M3-Kitchen-chemistry-EN-2.0 CITIES Project N. 129193-CP-1-2006-1-DE–COMENIUS–C21

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Chemistry for cooks - the alliteration

Leo Gros, Noreen Klein, Sascha KleinHochschule Fresenius

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Szent-Györgyi (1925) - observation:

patient brown skin(adrenalopathy)

apple apple (just cut) (brown)

apple apple (just cut) acids (brown)

1. Chemists are observers

citrus fruit juice

polyphenoloxidase

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Szent-Györgyi (1925) isolated an active substance

• „It had been an acid, it seemed to be descended from an unknown sugar, that I called „Ignose“ , the substance itself I called „Ignosinacid“. But the editor of the newspaper, to whom I send my publications, didn‘t like any jokes and rejected the name. „Godnose“ hadn‘t been anymore successful, therefore we agreed, the child ought to be called Hexuronacid. Later on, with advanced knowledge about the structure, it had to be renamed hastily and now it is called ascorbic acid (sometimes Vitamin-C-acid), since it is identical to Vitamin C and prevents scurvy. That's how I became a father without intending it, father of the Vitamin C.“

• Therefore: acid is good!

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http://www.gartendatenbank.de/photo/2004012583

http://www.fao.org/ag/Ags/agsi/ENZYMEFINAL/Enzymatic%20Browning.html#ASCORB

Ascorbic acid prevents polyphenoloxidase

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To observe something means,

to see something,that has already been seen by many,

and to think somethingthat nobody has thought about before.

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www.schule-bw.de/unterricht/faecher/biologie/archiv/tiere/voegel/Huhn2.jpg/view

2. Chemists know how to help themselves. A strange salt in the soup.

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The revealing indicator

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This way chemists see red light:

http://www.ieap.uni-kiel.de/plasma/ag-stroth/lehre/physik/HTML/f40_08.html

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http://lims.uni-duisburg.de/Lehre/Material/PMAll/vorproben.pdf

Based on this phenomenon, Bunsen and Kirchhoff developed an analysis principle:

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Today: Atomic emission is used in quantitative analysis

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http://www.uni-essen.de/chemiedidaktik/S+WM/NachteileSeife/Wasserh.htm

3. Chemists have to remove dirt from the bathtub like anyone else –but they know where it comes from

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http://de.wikipedia.org/wiki/Tenside

That's what surfactants look like:

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--

Ca 2+

This is how chemists see calcium-surfactant precipitates

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NaHCO3 + C6H8O7 → NaC6H7O7 + H2O + CO2

H3O+ + HCO3- → H2CO3 + H2O → CO2 + 2 H2O

• Brause (sherbet)• Schorle (spritzer)• Baking powder

http://de.wikipedia.org/wiki/Brausepulver

4. Chemists recognise the „underlying principles“: Three examples of effervescence – one principle

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http://www.gartendatenbank.de/photo/2004012583

5. Chemists know the tricks:How garlic destroys „poison“

(A story taking place at the Auer Dult near Munich)

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http://www.uni-bayreuth.de/departments/ddchemie/umat/knoblauch/knoblauch.htm#1

That’s only one part of the „chemistry“ of garlic

Alliin ((+)-(S)-Allyl-L-cysteinsulfoxid)

                              

                                                                         

    

Alliin                                       Allylsulfensäure    alpha-Aminoacrylsäure                                                                                                

Allylsulfensäure                                             Allicin

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http://www.chemie.uni-greifswald.de/~analytik/Lehre/Schr%F6der/Quanti/Wasserg%FCte.pdf

(Determination of oxalic acid)

An example of a chemical reaction using permanganate:

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http://www.springerlink.com/content/k85400x365p3q37h/fulltext.pdf

Water pollution in the Elbe river at the beginning of the 20th century.

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http://www.xlab-goettingen.de/pics/medien/1_1097848861/Wasseruntersuchungen.pdf

Procedure:

The following determination is accomplished simultaneously with the water sample and distilled water

1. Prepare in a 400 mL beaker boiling water for a water bath2. With a 25 mL pipette add of the water sample in a tall test tube and

add 5 mL of a 2 mol sulphuric acid. Likewise 25 mL distilled water are mixed with 5 mL sulphuric acid. The test tubes are put in boiling water for ten minutes to adjust the temperature.

3. Add exactly 5 mL potassium permanganate in both test tubes and leave them for exactly 10 minutes in the water bath. After ten minutes constant boiling add to each test tube 5 mL oxalic acid

4. Afterwards the colourless, hot fluid with potassium permanganate is titrated until a light pink colouration persists for about 30 seconds

Today in the labs it’s practiced like this:

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Here we show that human RBCs convert garlic-derived organic

polysulfides into hydrogen sulfide (H2S), an endogenous

cardioprotective vascular cell signaling molecule…. The vasoactivity

of garlic compounds is synchronous with H2S production, and their

potency to mediate relaxation increases with H2S yield, strongly

supporting our hypothesis that H2S mediates the vasoactivity of

garlic.

Gloria A. Benavides et al.,

http://www.pnas.org/cgi/content/abstract/0705710104v1

A recent publication tells us more:

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Angew. Chem. 2009, S. 121, 163-166

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http://www.physics.ubc.ca/~stm/news0229.pdf

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What does that teach us?

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How chemists see the world

… they see molecules dancing where other people see nothing

…and our benefit

We understand our world better – we can make substances, transfer and measure them – and we learn about dangers and benefits of our actions