Gritty Pears

Beach picnics leave something to be desired. That gritty texture as the sand blows into the sandwiches; the added crunch in the ice-cream. Sand is comprised primarily of tough silica (silicon dioxide) crystals that resist the constant grinding of waves on a beach.

Have you ever noticed how pears in some ways resemble beach food? When you chew a pear, you can feel a rough, gritty texture. It’s very similar to sand contaminated food. In fact, the similarities do not stop at the texture. The gritty particles in pears are actually silica as well – produced in the sclereid cells of the tissue layer called the sclerenchyma.

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6 Comments

Filed under Household Science, Kitchen Science

6 responses to “Gritty Pears

  1. David

    What is your reference on the silica thing? I thought the same thing and one of my classmate refutes this. I would like the silica reference to thwap over his head. Thanks,

    David

  2. Hi David,

    It was my second year biology course notes – Biology of Plants at Macquarie University. I think it was also in the textbook we used at the time (a while ago!).

    I had a look for a journal entry which supports this and I have had trouble finding one. I have found one which shows silicon in shoot tissue of other members of the Rosaceae family

    Hodson MJ, White PJ, Mead A, Broadley MR (2005) Phylogenetic variation in the silicon composition of plants. Ann Bot 96(6):1027-46.

    And one with some fabulous pictures of pear fruit sclereids

    Angeles G, Owens SA, Ewers FW (2004) Fluorescence shell: a novel view of sclereid morphology with the Confocal Laser Scanning Microscope. Microsc Res Tech. 63(5):282-8.

    but nothing that places silicon in the pear fruit itself. Nor, to be fair, anything that definitively refutes it either.

    Most people seem to be publishing work looking at silicon in leaves, shoots and roots.

    I’ll keep looking for one, but it is also possible that the information from my course is outdated or disproved (maybe I should not believe everything I learn at school).

    I’ll keep looking until I get a definitive answer.

    So maybe don’t thwap him yet!

  3. David

    I found many of the same articles you did. The laser spectroscopy one was really cool. It is an amazing idea that you can cause the different crystalline materials in a plant cell to lase, and use the light emitted to image the cells. Rock on! I love “in your face” academics.

  4. Laurel

    Well, on Wikipedia (i don’t know how credible you want to believe this is), it says the grit is caused by “lignified” cells, so it must be lignin. not silica, right? It also says the grit is from sugar turning to starch. Just thought this might help on the pear-grit-origin quest.

  5. Q

    Probably out dated info. Check out this….
    dro.deakin.edu.au/eserv/DU…/mcnaughton-provisionaldatabase-2005.pdf
    by JJ Powell – ‎2005 – ‎Cited by 54 – ‎Related articles
    The present study provides a provisional database for the Si content of UK … The silicon content of UK foods analysed by inductively coupled …. Pears, raw.

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