Baker's yeast is produced through a fermentation process using specific strains of Saccharomyces cerevisiae. The process involves developing an inoculum from stock cultures, then growing the yeast in large tanks through sequential fed-batch fermentations where sugar is added incrementally to promote respiration over fermentation. Final products are either compressed dry yeast (CDY) made by extruding and drying press cake, or activated dry yeast (ADY) made by further drying tiny yeast pellets which has better stability. Contaminants are controlled and final products are packaged for stability and viability during storage.

1. BAKER’S YEAST
PRODUCTION
Made by Ms. MANASI MORE
Mentor Ms. RENU NK JAISINGHANI

2. ➢HISTORY OF BAKER’S YEAST
PRODUCTION
▪ In olden days inoculum from preceding fermentation was used in dough for bread
making. It’s still used at considerable extent but it is not practical because yeast
grow very slowly, therefore dough has to be inoculated with large numbers of
yeast and the semisolid elastic nature of dough makes it difficult to store and
transfer.
▪ It is therefore, very much essential for baking industry to have large scale
commercial source of yeast , while the brewer’s yeast increases 5 to 10 times in
volume during beer and wine production , but in case of baker’s yeast there is
very little growth in dough during short period of baker’s fermentation.

3. ➢ ORGANISM:
Special strain of S.cerevisiae is used and it should have following properties:
▪ Uniform biochemical stability
▪ Ability to ferment flour dough vigorously (excellent dough raising capability)
▪ Ability to disperse easily in water.
▪ Good keeping quality (resist autolysis).
▪ Preservation at room temperature without any change in properties and
appearance should be possible.
▪ Should give better yield.
▪ Higher growth rate.
▪ Ability to withstand drying.

4. ➢RAW MATERIAL:
➢C-source: Commonly used is cane or beet molasses,
because yeast being invertase positive can assimilate
invert sugar or mixture of cane(20%)and
beet(80%)molasses is used as it supplies yeast with bios
factor for growth. Other sources are
grains,whey,hydrocarbon,SWL etc.
▪ Concentration of sugar should be adjusted to get
maximum cellular growth than ethanol production, so
0.5-1.5% sugar is used (high sugar concentration
prevents respiration even in presence of excess of 02 ).
Thus by slow and intermittent addition of sugar is
essential.

5. ➢ RAW MATERIAL:
▪N-source: The most common are ammonium salts, liquid NH3 or
Urea. Corn steep liquor (CSL)can also be used but not NO3 and
NO2
▪P-source: The common source are phosphoric acid, diammonium
phosphate. It is very much essential for fast growth and good
performance in fermentation.
▪ Mg++ from MgSO4 is used and it prevents autolysis of cells.

6. ➢RAW MATERIAL:
▪Trace elements – Fe,Zn,Cu,Mn and Mo are required.
▪Vitamins or bios factors- It is required for optimum
growth. Biotin,panthothenic acid and required
concentration 0.29 ppm,50ppm and 1200ppm. Sometimes
thiamine is added, as it improves activity of compressed
yeast in dough system.

7. ➢PRODUCTION OF BAKER’S YEAST:
❑ INOCULUM DEVELOPMENT
Stock culture on slant A loopful St. Molasses with 6% sugar 25*c , ph. 4.5anaerobic,12hrs Tank 1
Tank 2
fermenter 20% inoculum Tank 4 Tank 3
▪ At every stage from seed tank 1 tank 4 sugar concentration is increased from 6% to 10%.
▪ Stainless steel tanks are used as pH is acidic, any other metal fermenter like Cu may cause
solubilization of metals ions in the medium & that may affect growth of organism.

8. ➢FERMENTATION CONDITION :
▪ Temprature-28-300C, therefore efficient cooling system is required.
▪ pH-4.5-5.0,it is adjusted by adding phosphoric acid. Lower PH prevents
containment, but at very low PH yeast cell may absorb coloring material from
molasses. This affects color of final product. To prevent this pH is raised by
addition of ammonia or alkali at end of fermentation.
▪ Cooling system : Large amount of heat is released during aerobic fermentation,
thus to maintain temperature (at 280 to 300 c ) cooling system is required.
❑AERATION AND AGITATION SYSTEM:
▪ It is very essential as vegetative growth of yeast is favored under aerobic
condition at low sugar concentration and high aeration, maximum respiration
and thereby can be achieved.

