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Unit operations

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china vengaiah
china vengaiah

The document discusses unit operations in food processing. It defines a unit operation as a processing step where raw materials enter and a desired product exits. Important unit operations include heat transfer, drying, evaporation, separation processes, size reduction, mixing and shaping. Examples of specific unit operations used to produce many foods are provided, such as pasteurization, freezing, spray drying, centrifuging, grinding, blending and extrusion. The document focuses on freezing operations like plate, immersion, blast and fluidized bed freezing.

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Unit OperationsUnit Operations P C VengaiahP C Vengaiah
Unit OperationsUnit Operations What do we mean byWhat do we mean by ““Unit Operations”?Unit Operations”?
Unit OperationsUnit Operations ““Unit Operations” =Unit Operations” = AA food processingfood processing operation byoperation by which raw materials are thewhich raw materials are the input and the desired product isinput and the desired product is the outputthe output
Unit OperationsUnit Operations Using a material balance and an energyUsing a material balance and an energy balance, a food engineering processbalance, a food engineering process can be viewed overall or as a series ofcan be viewed overall or as a series of units.units. Each unit is a unit operation. The unitEach unit is a unit operation. The unit operation can be represented by a boxoperation can be represented by a box as shown inas shown in Fig. 1.1Fig. 1.1..
View of a Unit ProcessView of a Unit Process
Unit Operations - OverviewUnit Operations - Overview Important unit operations in the food industryImportant unit operations in the food industry are:are:  Heat transfer – thermal processing, freezing,Heat transfer – thermal processing, freezing, chillingchilling  Drying – dehydration and concentrationDrying – dehydration and concentration  EvaporationEvaporation  Contact equilibrium processes (which includeContact equilibrium processes (which include distillation, extraction, gas absorption,distillation, extraction, gas absorption, crystallization, and membrane processes)crystallization, and membrane processes)
Important Unit Operations (cont)Important Unit Operations (cont)  Mechanical separations (which includeMechanical separations (which include filtration, centrifugation, sedimentationfiltration, centrifugation, sedimentation and sieving)and sieving)  Size reduction – grinding, millingSize reduction – grinding, milling  Mixing, forming and shapingMixing, forming and shaping  ExtrusionExtrusion
Unit OperationsUnit Operations  Examples – what type of processExamples – what type of process or processes are used in theor processes are used in the manufacture of examplesmanufacture of examples handed around in class?handed around in class?
Mass & EnergyMass & Energy  Two very important laws which all unitTwo very important laws which all unit operations obey are the laws ofoperations obey are the laws of conservation of mass and energy.conservation of mass and energy.  The law ofThe law of conservation of massconservation of mass statesstates that mass can neither be created northat mass can neither be created nor destroyed.destroyed.  ““What goes in must come out".What goes in must come out".
Mass & EnergyMass & Energy  The law ofThe law of conservation of energyconservation of energy states that energy can neither bestates that energy can neither be created nor destroyed. The total energycreated nor destroyed. The total energy in the materials entering the processingin the materials entering the processing plant, plus the energy added in theplant, plus the energy added in the plant, must equal the total energyplant, must equal the total energy leaving the plant.leaving the plant.
Examples of Unit OperationsExamples of Unit Operations 1.1. Heat TransferHeat Transfer ==  Pasteurisation of milkPasteurisation of milk  Freezing of fishFreezing of fish  Ultra heat treatment (UHT) of juiceUltra heat treatment (UHT) of juice  Chilling meat patties/burgersChilling meat patties/burgers  Steam jacketed kettle used to saucesSteam jacketed kettle used to sauces  Canned fruitsCanned fruits
