So now that we've talked about both dry heat and moist heat as a means of controlling microbial growth, in this video we're going to talk about using low temperatures as a physical method to control microbial growth. Depending on the type of microbe, low temperatures can have varying effects, because recall that some microbes are capable of growing really well at low temperatures. However, generally, low temperatures are going to slow the growth of microorganisms. Recall from our previous lesson videos that psychrophiles and psychrotrophs are groups of microbes that are exceptions because they are actually capable of growing pretty well at freezing temperatures below 0 degrees Celsius. Other than these exceptions, most other organisms are going to generally grow slower with lower temperatures. Low temperatures can be, in many cases, a sufficient means of controlling microbial growth.
Refrigeration generally is going to delay, or once again slow the growth of many pathogens and spoilage microbes, which is why we refrigerate many of our foods in order to help delay the growth and slow the growth until we're able to eat those items. We can store those items in a refrigerator for longer periods of time by keeping them at these low temperatures. Freezing usually is going to preserve foods and other products by inhibiting microbial growth. But freezing does not always kill the microorganisms. Sometimes you're able to freeze foods and other products, and it can really extend the life of those items by a lot. But once you thaw those items, because the microbial growth is only being inhibited by the cold temperatures, sometimes thawing them will allow those microbes to continue to grow after those items have been thawed.
Recall from our previous lesson videos that the term "preservation" is referring to the process of delaying the spoilage of perishable products. Perishable products, once again, are items that are likely to go bad quickly, such as specific types of vegetables and fruits. If we take a look at our image down below, we can get a better understanding of how low temperatures can be used as a physical method to control microbial growth, specifically refrigeration and freezing. On the left-hand side, we are showing you refrigeration. Refrigeration can be used to store many of our foods that we eat on a daily basis, but also refrigeration can also be used in a laboratory setting. Here, this is showing you an image of a cold lab that is going to be maintained right around 2 degrees Celsius, and experiments are going to be performed at 2 degrees Celsius inside this cold room, in this lab.
On the right, we are showing you images of freezing. Of course, freezing is going to imply using temperatures below 0 degrees Celsius. Lab specimens can be stored in a freezer for really long periods of time because it inhibits the microbial growth completely in many cases, again, except for the exceptions of the psychrophiles and psychrotrophs. Generally, low temperatures such as refrigeration and freezing are going to help slow the growth of microorganisms. It is a means of controlling microbial growth. This here concludes our lesson on low temperatures, and we'll be able to get some practice applying these concepts and learn more about other physical methods of controlling microbial growth as we move forward in our course. I'll see you all in our next video.
