This calculator provides a written record, visual summary, and Pasteurization-Units calculation for a session of batch pasteurization. It is designed for home use of up to 50 bottles per session, divided into five batches of 10 bottles each. A description of the method I use, and of the technical aspects of pasteurization, are given in the links above.
It can be very valuable to have a saved record of information from pasteurization, because it allows you to go back and see how different parameters (such as warm- and hot-water temperatures and pasteurization times) affect the resulting Pasteurization Units (PUs) value. It can also be helpful to look back at a record in order to duplicate a previous year's efforts. It's up to you to decide whether the amount of record keeping that is required is worth the effort.
This calculator assumes that you have up to 50 bottles of cider, beer, or other beverage that you want to pasteurize, and that you're familiar with the equipment, process, and risks. The recorded times and temperatures are fit to a model of increasing temperature (as the bottles are held in hot water) and decreasing temperature (as the bottles cool off after heat treatment). The number of PUs is determind from this model. If the model doesn't provide a good fit to the measured data, a linear-interpolation model is also available. These options are described in more detail below.
All of the calculators on this site are (and always will be) completely free to use. No data (e.g. IP address or other identifying information, usage, history, or clicks) is tracked. There is no advertising, thanks to no-cost hosting by GitHub. I earn no money from this website. My motivation is to develop software tools that I find useful or interesting, and I'm happy to provide them to others who may also benefit from them.
To save settings to a text file or load them from a file, use the "Save" and "Load" buttons near the bottom of the page. Saved data is only stored on your local computer or device.
At the top of the page, there are two options for viewing the data: (1) "data entry" or (2) "printer/PDF friendly". The data-entry view is used to enter all of the data from a pasteurization session and see the summary. The printer/PDF-friendly view displays the same information but without any input fields or button selections. You can select this view and then print the page to either a printer or PDF file.
It's fine to leave a field blank. Also, if you're unsure of anything, the default value is probably fine.
How can I navigate the input fields?Other than the mouse, there are a few ways to navigate through the input fields. The <tab> key will take you to the next item and <shift+tab> will take you to the previous item. The <down arrow> key behaves the same as <tab> in the initial section, but in the times and temperatures section it will go down within the same column. Likewise, the <up arrow> key behaves the same as <shift+tab> in the initial section, but in the times and temperatures section it will go up within the same column. The <enter> key will also take you to the next item.
Times can be entered using a 24-hour format or 12-hour format (with AM/PM). This selection is made below the selection for input units. If using the 12-hour format, you can also specify which times before noon are assumed to be AM. For example, if you say that times before 8:30 are assumed to be AM, and if you enter 8:00, it will record as 8:00 PM. Times can also be entered using a colon (8:00) or a period (8.00).
When entering a time, if you enter only the minutes value (e.g. 10), the calculator will guess, if possible, the hour associated with this time, based on a previously-entered time. If the previous time was 8:05, then entering 10 will result in 8:10. If the previous time was 8:55, then entering 10 will result in 9:10. For times less than 10, enter a leading 0, for example "03" might represent 9:03.
See below for a description of both models. The choice of which model to use depends entirely on your preference. I always use the "smart" model, and I often find that an imperfect fit is due to a data-entry error on my part. If you hold the bottles in the hot-water bath so long that they start to cool down, then this model might not provide the best fit, since it assumes that the temperatures in the hot-water bath always increase. In this case, the linear-interpolation model may make more sense. The linear-interpolation model is also there as a backup method or if you're uncomfortable with the extrapolation performed by the smart model.
If you're unsure of what is meant by the reference temperature, the minimum effective temperature, z value, and/or D value, please see the technical explanation of pasteurization. If you know the target PU value but don't what values were used to derive this target, the defaults on this page are probably reasonable. The reference temperature of 60°C is quite common, and the default minimum effective temperature is a fairly conservative value. The z value is the most important, and the default value is commonly used for beer and cider. The D value is optional and the input field is only used to keep a record of this value.
The input field "bottles:" specifies the number of bottles of product (e.g. cider or beer) that are being pasteurized in this batch. The "+1 (meas)" indicates that there is one additional bottle in the batch, namely the bottle used to measure temperature. So an input of 10 means that heat treatment is applied to 10 bottles of product and one measurement bottle, for a total of 11 bottles.
