What is the detergent in soap nuts and how does it work?

Here at PureRescue we believe that plant-based shampoos are better for your hair because they avoid some of the nasty chemicals found in cheap alternatives. They also clean just as well, if not better, than their commercial counterparts. The reason these plant-based shampoos can outclass products made by big chemical companies is because of one or two incredible plants that have soap-like properties. The most prominent and widely-used of them all is appropriately named the soap nut.

The soap nut has enriched countless generations through its ability to clean clothes, bodies and hair. But what is it about this nut that makes it such a good cleanser, if at all?

The science

First of all, we have a little confession to make: The soap nut isn’t actually a nut, it’s a berry. To be fair, this is not a naming scandal, it just that when the small black berry, approximately one inch (2-2.5 cm) in diameter, hardens it ends up looking a lot like a nut. The berry, which grows on the sapindus mukorossi tree in the Himalayas, is deseeded and dried before being used. It contains a natural soap called saponin which functions like a surfactant — i.e. the chemical that binds both with oil and water. Like all surfactants, saponin reduces the surface tension of water, making it easier to get into the fibres your hair to dislodge dirt. When this process is combined with the vigorous movement of your hand, the grime can be rinsed away.

In contrast to commercial shampoos, products containing soap nut do not foam. This can be a little confusing for some consumers because modern marketing has created a strong link in our minds between froth and cleanliness. This is simply not true however — low-foam shampoos have been shown to get rid of grime and grease as well as foamy competitors.

The sustainability

First of all the soap nuts are wild-harvested. They are picked from trees without the use of chemicals, fertilizers and pesticides. That is the fortuitous consequence of the fact that most insects don’t like the taste of saponin. Soap nuts also require very little processing and packaging which means they score really well when it comes to sustainability.

This is no small accomplishment. A carbon footprint study done by Boots in 2008 found that the “raw material extraction” phase was the second biggest contributor to greenhouse gas emissions in the shampoo production process. It contributed approximately 85g of CO2 per 23,5g bottle of shampoo. Because the soap nut eliminates many of the production steps, it allows the environment to breathe just that little bit easier.

Bonus

Given that the soap nut isn’t actually a nut, even consumers with nut allergies can use it without any apprehension. Soap nuts are naturally hypoallergenic, odorless and particularly gentle on your hair. They are so soft in fact that when soap nuts are used as detergents in washing powders, there is no need for fabric softeners.

A word on aloe vera

Besides the soap nut, aloe vera is also a common addition to plant-based shampoos that deserves a mention here as well. Like its berry counterpart, aloe has a multitude of impressive cleaning properties. These arise primarily from the fact that aloe has a similar chemical composition to keratin — the protein that hair is made of. This means that it is great at rebuilding hair fibres and that it can penetrate the entire length of the hair shaft to repair it.

Aloe also contains 20 amino acids which form the building blocks of the hair and cells in the scalp. Add to that the conditioning properties inherent in aloe and you have an all-round nourishing experience that leaves your hair with a healthy glow.

Photo: Photo by Markus Spiske on Unsplash

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