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16207RE: [MedievalSawdust] Re: Bacteria filter properties of wood

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  • dukegavin
    Mar 6, 2014
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      Bacteria in the wood when it acts as a filter? Yes. That is exactly where you would expect to find it. Filtration captures material in the filter medium. That is entirely to be expected. Anticipate a gradient of smaller and smaller material from the entry side to the exit side of a filter medium.


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      -------- Original message --------
      From: leaking pen
      Date:03/05/2014 10:18 PM (GMT-05:00)
      To: medievalsawdust@yahoogroups.com
      Subject: Re: [MedievalSawdust] Re: Bacteria filter properties of wood

       

      Actually, my purpose of posting the original link was a simple logic puzzle.  The classic experiment of putting bacteria on the wood cutting board, and then supposedly later finding bacteria IN the wood fibers is now suspect, if those same wood fibers FILTER out bacteria, then how are those same bacteria supposed to have passed into the wood and been removed from the surface?

      (Hey, everyone who posted about there being no tie between, hows about ASKING what a person might have meant, instead of assuming and name calling.  Thanks!)


      On Wed, Mar 5, 2014 at 8:02 PM, Peter Ellis <dukegavin@...> wrote:
      Botulinus toxin is extremely potent.  To the best of my knowledge the toxin is not broken down by heating, which is part of why it is so dangerous in foods. 
      The thing that happens with the egg salad and the tuna salad is that the mayonnaise turns, the eggs and tuna are both cooked, but mayonnaise makes a first class culture medium and cannot be trusted at room temperatures for very long. Any time you notice the mayo turning clear, do not eat that ;)

      And none of that has any bearing on filtering water through wood, or on whether a wooden cutting board has natural anti-bacterial qualities.

      Note that black locust has a significant quantity of fungicide in it, enough to be measured as a significant percentage of weight!  Which might not make it really suitable for any sort of food handling, but perhaps good for countertops.

      Also worth noting that when sap is pulled for making syrups, it is effectively filtering ground water through the tree.
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      On Mar 2, 2014, at 3:10 PM, "Jerry Harder" <geraldgoodwine@...> wrote:

       

      Basically everything in my "hypothesis" is from modern food safety and home canning texts put out out by reputable universities continually researching such things.  Since this topic is lingering, I will mention one thing I didn't say before.  (read this fully and carefully) Botulism bacteria can be killed by normal canning practices BUT its spores, THE REAL DANGER, will linger on and can grow in a moist, low acid, environments such as a water-bath caned jars of corn or green beans.  Many modern tomato varieties no longer have sufficient acid to be water bath canned and must have a little extra acid added to be safe.  Low acid foods such as meat and many or most vegetables can be pressure caned.  Pressure canning uses time, pressure, and temperature tested for specific foods for given can sizes to achieve killing the botulism spores.  One should always use a tested recipe from a government or university type organization.  Standard practice also includes boiling home caned foods for 10 minutes to kill any toxins any living bacteria might have reproduced.  Any questionable caned item should be thrown away.  My understanding is it is the toxins produced by botulism bacteria not the bacteria itself that can be deadly.  There are many types of food illnesses other than botulism. You here of picnic things like egg and tuna salad being top "Carrier" culprits.  These foods start with no cooking thus no bacteria kill initially and any source of contamination can grow.  It is not refrigerated for a period of time before it is eaten, so if careful attention is not made to the ice in your cooler,  bacteria may have time to grow at full speed, (refrigeration simply slows bacteria growth) and third it is not cooked before eating thus not destroying any bacteria or toxins that might have developed.  I am not afraid of putting these foods on my plate but usually taste them when I first sit down.  If they are not still colder than the room temperature, I don't eat them.

      On 3/1/2014 4:17 PM, Broom wrote:
       
      > I think they are talking a a totally different thing here. They were
      > talking about using a slice of wood to filter bacteria from water, like
      > a tea strainer to removes chunks of tea from tea. The process does not
      > kill the bacteria, it just removes it.

      Indeed, Master Gerald - the OP confused cutting board sanitation with water filtration; two completely different issues.

      On cutting boards:
      To my knowledge the mechanism by which wooden cutting boards prevent bacterial reproduction has never been proven, although I personally subscribe to your hypothesis. If it has been established, I'd love to see a link to the research.

      On heartwood filters:
      One part of the article troubled me, but it's probably just typically bad science reporting:

      "The tree technology isn't perfect, researchers acknowledged. The sapwood was only able to filter out particles 70 nanometers and larger. That works fine for stopping bacteria, the vast majority of which are no smaller than 200 nanometers. Viruses, on the other hand, are much, much smaller, Karnik said, and would likely be able to bypass the wood filter.

      I've never heard of a water filtration system (designed for human water consumption, not lab use) that /does/ filter out viruses. 70 nanometers is an AMAZING filter level - it even blocks giardia spores, among the tiniest of tiny little bastards that can ruin camping trips.

      It's like complaining that "cars aren't perfect, because they be driven into elevators." Um, duh.

      I wonder how thick of a piece is required - because thickness = resistance to flow. Paper-thin (tubes a few dozen cells long) would mean a fairly reasonable flow - you could expect to process a gallon or more overnight.

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