VOLUME 3/NUMBER 4 Yeast Production

Practical technology from Lallemand Inc.

Bakers Yeast Production and Characteristics

HE WAY YEAST is grown and pro- cessed affects its composition, YEAST PRODUCTION Tpurity, and appearance. Infor- mation about yeast production can help bakers judge and use yeast better in their own processes. beet cane molasses molasses water pure PRODUCTION PROCESS culture fermentor Raw Materials. Cane or beet molasses is vial the primary raw material for bakers yeast flask sterile production. It supplies all the sugar that clarifier mash yeast needs for growth and energy along seed tank yeast with part of the needed nitrogen. Before it sterilizer is fed to the yeast, concentrated molasses is nutrients diluted with water, clarified, and heat steril- ized. It is then supplemented with addi- pH and tional nitrogen, phosphate, vitamins, and foam control production semi-seed seed minerals. fermentor fermentor fermen. Fermentation. Bakers yeast begins as a pure culture of the desired strain, which is cooling water inoculated from a small vial into a sterile flask of broth. From the flask it is transferred filtered air into a larger vessel, then through several yeast yeast cream broth storage tank fermentation stages of increasing volume. cooler The larger-scale fermentations take place cream yeast in 25,000- to 75,000-gallon (100- to 300- water cubic-meter) fermentors that are equipped for aeration, cooling, incremental molasses centrifuge emulsifier feeding, pH control, and antifoam addi- or oil tion. Each fermentation step requires salt, starch about a day, so that at the end of a week water extruder granulator more than 500,000 pounds (250 tons) can and cutter be produced from a single vial. Processing. Yeast broth from the fer- rotary cake granular vacuum mentor at about 5 percent solids is concen- yeast yeast filter trated in a centrifuge to about 18 percent solids and washed with water. Cream yeast is simply this liquid yeast that is cooled cake yeast bag yeast and delivered in bulk to the bakery. To packaging packaging make compressed (granular and cake) yeast, cream yeast is passed through a filter, which removes water and increases the palletizers solids concentration to about 30 percent. When a rotary vacuum filter is used, the cream is first treated with salt, then sucked onto a thin layer of starch, rinsed with cold yeast cooler distribution Continued YEAST PROPAGATION STAGES Yeast Production Biochemistry 0.00001 Pounds Vial 0.000005 Kilograms AKERS YEAST production depends of Yeast (at 30% solids) on the ability of Saccharomyces cere- B visiae to assimilate inorganic nitro- 0.1 Flask gen and grow via respiration instead of fer- 0.05 mentation. Assimilating inorganic nitrogen is im- Pure Culture 2,000 portant because it allows bakers yeast to be 1,000 grown on molasses as an economical source of sugar and other nutrients. Molasses is Seed 20,000 relatively low in nitrogen and has to be 10,000 supplemented so that yeast can synthesize the protein and the other cell constituents they need for growth. Because Saccharomy- 80,000 Semi-seed ces cerevisiae can use inorganic nitrogen, a 40,000 combination of ammonia and ammonium salts are added to provide economical 500,000 Production sources of nitrogen and pH control. 250,000 Growing via respiration is important because it is about eighteen times as effi- cient as fermentation at converting sugar into yeast. The tendency of yeast to grow Bakers Yeast Production and Characteristics via respiration when large amounts of oxy- (Continued) gen are present is known as the Pasteur effect. The tendency of yeast to grow via water to remove the salt, and scraped off Listeria, and E. coli, with low levels of col- fermentation when high levels of sugar are the starch. After filtering, small amounts iforms and other sanitation-indicator present is known as the Crabtree effect. of emulsifiers or oils are added to assist in organisms. Lactic acid bacteria and “wild” The combination of Pasteur and Crabtree the extrusion and cutting of the yeast and (non-Saccharomyces cerevisiae) yeast are effects in Saccharomyces cerevisiae is the rea- to improve its appearance. Granular yeast always present because they are common son commercial bakers-yeast fermenta- is then crumbled and packed in bags; cake in the environment and grow under the tions use high aeration and incremental yeast is extruded and formed into blocks. same conditions as bakers yeast. Normal feeding to maintain high oxygen and low levels of these other microorganisms are sugar levels throughout the process. FINISHED PRODUCT not a problem because they occur natural- Composition. Compressed yeast contains ly in flour, and the bakers yeast cells greatly about 70 percent water and 30 percent outnumber them. yeast solids. Of the yeast solids, about 50 Appearance. Compressed yeast can percent is protein, 40 percent is carbohy- range in color from dark brown to nearly drate, and the rest is fat and ash. The sol- white, and in texture from friable (easy to ids content can vary from about 27 to 33 crumble) to gummy. Appearance is affect- percent, depending on how it is filtered. ed by yeast strain, molasses source, fermen- The higher the yeast solids, the higher the tation conditions, processing aids, mois- activity. The protein level can vary from ture level, and age. Low fermentation pH Lallemand Baking Update is produced by about 45 to 60 percent and the carbohy- gives higher purity but darker yeast. Lallemand Inc. to provide bakers with a drate level from 30 to 45 percent, depend- Emulsifiers give lighter color and frozen source of practical technology for solving ing mostly on how fast the yeast is grown. storage gives mushier texture, but neither problems. You can find the latest issues Higher growth rates give higher protein, affects performance. High moisture makes online at www.lallemandbaking.com. higher activity, lower carbohydrate, and yeast darker but affects performance only If you have questions or comments, please contact us at: lower stability. Lower growth rates give to the extent that yeast solids are reduced. lower protein, lower activity, higher carbo- Storage time, temperature, and oxygen LALLEMAND Inc. 1620 Préfontaine hydrate, and higher stability. make yeast darker and gummier and Montréal, QC H1W 2N8 Canada Purity. Bakers yeast is grown under reduce its performance. Old or damaged tel: (800) 840-4047 (514) 522-2133 sanitary (not sterile) conditions to ensure yeast frequently appears dark and gummy, email: [email protected] that the strain remains true to type and but because there are so many other factors www.lallemand.com that no harmful organisms are present. involved, appearance alone is not a reli- To the best of our knowledge, the information in Better sanitation procedures, fewer fer- able indicator of yeast quality. Lallemand Baking Update is true and accurate. How- ever, any recommendations or suggestions are made mentation stages, and lower fermentation without warranty or guarantee. pH give lower contamination levels. All © 2018 Lallemand Inc. products should be free of Salmonella,