What is the F value for constant temperature process?
• For a constant temperature process, • Conservative F value is based on –Center temperature of can (for retorting) –Center temp. at holding tube exit (for aseptic process) •Fastest flowing fluid element or particle F0= F value when Tref= 250 °F & z = 18 °F(or Tref= 121.1 °C & z = 10 °C) t: Process time F0for Constant Temperature Processes
What does F-value (temperature) mean?
Z-value (temperature) "F 0 " is defined as the number of equivalent minutes of steam sterilization at temperature 121.1 °C delivered to a container or unit of product calculated using a z-value of 10 °C. The term F-value or "F Tref/z " is defined as the equivalent number of minutes to a certain reference temperature...
What is F value in microbiology?
The term F-value or "F Tref/z " is defined as the equivalent number of minutes to a certain reference temperature (T ref) for a certain control microorganism with an established Z-value. Z-value is a term used in microbial thermal death time calculations.
What is the difference between f 0 and F-value?
"F 0 " is defined as the number of equivalent minutes of steam sterilization at temperature 121.1 °C (250 °F) delivered to a container or unit of product calculated using a z-value of 10 °C. The term F-value or "F Tref/z " is defined as the equivalent number of minutes to a certain reference temperature (T ref)...
What is Z and F value?
The z-value of an organism is the temperature, in degrees Fahrenheit, that is required for the thermal destruction curve to move one log cycle. While the D-value gives us the time needed at a certain temperature to kill an organism, the z-value relates the resistance of an organism to differing temperatures.
What is F value in pasteurization?
The F-Value (or P-Value) is therefore the duration (in minutes) of the entire sterilisation or. pasteurisation process, at a defined temperature. In pasteurisation applications, especially for drinks, one encounters the term Pasteurisation Units – PU. One PU is defined as exposing a product at 60°C for 1 minute.
What is F not value?
F0 value is used to determine the exposure time of material for sterilization at a particular temperature. F0 value is the time in minute for the specified temperature that gives the same thermal lethality as at 121 °C in one minute.
What is D and Z-value in food processing?
D values are the time or dose required for a 90% reduction in microbial concentration via a sterilization process. Z values measure the resistance of the microorganism to death by the sterilization source.
What is the Fo value?
The Fo value expresses the heating time required for disinfection, and varies according to fluctuations in heat applied to the substance being sterilized.
What is z-value in thermal processing?
Z-value is a term used in microbial thermal death time calculations. It is the number of degrees the temperature has to be increased to achieve a tenfold (i.e. 1 log10) reduction in the D-value.
What is F0 in thermal processing?
F0 is the equivalent exposure time at 121.11°C of the actual exposure time at a variable temperature, calculated for an ideal microorganism with a temperature coefficient of destruction equal to 10 °C.
What is the F0 value in autoclave?
The F0 Cycle is especially useful for sterilizing large liquid volumes with, say, greater than 1 Liter of fluid. The term “F0 ” is defined as the number of equivalent minutes of steam sterilization at 250°F (121°C) delivered to a load (product)1.
What is thermal death curve?
The thermal death time curve provides information about the time required to kill a particular microorganism in a particular food at a variety of temperatures.
What is Z temperature?
A Z-value is defined as the number of degrees (Celsius or Fahrenheit) required to change a D-value by one factor of ten. In the practical sense, it is a measure of how susceptible a spore population is to changes in temperature.
Why is D-value important?
D value basically depends on the temperature, the type of the microorganism and the medium composition. Concerning usefullness, this measurement is very important in understanding the effectiveness of thermal inactivation of bacteria under different conditions, especially in food cooking and preservation.
How do you calculate D-value?
D Value CalculatorFormula. D = t / [ log10 (Q1) - log10 (Q2) ]Time (minutes)Initial Quantity.Final Quantity.
HOW IS F value calculated?
The F value is used in analysis of variance (ANOVA). It is calculated by dividing two mean squares. This calculation determines the ratio of explained variance to unexplained variance. The F distribution is a theoretical distribution.
How is pasteurization value calculated?
It is defined by an equation : PU = (time in minutes) x 1.393 exp(T-60), where T is the temperature in Celsius. Hence if you want 50 PU, you would need less than 2 minutes at 70C, or 10 minutes at 65C, or 50 minutes at 60C, or 250 minutes at 55C, or some combination that would yield the total desired.
What is sterilization value?
What is Sterilization Value (SV) ? Sterilization is expressed in a time-equivalent (minutes or seconds) spent at the constant reference temperature. It describes the level of microbian destruction obtained by heat treatment.
What is thermal death rate?
Thermal death time is how long it takes to kill a specific bacterium at a specific temperature. It was originally developed for food canning and has found applications in cosmetics, producing salmonella-free feeds for animals (e.g. poultry) and pharmaceuticals.
