Food Processing L5

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  1. if k is the parameter, which slope and what type of curve is it on the graph?
    • negative slope
    • survivor curve
  2. if D is the parameter, which slope and what type of curve is it on the graph?
    • negative reciprocal slope
    • survivor curve
  3. if Z is the parameter, which slope and what type of curve is it on the graph?
    • negative reciprocal slope
    • thermal resistance (D or TDT) curve
  4. what is the general format for a TDT equation?
    Image Upload 1
  5. what are the differences between destruction kinetics and thermal processing?
    • In destruction kinetics: there are small samples, instant come-up/come-down, constant temps, heating bath mostly pre-stabilized at target temps, and temp specific destruction kinetics are largely possible.
    • In thermal processing: food is in containers, larger sample size, heating and cooling lags, destruction over wide range of temps, cooked in pressurized retorts which need come-up time to reach stable operating temps (CUT), slow cooling, and temp effect needs to be integrated over the entire process to reduce over cooking.
  6. in destruction kinetics, what is Fo?
    the TDT or F value at 250°F
  7. in the canning process, what is Fo?
    • the process lethality
    • it is the equivalent heating time of the entire process expressed as minutes at 250°F
  8. what factors affect the product temp profile?
    • heating process (still vs. agitated, aseptic vs. in-package)
    • heating medium (steam, water (immersion or spray) with or without overpressure, steam-air)
    • heating conditions (retort temp, initial temp, loading pattern)
    • product type (solid, semisolid, liquid, particulate liquid, thermo-physical properties)
    • container type (material, shape, size)
  9. what are the thermal processing objectives from a safety aspect?
    need to monitor the temp and establish the process at the coldest point in the container so that the desired minimum heat lethality with respect to pathogen destruction applies to every point in the container
  10. what are the thermal processing objectives from a quality aspect?
    essential to integrate the destruction achieved during heating and cooling, product near or at the surface of the container will be cooked more than the product near the center, need to minimize the bulk cooking
  11. what is PE?
    process establishment (how long should the process be?)
  12. what is PV?
    process verification (how severe is the process?)
  13. what is the data needed for thermal process calculations?
    • TDT kinetics
    • heat penetration
    • additional data for PE: target level of destruction/lethality
    • additional data for PV: process time
  14. what are the 3 categories of process calculation methods?
    • general methods (graphical/numerical)
    • formula methods (Ball, Stumbo, Pham)
    • numerical methods (computer simulation)
  15. what is the sterilization value of a process?
    indicates the total extent of destruction at the cold point in the container over the entire process in relation to a target microorganism
  16. what does SV=1 mean?
    the effect is equivalent to heating a spore suspension at any given temp to a time equal to TDT at that temp
  17. what are the limitations of the general method?
    • tedious, limited to experimental set up
    • need heat penetration data for every condition
    • no generalization
    • based on an indicator microorganism
  18. how is the improved general method an improvement?
    • process calculation similar to the original general method
    • based on the reference TDT curve
    • Image Upload 2
    • the process lethality from improved method represents minutes at 250°F which can be used to determine the extent of any destruction of any microbe
  19. what can you do with the improved general method?
    • construct a hypothetical thermal destruction curve with Fo=1min
    • calculate the lethal rate for each data point Image Upload 3
  20. what are the limitations of the general methods?
    • process calculations and adjustment tedious
    • need to carry out separate runs to accomodate each change (can size, retort temp, initial temp, cooling water temp, product type)
    • some conversion factors exist but tedious
    • different RT or IT
Card Set:
Food Processing L5
2013-02-25 17:48:14
Food Processing L5

Food Processing L5
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