mould terrarium

There’s a slight YUK warning here.  Don’t read this when eating.Our latest science experiment was this mould terrarium.  The instructions are here at The Exploratorium.  We placed small pieces of bread, cheese, carrot and pineapple in a sealed jar and observed the growth of mould on the food.
For B this experiment helped him to understand that just because we can’t see things doesn’t mean they aren’t there (we didn’t put any mould in the jar, but still the food grew mould).  And we discussed how some of these things that we can’t see can make us sick.  Recently, he has been interested in why we need to keep certain foods in the fridge, and this experiment was perfect to demonstrate.

This is the terrarium after 2 weeks (sorry for terrible photo, but I’m sure crystal clear mould is not at the top of your greatest picture list).  The results were, for me, surprising.  I expected much more mould growth, especially because we are having very humid weather and practically everything is going mouldy without the need to grow it specially. 
Here are our observations

• it took 3 days before we noticed any mould growth
• the cheese and pineapple began to go mouldy first
• there were 2 different types of mould that grew green, scaly mould and white, hairy mould
• the cheese and pineapple grew a lot of mould whilst the carrot and bread were less affected (This was another surprise for me I definitely thought the bread would go mouldy)

I think that there is a lot more to be learnt in this experiment and we might repeat it with different foods.  I’m wondering if pineapple (or pineapple juice) acts as a preservative at all. 
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I’m entering this experiment in the Ordinary Life Magic science fair.  There is a list of entries there if you feel like a bit of science play with your children.