Agenda Pasteurization Process Control Materials Heat Transfer Test Next Week

1. Agenda Pasteurization Process Control Materials Heat Transfer Test Next Week Cumulative “Final” Test

2. Sterile Filtration • Alternative to pasteurization for microbiological stabilization • Avoid heat treatment, flavor deterioration • Occurs before packaging (could be contaminated after filtration, before package) • Process Requirements • Feedstock microbiological and non-mb loads (concentration and particle size) • Filtrate concentration, product spoilage concentration allowed • Product viscosity, density, flow characteristics

3. Microbiological Load Reduction – LRV • Sterile Filters = 99.9999999999% LRV • Filtration Mechanisms • Direct Interception – Pore smaller than particle • Charge Effects – Particles (-), so filter (+) • Inertial Impactation – Particles want straight path, fluid curves (different densities required) • Diffusional Impactation – Random motion (gas)

4. Key Features Effecting Filter Performance • Pore geometry • Membrane thickness • Surface Charge • Removal Ratings • Nominal – “An arbitrary micron value assigned by the filter manufacturer, based upon removal of some percentage of a given size or larger.” • Absolute – “The diameter of the largest hard spherical particle that will pass through the filter under a specified test condition.”

5. Factors effecting • flow rate and life: • Pressure Drop • Surface Area • P increases as dirt • blocks pores • Increased surface • area has great • increase on dirt • capacity

6. Surface area • can be increased • with pleats • Filter sizes: • Pre-filter: 1.5 m • Sterile: 0.45 m • Cleaning • Backwash (high V) • Hot Liquor • Sodium Hydroxide • Steam Sanitized • (120C, 20 min)

7. Pasteurization • Inactivate all microorganisms • Inactivate undesired enzymes (chem. changes) • Five Key Factors for Effective Pasteurization • Temperature • Time • Types of microorganisms present • Concentration of microorganisms present • Chemical composition of the product • Pasteurization Level • Decimal reduction time, D – Time required to inactivate 90% of microorganisms present • Temperature dependence value, Z – Increase in temp. require to increase D value by 90%

8. Pasteurization Units • Measure of effect of heat and time on microorganisms • 1.0 PU corresponds to 1 minute at 60C • PU = t * 1.393(T-60C) (t in minutes) • Rules of Thumb • Increase T by 2C, double PU’s for same time • Increase T by 10C, PU’s increase 10x • 20 PU’s indicates that 1 in 10 Billion microorganisms survive • Effect of PU’s on specific microorganisms needed

9. Plate/Flash Pasteurization • Typical plates: Stainless steel, 0.6 mm thickness • Can withstand 20 bar pressure

10. Design Factors for Plate Pasteurizer • Product Flow Rate and Properties of Liquid • Temperature Program and Pressure Drop • Hygiene and Cleaning

11. Plate Pasteurizer Design • 95% Heat Recovery in regenerator • Product enters Pasteurizer at  4C • Holding temperature  72C • Holding time  25 seconds • Hot water typically used for heating, 2C warmer than holding temperature • Level of Regeneration

12. Plate Pasteurizer Control • 0.15C corresponds to 1 PU

13. Flow Control Options • Fixed Flow • Range of Pre-set Flows • Fully Variable Flow • Most Suitable Option Depends Upon • Size of Outlet Buffer Tank • Importance of No Recirculation of Product • PU Variation Desired • Product Quality • Type of Filler • Minimum Flow typically 1/3 of maximum • Pressure drop 1/9 of max flow (must be adjusted downstream to avoid overpressure) • Heat transfer coefficient decreases, residence time increases

14. Best Practice - Full flow to 1/3 of full in 15 min while maintaining PU’s within 2.0 • Control Loops • Holding Cell Temperature • Critical for PU Control • Must be varied with changes in flow • Final Product Outlet • Flow – Upstream and downstream influences • Pressure – Varied with changes in flow • Interrelationships of many variables requires use of sophisticated control (PLC)

15. Tunnel Pasteurization

16. Factors Effecting Tunnel Pasteurization • Materials of Construction • Structure and weight – lighter stronger matl • Corrosion – chemical attack metal, cracking • Transport System – typically conveyor • Spray System – Votex or spray pan • Temperature • Heating • PU Control

