1. Thermal processing
Sterilization/pasteurization
Appertization
Canning

2. History 1810 Nicolas Appert
about 1860 Luis Pasteur provides scientific explanation
1920 Bigelow and coworkers described method of calculation
1945 Otto Rahn applies the principle that microorganisms die according to logarithmic order.

3. HEAT is the energy in transit due to a temperature difference between two regions and is always transferred from the region of higher temperature to the region of lower temperature.

4. HEAT TRANSFER MODES:
Conduction
Convection
Radiation

5. CONDUCTION
Transport of energy due to direct molecular interaction without appreciable displacement of molecules.

6. CONVECTION
Transport of energy from one point of fluid to another point by actual movement of fluid itself.
MODES OF CONVECTION:
Natural convection
Forced convection

7. RADIATION
Transport of energy in the form of electromagnetic waves between materials across the space.

8. HEAT PENETRATION TEST
Process of putting a temperature sensitive element in food container and gathering temperature data over a time course during a thermal process. Reports on penetration tests need to state the type of thermocouple used and where the thermocouple was placed.

9. For penetration test the thermocouple should be placed in the coldest place of the container
for conduction heating product it is
located at a geometric center of container
for convection heating products it is located
1/10 to 1/5 of the container height from the
bottom of the container

10. Primary Objectives of Canning are:
to kill microorganisms
to keep away microorganisms

11. Microorganisms:
public health hazard
economic spoilage

12. Public health hazard
Clostridium botulinum is the main public hazard b/c spores are heat resistant. Spores may survive when heat processing is insufficient. The health hazard is due to ability of Cl. botulinum to grow under anaerobic conditions and to produce toxin.

13. Economic spoilage is due to un-processing:
sporeformers from the genera Bacillus
sporeformers from the genera Desulfotomaculum
sporeformers from the genera Clostridium

14. FOOD CONTAINERS:
Metal containers
Glass containers
Retort pouches

15. Double seam

16. HEADSPACE
GROSS - vertical distance from the top of double seam or the top edge of the glass jar to the level of product in the container.
NET - vertical distance from the level of food to the inside surface of the lid (only metal containers).
A retort pouch does not have a true headspace, what is of importance is the volume of non con- densible gases.

17. Pasteurization < 100 oC
Classification of thermal processes based on processing temperature
Sterilization >100 oC
Pasteurization < 100 oC

18. Hot pack/hot fill processes
Classification of thermal processing based on method of product packaging
Terminal processes
Aseptic processes
Hot pack/hot fill processes

19. Food classification
Low acid food pH > 4.6
Acid food pH  4.6

20. “Acid” Foods pH ≤ 4.6 Generally all fruits Tomatoes, with added acid
Sauerkraut and fermented pickles
Foods to which large amounts of acid are added 20

21. “Low Acid” Foods pH > 4.6 Generally all vegetables Meats Poultry
Seafood
Soups
Mixed canned foods 21

23. Retorting consist of :
heating phase: removal of air, come-up time (CUT) , holding time at processing temperature
cooling phase

24. Types of retorts:
Still retorts (nonagitating retorts): vertical, horizontal, malo, hydrostatic.
Agitating retorts: sterilmatic, orbitort, rotomat,
Flame sterilizers
Aseptic systems

25. Still retort - vertical retort

26. Still retort -hydrostatic retort

28. Agitating retort - Sterilmatic

30. Agitating Retort - ORBITORT

33. Effect of heat on microorganisms
Yeast are the least resistant, followed by mold and then bacteria. All vegetative cells are destroyed instantly at 100 0C . Spores of C. botulinum, C. sporogenes, C. bifermentans, C. butiricum, C. pasteurianum, C. perfringens,
C. thermosaccharolyticum, D. nigrificans, and B. stearothermophilus are very heat resistance.

34. Equivalent processing times
min at 100 oC
min at 104 oC
min at oC
min at oC
5.27 min at oC
2.78 min at oC
1.45 min at oC
0.78 min at oC

35. The destruction of microorganisms is affected by:
their inherent resistance
by environmental influences during the growth and formation
the heating time & temperature pH
humidity
protective effect of food components: fat, proteins, salt

36. Order of destruction of microorganisms
The death of bacteria exposed to wet heat is of logarithmic order.
The logarithmic order means that theoreti- cally the survivors can be reduced to less than one. Thus the number of survivors may become very small such as one survivor in million units etc.

37. The survivor curve
The number of viable bacteria plotted on the logarithmic scale against the corresponding heating time (processing time) on the linear scale provides the graph known as
the survivor curve.

39. DECIMAL REDUCTION TIME, DT
The time in minutes required to reduce the viable cells in suspension of bacteria to one tenth of their original value. The slope of semilogarithmic survivor curve determi -nes the decimal reduction time.

40. The logarithmic model for microbial destruction is described by the equation
U =DT *(log N0 - log Nu)
U - the equivalent heating time at proces-
sing temperature
N0 - the initial numbers of microorga-
nisms
Nu -the number of microrganisms after
heating

41. Survivor Curves at Different Temperatures.

42. Comparison of D for Microbial Population

44. THERMAL DEATH TIME
The longest time when the unit test are positive for growth and the shortest time when the units are negative

45. The thermal death (TDT) curve
The value of F plotted on the logarithmic scale against the corresponding tempe- ra ture on the linear scale provides graph known as TDT curve.

46. Thermal Death Time Curve

47. The thermal resistance curve
Values of DT plotted on the logarithmic scale against the corresponding temperature on the linear scale provide a graph called phantom thermal death time curve or thermal resistance curve.

49. Parameter Z
The parameter Z represents the number of degrees of Fahrenheit, centigrade, or Kelvin necessary to cause the F-value or D value to change by a factor ten.

50. TDT curve is described by equation:
Log FT = ( Tref - T)/Z + Log Fref
Z = 10/log Q10
Q dry heat
Q wet heat

51. Lethal rate
It is described as minutes at T ref per minute at T. Can be calculated using the following equation:
L = Fref/FT = 10 (T -Tret)/ Z
Z = 10 C or 18 F, Tref = C or 250 F

52. Sterilization value of heat process, F
F = Dref * (log N0 - log NF )
F =  t *  Li
F = ∫ L *dt