1. PRODUCTION OF YEAST AND ITS APPLICATION IN FOOD INDUSTRY.

2. GROUP MEMBERS: NAME ROLL.NO. 1.SHEIKH BILAL #07 2.M.USMAN #14 3.A.QAYYUM #19 4.RANA BILAL #06 5.M.HUZAIFA #04

3. WHAT IS YEAST? YEASTS ARE EUKARYOTIC, SINGLE-CELLED MICROORGANISMS CLASSIFIED AS MEMBERS OF THE FUNGUS KINGDOM. THE YEAST LINEAGE ORIGINATED HUNDREDS OF MILLIONS OF YEARS AGO, AND 1,500 SPECIES ARE CURRENTLY IDENTIFIED. THEY ARE ESTIMATED TO CONSTITUTE 1% OF ALL DESCRIBED FUNGAL.EUKARYOTICCELLEDMICROORGANISMSFUNGUSKINGDOMSPECIES

4. PRODUCTION OF YEAST: YEAST IS PRODUCED BY A CONTROLLED AEROBIC FERMENTATION (GROWTH WITH AIR) WHERE YEAST BIOMASS – AND NOT ALCOHOL – IS THE RESULT. PURE STRAINS OF THE “MOTHER” CULTURE ARE MAINTAINED IN THE LABORATORY AND THEN TRANSFERRED TO THE PLANT PROCESS, WHERE THEY ARE GROWN IN A NITROGEN-ENRICHED SUGAR MEDIUM, FORTIFIED WITH VITAMINS AND MINERALS FOR OPTIMUM CELL ACTIVITY.

5. FLOW SHEET DIAGRAM:

6. PRODUCTION PROCESS: 1.PREPARATION: YEASTS CAN GROW IN THE PRESENCE OR ABSENCE OF AIR. FOR EXAMPLE, IN BREAD DOUGH YEAST GROWS VERY LITTLE. THE SUGAR IS USED MAINLY TO PRODUCE ALCOHOL AND CARBON DIOXIDE. ONLY A SMALL PORTION OF THE SUGAR IS USED FOR CELL MAINTENANCE AND GROWTH. IN THE PRESENCE OF A SUFFICIENT QUANTITY OF DISSOLVED OXYGEN YEAST GROWS BY USING MOST OF THE AVAILABLE SUGAR FOR GROWTH AND PRODUCING ONLY NEGLIGIBLE QUANTITIES OF ALCOHOL.

7. 2.RAW MATERIAL PREPARATION: BEET AND CANE MOLASSES ARE COMMONLY USED AS RAW MATERIAL BECAUSE THE SUGARS PRESENT IN MOLASSES IS A MIXTURE OF SUCROSE, FRUCTOSE AND GLUCOSE ARE READILY FERMENTABLE. YEAST ALSO REQUIRES CERTAIN MINERALS, VITAMINS AND SALTS FOR GROWTH.

8. SOME OF THESE CAN BE ADDED TO THE BLEND OF BEET AND CANE MOLASSES PRIOR TO FLASH STERILIZATION WHILE OTHERS ARE FED SEPARATELY TO THE FERMENTATION. A SEPARATE NUTRIENT FEED TANK CAN BE USED TO MIX AND DELIVER SOME OF THE NECESSARY VITAMINS AND MINERALS WHICH ARE REQUIRED FOR PROPER GROWTH OF YEAST.

9. REQUIRED NITROGEN IS SUPPLIED IN THE FORM OF AMMONIA AND PHOSPHATE IS SUPPLIED IN THE FORM OF PHOSPHORIC ACID. EACH OF THESE NUTRIENTS IS FED SEPARATELY TO THE FERMENTATION TO PERMIT BETTER PH CONTROL OF THE PROCESS. THE STERILIZED MOLASSES COMMONLY REFERRED TO AS MASH OR WORT IS STORED IN A SEPARATE STAINLESS STEEL TANK. THE MASH STORED IN THIS TANK IS THEN USED TO FEED SUGAR AND OTHER NUTRIENTS TO THE APPROPRIATE FERMENTATION VESSELS.