Which method is used to calculate F values in industry?
Two main methods are used, namely the Trapezoid rule and Simpson’s rules. The Trapezoid rule is the simplest to understand and implement and despite it being less accurate is generally the method used to calculate F values in industry.
How to find the F value of a time vs lethality curve?
The F value is calculated by determining L at appropriate points from the time vs lethality curve and integrating the time and L values using numerical integration to obtain the area under the time–lethality curve.
How do the spreadsheets and the free On Line thermal process calculators work on the Dairy Science and Food Technology website?
The calculated cumulative lethality at the Tref is known as the F value. This takes account of the lethal effects during heating, holding at the target processing temperature (this can be lower or higher than Tref) and during cooling. The F value obtained using a Z-value of 10 ℃, and a Tref of 121.1 ℃ is known as F0. Note when temperatures lower than 100°C are used (pasteurising temperatures) P or PU may be used instead of F value. This can be confusing and F value has been used throughout this website to denote the cumulative effects of heat on lethality.
How to calculate lethal rate?
Lethality is calculated using equation 1 by entering the formula “=10^ ( (B4-121.1)/10)” (remove the “”) at cell C3 and copying this down to C17. The lethal rates corresponding to each temperature are given.
What is the difference between T and L?
Where L is the lethal rate or lethality, T is the temperature, in Celsius or in Fahrenheit in the US, at which the lethal rate is required and Tref is the reference temperature.
What is the Z value of a temperature?
An alternative explanation and perhaps one that is easier to understand, and apply, is that Z is a value expressing the increase in temperature necessary to obtain the same lethal effect in 1/10 of the time. The higher the Z value of the organism, the greater its resistance to heat.
What temperature is used for UHT?
F values tend to be used up to 121.1 ℃. In UHT-processing, temperatures up to 150 ℃ may be used and while F values e.g. F0 must be calculated in some jurisdictions, it is increasing common to use B* and C* as indicators of the bacteriological effects of heat against thermophilic spore formers and the potential adverse chemical effects respectively. B* and C* are discussed further in the article on UHT-processing.
Why is thermal processing important?
Thermal processing is vital to the food industry. This type of processing is based on the external heating of foods for a period of time at an elevated temperature. Thermal processing, however, may cause undesirable degradation of heat-sensitive quality attributes and may reduce the content or bioavailability of some bioactive compounds. Thus, a continuing challenge exists in terms of developing advanced thermal processing for the food industry in line with the demand for enhanced food safety and quality.
How does heat transfer occur in a rotary kiln?
During the thermal processing of granular materials in rotary kilns, heat transfer within the bed material occurs by the same mechanisms as in any packed bed, such as shaft kilns. Heat transfer paths at play can be particle-to-particle conduction and radiation, as well as interstitial gas-to-particle convection (Figure 2.2 ). However, the movement of the particles themselves superimposes an advective component for energy transport, which has the potential to dominate heat transfer. Hence, the key feature of a rotary granular bed is the motion in the transverse plane, which sets the axial flow in motion and is dependent upon the rotation rate, degree of fill (volume of the kiln occupied by material), and the rheological properties of the particulate material.
What is the operating temperature of a steady state reactor?
The steady state reactor operating temperature can vary between 800°C and 1000°C depending on the raw ash feed rate, feed LOI, desired product LOI, and other desired product characteristics. Temperatures below this range can result in loss of adequate combustion to sustain the process and the initiation of gas burners to maintain operation. Temperatures exceeding this range can result in agglomerations in the reactor, cyclones, or J-valves, thus forcing a unit shut down.
What are the emissions of a flue gas?
Emissions: Due to the high operating temperature and the use of water spray to control temperatures, flue-gas emissions such as NOx, CO, and VOCs, are inherently controlled by the process and do not require any additional treatment. In certain cases, where the ash sulfur content is high enough, flue-gas desulfurization equipment must be added to control SO2. Of course, if the flue gas is routed back to the host utility plant, no additional control is necessary as the STAR SO2 is negligible compared to the plant. Table 12.2 shows the estimated emissions for a 140 mmbtu/hr STAR Unit ( SEFA, 2011 ). As shown, these are significantly lower than the CBO emission rates.
Where is the primary air induct burner located?
There is typically a primary air in-duct burner and burners located on the walls of the reactor. Once the reactor reaches adequate combustion temperature raw ash is pneumatically fed through injection ports on the wall of the reactor. The carbon in the ash ignites immediately and temperatures begin to rise.
What is the F value of a process?
