![]() ![]() Lethal PU calculation is available in Redpost Redlink software.I’ll admit, pasteurizing straw in hot water with a propane burner can be a bit of a pain. With some resilient microorganisms, the temperature curve is important and the product must be above the Lethal Cutoff for a certain time to ensure stability. ![]() The common reason for using this methodology is as a backup to ensure that the product has completed the expected temperature curve. The Total-PU cutoff would be set at say 55 ☌ and the Lethal-PU cutoff at 65 ☌ the PU Monitor would then give the two PU results. Rather than having just one PU Cutoff value, under this system, there are Total-PU values and Lethal-PU values. Lethal PUs are used by some brewers and bottlers as an extension to the PU system. To solve this problem all Haffmans Pasteurization Monitors are fitted with a sensor that determines when the PU monitor leaves the pasteurizer and the temperature of the product is recorded at this point. As the PU Monitor recording run may not be stopped immediately after the product leaves the tunnel, it may be difficult to determine the exit temperature by looking at the temperature graph alone. Because of this, some package specifications state a required product exit temperature. If the product leaves at too high a temperature the flavor of the product may be affected. The temperature that the bottles or cans leave the tunnel pasteurizer can be very important. The Haffmans RPU-353 has a pressure measurement channel as well as two channels for product and spray temperature. The graph of pressure can then be examined to observe maximum pressure along with any obvious spikes. When pasteurizing cans with internal pressure reservoirs or 'widgets' the internal pressure also needs to be monitored closely.Ī Pasteurization Monitor with a pressure measurement channel can assist with this it is attached to the bottle or can and is designed to make as little change to the headspace of the package as possible so as not to affect the results. Both these factors make problems of over-pressure more significant, with peaking or breakages the result. Over the years there has been a trend towards ever thinner-walled can packages, as well as reduced head space volumes. The practice of using nitrogen for purging containers and for fobbing produces a mixture of gases in the headspace that may increase the pressure rise. This is partly due to the rise in temperature acting on the CO 2 gas already in the headspace and partly due to the vibration, which encourages CO 2 to be released from supersaturated solution in the product. The Haffmans RPU-352 and Haffmans RPU-353 have two temperature channels to allow measurement of product and spray temperatures.ĭuring pasteurization the pressure in the container increases. This is of interest when pasteurizing bottles, as too great a Delta T during the heating or cooling cycles would likely lead to breakages. the difference between the temperature inside the package and outside. As the bed is in constant motion a sample time of at least 10 seconds is required to determine an accurate location for a damaged head.ĭelta T (ΔT) can also be measured i.e. Monitoring the spray temperature is used to view the temperature of the individual temperature zones and to identify the location of any bent or clogged spray heads. Setting the optimal automated PU values avoids over-pasteurization (loss of aroma and taste) and reduces energy consumption. Sufficient heat treatment of bottles or cans determined by multiple temperature probes during the pasteurization process is ensured by reaching the minimum required PU’s (at the coldest spot). Haffmans delivers equipment for reliable monitoring of tunnel pasteurizers in breweries and the soft drink industry.
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