10. 3.CULTURE PREPARATION: THE YEAST SERVES AS THE INOCULUM FOR THE PRE-PURE CULTURE TANK. A SMALL PRESSURE VESSEL IS USED TO GROW SEEDS UNDER STRICT STERILE CONDITIONS. THE CONTENTS OF THIS VESSEL ARE TRANSFERRED TO A LARGER PURE CULTURE FERMENTER WHERE PROPAGATION IS CARRIED OUT WITH SOME AERATION UNDER STERILE CONDITIONS. THESE EARLY STAGES ARE CONDUCTED AS SET-BATCH FERMENTATIONS. IN SET-BATCH FERMENTATION ALL THE GROWTH MEDIA AND NUTRIENTS ARE INTRODUCED TO THE TANK PRIOR TO INOCULATION.

11. DURING FED-BATCH FERMENTATION MOLASSES, PHOSPHORIC ACID, AMMONIA AND MINERALS ARE FED TO THE YEAST AT A CONTROLLED RATE. THIS RATE IS DESIGNED TO FEED JUST ENOUGH SUGAR AND NUTRIENTS TO THE YEAST TO MAXIMIZE MULTIPLICATION AND PREVENT THE PRODUCTION OF ALCOHOL. EXTENSIVE CLEANING OF THE EQUIPMENT, STEAMING OF PIPES AND TANKS AND FILTERING OF THE AIR IS PRACTICED TO INSURE AS ASEPTIC CONDITIONS AS POSSIBLE.

12. 4.FERMENTATION: TO START THE COMMERCIAL FERMENTATION, A VOLUME OF WATER IS PUMPED INTO THE FERMENTER. NEXT, IN A PROCESS REFERRED TO AS PITCHING SEMI-SEED YEAST FROM THE STORAGE TANK IS TRANSFERRED INTO THE FERMENTER. FOLLOWING ADDITION OF THE SEED YEAST, AERATION, COOLING AND NUTRIENT ADDITIONS ARE STARTED TO BEGIN THE 15-20 HOUR FERMENTATION.

13. AT THE START OF THE FERMENTATION THE LIQUID SEED YEAST AND ADDITIONAL WATER MAY OCCUPY ONLY ABOUT ONE-THIRD TO ONE-HALF OF THE FERMENTER VOLUME. CONSTANT ADDITIONS OF NUTRIENTS DURING THE COURSE OF FERMENTATION BRINGS THE FERMENTER TO ITS FINAL VOLUME. THE RATE OF NUTRIENT ADDITION INCREASES THROUGHOUT THE FERMENTATION BECAUSE MORE NUTRIENTS HAVE TO BE SUPPLIED TO SUPPORT GROWTH OF THE INCREASING CELL POPULATION. THE NUMBER OF YEAST CELLS INCREASE ABOUT FIVE- TO EIGHT- FOLD DURING THIS FERMENTATION

14. AIR IS PROVIDED TO THE FERMENTER THROUGH A SERIES OF PERFORATED TUBES LOCATED AT THE BOTTOM OF THE VESSEL. THE RATE OF AIRFLOW IS ABOUT ONE VOLUME OF AIR PER FERMENTER VOLUME PER MINUTE. A LARGE AMOUNT OF HEAT IS GENERATED DURING YEAST GROWTH AND COOLING IS ACCOMPLISHED BY INTERNAL COOLING COILS OR BY PUMPING THE FERMENTATION LIQUID, ALSO KNOWN AS BROTH, THROUGH AN EXTERNAL HEAT EXCHANGER.

15. THE ADDITION OF NUTRIENTS AND REGULATION OF PH, TEMPERATURE AND AIRFLOW ARE CAREFULLY MONITORED AND CONTROLLED BY COMPUTER SYSTEMS DURING THE ENTIRE PRODUCTION PROCESS. THROUGHOUT THE FERMENTATION, THE TEMPERATURE IS KEPT AT APPROXIMATELY 86 DEGREES FAHRENHEIT AND THE PH IN THE RANGE OF 4.5-5.5.