17. Typical temperature regime

20. Plate/Flash vs. Tunnel Pasteurization • Plate uses significantly less floor space • 15% reduction in operating cost • Reduced capitol costs • Beer tastes fresher (approx 92% less TIU) • Cleaning and contamination downstream

21. Why is Process Control Needed? • Safety • Quality Specifications, Consistency • Environmental Regulation, Environmental Impact • Optimum Operation of Equipment • Cost Effectiveness • Aims of Control System • Suppress Influence of External Disturbances • Ensure Stability of a Process • Example: External Disturbance on Shower • Flow rate of hot water increases? • Temperature of hot water decreases? • Flow rate of hot water decreases?

22. Stable vs. Unstable Variable • Goal: Boil Water in an Open Pot at 1 atm • Control Variables: Amount of Water, Rate of Heat • Given Quantity of Water, Sufficient Heat = Boiling • While Boiling: Temp is Stable (or Self-Regulating) • Water Level is Un-Stable, Requires Control • Pressure Cooker Example • No Pressure Relief – Temp and Press Unstable • With Pressure Relief – Temp and Press Stable • Level Unstable in Both • Weight = Inherent Control Scheme • Process Control – A system of measurements and actions within a process intended to insure that the output of the process conforms with pertinent specs

23. Basic Control Elements • Sensor – Receives Stimulus, Outputs Signal • Controller – Receives Signal, Compares to Desired Value, Sends Control Signal • Actuator – Receives Control Signal, Makes Corrective Action on Process • Process – “The Organized Method of Converting Inputs to Outputs • Functions of Control System • Measure • Compare to Desired Value • Compute Error • Corrective Action

24. Definitions • Controlled Variable • Setpoint • Measured Variable • Manipulated Variable • Example • Disturbance? • Variables • Controlled? • Measured? • Manipulated?

26. More Accurate More Complicated

27. On/Off Control • Valve Open or Closed, Heater On or Off • Inexpensive and Simple • Oscillatory, Wear on Switching Device

28. Sequence Control • Series of Events (Washing Machine) • CIP Sequence, Fermentation Temperature, Keg Washing and Filling • Achieved with PLC, Pegged Drum (Mechanical) • Closed-Loop Control

29. Open-Loop Control • Controlled Variable Measured Prior to Intervention by Manipulated Variable

30. Definitions • Overshoot – Ratio of maximum amount by which response exceeds steady state to final steady state value • Rise Time – Time required for response to reach final value for first time • Response Time – Time it takes for response to settle at its new steady state value

31. Control Example

32. Proportional Control

33. Proportional + Integral Control

34. Proportional + Integral + Derivative Control

35. Feedback vs. Feedforward Control

36. Carbon and Low Alloy Steels • Carbon Steel – Iron alloys with 0.05 to 1% C • Low Carbon Steel – aka mild steel • Low Alloy Steels – alloying elements with <2% • Advantages • Inexpensive and readily available • Easily worked and welded • Good tensile strength and ductility • Disadvantages • Corrosion • Protective coatings often required

37. Copper • Pure copper traditionally used • Brass – alloyed with zink • Bronze – alloyed with tin • Advantages • Soft and easily worked • Readily available for small pipes/tubes • Resists corrosion well • Resistant to caustic and organic acids/salts • Disadvantages • Strong acids and oxidizing acids attack • Cost

38. Stainless Steel • Considered stainless if chromium > 11% • Typical values 11-30% chromium • Cr2O3 oxidation layer gives ss it’s passivity

41. General Corrosion • Covers entire surface • “Best” kind of corrosion to have • Measurable and predictable (design for) • Galvanic Corrosion • Two metals in contact in same electrolyte • Less noble, less passive, more active metal corroded, other metal protected • Erosion and Cavitation • Abrasive particles and/or high velocity • Cavitation corrosion (bubbles near pumps) • Sensitisation – Inter-grainal corrosion (415-825C) • Pitting – Occurs below surface, chloride ion • Localized weak points in passive surface