TDT curve power Point presentation with lethal value

TDT curve explain with lethal value

1. TDT Curve The Thermal Death Time (TDT) Curve is a graphical representation showing the relationship between the temperature and the time required to kill a specific microorganism at a constant level.

2. Determination of TDT CURVE Microbial Sample Preparation : A specific microorganism (e.g., bacteria, spores) is cultured and used as the test organism. Temperature Selection : Multiple temperatures are selected, typically within a range relevant to the intended sterilization or pasteurization process. Exposure : The microorganism is exposed to each selected temperature for varying time intervals. Survivor Analysis : After each exposure, the number of surviving microorganisms is measured (e.g., by plating and counting colonies). Plotting the Curve : X-Axis : Time required for microbial inactivation at each temperature. Y-Axis : Temperature (often in °C). Each point represents the thermal death time (TDT) at a specific temperature. The curve typically shows a trend where higher temperatures require shorter times to achieve the same level of microbial inactivation.

3. Importance of TDT curve 1. Food Safety • Ensures harmful pathogens are eliminated.
• Prevents underprocessing and foodborne illnesses. 2. Sterilization Optimizes time-temperature combinations for complete sterilization. 3. Quality Preservation Avoids overprocessing to maintain product flavor , texture, and nutrients. 4. Regulatory Compliance Helps meet standards set by FDA, USDA, etc.

4. Lethal rate The lethal rate is the measure of the relative killing effectiveness of a specific temperature compared to a reference temperature (usually 121.1°C for sterilization). It quantifies how much microbial inactivation occurs at a given temperature over time. Key Formula : L= 10  (T- Tref /Z)

5. F - value The F-value is a measure of the total microbial lethality delivered by a heat treatment process, expressed in terms of the equivalent time (in minutes) required to kill microorganisms at a reference temperature, usually 121.1°C (250°F) for sterilization.

6. Z - value The Z-value is a measure of the heat resistance of a microorganism, indicating the temperature increase required to reduce the time necessary for killing a microorganism by 90% (a tenfold reduction in microbial survival). It is a crucial factor in determining the F-value and optimizing heat treatment processes.

7. D - value The D-value (Decimal Reduction Time) is the time required at a specific temperature to reduce the microbial population by 90%, or to achieve a tenfold reduction in the number of viable microorganisms. It is a key parameter in thermal processing and is used to assess the heat resistance of microorganisms.

8. Conclusion Thermal inactivation is a critical concept in microbiology, especially in food processing, pharmaceuticals, and sterilization. The determination of TDT, lethal rate, F, Z, and D values plays an essential role in designing and validating heat treatment processes that ensure microbial safety while preserving the quality of the product. TDT helps determine the necessary temperature-time combination to eliminate pathogens. Lethal rate indicates the effectiveness of heat at different temperatures. F-value ensures sufficient microbial lethality. Z-value assesses microbial heat resistance. D-value helps optimize time and temperature for sterilization.

9. Reference Smith, J. A., & Johnson, M. R. (2021). Thermal inactivation of microorganisms: Determination and importance of TDT, lethal rate, F, Z, and D values in food safety and sterilization processes. Journal of Food Science and Technology, 54(6), 1204-1217.

10. T H A N K Y O U