3 Tips for Improving Your Physical Fitness, When You're Starting from a Pretty Bad Place

Fitness is one of the most important things in life for overall health and wellness – and maintaining a regular fitness routine has all sorts of potential benefits, ranging from better medical outco...

News Company - avatar News Company

Top 5 Events to Enjoy in the United Kingdom Every Year

The United Kingdom as any country holds numerous engaging festivals throughout the year. What makes the UK offer to stand out from the rest is their exciting travel landmarks and cities that nearly ...

Goran Kezić - avatar Goran Kezić

Friday essay: YouTube apologies and reality TV revelations - the rise of the public confession

A little over a year ago, former Australian cricket captain Steve Smith made a tearful confession and apology to the public, having been banned from cricket for 12 months for ball tampering. Smith&rsq...

Kate Douglas, Professor, Flinders University - avatar Kate Douglas, Professor, Flinders University

Population DNA testing for disease risk is coming. Here are five things to know

Screening millions of healthy people for their risk of disease can be cost-effective. But it raises ethical and regulatory concerns.from www.shutterstock.comDNA testing to predict disease risk has the...

Paul Lacaze, Head, Public Health Genomics Program, Monash University - avatar Paul Lacaze, Head, Public Health Genomics Program, Monash University

Why Sydney residents use 30% more water per day than Melburnians

Melbourne's water supplies are running low after years of drought.shutterstockThis week Melbourne’s water storage dropped below 50%, a sign of the prolonged and deepening drought gripping easter...

Ian Wright, Senior Lecturer in Environmental Science, Western Sydney University - avatar Ian Wright, Senior Lecturer in Environmental Science, Western Sydney University

From gun control to HIV: six ingredients of successful public policy

Australia’s national policy response to HIV/AIDS has been lauded as one of the best in the world.ShutterstockIn the lead up to the recent federal election, there was plenty of negative rhetoric ...

Joannah Luetjens, PhD Candidate, Utrecht University - avatar Joannah Luetjens, PhD Candidate, Utrecht University

How the dangerous evolution of Pakistan’s national security state threatens domestic stability

Protests followed the terrorist attack that killed more than 40 Indian military personnel in the disputed state of Jammu and Kashmir. AAP/Jaipal Singh, CC BY-NDIn February, a terrorist attack by Jaysh...

Robert G. Patman, Professor of International Relations, University of Otago - avatar Robert G. Patman, Professor of International Relations, University of Otago

Taming wild cities: the tall buildings of Australia show why we need strong design guidelines

Towering canyons of concrete and glass are an increasingly dominant feature of fast-growing cities like Melbourne.ymgerman/ShutterstockPrivate enterprise has shaped the skylines of Australia’s c...

Timothy Moore, PhD Candidate, Melbourne School of Design, Monash University - avatar Timothy Moore, PhD Candidate, Melbourne School of Design, Monash University

Let them play! Kids need freedom from play restrictions to develop

Playing in nature improves children's learning, social and emotional skills.MI PHAM/unsplashYou may have heard of play. It’s that thing children do – the diverse range of unstructured, spo...

Brendon Hyndman, Senior Lecturer and Course Director (Postgraduate Education courses), Charles Sturt University - avatar Brendon Hyndman, Senior Lecturer and Course Director (Postgraduate Education courses), Charles Sturt University

If you think less immigration will solve Australia's problems, you're wrong; but neither will more

More by luck than design, recent recent levels of immigration seem to be in a 'goldilocks zone' that balances economic, social and environmental objectives.www.shutterstock.comAre we letting too many ...

Cameron Allen, Researcher, UNSW - avatar Cameron Allen, Researcher, UNSW

Gamers use machine learning to navigate complex video games – but it's not free

Playing Dota 2? You can do better with a little help from machine learning.Shutterstock/hkhtt hj Some of the world’s most popular video games track your activity as you play – but they&rsq...

