The Atoms in Watermelon

Posted by jns on 3 September 2009

I did not plan to become the expert on such an arcane topic–although I can answer the question as it arises–but once I had written a blog posting called “Atoms Are Not Watermelons“,^* my web was spun, my net set, the trap was ready for the unsuspecting googler who should type such an interesting question as

Are the atoms in a watermelon the same as usual atoms?

Perhaps you don’t find this question as surprising as I do. However, since I am the number-one authority on the atoms in watermelons, at least according to the google,^‡ I deem the question worth answering and I will answer it.

The answer to the question: yes. The atoms in a watermelon are definitely the same as the usual atoms.

It is, in fact, the central tenet of the atomic theory that everything in the universe is made from the same constituent particles that we know as “elements”, except for those things that are not made of atoms (subatomic particles, for instance, or neutron stars). Even in the most distant galaxies where there are atoms they are known to be the familiar atomic elements.

Watermelon (Citrullus lanatus) is about 92% water, 6% sugar (both by weight). Thus, by number, the vast majority of atoms in a watermelon are hydrogen, oxygen, and carbon. There are also organic molecules as flavors, amino acids and vitamins, plus trace elemental minerals like iron, magnesium, calcium, phosphorus, potassium, and zinc.

The USDA tells us that “Watermelon Packs a Powerful Lycopene Punch“, saying

Lycopene is a red pigment that occurs naturally in certain plant and algal tissues. In addition to giving watermelon and tomatoes their color, it is also thought to act as a powerful antioxidant. Lycopene scavenges reactive oxygen species, which are aggressive chemicals always ready to react with cell components, causing oxidative damage and loss of proper cell function.

I was interested to discover that one can even buy watermelon powder and Lycopene powder, both from the same source, Alibaba.com, which seems to be a diversified asian exporter.

By request from Isaac, here are some recipes for pickled watermelon rind (about which he says “I’ve always wanted to make it.” I never knew — and after 17 years living with someone you’d think I’d have found out):

• Sweet Pickled Watermelon Rind — most of the recipes that I turned up seemed to be variations on this sweet version, said to be a traditional “Southern” style of some indeterminate age; I’ve not located the ur-recipe yet. Some gussy it up, many vary the amounts of the ingredients while maintaining the same proportions, and one I read added 4 sliced lemons to the pot, which sounded like a nice variation.
• Watermelon Rind Pickles — this is the not sweet, more pickley version that I think I would find more to my taste. This recipe makes “fresh” pickle, simply stored in the refrigerator, versus processed & canned pickle as in the previous recipe.

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^* Having just read Richard Rhodes’ How to Write, the subject at hand was bad metaphors in science writing, which he expressed by saying “atoms are not watermelons”.

^‡ Oddly, Yahoo! and Bing do not agree, more their loss.