutes versus up to 20 minutes in a drum roaster. That is Better Efficiency!
The even distribution of heat is critical to preparing the beans for the roasting process. We force heated air between the beans so that they are all heated, not just the outside layer. There are small domestic roasters that also use air to create a fountain of beans. It is quite dramatic but if the air flows through a narrow passageway then the remaining beans are not being heated until they gradually make it to the fountain. Consequently, if you are looking for a home roaster look for one that pushes the air through all the beans. Typically, the batch will move upwards as the beans are levitated by the flowing air then the air will break through and mix the beans. The release of air pressure allows them to drop within the chamber but are then suspended again. The air cushion has the added advantage of keeping the beans off the hot metal which often causes tipping which appear as little pieces of the exterior wall that leave behind a shallow cavity.
It is a simple concept that is regulated by many variables which turn it into a complex process.
There is more to the efficiency quest than even thermal transfer and the recycling of air mentioned in the previous blog which leaves something to write about later. Now it is time for an espresso.
The testing results are unlikely to produce a clear graph such are joys of solving problems with multiple unknowns. The results will give a better idea about the trade-offs that are required before a process can be adopted. We maintained that coffee beans should be uniformly heated so that the chemical reactions that occur within the beans progress evenly. It was also deemed important that the beans not be thermally overloaded. To clarify; the bean has a certain capacity to transmit heat to its interior, if the heat applied is greater than what can be evenly distributed the exterior surface becomes much hotter and creates a risk of scorching. It is also for this reason that we roast at a relatively lower temperatures of 240°C to 250°C instead of ... In "Espresso Coffee" R. Eggers writes the typical gas temperature of a drum roaster is 400° - 550°C. The high temperature cooking analogy for beans hit by the super hot air is frying eggs while using the stoves highest heat setting. Yet this fluidized bed roaster has a cycle time of less than 12 minutes versus up to 20 minutes in a drum roaster. That is Better Efficiency!
The even distribution of heat is critical to preparing the beans for the roasting process. We force heated air between the beans so that they are all heated, not just the outside layer. There are small domestic roasters that also use air to create a fountain of beans. It is quite dramatic but if the air flows through a narrow passageway then the remaining beans are not being heated until they gradually make it to the fountain. Consequently, if you are looking for a home roaster look for one that pushes the air through all the beans. Typically, the batch will move upwards as the beans are levitated by the flowing air then the air will break through and mix the beans. The release of air pressure allows them to drop within the chamber but are then suspended again. The air cushion has the added advantage of keeping the beans off the hot metal which often causes tipping which appear as little pieces of the exterior wall that leave behind a shallow cavity.
It is a simple concept that is regulated by many variables which turn it into a complex process.
There is more to the efficiency quest than even thermal transfer and the recycling of air mentioned in the previous blog which leaves something to write about later. Now it is time for an espresso.
Monday, 21 October 2013
Improving Roasting Technology
The picture links were removed
because Photobucket decided to change the terms of usage in mid stream,
so to say, It is inconvenient for viewers but it is better to rid
yourself of such people as soon as possible. It is the attitude as much
as the action. We will try to repair that mess at NXTroasters.com
The conventional approach appears to be - buy a roaster and endure its limitations. Most conventional roaster owners spend more time developing marketing spin than improving their coffee roaster. The deficiencies i.e. emissions are already the focus of some legislative bodies which require permits for roasters in their jurisdictions. Oil burning engines, showing that blue smoke, are rarely seen on the road today yet many owners are complacent about roasting without pollution controls.
The roaster owners who are concerned that large plumes of smoke coming from their chimney are bad for their community image have purchased large gas fired after-burners that burn approximately three times more gas than the roaster itself. Imagine if automobile pollution controls involved using three times more gasoline than the engine.
Rather than maintain the polluting status quo which may or may not have visible smoke, NXT Roasters Inc., have developed an alternative (branded the Roastaire in Canada) approach that uses the smoke generated as a source of roasting heat rather than expend large amounts of additional energy to thermally neutralize the smoke. Both 15 Kg/hour concepts thermally treat the pollutants but one system uses a 400,000 to 700,000 BTU after-burner to accomplish the task.
The first picture is of the main air passageway of a Roastaire after five years of full time roasting. This revealing photo demonstrates the reason for their motto of "Clean Air Roasting". This illustrates how efficient and effective the air is scrubbed clean as it is re-circulated during the roasting process. This closed loop roasting process means that the air only has to be heated 20° to 40°C to return it to the roasting temperature. Compare that to a single pass air supply that is continually heated from ambient temperature then sent to the chimney. In "Espresso Coffee" R. Eggers writes the typical gas temperature of a drum roaster is 400° - 550°C. What a wasteful process.
They also have this picture of a drum roaster fan as a warning about the residue that coats some of their components. Roast Magazine had the following quotation "It's not IF you're going to have a roaster fire, but WHEN." Which roaster do you think requires the most maintenance? Which type of roaster do you think was responsible for nearly 1,800 chimney fires in the USA in 2010?
The conventional approach appears to be - buy a roaster and endure its limitations. Most conventional roaster owners spend more time developing marketing spin than improving their coffee roaster. The deficiencies i.e. emissions are already the focus of some legislative bodies which require permits for roasters in their jurisdictions. Oil burning engines, showing that blue smoke, are rarely seen on the road today yet many owners are complacent about roasting without pollution controls.
The roaster owners who are concerned that large plumes of smoke coming from their chimney are bad for their community image have purchased large gas fired after-burners that burn approximately three times more gas than the roaster itself. Imagine if automobile pollution controls involved using three times more gasoline than the engine.
