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Can brown sugar grow mold?

  1. Jan 16, 2016 #1
    Hi folks,
    I saw a previous (closed) thread stipulating that mold cant grow on sugar. I have an old package of dark Muscovado sugar from Mauritius stored in the original plastic bag; it has small area of white here and there on the clumps of sugar which looks like mold. Water and nutrients are needed for mold formation; perhaps due to the high molasses content, both of these are present. On the other hand, I have my doubts that it could be mold; candy and honey also have nutrients but dont grow fungi.... what do you all think?
  2. jcsd
  3. Jan 16, 2016 #2


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    Huh? Ferment honey all day making mead.
  4. Jan 16, 2016 #3

    I've seen that. It isn't mold. It is some kind of crystallization.

    Pure sugar sucks all of the water out of microorganisms.
  5. Jan 16, 2016 #4

    jim mcnamara

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    What @Hornbein is talking about is usually termed recrystallization. The formation of new crystals of sucrose removes the impurities - ie., the brown molasses residue
    - https://en.wikipedia.org/wiki/Brown_sugar

    Sugar and salt are used to preserve food from attack by bacteria and fungi. Drying food is a very good way to preserve food. Of course something like 'dried lettuce' may not be appealing.

    If you want to defeat the effect of these treatments add some water to the food either through high relative humidity or simply letting the food get wet. So.
    Foods preserved as described above are kept in sealed containers - to keep out water and humidity.

    From wikpedia on osmosis:
    This applies to water as a solvent.

    Why does it work to preserve food? Osmotic pressure is a way to understand. Jams and jellies have high enough levels of solutes - sugar - such that the osmotic pressure on bacterial cells is too high to allow the growth of species that would otherwise colonize the food. Water moves the 'wrong' way (out of cells) for growth to occur, so the cells dies and bacterial spores stay dormant. Jams and jellies have enough water for some species of fungi to grow, however.

    As an aside: In the first half of the 20th century ( see the very first addition of 'The Settlement Cookbook' ) people let a "mother" form on sweet pickles, jams and jellies. A mother is a fungal mat. What this does is to prevent bacterial spores and new fungi from getting into the food. This has a downside. For example, there are fungi that produce aflatoxins and will grow on/in nut butters, vegetable jellies and types of pickles.
    Aflatoxins are poisonous and cancer-causing chemicals that are produced by certain molds (ex: Aspergillus flavus and Aspergillus parasiticus)

    When food moisture content is low enough or osmotic pressure from sugars or salt is high enough, even fungi have a hard time growing.[/quote]
  6. Jan 18, 2016 #5
    "Pure sugar sucks all of the water out of microorganisms."
    Reference https://www.physicsforums.com/threads/can-brown-sugar-grow-mold.852478/

    Right, but this ain't pure sugar. In fact, this sugar is kind of moist, sticky, and clumped together to begin with. You can see parts which have clumps of molasses in them. This is not like your processed brown sugar you get in little packets at the restaurant. If the sugar content would be so high as to dry it out, why would it be moist? Plus sugar always seem to come in paper boxes or paper sacks, while this one is in an airtight (ziploc-closing) plastic. I have reason to believe this is not your ordinary sugar...

    On the other hand, I also have a jar of liquid molasses which has been around for years. Nothing happened to it, other than the fact that it seems to be getting more and more thick. (Probably the water content evaporating?)
  7. Jan 18, 2016 #6
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