Espresso yourself

Dhivyalakshmi Rajasekar

Introduction

Coffee is one of the most popular beverages con-sumed worldwide. Its

a brewed drink prepared from coffee beans. Coffee was the top agricultural export for twelve countries in 2004. It is rich in caffeine content and has a stim-ulating effect on humans(1).

History

According to a coffee history legend, an Arabian shepherd named Kaldi found his goats

dancing joyously around a dark green leafed shrub with bright red cherries in the southern tip of the Arabian Peninsula. Kaldi soon de-termined that it was the bright red cherries on the shrub that were causing the peculiar euphoria and

after trying the cherries himself, he learned of their powerful effect. The stimulating effect was then ex-ploited by monks at a local monastery to stay awake during extended hours of prayer and distributed to other monasteries around the world. Coffee was born(2). Coffee then spread to Italy, and to the rest of Europe, to Indonesia, and to the Americas(3).

The Plant

The coffee plant is a woody per-ennial evergreen dicotyledon that belongs to the Rubiaceae family. They are

evergreen shrubs or small trees that may grow 5 m (15 ft) tall when unpruned. The leaves are dark green and glossy, usually 10–15 cm (4–6 in) long and 6 cm (2.4 in) wide. The flowers are axillary, and clusters of fragrant white flowers bloom simultaneously and are followed by oval berries of about 1.5 cm (3). Several species of shrub of the genus Coffea produce the berries from

which coffee is extracted. The two main species commercially culti-vated are Coffea canephora (predominantly a form known as ‘robusta’) and C. arabica. Coffea arabica, known as Arabica coffee, accounts for 75-80 percent of the world’s production(3).

Processing (4)Roasting

Chemical process by which aromatics, acids, and other flavor components

are either created, balanced, or alteredin a way that should augment the flavor, acidity, aftertaste and body of the cof-fee as desired by the roaster. From 170-

200°C the sugars in coffee begin to caramelize. The dark color of coffee is directly related to the caramelization of the sucrose in coffee. There-

fore, to maximize sweetness you want to minimize the carmelization of sucrose, yet you do not want to roast too lightly.GrindingFor proper extraction, it is essential to grind coffee properly. Freshly grinding the beans before brewing coffee is one of the most important steps for achieving a quality

cup of coffee. Coffee should not be ground more than 2 minutes before brewing or major staling (oxidation) begins to take place.Coffee BrewingBrewing coffee is as much of an art as it is a science. Coffee should be brewed for 4.5-5 minutes using a ratio of 55 grams of ground coffee per liter of filtered water (195-205°F). It is convenient to use 2 tablespoons of coffee per 6 ounces of filtered water. Filtered water and spring water are recommended. Tap water imparts off flavors to the coffee and some minerals are essential to coffee flavor. The various methods include

French press Automatic drip coffee filter Espresso maker Vaccum pot

Different stages of maturation of coffee fruit

Chemistry of coffeeCoffee beans contain caffeine which is an alkaloid. Caffeine is a central nervous system stimulant. It belongs to the xanthine chemi-cal group In moderate doses, caffeine can increase alertness, reduce fine motor coor-dination, cause insomnia, cause headaches, nervousness and dizziness (9).Coffee aroma is

responsible for all coffeelflavor attributes other than the mouth-feel and sweet, salt, bitter, and sour taste attributes that are perceived by the tongue. Coffee aroma is per-ceived by two different mechanisms.

It can either be sensed nasally via smelling the coffee through the nose or retronasally. The perceived acidity of coffee results from the proton donation of acids to receptors on the human tongue (11).

Facts about caffiene (10). Caffeine was first isolated from cof-fee in 1820. 10g of caffeine is considered a lethal dose. It’s the most popular drug in the world.. Darkly roasted coffee has less caf-feine than lightly roasted

Coffee and Health (5, 6)-Coffee does not increase the risk for high blood pressure over time.-It might have anti-cancer properties.-Heavy coffee drinkers may be half as likely to get diabetes as light drinkers or nondrinkers.-Coffee seems to protect men, but not women, against Parkinson’s disease. One possible explanation for the sex difference may be that estrogen and caffeine need the same enzymes to be metabolized, and estrogen captures those enzymes.-Caffeine increases intellectual activity when fatigued or bored.-Coffee has a protective effect against cirrhosis of the liver-Coffee has four times the anti-oxidants of Green Tea, makes an excellent anti-depressant, and enhances performance and memory-The FDA considers caffeine to be “Generally Recognized as Safe.”

Coffee has virtually no calories or fats, no carbohydrates, no sodium.In fact, coffee is exempt from federal food label programs precisely because it has zero nutritive value. Cof-

fee does offer a number of trace minerals (Thiamin, Niacin, Folate, Phosphorus, Magnesium, Manganese) and is a good source of Potassium, Pantothenic Acid and Riboflavin (7).

Nutrition information

Bitterness

-The perceived bitter taste in the mouth from coffee is correlated to the extent of extraction (McCamey et al)-The extent of extraction is dependent upon the roast, the mineral content of the water, water temperature, time, grind size, and brewing procedure. -The total dissolved solids of a coffee-Quinic acid--a degradation product of chlorogenic acids--is present at twenty times its threshold value and is partly responsible for the perceived bitterness in cof-fee (McCamey, 176).-Furfuryl alcohol is thought to contribute a burnt and bitter taste to coffee (Shibamoto et al., 311).

