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In this article we will discuss about the commercial production and use of yeast.
Commercial Production of Yeast:
Pure cultures of the selected strains of Saccharomyces cerevisiae are maintained in test tubes in laboratory. The test-tube cultures are increased to suitable volumes for commercial production (Fig. 40.9) by transferring them to the tanks containing bulk medium. Great care has to be taken 10 prevent contamination at any stage of development of the culture.
The medium in tanks consists of molasses, corn-steep liquor and suitable source of nitrogen (ammonia, mineral salts, etc.) The medium is adjusted to a pH of 4-5 (acid pH) after yeast inoculation by addition of sulphuric acid (H2SO4) or ammonia (NH3) as per requirement. Acid condition of the medium is necessary to encourage yeast growth as well as to prevent unwanted bacterial growth. Temperature is maintained at 25-26°C and the inoculated medium is aerated during incubation period.
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The yeast cells multiply rapidly and utilize all the sugar within 10-12 hours of incubation after inoculation. The yeast cells are now harvested from the medium by centrifugation and washed thoroughly by suspending the yeast cells in water. The yeast cells are finally subjected to ‘filter-press’ to result in the production of ‘yeast-cakes’.
Use of Yeast:
Baker’s yeast is used in baking industry to bring about desired changes in texture and flavour of the baked products. These yeasts possess ability to ferment the sugar vigorously and to grow rapidly.
They differ from the yeasts used in brewing and wine industry in that their growth habit is aerobic, they produce high amount of cell mass in sugar containing media, remain viable for longer periods during storage and are superior in dough performance.