The F value** for a process is the number of minutes required to kill a known population of microorganisms in a given food under specified conditions. This F value is usually set at 12 D values to give a theoretical 12 log cycle reduction of the most heat-resistant species of mesophilic spores in a can of food. For example, if there were 10,000 spores of a species of spore in a can of food and a 12 D process was given, the initial 10,000 spores (10 4 spores) would be reduced to a theoretical 10 -8 living spores per can, or again in theory, one living spore per 10 8 cans of product (one spore per one hundred million cans). To refer back to the original example where the D 240 was 1 min., the F value for the process would be 12 min. or F 240 = 12 min.
Why is the actual processing time a can of food given in a retort always greater than the?
The actual processing time a can of food is given in a retort is always greater than the F value due to heat penetration requirements. Industry makes extensive use of F values in maintaining processes and in developing new schedules. Optimally the old and new processes are equated to acceptable F values.
When bacterial spores are heated to a lethal temperature as during retorting of canned?
Fig. 1 shows a hypothetical result from heating a species of spore at 240 Fahrenheit ( F).
What temperature is Tref?
Note: Generally, for canning & aseptic processing, Tref= 121.1 °C (or 250 °F) Also, zc>> z in most cases
Does F decrease as T decreases during cooling?
F value is cumulative and does not decrease as T decreases during cooling
What is the F0 value?
F0 value is used to determine the exposure time of material for sterilization at a particular temperature. F0 value is the time in minute for the specified temperature that gives the same thermal lethality as at 121 °C in one minute. It explains that temperature is not an ...
How long is thermal lethality at 121°C?
It shows that that the thermal lethality of 1 minute at 121 °C is equal to the lethality of 3.98 minutes at 115 °C.
Is temperature a factor in thermal sterilization?
It explains that temperature is not an important factor in thermal sterilization but lethality is important. Time of sterilization can be changed (decrease or increase) according to the lethality of the temperature. Δt = 60 Sec. = 1min. It shows that that the thermal lethality of 1 minute at 121 °C is equal to the lethality ...
What is the F0 value?
F0-Value at a particular temperature other than 121ºC is the time in minutes required to provide the lethality equivalent to that provided at 121ºC for a stated time. (As per USP 2008)
What is the Z value of a factor?
Z-Value is the number of degrees of temperature change necessary to change the D-Value by a Factor of 10.
What is the Fo value of an autoclave?
In general, for aqueous preparations, a microbiologically – Validated steam sterilization process that delivers, in total ( including the heating up & cooling down phases of the sterilization cycle ), an Fo-Value of Not less than 8 to every container in the autoclave load is considered satisfactory. (IP 2007)
What is the Z value of a microbial death?
It is the number of degrees the temperature has to be increased to achieve a tenfold (i.e. 1 log 10) reduction in the D -value. The D-value of an organism is the time required in a given medium, at a given temperature, for a ten-fold reduction in the number of organisms. It is useful when examining the effectiveness of thermal inactivations under different conditions, for example in food cooking and preservation. The z-value is a measure of the change of the D-value with varying temperature, and is a simplified version of an Arrhenius equation and it is equivalent to z=2.303 RT T ref /E.
What is the z value of an organism?
The z-value of an organism in a particular medium is the temperature change required for the D-value to change by a factor of ten, or put another way , the temperature required for the thermal destruction curve to move one log cycle . It is the reciprocal of the slope resulting from the plot of the logarithm of the D-value versus the temperature at which the D-value was obtained. While the D-value gives the time needed at a certain temperature to kill 90% of the organisms, the z-value relates the resistance of an organism to differing temperatures. The z-value allows calculation of the equivalency of two thermal processes, if the D-value and the z-value are known.
Introduction
How to Calculate F Values Using An Excel Spreadsheet?
- The time temperature results from a heat treatment process are given in Table 1. Table 1. Time-temperature readings from thermal treatment process How do we process these values to obtain a value for F0 for this heat treatment? There are several ways of implementing the Trapezoid Rule. One way is to create 4 columns in Excel as indicated in Table 2. Table 2. Excel spreadsheet for c…
Data Validation
- Some consideration should be given to data validation especially if other people might be using the spreadsheet. Most spreadsheets offer a range of data validation inputs for non-programmers, this facility can be accessed under the Data tab in Excel. Using validation you might wish to check input data for blank cells, text and negative numbers for example. Macros can also be written to …
Recommended Reading
- Billo, E.J. (2007). Excel for Scientists and Engineers – Numerical Methods. John Wiley and Sons, Inc. Liengme, B.V. and Ellert, D.J. (2007). A Guide to Microsoft Excel 2007 for Scientists and Engineers. Elsevier Ltd. Samaras, C. (2013). Numerical Integration in Excel Using the Trapezoidal Rule. Available from: https://www.myengineeringworld.net/2013/06/integration-in-excel-trapezoi…