Monthly Archives: September 2011
How is coffee decaffeinated?
Apparently it’s National Coffee Day today, read below to learn in less than a page how coffee gets decaffeinated – not an easy task!
Coffee contains over 400 chemicals important to the taste and aroma of the final drink: it is therefore challenging to remove only caffeine while leaving the other chemicals at their original concentrations.
To get rid of the caffeine, unroasted (green) beans are at first steamed. The beans are then rinsed with a “solvent” chemical that extracts the caffeine while leaving the other essential chemicals in the coffee beans. The process is repeated anywhere from 8 to 12 times until caffeine is removed in 97%-99.9%. So what is this magic “solvent” chemical. which is able to selectively remove caffeine while preserving the coffee aroma?
This solvent is nothing else but carbon dioxide (CO2), which is also found in our very own atmosphere. However, as you might have guessed, CO2 is not used for decaffeination as a gas from the atmosphere. For the decaffeination process, the coffee beans are soaked in a special form of CO2 called “supercritical” CO2. OK, so now you naturally have to ask what the heck is this “supercritical” CO2??
Every substance (water, hydrogen, oxygen, etc) has a so-called “critical point”. The critical point is the point above which, the distinction between liquid and gas phases of that substance stops being meaningful. That is you cannot tell any more whether this substance is gas or liquid. This new “phase”, being neither gas or liquid is called “supercritical”. A “supercritical fluid” can effuse through solids like a gas, and dissolve materials like a liquid.
So how does supercritical CO2 look like?
To achieve the supercritical state for most substances requires extreme temperatures and pressures. Carbon dioxide, however, has a fairly accessible critical point at ~ 31.1°C and 73 atm (our atmosphere has 1 atm). And it seems that supercritical CO2 has unique properties such that it can selectively extract caffeine from coffee beans, producing decaf coffee.
Carbon dioxide pressure-temperature phase diagram. The critical point is found at T=31.1°C and 73 atm. Above the critical point, one cannot really tell whether CO2 is liquid or gas. This new phase is called “supercritical”.
What are we really made of?
Watch this!! – I just found this amazing video that offers a very entertaining introduction into the particles and forces that make up me, you, the earth, the universe. Featuring Morgan Freeman, Stephen Hawking, Michio Kaku, Brian Cox, Richard Feynman, and Frank Close, this video offers a cursory introduction to quantum chemistry – the science that governs the interactions of subatomic particles, atoms, and even molecules.
Basically, in 3 and a half minutes, the video tries to explain that:
Dig deep inside the atom
and you’ll find tiny particles
Held together by invisible forces
The atoms that we’re made of have
Negatively charged electrons
Whirling around a big bulky nucleus
The universe is made of
Twelve particles of matter
Four forces of nature
The world is a dynamic mess
Of jiggling things
In the quantum world electrons behave as waves and as particles
For the ultimate triumph of science
We need a theory of everything
Which is still just beyond our grasp
The theory of everything is the Holy Grail of Physics: A theory that will explain through a single model everything from Creation, to supernovas, to atoms and molecules, perhaps even DNA, people, and love. (The four yet unified forces of nature are: gravitation, electromagnetism and the weak and strong nuclear forces that keep together elementary particles.)
If we ever create this theory, we might answer questions such as:
- What happened before the big bang?
- Is it possible to build a time machine?
- Can we punch a hole in space?
“The Quantum World” music video is the eleventh installment in the ongoing Symphony of Science music video series. Materials used in the creation of this video are from:
http://symphonyofscience.com for downloads & more videos!
How does a sunblock work?
This is a question that I got very often during the summer. A sunblock can have two types of active ingredients: organic and inorganic chemicals, which reflect or scatter the light away so that it doesn’t reach the skin at all. The most common ingredients of a sunblock are zinc oxide or titanium oxide. You can usually tell who is using a sunblock just by looking, because the sunblock whites out the skin. Sort of.. like this:
Sunblocks are usually white because of the large amount of titanium dioxide that reflect UV light.
Titanium dioxide (TiO2) is a white powder that has strong UV light absorbing capabilities. This property enhances TiO2 stability and enables it to protect the skin from ultraviolet light. Sunscreens designed for infants or people with sensitive skin are often based on titanium dioxide, as these mineral UV blockers are believed to cause less skin irritation than other UV absorbing chemicals. The titanium dioxide particles used in sunscreens have to be coated with silica or alumina, because titanium dioxide creates radicals in the photocatalytic reaction. These radicals are carcinogenic, and could damage the skin.
In newer formulations of sunscreens, TiO2 is combined with oil and is made up from smaller TiO2 particles (sized 40-50nm called nanoparticles). The oil in a sunscreen formula helps wet TiO2 and gives the optical effect of transparency so that you don’t have to look like someone’s painted you white.
For those who are wondering about the organic ingredients, these work primarily by absorbing UV light and dissipating it as heat. One of the most common organic molecules used in sunscreens is para-aminobenzoic acid, also know as PABA. The mechanism which allows PABA to absorb UV radiation is due to the resonance of the molecule. Resonance can be explained by saying that many molecules have more than one possible way in which the valence electrons could be placed. These electrons move freely across many nuclei. In PABA, a carbonyl group, a functional group where a carbon is double bonded to oxygen, can produce resonance by moving the valence electrons. The shift or movement of the electrons closely matches the frequency of UVB light, absorbing the light energy and releasing it as heat and or longer wavelengths of light. Source: http://www.sas.upenn.edu/~rosema/sunscreenchemistry.html
PABA
What Sunscreens/Sunblocks Screen
The portion of the sunlight that is filtered or blocked is ultraviolet radiation. There are three regions of ultraviolet light.
- UV-A penetrates deeply into the skin and can lead to DNA damage and premature skin aging.
- UV-B is involved in tanning and burning of your skin.
- UV-C, the most dangerous radiation is almost completely absorbed by the ozone in the atmosphere.
Sun is good for you, too
Although the sun can cause many aliments, UV rays are extremely important to a healthy functioning body. Vitamin D, which can not be produced by the body, is synthesized by the photolysis of a steroid in the deep epidermis of the skin. Without the exposure to natural light, the biochemical mechanism will not pursue causing disorders in both children and adults including rickets, ostomalaica, and osteoporosis.
For more info check this link.
Life is Chemistry 