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. botulinum).
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 Tref/E.
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.
Summary – D Value vs Z ValueD value measures the time required to kill 90% of the population of a particular microorganism in a specific medium at a specific temperature. In contrast, Z value is the temperature change that is required to achieve a tenfold reduction in the D-value.
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).
The particle diameters defining 10%, 30%, and 60% finer from the grain-size distribution curve are estimated as: D10 = 0.14 mm , D30 = 0.27 mm, and D60 = 0.42 mm.
D10: The portion of particles with diameters smaller than this value is 10%D50: The portions of particles with diameters smaller and larger than this value are 50%. Also known as the median diameter.
D10 is called as effective particle size. This means that 10% percent of the particles are finer and 90% of the particles are coarser than D10. This is the size at 10% finer by weight. Similarly, D60 is the particle size at which 60% of the particles are finer and 40% of the particles are coarser than D60 size.
D50 =
2540 µm. D(4,3) = 2670 µm.
Some of the more common representative diameters are:
- D‾10 = arithmetic or number mean.
- D‾32 = volume/surface mean (also called the Sauter mean)
- D‾43 = the mean diameter over volume (also called the de Brouckere mean)
Active Pharmaceutical Ingredients have several important physical properties including polymorphism, water content, density and particle size. Particle Size Distribution, or PSD, has a direct influence on material properties such as: flowability, handling, dissolution rate, stability, and efficacy of delivery.
It is usually measured as the effective size and the uniformity coefficient. The effective size of a given sample of sand is the particle size where 10% of the particles in that sample (by weight) are smaller, while 90% are larger. Usually this is denoted as the D10.
Related DefinitionsSpan Value means for most incinerators, a 50 parts per million (ppm) propane span. Higher span values may be necessary if propane emissions are significant. For convenience, the span value should correspond to 100 percent of the recorder scale. Sample 1. Sample 2.
particle size: x1, min. particle size: xn+1) is divided intonseparate intervals, and each of these particle size intervals is taken to be [xi, xi+1] (j = 1,2,. n). The element of q qj(j= 1,2,.n) is the particle amount corresponding to the particle size interval [xi, xi+1]. Normally, the volume standard is used.
uniformity coefficient (u-ni-form'-i-ty). A numerical expression of the variety in particle sizes in mixed natural soils, defined as the ratio of the sieve size through which 60% (by weight) of the material passes to the sieve size that allows 10% of the material to pass.
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.
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).
What is Retorting? Retorting is heating of low acid foods prone to microbial spoilage in hermetically sealed containers to extend their shelf life. The goal of retort processing is to obtain commercial sterilization by application of heat.
It is defined as number of minutes of heating required to destroy a specified number of organisms at a given temperature. When TDT plotted on the log scale and temperature of heating on linear scale, a straight line of best fit is known as thermal destruction curve or thermal death time (TDT) curve.
In microbiology, in the context of a sterilization procedure, the D-value or decimal reduction time (or decimal reduction dose) is the time (or dose) required, at a given condition (e.g. temperature) or set of conditions, to achieve a log reduction, that is, to kill 90% (or 1 log) of relevant microorganisms.
A z-score does not have any units. It represents the number of standard deviations from the mean. For example, z=±2 represents the region under the probability curve that is within two standard deviations of the mean.
The F0 value tells us the equivalent amount of sterilization (in minutes) that would have been completed had the load been at 250°F. (As temperature increases, so does sterilization/kill rate.)
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.
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 important factor in thermal sterilization but lethality is important.
If your CFU is 25, your aliquot is 1cc, and your dilution factor is 10-2, the calculation of the log CFU/mL is: Log CFU/mL = Log10(CFU / (dilution factor*aliquot)) = Log10(25/(10-2*1)) = 3.40.
Z-Value is the number of degrees of temperature change necessary to change the D-Value by a Factor of 10.
- For example, if D-Value at 121ºC is 1.5 min & Z-Value is 10ºC.
- Sterility Assurance Level (SAL)
- Required SAL for steam sterilization process = 10 -6 or better.
- Fo = D121 ( logNo – log N )
Simple Interest Formulas and Calculations:
- Calculate Interest, solve for I. I = Prt.
- Calculate Principal Amount, solve for P. P = I / rt.
- Calculate rate of interest in decimal, solve for r. r = I / Pt.
- Calculate rate of interest in percent. R = r * 100.
- Calculate time, solve for t. t = I / Pr.
To solve for speed or rate use the formula for speed, s = d/t which means speed equals distance divided by time. To solve for time use the formula for time, t = d/s which means time equals distance divided by speed.
Cohen's d in statistics - The expected difference between the means between an experimental group and a control group, divided by the expected standard deviation. It is used in estimations of necessary sample sizes of experiments.