Ben Egliston, PhD candidate in Media and Communications, University of Sydney - avatar Ben Egliston, PhD candidate in Media and Communications, University of Sydney

Grattan on Friday: Shocked Labor moves on – but to what policy destination?

Bill Shorten has said he likes doing the family shopping, nevertheless Tuesday’s front page picture in The Australian did capture the savagery of changing political fortunes. There was Shorten, ...

Michelle Grattan, Professorial Fellow, University of Canberra - avatar Michelle Grattan, Professorial Fellow, University of Canberra

Narendra Modi has won the largest election in the world. What will this mean for India?

Narendra Modi's image was ubiquitous on the campaign trail – a sign of how much Indians have gravitated toward his cult of personality and nationalist rhetoric.Harish Tyagi/AAP The resounding vi...

Amitabh Mattoo, Honorary Professor of International Relations, University of Melbourne - avatar Amitabh Mattoo, Honorary Professor of International Relations, University of Melbourne

Inside the story: the ABC of screenwriting as demonstrated by ABC's The Heights

Roz Hammond as Claudia in The Heights.Bohdan Warchomij/ABCWhy do we tell stories, and how are they crafted? In this series, we unpick the work of the writer on both page and screen.The rule of three i...

Philippa Burne, Lecturer, BFA Screenwriting, Victorian College of the Arts, University of Melbourne, University of Melbourne - avatar Philippa Burne, Lecturer, BFA Screenwriting, Victorian College of the Arts, University of Melbourne, University of Melbourne

imageBeans have travelled a long way to make your cup of coffee.Jack Fussell/Flickr, CC BY-NC-ND

Welcome to the third instalment in our series Chemistry of Coffee, where we unravel the delicious secrets of one of the most widely consumed drinks in the world. As you listen to the whirring grinders in your local cafe, think of the long journey those beans have made – and what they’ve gone through to be there.

The vast majority of the brewed coffee we drink in Australia comes from the arabica species (Coffea arabica), despite 30% of world coffee production being the “robusta” variety (Coffea canephora).

Coffee is a member of the botanical family Rubiaceae, which is widely distributed in the tropics and subtropics. Other members of the family include chincona, the source of quinine, and gardenias, the boldly scented ornamental.

In terms of taste, connoisseurs agree that arabica produces a superior cup of coffee. Robusta beans produce coffee much more bitter and grainy in taste, but higher in caffeine than arabica.

And as the name suggests, robusta is a much more hardy plant than the delicate arabica, and less susceptible to insect pests (mostly due to its higher caffeine content) and fungal infections. It also grows in a wider range of environmental conditions and has a higher yield per acre than arabica, so is cheaper to produce and buy. On the open market green arabica beans sell for around A$5 per kilogram, and robusta beans retail for approximately A$2.50 per kilogram.

Australia only grows arabica coffee. The cool climate and absence of insect and fungal pests create ideal growing conditions. Flowering occurs for a period of a couple of days sometime between October and December, depending on spring rainfall.

The coffee cherries begin to ripen in June and are harvested three to four months later depending on the season. The coffee fruit are a deep red purple colour when they are ready for harvest.

imageJason Diceman/Flickr, CC BY-NC-SA

Harvesting

Some coffee producers in Australia still harvest beans by hand, but this is a labour-intensive and time-consuming process. The larger plantations employ mechanical harvesting to increase yields and lower costs.

The harvesters themselves are quite refined bits of equipment. They straddle the rows of coffee and employ oscillating nylon fingers to gently shake the branches of the coffee bush. The ripe coffee beans that have been gently dislodged from the branch fall onto a conveyor belt which carries the beans to a collection hopper on the back of the harvester.

Like any fruit, coffee beans are covered by a fleshy layer which is high in sugars. The the fleshy pulp is removed using machines that are basically rotating cheese graters. The coffee fruit is fed into the top of the de-pulper with water and the rotating grater strips fruit from coffee bean.

imageA coffee harvester gently teases ripe coffee fruit off the bush.Terence Wei/Flickr, CC BY-NC

The coffee beans are sent one direction, through a gap just wide enough for them to pass, and the pulp is sent another direction to be composted.