16. 5.SEPARATION: AT THE END OF THE SEMI-SEED FERMENTATION THE CONTENTS OF THE VESSEL ARE PUMPED TO A SERIES OF SEPARATORS THAT SEPARATE THE YEAST FROM THE SPENT MOLASSES. THE YEAST IS THEN WASHED WITH COLD WATER AND PUMPED TO A SEMI-SEED YEAST STORAGE TANK WHERE THE YEAST CREAM IS HELD AT 34 DEGREES FAHRENHEIT UNTIL IT IS USED TO INOCULATE THE COMMERCIAL FERMENTATION TANKS.

17. 6.PACKAGING AND TRANSPORT: AT THE END OF FERMENTATION, THE FERMENTER BROTH IS SEPARATED BY NOZZLE-TYPE CENTRIFUGES, WASHED WITH WATER AND RE-CENTRIFUGED TO YIELD A YEAST CREAM WITH A SOLIDS CONCENTRATION OF APPROXIMATELY 18%. THE YEAST CREAM IS COOLED TO ABOUT 45 DEGREES FAHRENHEIT AND STORED IN A SEPARATE, REFRIGERATED STAINLESS STEEL CREAM TANK.

18. CREAM YEAST CAN BE LOADED DIRECTLY INTO TANKER TRUCKS AND DELIVERED TO CUSTOMERS EQUIPPED WITH AN APPROPRIATE CREAM YEAST HANDLING SYSTEM. THE YEAST CREAM CAN BE PUMPED TO A PLATE AND FRAME FILTER PRESS AND DEWATERED TO A CAKE-LIKE CONSISTENCY WITH 30-32% YEAST SOLIDS CONTENT. THIS PRESS CAKE YEAST IS CRUMBLED INTO PIECES AND PACKED INTO 50-POUND BAGS THAT ARE STACKED ON A PALLET.

19. THE YEAST HEATS UP DURING THE PRESSING AND PACKAGING OPERATIONS AND THE BAGS OF CRUMBLED YEAST MUST BE COOLED IN A REFRIGERATOR FOR A PERIOD OF TIME WITH ADEQUATE VENTILATION. PALLETIZED BAGS OF CRUMBLED YEAST ARE THEN DISTRIBUTED TO CUSTOMERS IN REFRIGERATED TRUCKS.

20. USE OF YEAST: YEAST IS USED IN FOOD INDUSTRY GIVEN BELOW: 1. AS FOOD ADDITIVES 2.IN BAKING INDUSTRY 3.IN BREWING INDUSTRY 4.IN WINE INDUSTRY 5.IN DISTILLING INDUSTRY 6.AS WHEY YEAST 7.IN SOUR DOUGH INDUSTRY

21. 1.AS FOOD ADDITIVES: THEY ARE CONSIDERED AS A SAFE SOURCE OF INGREDIENTS AND ADDITIVES FOR FOOD PROCESSING. PREPARATIONS OF BAKER’S AND BREWER’S YEASTS HAVE BEEN AVAILABLE FOR MANY YEARS AS DIETARY NUTRIENT SUPPLEMENTS BECAUSE OF THEIR HIGH CONTENTS OF B VITAMINS, PROTEINS, PEPTIDES, AMINO ACIDS AND TRACE MINERALS. YEASTS AND ARE OFTEN CONSIDERED AS AN ALTERNATIVE SOURCE OF PROTEIN FOR HUMAN CONSUMPTION. THE PRODUCTION OF ANTIOXIDANTS, AROMAS, FLAVOURS, COLOURS AND VITAMINS BY YEASTS HAS ALSO BEEN REPORTED.

22. FLAVOURS INGREDIENTS BASED ON YEAST EXTRACTS, YEAST AUTOLYSIS AND DRIED YEAST PREPARATIONS REPRESENT THE MOST COMMERCIALLY SIGNIFICANT PRODUCTS EXTRACTED FROM YEASTS AND ARE USED EXTENSIVELY IN THE FOOD INDUSTRY AS A SOURCE OF SAVOURY, ROASTED, NUTTY, CHEESY, MEATY AND CHICKEN FLAVOURS. SOME EXTRACTS ARE SPECIFICALLY ENRICHED IN THEIR CONTENTS OF GLUTAMIC ACID AND NUCLEOTIDES THAT FUNCTION AS STRONG FLAVOUR ENHANCERS. WHILE BAKER’S AND BREWER’S YEASTS HAVE BEEN THE TRADITIONAL SOURCES OF THESE