Examples of Unit OperationsExamples of Unit Operations 2.2. DryingDrying ==  Spray dried milk powderSpray dried milk powder  Sun dried tomatoesSun dried tomatoes  Freeze dried vegetablesFreeze dried vegetables  PastasPastas Types:Types: Air drying, freeze drying, vaccum dryingAir drying, freeze drying, vaccum drying
Examples of Unit OperationsExamples of Unit Operations 3.3. EvaporationEvaporation ==  Concentrated tomato pasteConcentrated tomato paste  Evaporated milkEvaporated milk  Concentrated fruit juicesConcentrated fruit juices  Condensed soupsCondensed soups
Examples of Unit OperationsExamples of Unit Operations 4.4. Contact equilibrium processesContact equilibrium processes ==  Crystallisation – sugar, saltCrystallisation – sugar, salt  Extraction – oilsExtraction – oils  Ultra-filtration of milksUltra-filtration of milks  Distillation of mixtures containingDistillation of mixtures containing alcohol, vinegarsalcohol, vinegars
Examples of Unit OperationsExamples of Unit Operations 5.5. Mechanical separationsMechanical separations ==  Centrifuging – cream, butterCentrifuging – cream, butter  Separation of oil and water eg.Separation of oil and water eg.  Filtration – of oils using a pressFiltration – of oils using a press  Sieving – flours, cereals, grainsSieving – flours, cereals, grains
Examples of Unit OperationsExamples of Unit Operations 6.6. Size reductionSize reduction ==  Grinding of sugarGrinding of sugar  Crystallization of saltCrystallization of salt  Grinding & milling of herbs and spicesGrinding & milling of herbs and spices
Examples of Unit OperationsExamples of Unit Operations 7.7. Mixing, forming, shapingMixing, forming, shaping ==  Using blenders to combineUsing blenders to combine ingredientsingredients  Soup mixes – blends of starch, vegiesSoup mixes – blends of starch, vegies  Blending – flavours for potato chipsBlending – flavours for potato chips  Premixes of flavourings for sausagesPremixes of flavourings for sausages
Examples of Unit OperationsExamples of Unit Operations 8.8. ExtrusionExtrusion ==  Puffed corn, rice or other cerealPuffed corn, rice or other cereal productsproducts  ““Cruskits”Cruskits”  Corn thinsCorn thins  Pasta shapesPasta shapes
Examples of Unit OperationsExamples of Unit Operations  Using the examples given, revise yourUsing the examples given, revise your list of which “process” you think wouldlist of which “process” you think would be used in to manufacture the foods.be used in to manufacture the foods.
FreezingFreezing  Contact withContact with solidsolid –Plate freezersPlate freezers VerticalVertical HorizontalHorizontal Contact Plate FreezerContact Plate Freezer Vertical Plate FreezerVertical Plate Freezer
Unit operations
FreezingFreezing  Contact with LiquidContact with Liquid –Liquid brineLiquid brine –Synthetic coolantSynthetic coolant
Immersion freezerImmersion freezer  The immersion freezer consists of aThe immersion freezer consists of a tank with a cooled freezing media, suchtank with a cooled freezing media, such as glycol, glycerol, sodium chloride,as glycol, glycerol, sodium chloride, calcium chloride, and mixtures of saltcalcium chloride, and mixtures of salt and sugar.and sugar.  The product is immersed in thisThe product is immersed in this solution or sprayed while beingsolution or sprayed while being conveyed through the freezerconveyed through the freezer
Contact with LiquidContact with Liquid Immersion freezingImmersion freezing
FreezingFreezing Contact with gasContact with gas Blast freezerBlast freezer Fluidized bedFluidized bed
Contact with GasContact with Gas  Blast FreezerBlast Freezer
Tunnel FreezerTunnel Freezer
Spiral Blast FreezerSpiral Blast Freezer
Fluidized bed FreezingFluidized bed Freezing
Cryogenic FreezingCryogenic Freezing  Liquid nitrogen, with a boilingLiquid nitrogen, with a boiling temperature of -196 °C at atmospherictemperature of -196 °C at atmospheric pressurepressure  Liquid carbon dioxide the gas isLiquid carbon dioxide the gas is released to the atmosphere at -70 °C,released to the atmosphere at -70 °C, half of the gas becomes dry-ice snowhalf of the gas becomes dry-ice snow and the other half stays in the form ofand the other half stays in the form of vapor.vapor.
Cryogenic tunnelCryogenic tunnel

