Freshly Roasted Coffee & Solubles

It is accepted that Freshly Roasted Coffee Beans are essential to a great coffee experience.

This is a preliminary exploration of two brewing methods; modified Turkish and espresso.  The hypothesis is that it is possible to increase the G forces on the brew for accelerated sedimentation of the coffee fines.  The accumulation of solids in the bottom would support the idea that it is possible to quantify the coffee strength for various brewing methods.  For now, it is assumed that the amount of solubles is directly related to the strength of the coffee.

At the top is a modified Turkish brew without the addition of Cardamon and Cinnamon.  Essentially it is coffee made with a very fine grind which remains in the cup.  Of course if the drinker insists on consuming the proverbial last drop he/she will also have a 10 g breakfast.  For this comparison the water to coffee ground ratio of 10:1 was used.  The brew decanted for approximately 2 minutes before 14 ml were removed and placed into the vial or tube.

 The espresso was made with 15 g of coffee which was pulled in 29 seconds to yield two ounces or 60 ml.  Again, 14 ml was transferred to a tube for further processing or accelerated decantation.

The espresso grind is tamped in the porta-filter which only allows smaller particles to pass through with the water.

The fine grind, brew in a cup on the other hand is initially separated by gravity alone.  Since it is not filtered it is possible that the larger grounds are decanted in the first 2 minutes.  The larger the grind the longer it takes to decant but since this is an extra fine grind it is possible that the 2 minutes was sufficient to decant even the largest particles.  Smaller particles may be held in suspension in the liquid whether by turbulence, Brownian forces, or magic.

Both brews were initially opaque when held in front of a light.

The results above are open to interpretation until further experiments are done.  All three vials show signs of sedimentation but the Turkish Grind had significantly more grinds in the bottom.  It may be possible to conclude that the particles were larger than those in the espresso.  The increased transparency does support the premise that the previous opaqueness was due to the larger particles.

The espresso remained largely unchanged.  It is difficult to establish with precision that .25 ml of fines were decanted.  The opaqueness of the processed espresso does support the idea that extremely fine particles are held in suspension.

The experiment did not support the hoped for conclusion where the amount of solubles could be measured and even categorized.  It appears that a greater G force will be required to compare drip coffee, to say, a brew done in a French Press.  Or to compare the brew of large chains to that of a K cup.

Hopefully, another iteration of this test will allow the measurement of a solubles so that  brewing can be optimized.  Without measurement it is difficult to optimize so many variables.

Now, a cup of coffee is needed to start the process.

NXT Coffee Roaster Design not "off the shelf"

To Google Maps
Most coffee roasters are heated by  a natural gas flame.  Natural gas is a cheaper form of energy than electricity but it comes with inherent limitations.  Since the flame requires a continual supply of oxygen it requires a lot of air which must be raised from ambient to combustion temperature, this  is not the end of the energy waste.  The coffee roasting is usually done in the exhaust gasses of the flame which, are not hot enough after passing through the Roasting Chamber, to break down the roasting smoke.  That smell is similar to burnt toast, in the later stages, - imagine several kilo grams of burnt toast.  Hence, an Afterburner is required to raise the temperature to over a 1000°F to break down the smoke.  The large amount of air required by the flame means that a large amount of air must be raised from ambient temperature to over 1000°F.  Consequently, the Afterburner burns, depending on the model,  three times as much energy as the roaster (the equivalence of 6 home furnaces) just so that the neighbourhood will not see nor smell the roaster emissions.  Of course the emissions from such burners are always present but the operators hope that they become sufficiently diluted by the outside air that they will not trigger calls to the environmental agency.  Pollution awareness is upon us and some areas already require permits for coffee roasters with 5 kg or more capacity.

Are there alternatives?
There is, if the fabricator begins with a clean design slate rather than use off the shelf technologies.  First, the amount of air needs to be reduced to greatly reduce the waste of energy.  It is true that often the electricity is generated by the combustion of natural gas but the electrical companies have specialized equipment to remove and neutralize gas volatiles that individual roasters do not use.  Nevertheless, the electrical Roastaire™'s biggest advantage is virtually eliminating the continual feeding of air to the roasting process.  It is possible to recirculate the air with electrical heating because you do not need to feed a flame.  The advantage, is that less energy is required to heat the returning air than to heat room temperature air (ambient) to roasting temperatures.  There is less air to treat when neutralizing the emissions therefore it can be done on a continual basis. A minor advantage is that the oily smoke, as part of the re-circulation process, is burnt which helps to heat the roaster.

Does the design work?

 Below is a photo of the tubing that guides the re-circulated air to the Roasting Chamber.  The roaster was in service for 5 years before this photo was taken.  It had roasted about 30 tonnes of coffee.  It does illustrate why Fresh Cup Roastery Café (Saanichton & Vancouver) clients refer to it as  "Clean Air Roasting"

 Now compare the above photo with one taken of a drum roaster after one year of service.

There wasn't a copyright on the photo but I am not attributing the photo because there is little benefit to kicking a hornet's nest.

In 2010, it is reported that there were 1800 chimney fires, in the USA, that were attributed to coffee roasters.  What heating method do you think was responsible for this incredible statistic?












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In the Roastaire the exhaust is passed through a second SmokEater© before it is discharged.  It roasted hundreds of batches inside the Toronto and Vancouver convention centres without the use of a vent or chimney.

What is exhausted?
 Only the air cooling the roasted coffee is exhausted after scrubbing it twice.  More details about the design reasoning will be forthcoming when the topic of Bean Cooling is approached.  In the interim here is some more information on an earlier NXT    blogspot page.