Rather than maintain the polluting status quo which may or may not have visible smoke, NXT Roasters Inc., have developed an alternative (branded the Roastaire in Canada) approach that uses the smoke generated as a source of roasting heat rather than expend large amounts of additional energy to thermally neutralize the smoke. Both 15 Kg/hour concepts thermally treat the pollutants but one system uses a 400,000 to 700,000 BTU after-burner to accomplish the task.
The first picture is of the main air passageway of a Roastaire after five years of full time roasting. This revealing photo demonstrates the reason for their motto of "Clean Air Roasting". This illustrates how efficient and effective the air is scrubbed clean as it is re-circulated during the roasting process. This closed loop roasting process means that the air only has to be heated 20° to 40°C to return it to the roasting temperature. Compare that to a single pass air supply that is continually heated from ambient temperature then sent to the chimney. In "Espresso Coffee" R. Eggers writes the typical gas temperature of a drum roaster is 400° - 550°C. What a wasteful process.
In comparison,
one drum roasters Maintenance Manual draws attention to the chimney, "Even if residue build-ups do not exceed 1/8 inch (.3 cm) per year, clean system annually ". The quotation is not properly cited nor acknowledged but I will do so if the manufacturer requests it.They also have this picture of a drum roaster fan as a warning about the residue that coats some of their components. Roast Magazine had the following quotation "It's not IF you're going to have a roaster fire, but WHEN." Which roaster do you think requires the most maintenance? Which type of roaster do you think was responsible for nearly 1,800 chimney fires in the USA in 2010?
Which roaster do you think roasted hundreds of pounds of green beans inside the exhibition hall of the last four annual
Canadian Coffee & Tea Shows?
Monday, 2 September 2013
French Press Grind
The picture links were removed
because Photobucket decided to change the terms of usage in mid stream,
so to say, It is inconvenient for viewers but it is better to rid
yourself of such people as soon as possible. It is the attitude as much
as the action. We will try to repair that mess at NXTroasters.com
The French Press is a classical brewer that has garnered many comments. Often it is used for comparisons when authors are promoting a new device. Many instructions and guides have been published yet there are recurring themes i.e. the medium grind with less than boiling temperature water.
Of course these demonstrations use freshly roasted coffee, otherwise what is the point of drinking coffee.
To the left the coffee beans were ground with a blade type grinder which is unable to attain the finer grinds. The larger particles initially contain a lot of CO2 hence the large amount of foam. I hesitate to call this crema because it is a mixture of foam and coffee grounds.
The foam develops very quickly when the nearly boiling water (that point will be argued later) is poured into the container. Much of that is likely due to the sudden rise in temperature which causes the CO2 and other gases to rapidly expand, in the bean, when immersed in the hot water.
In the first minutes much of the coffee grounds are buoyed by the foam therefore they do not absorb sufficient liquid to decant.
Relying on the Mesh Plunger to do the solids / liquid separation will not give satisfactory results. Either the screen will plug with grounds and/or the screen will deflect inwards let the ground migrate to the top of the mesh.
To the left is a coffee ground with a burr grinder using a very fine setting which usually makes a variation of in the cup Turkish coffee. The Mesh Plunger only comes into play once the grounds have decanted. The settling process is greatly accelerated by the fine grind which yields grounds that have a high ratio of surface area to volume, hence a rapid and thorough extraction.
The French Press is a classical brewer that has garnered many comments. Often it is used for comparisons when authors are promoting a new device. Many instructions and guides have been published yet there are recurring themes i.e. the medium grind with less than boiling temperature water.
Of course these demonstrations use freshly roasted coffee, otherwise what is the point of drinking coffee.
To the left the coffee beans were ground with a blade type grinder which is unable to attain the finer grinds. The larger particles initially contain a lot of CO2 hence the large amount of foam. I hesitate to call this crema because it is a mixture of foam and coffee grounds.
The foam develops very quickly when the nearly boiling water (that point will be argued later) is poured into the container. Much of that is likely due to the sudden rise in temperature which causes the CO2 and other gases to rapidly expand, in the bean, when immersed in the hot water.
In the first minutes much of the coffee grounds are buoyed by the foam therefore they do not absorb sufficient liquid to decant.
The argument that the grind has to be sufficiently coarse that the Mesh Plunger is not plugged ignores the importance of the extraction. I maintain that the purpose of the Mesh Plunger is to keep the decanted coffee grounds on the bottom of the container when the coffee is poured into the cups. The aim is to drink coffee not to have coffee grounds for breakfast.
The picture to the right was taken 1.5 minutes later. We can see that the liquid line has risen but that more water will have to be added if the vessel needs to be full. Very likely it will have to be filled twice to prevent the foam from overflowing.
In this case the Mesh Plunger was depressed 4 minutes after pouring the water.
To the left is a coffee ground with a burr grinder using a very fine setting which usually makes a variation of in the cup Turkish coffee. The Mesh Plunger only comes into play once the grounds have decanted. The settling process is greatly accelerated by the fine grind which yields grounds that have a high ratio of surface area to volume, hence a rapid and thorough extraction.
The crema, discerned from foam by the size of the gas bubbles, is similar to an espresso shot. The brewing was well behaved therefore no water had to be added. The brew decanted within seconds and was served sooner than the coarser grind.
The water was brought to a boil then poured over the coffee. The comments about near boiling water scalding the beans must originate with manufacturers and distributors of machines that are unable to heat water over 85°C.
The roasting chemical process is halted when the beans are cooled below approximately 150°C which hardly supports the claims that 90°C water scalds the beans. On the contrary experiments show that the extraction is better developed at higher temperatures.
Do your own experiments and note the observations. If possible measure the temperature of the water for different extractions so that you can optimize your procedure. In the meantime enjoy the fruits of your experiments.
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