Download Thermal Process Calculations

11/21/2012
Thermal Process Calculations
Thermal Processing
Overview of the General Method, Ball Formula and NumeriCAL
Kill Bacteria in Food by
exposing the product/container
to HEAT (at a specific
temperature) for an specific
TIME
IFTPS SOUTH EAST ASIA
TECHNICAL OUTREACH SEMINAR
November 27, 2012
Terry L. Heyliger
Thermal Processing Manager
JBT FoodTech
Madera, CA USA
Process Calculations
• Upon completion of the heat penetration test
one must analyze the time / temperature data
and use the results of the analysis to calculate a
thermal process that will render the product
commercially sterile.
Process Calculations
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•
•
•
Sterility (Fo value)
The General Method
Ball Formula Method
NumeriCAL™
HEAT
Process Calculations
• A critical step in the design of a safe thermal
process is the process calculation. It is
important that one understands the calculation
method employed as well as any conditions that
may restrict the use of a particular method.
Sterility
• Death of a microorganism is defined as when it
has lost the ability to reproduce
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Commercial Sterility
1. Containers are free of viable microorganisms
of public health significance –
MINIMUM PUBLIC HEALTH
2. Containers are free of microorganisms
capable of reproducing under normal conditions
of storage and distribution
12D – Concept – Minimum Public Health
• Minimum processes are established to reduce any
population of the most heat resistant C. botulinum
spores by 10-12 or 12 log cycles
or
probability
y of survival to:
• Reduce the p
1 C. botulinum spore in 1x1012
or
•
1 in 1,000,000,000,000
COMMERCIALLY STERILE
5 D Concept – Commercially Sterile
D-value
• Reduce the population of a common mesophilic
sporeformer, C. sporogenes, by 5 log cycles or
10-5
• Time in minutes to reduce the population
of bacteria by 90% at a specific lethal
temperature
Effect of Temperature on D-value
Effect of Temperature on D-value
• As exposure temperature increases the rate of
bacterial death also increases
Temperature (°F)
D-Value
111.1
20.0
115.5
7.3
121.1
2.0
126.1
.63
131.1
.20
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11/21/2012
Unit of Lethality
“F-Value”
z-Value
• Reflects the resistance of bacteria to different lethal
temperatures.
• Equal to the number of degrees (F or C) required to
change the D-Value by 1 log cycle ( factor of 10)
Unit of Lethality
“Fo-Value”
• Sterilization value “F” expressed as the equivalent
minutes at a specified temperature
• Based on the destruction of a population of bacteria
having a known z-value
Lethal Rate Value
• Represents the equivalent minutes at 121.1oC
the slowest heating point in the container
(250ºF) at
• Based on the destruction of a population of bacteria
having a z-value of 10ºC (18oF)
• The lethal-rate value assigned to each temperature is
numerically equal to the reciprocal of the number of
minutes required to destroy the same population of
spores in one minute at the reference temperature,
121.1oC
L = 10 (T-121.1)/10
Lethal Rate Value
Temperature,
(oC)
101.1
Minutes to
Destroy Spores*
100
Lethal Rate
Value
0.01
111.1
10
.1
121.1
1
1
131.1
.1
10
Lethal Rate Table
* Same Population of spores with know z-value of 10oC
1