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Re: [foodees] How can they grow?

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  • keyur kumar
    hi well regarding water activity of the medium, we generelly add 1.8 % (1.5 to 2%) agar as per the specifications of manufacturer the most common value is
    Message 1 of 3 , May 31, 2006
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      hi
       
      well regarding water activity of the medium, we generelly add 1.8 % (1.5 to 2%) agar as per the specifications of  manufacturer
      the most common value is 1.8%
       
      at this conc. there is still more than suffi free water to grow for microbes,  but yes obviously  if conc is more than 2% definitely inhibites the growth and at 4% conc there is virtuaaly no growth occurs,
       
      looking to only physical strucure of gel we can't say that it has bound all the free water. but yes the org which require full water activity to grow they are defi inhibited and so for special org of this type special care and enumeration technique need to be used
       
      sorry dear i m unable to site the refference for this, i have read it in some book during 8 sem

      Tapan Dave <tapandave@...> wrote:
      Hello Friends,
      For getting the growth of microorganisms we are cultivating them in various type of nutrient containing agars at their optimum growth temperature. Now my question is, Agar is Gel and it will bound the water from the medium so that water activity of medium will reduce to very less. If the water activity is reduced then how can microorganisms grow optimally in the medium? (F.Y.I:- even 3-4 % of gel addition in our foods will reduce the aw to prevent growth of microorganisms!)
       
      From,
      Tapan Dave


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    • SAKTHI VIJAYAKUMAR
      hi.. i think that solid nutrient media for bacteria r prepared using 1.5 to 2% agar concentration only.. this conc wont b reducing the water activity to the
      Message 2 of 3 , Jun 1, 2006
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        hi.. i think that solid nutrient media for bacteria r prepared using
        1.5 to 2% agar concentration only.. this conc wont b reducing the
        water activity to the level that wud prevent the growth of microbes..
        and in case of semisolid media, the agar conc is slightly less than
        1%.. correction & suggestions r welcomed...

        SAKTHI.V

        --- In foodees@yahoogroups.com, "Tapan Dave" <tapandave@...> wrote:
        >
        > Hello Friends,
        > For getting the growth of microorganisms we are cultivating them in
        various
        > type of nutrient containing agars at their optimum growth
        temperature. Now
        > my question is, Agar is Gel and it will bound the water from the
        medium so
        > that water activity of medium will reduce to very less. If the water
        > activity is reduced then how can microorganisms grow optimally in the
        > medium? (F.Y.I:- even 3-4 % of gel addition in our foods will reduce
        the aw
        > to prevent growth of microorganisms!)
        >
        > From,
        > Tapan Dave
        >
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