In this video, we're going to review the chemicals used to control microbial growth that we already covered in our previous lesson videos. In order to review all of those chemical methods for controlling microbial growth, we're going to fill out all of the interactive blanks in our table down below. Notice that this table is a table of the chemical methods to control microbial growth, and we group these chemical methods as either being liquid chemical methods or gaseous chemical methods. That is what is indicated in the far left column. Then we have the specific control method in the next column and the description of the control method in the far right column. First, we discussed the liquid chemicals then we moved on to the gaseous chemicals. The first liquid chemical that we talked about was the alcohols. Alcohols are organic compounds with at least one hydroxyl group or -OH functional group. Then we moved on to talking about the aldehydes, and the aldehydes are organic compounds with at least one aldehyde functional group. The aldehyde is a -CHO functional group. Then we moved on to the biguanides. Biguanides are a class of molecules, a group of chemicals derived from the molecule called biguanide. Then we moved on to talking about the halogens, which includes chlorine and iodine. Chlorine is a halogen chemical used for disinfecting swimming pools and drinking water, depending on the concentration and the form of chlorine that is being used. Then iodine is a halogen chemical that is often used as an antiseptic in the form of a tincture or an iodophor.
Next, we discussed the surfactants or surface active agents, including soaps, detergents, and quats. Soaps are not antimicrobial, meaning that they do not kill microbes. Instead, they are degermers, meaning that they remove the microbes from the surface. They can be used to wash microbes away. Soaps are biodegradable natural surfactant molecules, with fatty acids containing a salt atom such as a sodium or potassium ion. Then we have detergents. Detergents are non-biodegradable synthetic surfactant molecules that do not consist of fatty acids and tend to have sulfonate groups. Detergents do not form soap scum in hard water that has lots of salts and minerals, whereas soaps do tend to form soap scum in hard water with salts and minerals. Quats are a specific type of detergent. These are cationic detergents, or in other words, these are positively charged detergents. These detergents, these quats, are deemed safe enough to use in food preparation. These quats do have antimicrobial features, meaning that they can kill microbes by disrupting their membranes.
Then we moved on to other types of liquid chemicals, including heavy metals, which included metals such as copper and silver. These are metals with relatively high densities, atomic numbers, or atomic weights. Then we moved on to the phenolics, and the phenolics are a class of chemicals, a group of chemicals derived from the molecule phenol. Phenols were originally used as surgical sterilizers by Joseph Lister. Then we talked about the peroxygens, which included peracetic acid and hydrogen peroxide. These are strong oxidizing agents, meaning that they can cause other molecules around them to become oxidized and lose electrons. They can be used to sterilize objects, but they are toxic at high concentrations, and therefore they have to be used at lower concentrations.
Then we discussed the gaseous chemicals used to control microbial growth. This included ethylene oxide, a highly flammable and potentially explosive gas sterilizer that requires a long and controlled treatment within a specific type of chamber. Then we talked about formaldehyde gas, which is a colorless and strong-smelling gas made by the oxidation of methanol. Last but not least, we discussed ozone, which is an unstable form of oxygen, which has a chemical formula of O3 and is a strong oxidizing agent that can lead to cell lysis and can be used to control microbial growth. This here concludes our brief review of all of the chemical methods that we talked about in our previous lesson videos to control microbial growth. That concludes this review, and we'll be able to get a little more practice moving forward. I'll see you all in our next video.
