Manufacturing Yeast

The main part of producing yeast is molasses fermentation in order to provide proper conditions for multiplying of yeast cells and eventually, the final product might be offered to the market in form of dry or wet yeast.
The first step is to culture a chain of Saccharomtces Cervisia bacteria in a laboratory and to transfer them to the major production unit. This step is taken prior to fermentation and will continue until sufficient development of bacteria growth is fulfilled and yeast can be produced. In this phase, a small amount of yeast is produced (20% of the total production). Temperature should be controlled precisely and beside salt and molasses, particular nutrients should be added to expedite the production process. Ferment grains are taken out via the centrifuge and clearing and washing proceeds up to the time that the final ferment is made. The, it is conducted to the reservoir to be preserved in 4°C heat for various uses.
In order to produce industrial yeast in vast commercial scales, the following phases are commonly performed in production lines:

1. Preservation of molasses and raw materials
Main raw materials of the production line include sugarcane or sugar beet molasses which is stored in black sheet tanks of 14 meter dimension.
Other chemicals are kept in barrels, bags or special packages in raw materials storages close to the production line.

2. Preparation, dilution and pasteurization of molasses
In this stage, molasses is diluted and is prepared for being delivered to the fermentation section after being pasteurized (in about 110°C) and cooled. Simultaneously, clearing operation is conducted on the product so that slime and other non-solvent materials are disconnected from molasses.

3. Preparation of chemicals
In this stage, a series of chemicals, emulsifiers and minerals are prepared to be sent to tanks of fermentation, washing and sterilization sections.

4. Laboratory fermentation
The primary motive is cultured, multiplied and eugenized in the microbiological laboratory. Pure ferment culture is performed in absolute sterilized laboratory conditions and the product is delivered to the production line.

5. Molasses fermentation in the production line
Primary and secondary fermentation are performed in big rustproof steel tanks where the precise control of air, PH and temperature is essential and the culture condition is sterilized. Following the culture stage of the pure yeast, the product is systematically injected into fermentors.
In the fermentors, proper conditions are provided for culture and growth of motives and fermentation operation is conducted in monitored complicated conditions.
The equipment for preventing contaminators has a great role in this phase. Also, other auxiliary materials and nutrients enter fermentors in form of solutions. Ammonium compounds form the major proportion of the chemicals. In this stage, the heat provided by heat transformers is exited the production line using water and is then transferred to cooling towers. The proper conditions for growth is provided under 30-34°C. The required oxygen is maintained through airification systems and the solution PH is controlled using additives such as sodium carbonates and sulphuric acid.
The material of one fermentor is transferred to other fermentors following the completion of fermentation operation so that the determined capacity of the production line is maintained. The number of fermentors depend on the production capacity.

6. Separators
The yeast is separated from the culture environment by centrifugal separators and is sent to the yeast milk section through several stages.

7. Keeping yeast milk
The yeast solution is diluted by cold water and is gathered and kept in yeast milk tanks.

8. Drying unit and strip making
In order to increase the thickness, the yeast solution is passed through vertical filters and its dry matters substance increases to 28-32%.
The product which is called yeast cake is transferred to strip making machines.
The water separated from the yeast is conducted to sewage. In strip makers, the product is stripped into a specific size and is conducted to the drier.

9. The drying unit
Continuous driers are used in the first drying stage. Yeast granules are dried in driers using dampless, dry heat and the dry matters substance increases to 91%. It is then pushed to the second drying station where dry air makes its damp decrease to less than 5%.
High dry matters substance and activeness of the yeast are the most significant characteristics of the driers.

10. Packaging
Active instant dry yeast is conducted from driers to bonkers of the packaging section and is packed in two lines for entering the market. Vacuum packaging and bulk (in P.P. bags) are used for special domestic markets as well as bakery and breas manufacturing factories, respectively.
Packed products are preserved in cold storages to be delivered to consuming centers.
The following diagram briefly demonstrates the step-by-step method of producing yeast and all types of utilizable yeasts.

1. Molasses
2. Preparation, attenuation and pasteurization
3. Preparation of chemicals
4. Laboratory fermentation
5. Fermentation in the production line
6. Separators
7. Liquid yeast
8. Dehydration
9. Fresh yeast
10. Drier
11. Dry yeast
12. Regular packaging
13. Vacuum yeast