Fresh yeast: This should look firm and moist, cream coloured and cool to touch. If it's crumbly, dryish and dark in places it is stale and might not do its work. To use it simply mix the required amount into the liquid and mix into the dough straight away. Fresh yeast can be bought in bulk and stored in a deep freezer in, say, wrapped 1 oz (25 g) portions. It will keep in a freezer for three months, or in a refrigerator for three days.