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Unit operations

  • 1. Unit OperationsUnit Operations P C VengaiahP C Vengaiah
  • 2. Unit OperationsUnit Operations What do we mean byWhat do we mean by ““Unit Operations”?Unit Operations”?
  • 3. Unit OperationsUnit Operations ““Unit Operations” =Unit Operations” = AA food processingfood processing operation byoperation by which raw materials are thewhich raw materials are the input and the desired product isinput and the desired product is the outputthe output
  • 4. Unit OperationsUnit Operations Using a material balance and an energyUsing a material balance and an energy balance, a food engineering processbalance, a food engineering process can be viewed overall or as a series ofcan be viewed overall or as a series of units.units. Each unit is a unit operation. The unitEach unit is a unit operation. The unit operation can be represented by a boxoperation can be represented by a box as shown inas shown in Fig. 1.1Fig. 1.1..
  • 5. View of a Unit ProcessView of a Unit Process
  • 6. Unit Operations - OverviewUnit Operations - Overview Important unit operations in the food industryImportant unit operations in the food industry are:are:  Heat transfer – thermal processing, freezing,Heat transfer – thermal processing, freezing, chillingchilling  Drying – dehydration and concentrationDrying – dehydration and concentration  EvaporationEvaporation  Contact equilibrium processes (which includeContact equilibrium processes (which include distillation, extraction, gas absorption,distillation, extraction, gas absorption, crystallization, and membrane processes)crystallization, and membrane processes)
  • 7. Important Unit Operations (cont)Important Unit Operations (cont)  Mechanical separations (which includeMechanical separations (which include filtration, centrifugation, sedimentationfiltration, centrifugation, sedimentation and sieving)and sieving)  Size reduction – grinding, millingSize reduction – grinding, milling  Mixing, forming and shapingMixing, forming and shaping  ExtrusionExtrusion
  • 8. Unit OperationsUnit Operations  Examples – what type of processExamples – what type of process or processes are used in theor processes are used in the manufacture of examplesmanufacture of examples handed around in class?handed around in class?
  • 9. Mass & EnergyMass & Energy  Two very important laws which all unitTwo very important laws which all unit operations obey are the laws ofoperations obey are the laws of conservation of mass and energy.conservation of mass and energy.  The law ofThe law of conservation of massconservation of mass statesstates that mass can neither be created northat mass can neither be created nor destroyed.destroyed.  ““What goes in must come out".What goes in must come out".
  • 10. Mass & EnergyMass & Energy  The law ofThe law of conservation of energyconservation of energy states that energy can neither bestates that energy can neither be created nor destroyed. The total energycreated nor destroyed. The total energy in the materials entering the processingin the materials entering the processing plant, plus the energy added in theplant, plus the energy added in the plant, must equal the total energyplant, must equal the total energy leaving the plant.leaving the plant.
  • 11. Examples of Unit OperationsExamples of Unit Operations 1.1. Heat TransferHeat Transfer ==  Pasteurisation of milkPasteurisation of milk  Freezing of fishFreezing of fish  Ultra heat treatment (UHT) of juiceUltra heat treatment (UHT) of juice  Chilling meat patties/burgersChilling meat patties/burgers  Steam jacketed kettle used to saucesSteam jacketed kettle used to sauces  Canned fruitsCanned fruits
  • 12. Examples of Unit OperationsExamples of Unit Operations 2.2. DryingDrying ==  Spray dried milk powderSpray dried milk powder  Sun dried tomatoesSun dried tomatoes  Freeze dried vegetablesFreeze dried vegetables  PastasPastas Types:Types: Air drying, freeze drying, vaccum dryingAir drying, freeze drying, vaccum drying
  • 13. Examples of Unit OperationsExamples of Unit Operations 3.3. EvaporationEvaporation ==  Concentrated tomato pasteConcentrated tomato paste  Evaporated milkEvaporated milk  Concentrated fruit juicesConcentrated fruit juices  Condensed soupsCondensed soups
  • 14. Examples of Unit OperationsExamples of Unit Operations 4.4. Contact equilibrium processesContact equilibrium processes ==  Crystallisation – sugar, saltCrystallisation – sugar, salt  Extraction – oilsExtraction – oils  Ultra-filtration of milksUltra-filtration of milks  Distillation of mixtures containingDistillation of mixtures containing alcohol, vinegarsalcohol, vinegars
