Coffee

I- Purpose/Objective:

Week one will examine green beans.

There will be 5 stations and 3 groups:

  1. FTIR - samples will be ground to a powder and each person will run their coffee at least 3 times to ensure reproducibility (more if necessary).  This data will only be used by the group that collects it.  This should take an hour.
    SOP: Jasco FT/IR 4100 with Diamond/ZnSe ATR crystal

  2. DSC – A background will be run with a standard roast profile of about 50¡ F per minute to about 520¡ F (maximum temperature before combustion) followed by an air quench.  Then each group will run two types of coffee.  This will take about an hour.  We will share this data.
    SOP: Perkin Elmer DSC-6 Thermal AnalyzerPerkin Elmer Auto Balance AD6

  3. SEM – A bean will be cut in half and mounted with silver print or glue on an SEM stub.  A thin layer of metal will then be evaporated on the sample.  SEM analysis will then be performed to study the cellular structure of the bean.  Images will be used only by the group that collects them.  This should take 30 minutes.
    SOP: FEI (Philips) XL30 Teaching SEM with BSE mode and EDAX analysis

  4. X-ray powder diffraction – a powdered sample will be prepared for each bean to be studied.  The group will collect data from each of their samples and share the data.  Theta-two-theta X-ray data will only be used by the group that collects it.  This should take 30 minutes.
    SOP: Rigaku Miniflex X-ray Diffraction System

  5. Other techniques - Optical Microscopy, hardness testing, mechanical testing, etc. are all available if desired. 
    SOP: Nikon Optiphot Planar MicroscopeClark Microharness Tester (Vickers/Knoop) CM-400ATMTS Insight 10 ...


Week 2 will examine beans at different levels of roast:

 

Coffee roasting – During the first week the GSI’s will be roasting quantities of coffee for a tasting the second week. Coffee should rest for at least 3-5 days before drinking.  The coffee will still be good until 10-14 days.  During the second week, each group will roast a small batch of each coffee to various stages of roast.  We will want to study each quality bean at 4 stages of roast; just before the first crack, after the first crack but before the second, after the second crack, and just before catching fire.  Because we have 4 types of coffee to study and 4 stages of roast, we will follow the schedule below:

 

 


Table 1.  The roasting/sampling schedule for each group as a function of the coffee we will be roasting.  a,b,c,d refer to the four stages that we are sampling respectively.

 

Each group will perform two roasts. The first roast will be a quality coffee.  We will remove a few(like 5) beans just before the first crack (they will just be starting to turn brown and the temperature should be around 360oF), just after the first crack, right after you hear the second crack start, and ~2-4 minutes after that when the beans begin to turn oily.

 

The second roast will be the UGH.  We will only sample the beans right after the first crack and right after the second crack.  (30 minutes)

 

Then each group will perform FTIR, XRD, and SEM on the samples that they have just roasted.  These data will be posted and the entire class will use the data to draw conclusion.

 

We will be able to sample each of the 4 coffees during this lab period.

We will get a second chance to sample the coffees in the final poster session.  There will be more about that soon.


II - Experimental Procedure:


III - Theory/Background Information:


IV - Theory/Background References:


V- Activity Schedule:


VI -Format and Important Questions for Lab Report:

  1. The paper should be written as an MRS proceedings paper as in lab 3.  Directions are given in the lab 3 folder on Ctools.

  2. You should discuss whether or not there was evidence for distinguishing one coffee from another as well as one roast progression from another.

  3. If there was no difference in some of the data from one set of conditions to another, then you should discuss why.

  4. You should consult the literature that is provided in the resources section to comment on where you would be likely to see differences between roast stages and coffees.  Please don’t limit yourselves to just those papers.  Take a look at INSPEC or Google Scholar and find your own references.

  5. You should discuss the chemistry that may or may not be occurring and relate it to the SEM images of the microstructure of the coffee bean at the different stages of the roast.  You will need to consult the literature to learn about the chemical changes that occur during roasting.

  6. You should discuss the gasses that are escaping and causing the beans to fracture and swell at different times during the Roast.

  7. You should develop a physical model for your deductions and make some predictions that could be tested by an experiment.  Discuss these models and predictions in your discussion section.

  8. You should comment on whether or not the physical measurements we have made here have any bearing on the quality of the cup.