The Governments of Canada and British Columbia, and the Investment Agriculture Foundation of BC, and their directors, agents, employees, or contractors will not be liable for any claims, damages, or losses of any kind whatsoever arising out of the use of, or reliance upon, this information.Pasteurization is the process of heat treating beer to inhibit the growth of potential beer spoilage microorganisms and prolong the shelf life of the beer. Opinions expressed in this document are those of the author and not necessarily those of the Governments of Canada and British Columbia or the Investment Agriculture Foundation of BC. The program is delivered by the Investment Agriculture Foundation of BC. 2nd edition.įunding for this project has been provided by the Governments of Canada and British Columbia through the Canadian Agricultural Partnership, a federal-provincial- territorial initiative. Piggott, editors.įermented Beverage Production. Proceedings of the American Society of Brewing Chemists, 1951, page 45.Īndrew G. Thermal death time studies on beer spoilage organisms. In Part 2, we’ll share how to put this theory into practice and pasteurize craft fermented beverages on a small scale. Temperatures and `PU` plots are stored and can be reviewed from the Craft Metrics app. It includes a temperature probe to measure the continuous temperature inside the bottle, and accumulates `PU` at 10-second intervals. The Craft Metrics Pasteurization Computer is a measurement device that does this. To know the true total, you would need to calculate the `PU` based on the average temperature during each minute, or each second, and add them all up. It doesn’t account for the ramp up to 63☌ and the ramp back down, during which `PU` are still accumulating, albeit at a slower rate. For this reason, the Craft Metrics Pasteurization Computer only counts `PU` that occur above `T_(ref)`.Īnd simply plugging in a temperature and time isn't realistic. Even worse, low temperatures may actually be an ideal pathogen incubation temperature. Technically you could run at 40☌ for a million minutes until it shows `PU=6`, however, you don't really achieve lethality until reaching `T_(ref)`. It's important to remember that this is a mathematic model, and reality is more complicated. So if you pasteurize for 15 minutes at 63☌, your formula would be: To calculate the number of `PU`, you can simply substitute the temperature `T` and a time `t` into the formula above. `PU = t*1.393^(T-60)` OK great, but how do I use that? That led to the common calculation, published in Andrew Lea’s Fermented Beverage Production and often cited on brewing forums: observed the sterilising effect of various temperatures applied to brewing, and derived the constants `T_(ref)=60☌` and `Z=6.94` for use in brewing and fermented beverages. In their paper Thermal death time studies on beer spoilage organisms, Del Vecchio et. Luckily, these constants are well-established for fermented beverages. `Z`: Coefficient of thermal resistance (In Celsius)ĭifferent species of organisms have different thermal resistance, and thus different values for `T_(ref)` and `Z`, so choosing values appropriate for the type of food being pasteurized (and the type of organisms that like to live in that food) is paramount. `T_(ref)`: Reference Temperature (In Celsius) `PU` are calculated by the following equation: The sterilising effect increases exponentially with temperature at a rate defined by the coefficient of thermal resistance (`Z`). Pasteurization is measured in pasteurization units (`PU`) which are defined as the sterilising effect observed for one minute at a temperature known as the reference temperature (`T_(ref)`). Many foods and beverages are treated with pasteurization, but in this article we’ll focus on beer, cider, and wine. By accurately measuring pasteurization units (`PU`), you can make an informed decision about how much heat to use, and how much time is right for your product. Too little and you may end up dealing with wasted product, spoilage, and a costly recall. Too much heat can affect taste, aroma, and mouthfeel. That means pasteurization is a balancing act of risk management and trade-offs. Rather, it is designed to use just enough heat to prevent spoilage, while minimizing the impact on the flavour and aromatic qualities of the product. Pasteurization differs from full sterilization in that does not completely eliminate all biological agents. Pasteurization is the process of heating foods and beverages to kill pathogens and make them safe for human consumption, and to ensure they remain safe for months or even years.
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