9. ➢ADDITION OF SUGAR:
▪ Production is mainly done by ‘Fed batch fermentation’ and
carried out with incremental feeding of the substance for growth
specially to prevent glucose effect.
▪Intermittent addition is done to maintain sugar concentration at
low level that can favor respiration and not fermentation.
▪Their is no simultaneous removal of fermentation content and
fermentation is finished when fermenter is full.
▪ The addition of sugar is reduced at the end of fermentation in
order to “mature” the yeast, as matured cells may have lower
fermentation activity but better storage stability.

10. ▪Nutrient addition - Sugar is added intermittently to maintain its
concentration at 1.5 % so that organisms grow without fermentation
or ethanol production. Ethanol produced should be 0.055 or less. It is
stopped at the end of fermentation for maturation or ripening i.e.
number of budding cells in total population should be less than 5-10%
▪Cooling-using cooling coils to prevent increase in temperature.
▪Yield -4 to 6 % yeast solid is obtained

11. ➢ YIELD:
▪6% yeast concentration is obtained but 10% can be
obtained. But 10% yeast solid occupy 25% of liquid
fermenter volume and such broth cannot be pumped
at all that is there is always a practical limit to the
concentration of yeast solid that can be achieved in
the fermenter.

12. ➢ HARVESTING OF YEAST CELLS/RECOVERY:
▪ Broth is cooled.
▪ Yeast cells are separated by sedimentation or centrifugation to triple the yeast
concentration.
▪ The white colored pumpable liquid that is obtained is called yeast cream, it is
further concentrated by filtration(usually by plate &frame filter or RVF is used).
▪ During filtration salts may be added for osmotic effect, this salt is then removed
by spraying water directly on filter thus resulting crumbly mass of yeast cell
called as press cake .It has 27 to 28% yeast solid.
▪ The final product can be in form of CDY(Compressed Dry Yeast) or
ADY(Activated Dry Yeast)

13. ➢ Plate and Frame Filter
https://www.youtube.com/watch?v=M4wBd1_CvNw

14. ➢COMPRESSED DRY YEAST (CDY):
▪ The yeast press cake is mixed in blender with small amount of
emulsifier or cutting oils at concentration 0.1 to 0.2 %.
▪ Function of emulsifier : Facilitate extrusion, give better, lighter
appearance to yeast cake
E.g. -Monoglycerides, Diglycerides, sorbitol esters or lecithin
▪ Yeast press cake is now extruded through nozzle in the form of
thick strands with rectangular cross section.
▪ These are then cut into appropriate length Wrapped in wax
paper
▪ Packed and marketed

15. ➢ COMPRESSED DRY YEAST (CDY):
▪ Immediate rapid cooling is required after packaging because
the mass warms up during processing. This is done by
refrigerating with rapid supply of cool air for 24 to 48 hrs.
▪ Final product is stored at refrigeration temperature 5 to 8 0c
(stability depends on condition during processing & % of
budding cells)

16. ➢ACTIVATED DRY YEAST (ADY):
▪It is product of dried yeast cells without loss of viability with 8%
moisture.
▪Yeast press cake is passed through screen to get tiny pellets
which are dried (tunnel drier or rotatory drier) at 28 to 40o c for 2
to 4 hours. Even fluidized bed driers can be used to dry product
within 1 to 2 hrs.
▪Butylated hydroxy anisole (BHA) is added at 0.1% concentration
to provide protection from oxidative deterioration. This also
improves stability & keeping quality of product to greater extent,
therefore product is called Protected ADY.

17. ❑COMMON CONTAMINANTS :
▪Lactic acid bacteria – Leuconostoc & lactobacillus & molds.
❑STABILITY OF ADY:
▪ADY is packed without protective packaging in polyethylene
lined bags, loses 7% activity per month & has storage life of 1 to 2
years, but if packed under vacuum then loses only 1% activity per
month

18. References
◦ Casida L. E., "Industrial Microbiology” (2009) Reprint, New Age International
(P) Ltd, Publishers, New Delhi.
◦ Prescott and Dunn's ‘’Industrial Microbiology’’(1982) 4th edition, McMillan
Publishers

19. THANK YOU