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There are many foodstuffs that are ionically conductive (for example, anything moist and salty). What about foods that have a high electronic conductivity?

The only thing I can think of would be something which has been charred – presumably the char, being mostly carbon, would have a fairly high conductivity.

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    $\begingroup$ If it is charred until it conducts electricity - is it still food? $\endgroup$ – Martin - マーチン Apr 15 '14 at 5:46
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I wonder why nobody mentioned the famous vodka with gold flakes. Admittedly, this hardly qualifies as food, and the amount of gold is minuscule, but in the absence of any solid examples with true metallic character I think it may deserve a curious look.

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Many foods conduct electricity. The charge carriers are ions, and the conductivity is a function of temperature and ion mobility. Liquids, therefore, are generally better conductors. The electrical properties of foods are important parameters to consider in food processing operations such as ohmic heating, microwave heating, pulsed field irradiation and induction heating. This has implications in a number of important areas, such as, the industrial microwave pasteurisation of egg-whites, and high temperature short exposure sterilisation of certain food products. A quick search of the Thomson Reuters Web Of Science database returns over 350 hits for "electrical conductivity of foods". Indeed there are whole book chapters dedicated to the subject. See for example this and this.

So, what about some numbers then?

Conductivity for some general materials at 20 °C are given on this page in Wikipedia. (All values in S/m)

  • Copper $6 \times 10^7$
  • Sea Water $4.8$
  • Drinking Water $10^{-4}$ to $10^{-2}$
  • Deionized water $10^{-6}$
  • Glass $10^{-15}$
  • Carbon $10^3$

    The following values for foods have been taken from a variety of published literature sources. Again units are S/m. Most temperatures are at or near 20 °C, where I can find the value stated.

  • Beer 0.1

  • Coffee 0.18
  • Coffee with milk 0.36
  • Orange juice 0.36
  • Apple Juice 0.24
  • Cranberry Juice 0.09
  • Milk 0.5
  • Carrot Juice 1.3
  • Tomato juice 1.7
  • Beef 0.26
  • Chicken 0.19
  • Tomato paste 0.35-0.82
  • Gatorade 0.2
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    $\begingroup$ My question is specifically about electronic conductivity, not ionic conductivity. That is, I'm wondering about foods where charge transport is mediated by electrons rather than ions. $\endgroup$ – Max Radin Apr 21 '14 at 0:25
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Char need not be complete. It need only be sufficient to form a conducting network, and so is a legitimate answer for electronic conductivity of food. An organic conductor generally pi-stacks and preferably has unpaired spins. Look up the conductivity of melanins (if you like eating long pig or naked goat). DNA is a pi-stack!

http://www.drproctor.com/os/amorphous.htm

https://www1.ethz.ch/lbb/Education/Biosensors/DNA_conductivity.pdf
http://mike.zwolak.org/publications/DNA_Electronics.pdf
http://physicsworld.com/cws/article/news/2007/dec/17/conduction-seen-in-dna-backbone
http://www.physics.ucla.edu/research/biophysics/news/pdf/outlook.pdf
http://www.ceesdekker.net/files/PW_DNA.pdf

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  • $\begingroup$ You may want to add that DNA's conductance is minimal in macroscopic sense, and therefore may not qualify as an answer. $\endgroup$ – Greg Aug 31 '15 at 15:33
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I found this question when contemplating this recent news article about 3d printing and Vegemite, a naturally electrically conductive spread for bread that is consumed in Australia.

http://munchies.vice.com/articles/3d-printed-vegemite-could-be-the-future-of-edible-electronics

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