PRINCIPLES OF THERMAL PROCESSING

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PRINCIPLES OF THERMAL PROCESSING

• Arthur A. Teixeira
• Agricultural and Biological Engineering
• Institute of Food and Agricultural Sciences
• University of Florida, Gainesville

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Why Thermal Processing?Origins of the 12-D
Concept
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Complete destruction of 60 billion spores of B.
Botulinus (Esty and Meyer, 1922)
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Ideal destruction curve of B. botulinus strains
19, 23 and 97 grown in double strength veal
peptic digest at 37 C for 10 days, 60 billion in
M/15 PO4 solution.
(Esty and Meyer, 1922)
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Classical Thermal Death Time CurveC. Botulinum
in Phosphate Buffer
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Exponential Decay in PopulationDriven by Random
Lethal Energy
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Public Health Significanceof12-D Concept

• 100 million persons consume canned foods each day
  worldwide.
• 100 million x 365 days/yr 3.65 x 1010/yr
• 3.65 x 1010/yr x 100 years 3.65 x 1012
• (12-D)
• 3-4 outbreaks in 100 years, or one outbreak every
  25 years worldwide.

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Thermal Resistance of Spore Formersused as a
Basis for Thermal Processing
o
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Specification of Process Lethality

• 12-D concept for C. botulinum (D0.21)
• Economic spoilage probability of 10 5 for
  Mesophiles such as C. sporogenes (D1.0)
• Thermofilic spoilage probability of 10-2
• from B. stearothermophilus (D4.0)

F 0.21 x 12 2.5
F 1.0 x 5 5.0
F 4.0 x 2 8
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