What is the F value\**\ for 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.
What is the F value of F value?
F Value • 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)
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 is the difference between P and F values in heat treatment?
P or PU values are often used to designate pasteurization-type heat treatments that typically give 6-log reductions of target organisms, whereas F values are often used to designate much higher heat treatment processes giving higher log reductions.
What is Z value and F value?
The term F-value or "FTref/z" is defined as the equivalent number of minutes to a certain reference temperature (Tref) for a certain control microorganism with an established Z-value.
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 value in autoclave?
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 F in sterilization?
The F value is the time (at a given temperature) that a product receives a lethal amount of sterilization. In other words, the F value is a measure of sterilization lethality per unit time. Sterilization lethality is often determined using biological indicators like bacterial spores.
What does an F value mean?
The F value is a value on the F distribution. Various statistical tests generate an F value. The value can be used to determine whether the test is statistically significant. The F value is used in analysis of variance (ANOVA). It is calculated by dividing two mean squares.
What is z-value in autoclave?
The z-value is defined as the temperature coefficient of microbial destruction, i.e. as the number of degrees of temperature which causes a 10-fold variation of D (or, more generally, of the sterilization rate).
How do you find the F value of sterilization?
F-value: – 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....F0 = D250℉(log a – log b), where a = initial population and b = final population.So F0 = (0.21min.)( ... So, F0 = (0.21min.)(
How do you test F?
State the null hypothesis and the alternate hypothesis. Calculate the F value. The F Value is calculated using the formula F = (SSE1 – SSE2 / m) / SSE2 / n-k, where SSE = residual sum of squares, m = number of restrictions and k = number of independent variables. Find the F Statistic (the critical value for this test).
Why do we autoclave at 121 degree Celsius?
The reason for 121°C and not 120°C is due to how autoclaves work and how they were developed. They sterilize with saturated steam under pressure. Historically, we measure the pressure generated by the steam. Which leads directly to the answer.
What is the F value in microbiology?
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.
What is F0 value in steam sterilization?
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 F 12D concept?
12D concept refers to thermal processing requirements designed to reduce the probability of survival of the most heat resistant C. botulinum spores to 10-12. This helps to determine the time required at process temperature of 121oC to reduce spores of C.
How does high temperature affect microorganisms?
The lethal effect of high temperatures on microorganisms is dependent on several factors, including temperature, holding time, pH and water activity. Note fat, sugar, salt and chocolate content have a major effect on sensitivity of microorganisms to heat; in general they markedly increase their resistance to heat e.g. salmonella can survive several hours at high tempertures in molten chocolate.
How to calculate lethal rate?
Equation 1, Lethal rate = 10 (T-Tr)/z where T is the temperature, in Celsius, at which the lethal rate is calculated and Tr is the reference temperature at which the equivalent lethal effect is compared. The z-value measured in °C is the reciprocal of the slope of the thermal death curve for the target microorganism or spore; 10° C is the value frequently used in Fo calculations performed on low acid foods.
Why is it necessary to calculate the cumulative effect of heat on microbial destruction during both heating and cooling?
Because microorganisms in foods are exposed to lethal temperatures as they reach the target processing temperature, during holding and during cooling , it is necessary to calculate the cumulative effect of heat on microbial destruction during both heating and cooling as well at the holding time at the target temperature to obtain a true estimate of the lethal effects of a heat treatment process.
Can you perform lethality calculation using CSV?
There is also a facility to perform a lethality calculation using an uploaded CSV file. Basic instructions are provided in the help file. The application can be tested using internal data and you can also upload a data file for analysis of a process.
Can a Z value be varied in Tr?
Tr can be varied by the user. The default Z-value has been set at 10° C and can be varied by the user in this application. Note that the Z-value has a significant effect on F value, refer to the free download of lethality tables formulated using Z-values of 6°,8°,10° and 12°C.
Can you download thermal processing spreadsheets?
Spreadsheets for undertaking thermal processing calculations can be downloaded, some are also available for free download.
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.
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).
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.
Why did Napoleon lose more soldiers?
Napoleon Bonaparte's army lost more soldiers due to spoiled foods than from battle a. As a result, Nicolas Appert, a french candy maker in 1810, collected a 12,000 franc prize for inventing a "cook, seal-with- wax, cook again" method for preserving foods.
What is the F value of a process?
F-value: – 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 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.
What does the z value do?
So, the z-value allows us to calculate a thermal process of equivalency, if we have one D-value and the z-value.
What is the D value of a microorganism?
D-value is the time required to kill 90% of the spores or vegetative cells of a given microorganism at a specific temperature in a specific medium. D-values can be determined from survivor curves when the log of population is plotted against time, or by the formula:
What is the D value of a microbial inactivation?
It is often more convenient to use the D-value as a measure of rate of microbial inactivation. The D-value is the exposure time required for the number of survivors to change by a factor of 10 or the time required to achieve a decrease of one log cycle in the survivor curve, in other words the temperature or radiation dosed required to reduced the initial population by 90% . The D-value may be estimated graphically see graph or mathematically from the equation
What is thermal death time?
Thermal Death Time (TDT):- Thermal death time is the amount of time that is necessary to kill a specific number of microbes at a specific temperature. This value is obtained by keeping temperature constant and measuring the time necessary to kill the number of cells specified.
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.
How is a reactor heated?
The primary air is heated using an air pre-heater prior to entering the reactor. Raw feed ash is pneumatically conveyed from existing storage silos to a process feed bin. The reactor is heated to combustion temperature using a supplemental fuel, such as propane.
What is the function of air distribution system?
This proprietary system provides the optimum fluidizing velocity across the range of load and operating conditions. The superficial velocity must be maintained at a level well above the minimum fluidizing velocity for all of the particles in the process in order to avoid potential areas of agglomeration.
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.
Why is minimally processed food important?
Recently, the majority of food production increasingly has focused on minimally processed food, to meet the consumer demand for freshlike high-quality convenience foods. These products are subjected only to mild treatment and nonthermal processing and with (possibly) no additives or preservative substances. This means that microbial growth must be controlled and limited below harmful thresholds, while at the same time, preserving the nutritional and organoleptic properties of foods. Thus, the challenge is to use processes that can produce bacteria-free or -reduced products while retaining the natural flavor, odor, and texture.
Where does ash exit a cyclone?
Ash can also exit the system at the bottom of the reactor or J-valve.
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.
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.
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.
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
Is honey at 20% MC shelf stable?
Importance of aw: Honey at 20% mc is shelf stable, while potato at 20% is not
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.
