Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
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 • • • • 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 1 11/21/2012 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 2 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