 In this module we will talk about again about medium sterilization, but actually in this module we will talk about the calculation of the holding time at constant temperature. As we have seen in our previous module that the calculation of the del factors during the heating cycles and the cooling cycles. So, the overall del factors can be calculated by the previous equation as we have deal and discuss in our previous modules that the overall del factors include the del factor of holding time, heating time and the cooling time. So, if we want to calculate the del factor of the holding time, so then the del factors which is overall del factors minus the del factor of the heating and the minus of the del factor of the cooling. So, if we take in previous example as we have calculated that the when we are dealing with the basilless stereothermophilus, the overall del factor of basilless stereothermophilus is 32.2 and if it is taken that the heating del factor is 9.8 and then the cooling factor the del factor 10.1, so then the holding factor can easily be calculated. So, by this equation, so 32.2 minus 9.8 minus 10.1, so the answer will be the 12.3. So, this will be the del factor of the holding time, so as we know that the del factor is equal to k t and from the data of the D endophor and Humphrey in 1961 the specific death rate of basilless stereothermophilus spores at 121 degree Celsius is 2.54 per minute, then by using this equation, so the t is equal to del factor divided by the specific death rate. So, the time is equal to as we have calculated in our previous slide that 12.3 is and divided by 2.54 which is the specific death rate, then the answer is 4.84 minute, so this is the time that need for the holding time. So, if the contribution made by the heating and the cooling part of the cycle were ignored, then the holding time would be given by this equation. So, the t and overall del factor divided by k, so as we know that overall del factor is 32. that, so that by this equation we can easily calculate the total holding time of the sterilization. So, in this case when we calculate by the example of basilless stereothermophilus the answer is 12.68 minute. So, when we consider the contribution made by the sterilization process by the heating and the cooling part of the cycle, a considerable reduction is exposure achieved. So, when we calculate the holding time just based upon that equation which we already discussed that t is equal to d delta over k, then we can calculate the holding time as well as the other factors in this sterilization mode.