Yeast
The yeast used in bakeries to ferment dough is a living plant organism belonging to the fungi. These organisms require food, moisture and heat if they are to grow and reproduce. Yeast is made by selecting strong sturdy species and culturing the same on good nutritious food under ideal conditions. After a culture is made, given quantities are sowed into large tanks or vats containing solutions to which the proper food, possessing sugars, proteins, mineral matter, traces of organic fat and oxygen is added. To furnish oxygen, air is usually blown through the tanks while the yeast is growing.
In these tanks the yeast takes on food, grows strong and sturdy and reproduces itself many times. After it grows long enough in the tanks, the solution is passed through centrifugal machines in which the major portion of the water is removed leaving the yeast in a sort of creamy semi-fluid state. This mass of yeast is now placed on cloth-lined trays which are put into filter presses and more water is removed.
The yeast taken from these filter presses is now in a solid condition and can be handled easily. It is now moulded into shapes and then forwarded to dividing and weighing machines where it is divided, weighed and put into wrappers, then placed into refrigerators from where it is carried to the baker ready for use.