Prufrocker: The Blog

Smells and Solutions

The bouquet of coffee: fragrance, aroma, nose, and after-taste.

by  |   |  Coffee Science


Dale Cooper enjoys the aroma.

Divide smell into 4. The bouquet of coffee:

Fragrance is the smell of the dry grinds.

Aroma is the smell directly from the cup and is assessed before swallowing. This is what we are scoring as we sniff and break the crust when cupping.

The Nose of a coffee is the gases it emits as we drink and swallow. Gases are pushed up to the top of the palate as you swallow. This is why we aspirate (slurp) when cupping. Remember coffee is the universal solvent and also dissolves gases. The aeration of coffee through slurping changes the vapour pressure in the coffee and forces many gases that have dissolved to turn back into gases.

After-Taste is an aromatic sensation. You have residue of coffee in your mouth and throat and this residue emits gases minutes after after you swallow. The tendency is for heavier molecules to leave more residue. This means there is a tendency for after-taste to include more dry distillation smells and less enzymatic ones.

Types of Smells

Divide coffee smells into three.

  1. Enzymatic
  2. Sugar Browning
  3. Dry Distillation

The SCAA flavour wheel from the amazing Coffee Cuppers Handbook is divided into three categories of smell. It is assembled like this to help us understand roasting:

Enzymatic aromas have survived the roasting process without converting into something else. They smell of the living coffee plant and cherry.

Sugar browning caramelisation stage giving us smells of nuts caramel and chocolate.

Dry distillation is burning. This is either by design or accident. If a roaster seeks to reduce acid levels in coffee this will come at a price. Prufrock Considers Dry Distillation aromas to be undesirable. Imagine your coffee tastes very smokey. There is a point in roasting where coffee pops like popcorn. This is called the first crack. If you continue to roast for another minute or two the coffee pops again: second crack. After this point is reached there is no enzymatic material left and the aromas will be all the product of caramelisation and burning.

Flavour Taints

A good cupper needs to do some detective work. A taints wheel allows you to work backwards. You identify a taste, say it’s earthy. Then you locate a similar discripter on the wheel. Work inwards and you notice it’s moved towards fats absorbing odours. Towards External Changes. Imagine butter left open in the fridge next to some smoked mackerel also uncovered. Fats tend to absorb odours. Coffee beans can contain up to 17% fat. The only time coffee was likely to be left near soil is on the farm or at the mill. Many farms lack the infrastructure to build raised drying beds or concrete patios so the beans will have been dried on the naked earth.

Tipping

Perhaps you pick up a smokey carbony taste in what appears to be a very light roast. Beans are not perfectly round. Even the best roaster cannot prevent some slight uneveness in the roasting of beans as they are marginally different sizes and pointy at the tips. At origin beans are sieved through screens to help make them a more uniform size.

Specialty Coffee Association of America’s Grading Standards

http://www.coffeeresearch.org/coffee/scaaclass.htm

Specialty Grade Green Coffee (1): Specialty green coffee beans have no more than 5 full defects in 300 grams of coffee. No primary defects are allowed. A maximum of 5% above or below screen size indicated is tolerated. Specialty coffee must possess at least one distinctive attribute in the body, flavour, aroma, or acidity. Must be free of faults and taints. No quakers are permitted. Moisture content is between 9-13%.

Premium Coffee Grade (2): Premium coffee must have no more than 8 full defects in 300 grams. Primary defects are permitted. A maximum of 5% above or below screen size indicated is tolerated. Must possess at least one distinctive attribute in the body, flavour, aroma, or acidity. Must be free of faults and may contain only 3 quakers. Moisture content is between 9-13%.

Exchange Coffee Grade (3): Exchange grade coffee must have no more than 9-23 full defects in 300 grams. It must be 50% by weight above screen size 15 with no more than 5% of screen size below 14. No cup faults are permitted and a maximum of 5 quakers are allowed. Moisture content is between 9-13%.

Below Standard Coffee Grade (4): 24-86 defects in 300 grams.

Off Grade Coffee (5): More than 86 defects in 300 grams.

Below is a chart for grading coffee beans. It is based on the primary defect and the number of defective coffee beans:

Primary Defects

Primary Defect

Number of occurrences equal to one full defect.

Full Black

1

Full Sour

1

Pod/Cherry

1

Large Stones

2

Medium Stones

5

Large Sticks

2

Medium Sticks

5

Secondary Defects

Secondary Defect

Number of occurrences equal to one full defect

Parchment

2-3

Hull/Husk

2-3

Broken/Chipped

5

Insect Damage

2-5

Partial Black

2-3

Partial Sour

2-3

Floater

5

Shell

5

Small Stones

1

Small sticks

1

Water Damage

2-5

What makes a coffee more Aromatic?

http://www.coffeeresearch.org/science/aromamain.htm

Freshness

There are two issues with coffee freshness. We are looking for an optimum displacement of time from roast. 100 days after coffee is roasted, it should have lost about all the C02 it once contained. As this gas makes its way out of the tiny cracks and caves inside a roasted bean, it brings aromatic gases with it. Studies by VST and Vince Fedele have indicated that a roasted bean contains such an abundance of C02 inside it as to be pressurised up to 12bars directly after roasting. 100 days later this pressure will have completely dispersed. Such a high pressure can cause water that is trying to get into grinds to dispel water as there is such copious out-gassing going on at the same time. For the kind of coffee we use, about 10days later seems to create the right balance of ease of extraction and intensity of aroma.

Green bean freshness seems to promote fresher aromas. The outsides of beans dry out as beans are stored and we have an expression Loomey to describe old coffee. Loss Of Organic Material.

Coffee that has passed the 12 month mark usually has a flatter aroma and will remind you of wood. The dryer outside roasts faster than the moister inside. This coffee is known as past crop. London has developed an acute consciousness of green bean freshness. Some of our best roasters have had a very hard time keeping any variety in their offerings from around Christmas time to April. This is no bad thing. I go out of my way to get a harvest map to every BRaT student that comes through our centre. A customer having an awareness of tropical seasons and our endeavours to keep ahead of the seasons forges stronger links to origin. We encourage our customers in auditing Roasters on quality and greens freshness. This is helping keep more sparkle in the coffees of London.