|Brewing and baking yeast (Saccharomyces cerevisiae)|
If you like macro photography, then you will love these pictures which must be the ultimate in macro photography. They are taken using an electron microscope and some of these cells are just 7 micrometers long! One of these pictures is probably Dad's favourite fungi, I'm talking today about Yeasts!
|Zygosaccharomyces bailii - this one spoils food|
- Yeasts are estimated to make up around 1% of all fungal species. There are over 500 species but there can be lots of different strains of each yeast. (There are 4000 different strains at the National Collection of Yeast Cultures)
- Now I said above the are very small, each cell being around 7 micrometers long but I couldn't imagine how small that was until I found on a website that it would take 20 billion yeast cells to weigh one gram!
- How long does yeast live? Well it seems you don't measure age by time with yeast but by the amount of times the cell splits before it dies.
- So what does yeast do for us. Well, the one at the top of the page is used in brewing (that's why Dad likes it!) and also in baking.
|Another brewing yeast with budding scars|
- The Romans discovered that you could dry yeast and revive yeast by drying dough in the sun and later reviving it with sugar.
- The scientific name for the yeast that baker’s use is Saccharomyces Cerevisiae, or “sugar-eating fungus" I wonder why that is....
- Well its because the favourite food of this yeast is fructose and glucose, types of sugar found in honey, maple syrup and fruit etc.
- When they eat the sugar they produce alcohol and carbon dioxide. In baking the carbon dioxide is what makes the bread rise, the alcohol is evaporated I guess. In brewing the gas escapes and the alcohol is left behind.
|Cryptococcus shivajii - looks a bit furry|
- A yeast cell can ferment its own weight of glucose in one hour!
- Yeasts reproduce on their own by growing a small bump which enlarges, matures and detaches. This is called budding. You can see budding scars on some in the pictures.
- Some yeasts though reproduce by fission.
- Not all yeasts are quite so useful though. The one in the second picture is one that is known to to spoil food!
- Worse than that some yeasts can cause infections in humans and animals some of which can be quite nasty.
|Saccharomyces paradoxus - opening with spores inside|
- Yeast like brewers yeasts can be useful in our diet. They have 50% protein and vitamins like B1 and B2 so you can take yeast as a vitamin supplement.
- Dad said one thing he learnt while he was away is that yeasts can make things other than alcohol and people are looking for yeasts that can make useful chemicals for us from plants instead of having to make them from things like oil.
Hope you enjoyed,