hey everybody dr. Rowe here I'm going to start our series of physical methods of microbial control by talking about heat so we will cover the autoclave and pasteurization in more detail in separate videos this video won't really want to focus on moist heat versus dry heat before we do that a couple of terms you have to know when dealing with using heat and that is the thermal death point and thermal death time so the thermal death point is what temperature do you have to cook it might grow that for 10 minutes to kill all of them the thermal death time is at a given temperature how long does it take to kill all the microbes in the sample so I personally feel like thermal death time is a more a better number because it's a better comparison directly of two organisms so just a couple terms you have to know thermal death point versus thermal death time all right jumping in we do so we have moist versus dry heat before I give you the examples just think about it both moist and dry heat can work but in generally speaking I like to say that moist heat is more effective right I think this makes sense turn your oven on to 350 or 400 degrees let it warm up and put your arm in the oven don't touch anything of course and your arms gonna get warm but you take take that same arm and put it in boiling water which is boiling at 212 degrees Fahrenheit and you will serious injury self so please don't do that but you'll see that it takes a much lower temperature to have a much more aggressive response with individual cells so moist heat is able to surround and and work and when it comes to cells a lot better so dry heat can be equivalent though so we'll talk about that in just a moment so first we have boiling boiling is generally not considered good enough for a microbiology lab obviously you can use it at you know at home it's better to boil your water there not boil it if there's if there's some sort of issues or you can boil baby bottles and that kind of thing but some endospores have been proven to survive at in boiling water for 20 hours and the issue is that sea level water boils at 100 degrees Celsius and one really important example would be Clostridium botulinum takes a hundred and sixteen degrees to kill it so the water is boiling before it actually reaches a temperature that would kill the Clostridium botulinum endospores so certainly using it's better than not using it but it's definitely not seen as effective enough to be used in a laboratory so then we have dry heat comparing that to moist heat so dry heat for as I said before takes a lot longer in a higher temperature so dry heat can sterilize things but it takes a hundred and seventy degrees for two hours so I think if you have the time and things are heat stable enough to to use it to use a dry heat oven then it's very effective but as an equivalent treatment it takes a hundred and seventy degrees for two hours to do it an autoclave can do at a hundred and twenty-one degrees for 15 minutes so as you can see the moist heat is quicker and generally more effective because moist heat is more effective all right the last last one here is incineration so you can certainly burn and incinerate things the key example we use in the lab would be flaming our wire loops so it says here's destroys by burning but the term I like to use is destroys by oxidation so you're oxidizing your pealing electrons off of or burning electrons off of whatever is on that wire loop when you sterilize it so using incinerators flaming your wire loops with a Bunsen burner these are examples of using incineration alright so that is moist versus dry heat and like I said before we'll come right back with a separate video on the autoclave and pasteurization I hope this helps have a wonderful day be blessed