 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 several videos. This video I 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 a microbat for ten 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 a sample. So I personally feel like thermal death time is more a better number because it's a better comparison directly of two organisms. So just a couple of 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 350-400 degrees let it warm up and put your arm in the oven. Don't touch anything of course and your arms are going to get warm but you take that same arm and put it in boiling water which is boiling at 212 degrees Fahrenheit and you will seriously injure yourself 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 work 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 than not boil it 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 in boiling water for 20 hours and the issue is that at sea level water boils at 100 degrees Celsius and one really important example would be Clostridium botulinum takes 116 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 the reasons I said before takes a lot longer in a higher temperature so dry heat can sterilize things but it takes 170 degrees for two hours. So if you have the time and things are heat stable enough to use a dry heat oven then it's very effective. But as an equivalent treatment it takes 170 degrees for two hours to do what an autoclave can do at 121 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 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 is destroyed by burning but the term I like to use is destroyed by oxidation so you're oxidizing, you're peeling 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. All right 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.