What is it?
Agar is a vegetarian gelling agent derived from dried seaweed. Although some agar is wild harvested, it is more commonly farmed commercially.
Like gelatine, agar is thermo-reversible but at much higher temperatures, and it has around 5 times the setting properties – so much less is needed. Unlike gelatine, agar sets at room temperature but will hold its shape when hot.
How does it work?
It forms a ‘framework’ that holds liquid molecules in place. A 1.5% solution of agar forms a gel on cooling to room temperature that does not melt below 85º C.
Its interesting to see that it holds its shape when hot, which I guess is why it’s good as it can be incubated..I wonder how it would react if you froze it? How does bacteria react to rapid freezing?
Agar seems to have many uses, this information was taken from a cooking website, which seemed to have more information about its heating qualities. From a scientific angle, it is exactly the same however is used as a culture medium for bacteria. Here are some photos I found from google to demonstrate the different types and uses of agar… I’m going to be doing a little more research into the ‘types’ of Agar …. I’m wondering if there are various consistencies or properties that are more suitable to certain bacteria growth? I know you can get different colours, but is that just food colour? How does food colouring effect the bacteria? Will they take up the dye? So many questions to ask Mark when we can get into the labs.