  • 15. Examples of Unit OperationsExamples of Unit Operations 5.5. Mechanical separationsMechanical separations ==  Centrifuging – cream, butterCentrifuging – cream, butter  Separation of oil and water eg.Separation of oil and water eg.  Filtration – of oils using a pressFiltration – of oils using a press  Sieving – flours, cereals, grainsSieving – flours, cereals, grains
  • 16. Examples of Unit OperationsExamples of Unit Operations 6.6. Size reductionSize reduction ==  Grinding of sugarGrinding of sugar  Crystallization of saltCrystallization of salt  Grinding & milling of herbs and spicesGrinding & milling of herbs and spices
  • 17. Examples of Unit OperationsExamples of Unit Operations 7.7. Mixing, forming, shapingMixing, forming, shaping ==  Using blenders to combineUsing blenders to combine ingredientsingredients  Soup mixes – blends of starch, vegiesSoup mixes – blends of starch, vegies  Blending – flavours for potato chipsBlending – flavours for potato chips  Premixes of flavourings for sausagesPremixes of flavourings for sausages
  • 18. Examples of Unit OperationsExamples of Unit Operations 8.8. ExtrusionExtrusion ==  Puffed corn, rice or other cerealPuffed corn, rice or other cereal productsproducts  ““Cruskits”Cruskits”  Corn thinsCorn thins  Pasta shapesPasta shapes
  • 19. Examples of Unit OperationsExamples of Unit Operations  Using the examples given, revise yourUsing the examples given, revise your list of which “process” you think wouldlist of which “process” you think would be used in to manufacture the foods.be used in to manufacture the foods.
  • 20. FreezingFreezing  Contact withContact with solidsolid –Plate freezersPlate freezers VerticalVertical HorizontalHorizontal Contact Plate FreezerContact Plate Freezer Vertical Plate FreezerVertical Plate Freezer
  • 22. FreezingFreezing  Contact with LiquidContact with Liquid –Liquid brineLiquid brine –Synthetic coolantSynthetic coolant
  • 23. Immersion freezerImmersion freezer  The immersion freezer consists of aThe immersion freezer consists of a tank with a cooled freezing media, suchtank with a cooled freezing media, such as glycol, glycerol, sodium chloride,as glycol, glycerol, sodium chloride, calcium chloride, and mixtures of saltcalcium chloride, and mixtures of salt and sugar.and sugar.  The product is immersed in thisThe product is immersed in this solution or sprayed while beingsolution or sprayed while being conveyed through the freezerconveyed through the freezer
  • 24. Contact with LiquidContact with Liquid Immersion freezingImmersion freezing
  • 25. FreezingFreezing Contact with gasContact with gas Blast freezerBlast freezer Fluidized bedFluidized bed
  • 26. Contact with GasContact with Gas  Blast FreezerBlast Freezer
  • 28. Spiral Blast FreezerSpiral Blast Freezer
  • 30. Cryogenic FreezingCryogenic Freezing  Liquid nitrogen, with a boilingLiquid nitrogen, with a boiling temperature of -196 °C at atmospherictemperature of -196 °C at atmospheric pressurepressure  Liquid carbon dioxide the gas isLiquid carbon dioxide the gas is released to the atmosphere at -70 °C,released to the atmosphere at -70 °C, half of the gas becomes dry-ice snowhalf of the gas becomes dry-ice snow and the other half stays in the form ofand the other half stays in the form of vapor.vapor.

Editor's Notes

  1. Into the box go the raw materials and energy, out of the box come the desired products, by-products, wastes and energy. The equipment within the box will enable the required changes to be made with as little waste of materials and energy as possible. In other words, the desired products are required to be maximized and the undesired by-products and wastes minimized. Control over the process is exercised by regulating the flow of energy, or of materials, or of both.
  2. For example, if milk is being fed into a centrifuge to separate it into skim milk and cream, under the law of conservation of mass the total number of kilograms of material (milk) entering the centrifuge per minute must equal the total number of kilograms of material (skim milk and cream) that leave the centrifuge per minute.
  3. For example, considering the butter fat in the milk entering the centrifuge, the weight of butter fat entering the centrifuge per minute must be equal to the weight of butter fat leaving the centrifuge per minute. A similar relationship will hold for the other components, proteins, milk sugars and so on.