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Rust and pathogens

  1. Nov 27, 2007 #1

    wolram

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    Working in the food industry and quality control people can not tell me why rusty metal is all ways put down as a pathogen risk, what is this risk please.

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    Last edited: Nov 27, 2007
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  3. Nov 28, 2007 #2

    Ouabache

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    The biggest risk that comes to mind; rusty metal is known to harbour Tetanus bacteria*, so if you should cut your skin on a piece of "rusty metal", it is a good idea to check your tetanus immunization and if needed, get a booster shot. If there was rusty metal in my food, I would be concerned about it tearing some skin on its journey to my stomach. :bugeye:


    *tetanus bacterium: Clostridium tetani, anaerobic bacillus, produces the neurotoxin tetanospasmin. Thanks ian for catching my oversight on category of microorganism.
     
    Last edited: Nov 28, 2007
  4. Nov 28, 2007 #3

    iansmith

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    Tetanus is a toxin produce by a bacterium not a virus. Being a microbiologist, the difference is important.

    For rusting iron, it probably has to do with iron availability for bacteria and other pathogen. Virtually all bacteria requires iron and they need to get it from somewhere. One way to limit bacterial grow, which reduces pathogen/spoilage risk, is to remove or reduce accessibility to freely available iron. Human do that with transferin, lactoferrin and haem. Changes in iron availability will greatly impact how a pathogen grow, so rusting iron might increase the amount of freely available iron in the environment and bacteria would grow much faster. This is, however, speculation on my part.
     
  5. Nov 28, 2007 #4

    wolram

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    Thanks guys, i should have said that there is zero possibility of this rust getting into any food product, it seems to be iansmiths suggestion that rust is a possible feeding area,that is the cause.
     
  6. Nov 28, 2007 #5

    Moonbear

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    Another reason is simply the challenge of disinfecting something as porous as rusted metal since there are lots of nooks and crannies for the bacteria to hide in away from the disinfectants you're cleaning it with. Sand it down and give it a coat of paint and folks are happy that it's again a non-porous surface that can be properly disinfected.
     
  7. Nov 28, 2007 #6

    DaveC426913

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    Yes, but I've never heard of any other common warning about tetanus except rust.

    I've always wondered what the connection was. Now I know.
     
  8. Nov 28, 2007 #7

    Moonbear

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    Actually, it's any deep puncture wound. The rust in those cases usually implies a dirty surface...something old, lying around a long time. You'd want a tetanus booster if you got any sort of deep puncture wound, such as an animal bite, not just the proverbial rusty nail. It's an anaerobic bacteria, so can thrive deep in those wounds.
     
  9. Nov 28, 2007 #8

    chemisttree

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    I believe that would be Micobially Induced Corrosion (MIC) as well. A bacterial colony's biofilm and associated exudations can cause the underlying metal to corrode. It could even be galvanic corrosion from differential aeration due to the overlying biofilm.
     
    Last edited: Nov 28, 2007
  10. Nov 28, 2007 #9

    wolram

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    Thanks all, i guess i should not moan about the cost of constantly replacing rusty hardwear.
    MoonB, painting parts is frowned upon, we can get away with it in extreme cases.
     
  11. Nov 28, 2007 #10

    Ouabache

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    On the other hand, food exposed to rusty (oxidized) metal, may not necessarily, be harmful (ref: scientist's opinion) . I've tasted a metallic flavor when I cooked chili in a cast-iron dutch oven (lesson: don't cook anything acidic in cast-iron), and also in breads or cake baked in a pan with small amount of oxidation on its surface.
     
  12. Nov 28, 2007 #11

    Moonbear

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    You'd just have to label it all iron-fortified! :biggrin: (Though, it would defeat the purpose if it's calcium-fortified too.)
     
  13. Nov 28, 2007 #12

    Astronuc

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    Rusty iron or steel is usually associated with a moist and dirty environment, hence the concern that rust would also mean bacterial contaminiation. Certainly a rusty nail on the ground or in a rotten piece of wood outdoors would likely have bacteria such as Clostridium tetani resident.

    Rust films are porous and can absorb moisture, so could conceivably become breeding grounds for bacteria. On the other hand, a cast iron pot with a little rust which develops if the pot is washed in water (usually with soap), dried in the dish rack, and then stored in a clean, dry cabinet would likely not have bacteria in the rust. Nevertheless, wash it or even heat it before use.

    As Ouabache indicated, it might change the taste of the food.

    Interesting, MIC can occur in certain stainless steels, which have an increased sulfur content. These are usually anaerobic bacteria however.
     
  14. Nov 29, 2007 #13

    jim mcnamara

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    Iron oxides can affect food colors, as well as taste.
     
  15. Nov 29, 2007 #14

    Ouabache

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    The title of this thread is an attention getter. What is the first thing that comes to mind, when you see "rust and pathogen" in the same phrase?

    The ubiquitous rust diseases of course. If, by chance you want to take a closer look at some rusts, there is an extensive herbarium at Purdue Univ, with 100,000 rust specimens (the largest collection of Uredinales in the world). I recall a fellow there, who made regular trips to South America (early 1980s) to collect specimens in the wild, before many areas of plant (and fungal) diversity were destroyed.
     
    Last edited: Nov 30, 2007
  16. Nov 30, 2007 #15

    Moonbear

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    I think only a mycologist, or maybe plant scientist, would think of that first. :biggrin: Most of us think rusty nail and tetanus.
     
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