23. THEY ALSO ABSORB MYCOTOXINS AND COULD OFFER A METHOD FOR REMOVING THESE SUBSTANCES FROM BEVERAGES SUCH AS WINE. FOOD COLORANTS SUCH AS ASTAXANTHIN AND OTHER CAROTENOID PIGMENTS AND A DIVERSITY OF VITAMINS CAN ALSO BE DERIVED FROM YEASTS.

24. 2.IN BAKING INDUSTRY: YEAST IS USED IN BAKING INDUSTRY DUE TO ITS COMPOSITION I.E. 30–33 % OF DRY MATERIALS, 6.5–9.3 % OF NITROGEN, 40.6–58.0 % OF PROTEINS, 35.0–45.0 % OF CARBOHYDRATES, 4.0– 6.0 % OF LIPIDS, 5.0–7.5 % OF MINERALS AND VARIOUS AMOUNTS OF VITAMINS DEPENDING ON ITS TYPE AND GROWTH CONDITIONS. INACTIVE DRY YEAST IS A PRODUCT WITHOUT LEAVENING PROPERTIES USED FOR THE CONDITIONING OF DOUGH PROPERTIES IN BAKING OR THE DEVELOPMENT OF CHARACTERISTIC FLAVOUR.

25. SCHEMATIC DIAGRAM:

26. TOP-FERMENTING YEASTS ARE USED FOR THE PRODUCTION OF ALES, PORTERS, STOUTS AND WHEAT BEERS ETC. BOTTOM-FERMENTING YEASTS ARE USED FOR LAGER BEERS LIKE PILSNERS, BOCKS, AMERICAN MALT LIQUORS, ETC. INACTIVE BREWER’S YEAST PREPARATIONS, MADE FROM INACTIVE YEAST AND OTHER SPECIAL INGREDIENTS, ARE PRODUCED COMMERCIALLY TO BE USED AS NUTRIENTS TO REINITIATE OR AVOID SLUGGISH AND STUCK FERMENTATIONS.

27. 3.IN BREWING INDUSTRY: USUALLY TWO SACCHAROMYCES SPECIES ARE USED: S. UVARUM FORMERLY KNOWN AS S. CARLSBERGENSIS WHICH IS USED FOR THE PRODUCTION OF SEVERAL TYPES OF BEER WITH BOTTOM FERMENTATION (LAGER YEASTS) AND S. CEREVISIAE WHICH CONDUCTS TOP FERMENTATION YEASTS

28. BOTTOM-FERMENTING YEASTS ARE USED FOR LAGER BEERS LIKE PILSNERS, BOCKS AND AMERICAN MALT LIQUORS ETC.

29. 4.IN WINE INDUSTRY: A WIDE VARIETY OF PURE YEAST CULTURES, MAINLY SACCHAROMYCES (S. CEREVISIAE, S. BAYANUS, S. UVARUM, S. OVIFORMIS, S. CARLSBERGENSIS, S. CHEVALIERI, S. DIASTATICUS, S. FRUCTUUM, S. PASTEURIANUS, S. SAKE AND S. VINI ETC.) ARE PRODUCED INDUSTRIALLY FOR THE USE IN INDUCED WINE FERMENTATIONS. ACCORDING TO THE INDUSTRIAL DEMANDS FOR FERMENTATION EFFICIENCY AND PRODUCTIVITY.

30. THE SUITABLE TYPE OF YEAST IS SELECTED WITH RESPECT TO THE GEOGRAPHICAL AREA, CLIMATE, TYPE OF GRAPES AND DESIRABLE ORGANOLEPTIC QUALITY OF THE PRODUCT (TASTE, AROMA, COLOUR, TANNIN AND GLYCEROL CONTENT ETC.). PURE YEAST CULTURES ARE ALSO USED TO CONDUCT SPECIFIC TYPES OF FERMENTATIONS LIKE BOTTLE FERMENTATION OF CHAMPAGNE AND SPARKLING WINE OR TO TREAT STUCK AND SLUGGISH FERMENTATIONS.