Drying

The de-pulped coffee beans are then dried down to about 12% moisture either in the sun or in mechanical driers. Once the beans are dry they can be stored for years under suitable conditions before being roasted.

To ensure that you get the best return for your effort all the process as described above must be carefully controlled:

  • the fruit must not be allowed to over-ripen on the tree as they will ferment and grow mould
  • the harvester must not be too vigorous and remove green fruit which produces a roast coffee that is underdone.

imageThese coffee beans in Costa Rica are sunbathing before the journey to your cup.smilla4/Flickr, CC BY-NC

The processing of the coffee beans after process is critical. If coffee beans are allowed to go mouldy the taste of the roast coffee can be described as “earthy”. This earthy taste is unpleasant – we tend to associate the sensation with food that has gone off.

So if the coffee producers get everything right, their beans will be clean and dry and ready to be roasted. The beans will come out of the de-pulper intact, and be washed and dried before mould has a chance to take hold.

Now it’s up to the roaster to produce the perfectly roasted bean.

Roasting

When coffee beans are roasted the beans are heated to over 200C. Surprisingly, the difference between a light roast and the dark roast is only about 10C:

  • for a light roast the final temperature is about 215C
  • for a dark roast the final temperature is about 225C.

This subtle difference in temperature makes the difference between a delicate-tasting coffee and a heavier, fuller taste of a dark roast cup.

imagePete Spande/Flickr, CC BY-NC

What about instant coffee?

Instant coffee was invented and patented by David Strang of Invercargill, New Zealand in 1890. (Of course Invercargill’s other famous son is Burt Munro, the dashing motorcycle racer of The World’s Fastest Indian fame.)

Strang produced his instant coffee using a spray drying process, much like the process used today to produce powdered milk. The roasted, ground coffee was extracted using water at around 80C, then filtered, concentrated under vacuum and sprayed through a nebuliser into a hot airstream. This process produced a fine powder with an average particle radius of about 300μm.

Today, most instant coffee is made using a freeze drying process. This employs the principle of the sublimation of water (phase change directly from solid to gas) under vacuum.

Frozen coffee is placed on metal trays in the drying chamber and then the entire chamber is placed under vacuum. The chamber is warmed using infrared radiation or by heating the trays using conduction. The water vapour is removed by condensation and the chunky coffee granules are removed and are ready for packaging.

In terms of taste, what is the difference between brewed coffee and instant coffee? I invite you to compare the two headspace gas chromatograms below. (In headspace gas chromatography about a gram of ground coffee and one millilitre of water is heated and agitated, then a sample of “headspace” gas above the coffee is removed and injected into a gas chromatograph.)

imageAuthor provided

The profile on the left is of an instant coffee, while the one on the right is that of an Australian roast coffee. You can see that the chromatogram of the roast coffee is much more complex than that of the instant. We know that the depth of flavour and complexity of the taste of coffee is mostly due to the volatile components produced in the roasting process.

The majority of the volatile compounds in instant coffee are removed when the coffee is heated under vacuum in the freeze-drying process. Just as the water is removed through sublimation the compounds responsible for the complex taste and aroma of coffee are “flashed off” as well.

I’m sure that the atmosphere in an instant coffee factory smells fantastic, but unfortunately, those wonderful compounds that should be in the coffee are now lost.


Further reading:Wake up and smell the coffee … it’s why your cuppa tastes so goodThe perfect cup of coffee boils down to four factors

image

Don Brushett does not work for, consult to, own shares in or receive funding from any company or organisation that would benefit from this article, and has no relevant affiliations.

Read more http://theconversation.com/wheres-that-bean-been-coffees-journey-from-crop-to-cafe-30207