Soil removal - how does it work?
Malin Edvardsson Nov 9, ’20 > 10 min

Soil removal - how does it work?

Cleaning products are something that we all can relate to - we use them every day, soap, shampoo, laundry detergents, dishwash detergent. But how do these products work? We talked to Lars Mathiesen at Novozymes, to learn more about what components cleaning products contain and how they work on a molecular level.

What components are included in a cleaning product?

Typically, cleaning products have been based on high pH of soda, soda ash, or caustic soda, and also surfactants. This is the basis of how cleaning products originally were composed, Lars says. Then of course, over time, development - especially over the last 100 years, and with a rapid acceleration the last 20 years - has added a lot of different ingredients that enables better cleaning in different ways.

Listen to Pod Episode: The Science of Soil Removal

The pH is the most important aspect for efficient cleaning

Fat and protein stains tend to be very sticky, and at higher pH, they get more dispersed and will be easier to remove in a water rich formulation. So, in all cleaning, you will have a buffer system that helps to get the right pH to address the cleaning that you need, Lars says.

The main ingredient of a cleaning product is surfactants

Surfactant molecules have a hydrophilic part and a hydrophobic one. The hydrophobic end does not like water and will interact with the soil, whereas the hydrophilic end stays in the water phase. This means that surfactants can lift soil from the surface and into the water phase of the cleaning solution, Lars explains. For example, fat on a textile surface can be removed this way, Lars explains. The surfactant will help disperse and remove soil and suspend them and keep them in the washing solution.

The builder system makes the aquatic solution just right

Talking about builders, this takes us back to the importance of the pH. Builders are chemicals that are added to modify the water solution. They do that by modifying the pH, typically driving the pH up if you desire to remove fat or protein. You can, however, also drive it down if you want to remove soils that are easier to remove in low pH, like rust or wine. So, it depends a bit on what the purpose is with your cleaning system, Lars says. You can optimize the cleaning product one way or the other, but either way, these builder systems will help you build the right aquatic solutions and to get the right pH.

The builder system also helps you get the right water hardness. Most consumers use tap water. The water hardness of tap water varies geographically, from household to household and from country to country. To get the same cleaning efficiency no matter where you live, the water hardness needs to be corrected for, and this is the task of the buffer system – it will capture the ions in the water so that you get the same benefit from the surfactants no matter where you get the water from.

Clean fabric

Bleach makes colored stains invisible

Bleach is typically percarbonate, it can go in and react with colored components. If you look at most of the colored stains that we have in a consumer setting, it could be red wine, tea, and coffee. If you zoom in on how the colored molecules look, they will have some double bonds between their carbon atoms. These double bonds are what trap the light and radiate it in a different direction and that is what you want to prevent, Lars explains. Therefore, if you want to remove those stains you need to break the bonds so that they do not radiate the color that you have coming in. This means that the molecule is still there, but it is no longer reflecting that particular wavelength, and that is why you cannot see it.

Perfume provides a sense of cleanliness

Most consumers expect a sensorial experience when they do cleaning, Lars says. And that goes for all sorts of surface cleaning, i.e. laundry, dishwashing, floor cleaning. It needs to smell like the cleaning process has been effective. There are a few different ways that this perfume should interact with the consumer. The first occasion, and probably the most important one, is in the supermarket when the consumer will smell the bottle. A common practice by the consumer is to select the smell they prefer already in the store. Therefore, you would like a perfume that stands out already in the bottle format. You also want something that smells good right after the use, when you just have completed for example your laundry. The consumer also wants to experience the same fragrance sensation when they start wearing the clothes.

About 10 years ago, the perfume houses started launching encapsulated perfumes. These are mixed into the detergent, so once you have completed the washing you will have all these tiny fragrance capsules hidden in your washed fabric. Then, when you move, the friction of your motion will make some of these small capsules burst and release the fragrance. So, there is a mechanical activation of the fragrance release when you use the clothes. The fragrance molecules are maintained in the clothes until you start using them, and then they are released.

Polymers play lots of different roles

In a cleaning solution there are typically lots of different polymers special benefits, Lars says. For example, there are anti-redeposition polymers. These are long molecules that can grab dirt and prevent it from redepositing at the surface. For example, when you wash dirt out of your clothes, then the removed dirt will not redeposit on other garments in your wash. Then you have soil release polymers. These are polymers that will stick to your clothes. The next time you wear your clothes and get dirt on them, the dirt will stick to these polymers, and when you wash your clothes, you will wash off the polymer and the dirt will follow. Another type of polymer is used in automatic dishwash, where you have polymers that help the drying of glass.

Enzymes make the job easier for the surfactants

Enzymes are proteins that catalyze a certain chemical reaction. For example, when you eat, your body will release protease that will cut the protein into amino acids. You also have amylases cutting the starch into sugar, and the fat in your food will be digested by lipase which cut the fat into free fatty acids. The resulting molecules are much smaller than the original ones and can be absorbed into the blood and travel around in the body. This same process is being utilized in cleaning products, Lars explains. Enzymes are used to cut the molecules in the food-based soils into smaller pieces which make them easier to be removed by surfactants and to wash off. It is much easier for surfactants to lift small molecules from the surface than to lift large ones, so you can say that the enzymes and surfactants work like a team.

Science on surfaces – a bigger perspective on the small

Listen to the full interview with Lars Mathiesen in this pod episode, where we talk about the science of soil removal and why some types of soil, like sweat, are much harder to remove than others. Lars shares lots of interesting facts and anecdotes related to soil removal, and he also provides us with some tips and tricks on how to make the most of our cleaning products!

Podcast  Episode: the Science of Soil Removal  Listen

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