Microstructure

Figure 4 Transverse cut of a healthy, fully developed coffee seed/ green bean

Fig 5 Coffee Leaf400x

The microscopy of coffee is, on the whole, more important to the planter than to the consumer and the dealer; while, on the

other hand, the microscopy is of paramount im-portance to the consumer and the dealer as fur-nishing the best means of determining wheth-er the product offered is adulterated or not. The coffee fruit has, an outer fleshy portion called

the pericarp. Beneath this is a part like tissue paper called the endocarp. Next in position to this, and covering the seed, is the so-called spermoderm(seed/ silver skin). The coffee bean is the embryo and its food supply; the embryo is that part of the seed which, when supplied with food and moisture, develops into a new plant. The embryo of the coffee is very minute consisting of hard and soft endosperm. (12).

Fig 2 Coffee bean under light microscope x30

Fig 3 Cross section of coffee bean un-der light microscope x30

Figure 1

Fig 6 Closer view of cellular “compart-ment” structure of a healthy green cof-fee bean with “full” content of proteins, lipids, etc

Fig 7 Underdeveloped, immature coffee bean, with insufficient cellular content

Image of the cell that form the epicarp of coffee fruit: (a) AFM image with anincrease approximately of 5000 and (b) image obtained by LM techniquewith increase 20

Fig 8, 9 Carsely ground coffee particles under light microscope x15

Fig 8

(13)

Fig 10 Commercially ground for espresso cof-fee. It has a much finer structure than ground cof-fee to allow more flavour to be extracted quickly (15)

Fig 11 Instant coffee (15)

Fig 12 Ground coffee from a coffee bean, commercially ground for a drip-filter coffee machine. Most of the detailed structure is due to the grinding process and it does not show you much about the internal structure of the coffee (15)

Fig 13 Confocal micros-copy of whole coffee bean showing the autofluores-cent compounds

(14)

Fig 14 SEM of gold coated ground coffee particles gave better resolution to analyze the particle size of ground coffee (16)

Fig 15 SEM of uncoated ground coffee particles (16)

Fig 16 Polarization microscopy of coffee cooler contsisting of vodka, heavy cream, sugar syrup, iced coffee, and coffee ice cream (17)

Fig 17 Polarization microscopy of caf-feine (17)

Robur grinder (gold deposition). Light areas are "charged" with electrons.

Super Jolly grinder

The large particles appear rounder (more spherical) on the conical grinders, and more irregularly shaped on the flat burr Super Jolly.

Dark field microscope x40 Dark field microscope x100

Phase contrast microscope x40 X ray tomography

Ultrastructural analysis of drying damage in parchment Arabica coffee endosperm cells (Borém et al., 2007) (18)

Fig 19 Scanning electron micrographs of coffee seeds dried at 40 °C (arrow) empty intercellular spaces (a); coffee seeds dried at 50 °C (arrow) partially occluded intercellular spaces (b); coffee seeds dried at 60 °C (ar-row ) intercellular spaces completely occluded (c).

Fig 20 Transmission electron micrographs of coffee seeds dried at 40 °C (a), at 50 °C (b) and at 60 °C (c).

Fig 18 Light micrographs of coffee seeds dried at 40 °C, (arrow) oils in globular shape inside the cells (a); coffee seeds dried at 50 °C (arrow) oils in the extremity of the endosperm tissue, occlusion of the intercel-lular spaces (b); coffee seeds dried at 60 °C (arrow) oils spread throughout the cellular surface forming large droplets in the intercellular spaces (c).

References:

1) http://en.wikipedia.org/wiki/Coffee2) http://www.coffeeresearch.org/coffee/history.htm3) http://www.ncausa.org/i4a/pages/index.cfm?pageid=674) http://www.coffeeresearch.org/coffee/roasting.htm5) http://www.health.harvard.edu/press_releases/coffee_health_benefits6) http://www.pnf.org/CoffeeEdited041001.pdf7) http://www.cariboukcups.com/~/media/40D4C82E42274B5D841201473709A7B2.ashx?w=200&h=314&as=18) http://caloriecount.about.com/starbucks-coffee-nutrition-m4-19) http://faculty.washington.edu/chudler/caff.html10) http://coffeetea.about.com/library/blcaffeine.htm11) http://www.coffeeresearch.org/science/aromamain.htm12) http://www.web-books.com/Classics/ON/B0/B701/21MB701.html13) Cardona et al., 2008.J.Food Eng 86: 167-17114) http://www.scielo.br/img/revistas/cta/v24n4/a27fig07.gif15) http://pwatlas.mt.umist.ac.uk/internetmicroscope/micrographs/curi-ous/espresso-coffee_z3.html16) http://www.home-barista.com/reviews/titan-grinder-project-scan-ning-electron-microscope-sem-analysis-of-ground-coffee-t4205.html17) http://micro.magnet.fsu.edu/cocktails/pages/coffeecooler.html18) Borém et al., 2008 J.Biosystems Eng 99: 62-66