Question and Challenge What you Read

Company Blogs which very often are prone to being commercials should not be taken at face value or believed without reflection and sometimes, some research.  

One blogger (Blogger B) submitted a comment to a competitor " I read with interest your article entitled “Roasting with Hot Air: Benefits of Air Roasters” in your company’s newsletter."  He then proceeds to authoritatively expound on his own lack of knowledge in the roasting process.  The complication here is that the article, by Blogger A, he refers to has some rather glaring falsehoods i.e. "During the roasting process, the green coffee beans go through two major “pops” or “cracks” The first occurs when the internal temperature of the bean reaches approximately 356 degrees fahrenheit.".  The problem here is that no matter how long you boil water the temperature remains no higher than 212°F or 100°C.  The evaporative process greatly slows the bean from continually increasing in temperature until virtually all the moisture is evaporated.

It appears that Blogger B then proceeds to confuse degrees Fahrenheit with degrees Centigrade.  Blogger A writes "This hot air reaches temperatures of between 450 and 485 degrees fahrenheit" (232°C to 251°C) which is slightly above the 195°C to 205°C where the beans undergo an exothermic reaction.  A much lower temperature would essentially bake the beans.  Despite Blogger B's assertion that the air roaster is way too hot it is 100°C to 200°C less hot than a typical gas fired drum roaster.  It is true that the air roaster has a faster roast cycle but 4 minutes is absurd while 11 minutes is quite normal because the heat is quite evenly applied to all sides of the bean as they are churned in the fluidized bead.  Drum roasters only have fans which are incapable of pushing the air through the batch of beans therefore they only heat the top layer, the beans touching the drum, and beans that are falling off the rotating blades.  Blogger B's comments "Regardless of how heat is applied to the outside of the beans, heat reaches the insides of the beans by conduction. And, when it comes to heat conduction, coffee beans are not very good at it. Therefore the development of the insides of the beans always trails the development of the outsides of the beans."  Ironically he is presenting a case that favours the lower temperature of the air roaster (for the same reason you do not fry eggs on high settings).  This, however, is not true for the entire roasting session.  The heat moves inwards in the endothermic phase until the bean enters the exothermic phase.  

Think of lighting a damp piece of paper.  There is a reason why you can boil water, on a flame, inside a paper bag.  It is because the water seeping through the material prevents the paper from reaching its combustion point.  However remove that water, the paper will dry, and will then burst into flames.

Blogger B apparently does not realize that a full roast includes the exothermic phase where the heat is generated inside the bean.  See sectioned bean photo.  At this point the roasting process has to be monitored closely to "kill the roast" at the right time.  We prefer to cool within the Roasting Chamber because it is quicker and easily repeatable.  At this stage the transformation is very rapid therefore it is challenging to guess "the kill point" half a minute to a minute in advance because it takes that long to dump the beans never mind cool them.

Blogger B also comments on the single pass air roaster even though his system not only is a single pass air supply but it is roasting with the exhaust of the flame.  Imagine cooking supper with the car exhaust (maybe a propane powered vehicle is slightly more appropriate", it will certainly contribute all kinds of flavour.  Recirculating hot air cannot be done with a gas fired roaster because it starves the flame.  We do it in an electric roaster but it took five years to develop a blower that would survive the temperature.   Re-circulation improves the efficiency and makes it possible to significantly cut emissions.  

A gas fired Afterburner burns on average 3 times more gas than the roaster.  It decreases the visible smoke but really loads the exhaust with volatile organic compounds known as pollution.

Off the Shelf Machines

My perception is that most companies are buying off the shelf devices which were built without their input.  In other words they are saddled with the compromises without having the opportunity of prioritizing them.  Buying a known technology does defer to the manufacturing company goals rather than to those of the end user.  Of course the manufacturing company wants their clients to succeed but the manufacturer's survival is viewed as being way more important.

Certainly we have purchased off the shelf technology but the moment we took possession of it the discussion began on improving the device to meet our needs.  Control systems were bypassed in favour of Labview based data acquisition and controls.  The equipment claims were compared to the measured performance then we searched for better and more effective ways to enhance the process.

Sometimes we contacted the evaluated equipment's manufacturer to test the waters about incorporating what we considered to be improvements while at other times we either kept the results in house or dropped the project in favour of a fresh approach.

It is possible to learn by analyzing existing machines.  Rarely will they prove to be an ideal fit to your needs but if you are attentive in its usage you will make up a list of Pros & Cons.  That conclusion will at least give you concepts to analyze and sometimes an appreciation for the work that went into the original design.  Falling into the trap of flippant analysis often leads in the wrong direction because it fails to take into consideration the battles of formulating the original design which after all usually achieved commercial status.  "Armchair quarterbacks" are known for their 20/20 hindsight  vision which does not make room for the Law of Unintended Consequences or even a thoughtful analysis.  Having said that sometimes a fresh look does provide insight because the person is not constrained by the history of the project or the emotional aspect of the design.

Modifying machines can mean living with the Law of Unintended Consequences especially in complex systems where there is interaction between many elements.  I think of it as the battle of the laws of physics which can be predictable or result in a complete surprise that should be explored or abandoned.  Abandoned projects can be revived when new techniques or solutions are found but until that moment manifests itself they are on the back burner if not in the deep freeze so to say.

Concluding now, for the sake of brevity, first; formulate an analysis plan by listing the requirements in order of priority, second; decide on the evaluation criterea, third; pay hommage to Genrikh Altshuller and examine patents to understand how others might have tackled the problem, fourth; undertake the challenge of melding the many ideas into a workable solution so that you can build your prototype.