31. 5.IN DISTILLING INDUSTRY: DISTILLER’S YEASTS ARE USED FOR THE INDUSTRIAL PRODUCTION OF ALCOHOL AND SPIRITS (BRANDY, WHISKEY, RUM, TEQUIL ETC.). THEY ARE USUALLY ISOLATED FROM INDUSTRIAL FERMENTATIONS OF FRUIT PULPS AND BEET OR SUGAR CANE MOLASSES. THEIR SELECTION DEPENDS ON THE DESIRED PRODUCT PROPERTIES, INCLUDING FLAVOUR, ALCOHOL YIELD, PRODUCTIVITY AND OTHER TECHNOLOGICAL FEATURES.

32. DISTILLER’S YEASTS MUST BE ABLE TO FERMENT VARIOUS SUBSTRATES SUCH AS CORN, BARLEY, WHEAT, POTATO ETC. AFTER HYDROLYSATION IN FERMENTABLE SUGARS. THEY MUST BE ABLE TO CONDUCT FAST FERMENTATIONS WITH HIGH PRODUCTIVITIES AND LOW PRODUCTION COSTS AND TOLERATE HIGH TEMPERATURES, OSMOTIC PRESSURES AND ALCOHOL CONCENTRATIONS

33. 6.AS WHEY YEAST: A VARIETY OF MICROORGANISMS THOSE PRESENT IN MILK MICROFLORA ARE ABLE TO UTILIZE WHEY THE MAIN BY-PRODUCT OF THE DAIRY INDUSTRY. THE YEASTS MOST WIDELY STUDIED AND USED AT INDUSTRIAL SCALE FOR THE PRODUCTION OF YEAST BIOMASS FROM WHEY ARE THE LACTOSE FERMENTING. KLUYVEROMYCES YEASTS K. LACTIS AND K. MARXIANUS (FORMERLY CLASSIFIED AS K. FRAGILIS). KLUYVEROMYCES YEASTS CAN EFFICIENTLY GROW ON LACTOSE AS SOLE CARBON SOURCE.

34. LACTOSE FERMENTING YEASTS ARE ALSO FOUND IN KEFIR, A NATURAL MIXED CULTURE FOUND IN THE CAUCASIAN MILK DRINK. KEFIR YEASTS HAVE BEEN USED AT SEMI-INDUSTRIAL SCALE FOR WHEY LACTOSE UTILIZATION AND PRODUCTION OF VALUE ADDED PRODUCTS SUCH AS ETHANOL, BIOMASS, LACTIC ACID AND ALCOHOLIC BEVERAGES. KEFIR PRODUCED USING WHEY HAS ALSO BEEN EVALUATED AS STARTER CULTURE IN BREAD MAKING AND MATURATION OF CHEESE WITH GOOD RESULTS.

35. 7.IN SOUR DOUGH INDUSTRY: SOURDOUGH IS A MIXTURE OF FLOUR AND WATER CONTAINING YEASTS AND LACTIC ACID BACTERIA USED AS STARTER CULTURE TO LEAVEN BREAD. THE USE OF SOURDOUGH HAS A NUMBER OF IMPORTANT ADVANTAGES OVER BAKER’S YEAST SUCH AS THE DEVELOPMENT OF CHARACTERISTIC FLAVOUR AND TEXTURE.

36. AS WELL AS EXTENSION OF PRESERVATION TIME THROUGH THE IN SITU PRODUCTION OF ANTIMICROBIAL COMPOUNDS E.G. BACTERIOCINS. THEREFORE, SOURDOUGHS ARE PRODUCED AT COMMERCIAL LEVEL USING VARIOUS COMBINATIONS OF YEASTS AND BACTERIA AND ARE USED FOR THE CONDITIONING OF DOUGH, IMPROVEMENT OF PRESERVATION TIME AND THE DEVELOPMENT OF BREADS AND BAKING PRODUCTS WITH SPECIAL ORGANOLEPTIC PROPERTIES.