The "when add" input field is the temperature of the warm-water bath just before bottles are added to this water. The "pre mix" input field is the temperature of the warm-water bath before mixing in the 3.5 quarts (3.5 L) of boiling water. The "post mix" input field is the temperature of this water bath after mixing in the boiling water and just before adding the bottles. The "when add" and "post mix" values will hopefully be close to the value of the "target temperature of warm-water bath". These inputs don't affect the output and they are only provided for recording purposes. Feel free to leave them blank.
The word "xfer" is an abbreviation of the word "transfer", and these inputs refer to the times when bottles are transferred into the warm-water bath, the hot-water bath, or to the cooling rack. The "xfer to warm" input has no effect on the output (being there only for recording purposes), but the "xfter to warm" and "xfter to cool" are used by the "smart" model to compute pasteurization units before the first recorded "hot" temperature and to know when to switch the model from heating to cooling.
The times and temperatures of the test bottle in the warm-water bath are only for recording purposes. They have no effect on the output and can be left blank.
The more often you record times and temperatures, the better your esimate of pasteurization units will be. Recording is not needed as often when using the "smart" model. I try to record times and temperatures every two to three minutes.
To get back to a default value, enter 'd'. To clear all inputs and reset the page to default values, use the "clear" button at the bottom of the page.
The "smart" model fits the time and temperature points of the test bottle as it's getting hotter to one or two exponential functions, and it fits the points of the test bottle as it cools down to a different exponential function. If the temperatures in the hot-water bath are all increasing over time (the peak temperature is the last value), then a single exponential function is used to model this increase in temperature. If the bottles start to slowly cool down while in this hot-water bath, then a second exponential function is used to model this flat or slightly decreasing set of temperatures. This set of functions gives a good fit to the pasteurization data I've seen. This model has two advantages: (1) it can construct a reasonable plot of time and temperature from very few data points, and (2) it can provide a reasonable extrapoation at times that weren't recorded. The more data points that it's given, the more confident one can be in the model, but one doesn't need to record times and temperatures at every minute. As the bottle cools down over a period of 30 minutes or more, only a few data points at the beginning are needed to estimate the temperature function as it drops to the minimum pasteurization temperature.
I put the "smart" model in quotes because it's smart until something goes wrong, and then it's not so smart after all. The linear-interpolation model can be used when the output from the smart model doesn't give a good fit to the data. The linear-interpolation model doesn't extrapolate beyond the recorded times, and so it will give a lower PU estimate than the smart model.
The "Total PU" output shows the total number of pasteurization units computed from the data using the specified model.
The "Total time" output shows the duration of the pasteurization session over all batches.
There are three output plots. The first plot shows the recorded times and temperatures from each batch (as single points) as well as the times and temperatures according to the specified model. The pasteurization units are computed from the model, not from the recorded values.
The second plot shows the number of pasteurization units that are applied at each moment of time. This value increases while the bottles are becoming hotter, and then it decreases when the bottles are transferred to the cooling rack.
The third plot shows the total number of pasteurization units that accumulate during the heat treatment, as a function of time. The "Total PUs" value for a batch is the same as the highest value from the third plot.
I hope that you find this page useful, but I make no guarantees about the accuracy or suitability of the results. While I have pasteurized hundreds of bottles of carbonated and sweetened hard cider for years without incident, there are always risks when pasteurizing at home. There is the definite risk that during the pasteurization process an exploding bottle will send shards of sharp and burning-hot glass into your body, possibly even into your eye. Very hot glass bottles may cause burns even when they're intact. The hot water may scald or burn your flesh. The hot stove may burn your flesh or your clothing. Bottles full of hot cider may break due to a sudden change in temperature or a manufacturing defect. You might drop a bottle, sending burning hot liquid and sharp shards of hot glass all over your floor. The computed pasteurization units on this web page, while based on the best information available to me, are only an approximation. The computed values might also be incorrect due to temperature readings that are not taken at the coolest region within the bottle or possible bugs in the code. Bottles that have not been sufficiently pasteurized may explode at any time. This is by no means an exhaustive list of things that might go wrong, even under the assumption that you know what you're doing. Please prepare well, use great caution, always assume that anything might go wrong at any time, and accept responsibility for the consequences of your actions. Nothing on this website absolves you of that responsibility or transfers any of that responsibility to me or this site. Use the information provided here at your own risk. With all of that said, I hope that you have the best of luck, many years of safe and incident-free pasteurization, and many delicious pasteurized beverages!
Copyright © 2024-2025 John-Paul Hosom, all rights reserved. Please feel free to contact me with comments, questions, suggestions, and/or bug reports.