Soapberries or soap nuts come from the Sapindus mukorossi tree. They contain saponin,1 which is a glucoside with foaming characteristics, i.e. lathers like soap. Structurally, saponins have both hydrophilic and lipophilic functionalities but are weaker than soap.2,3 Water-soluble saponins are toxic to fish.
Soapberries don’t actually clean anything well or adequately remove soiling.
Detergent testing from consumer advocacy group CHOICE found soap nuts performed worse than washing with water alone.4 These results were true in both front loaders (soap nuts receiving a rating of 42%,5 compared to 43%6 for water alone) and top loaders (46%6 vs 47%7).
- Wikipedia, Saponin <https://en.wikipedia.org/wiki/Saponin>.
- S Balakrishnan, S Varughese and A P Deshpande , Mizellare Charakterisierung von Saponin aus Sapindus Mukorossi <https://www.degruyter.com/document/doi/10.3139/113.100315/html>.
- A Cook, S R Turner, J M Baskin, C C Baskin, K J Steadman and K W Dixon, Occurrence of Physical Dormancy in Seeds of Australian Sapindaceae: A Survey of 14 Species in Nine Genera <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2710253/>.
- CHOICE, Laundry detergents > Laundry ball reviews (October 19, 2021) <https://www.choice.com.au/home-and-living/laundry-and-cleaning/laundry-detergents/review-and-compare/laundry-balls>.
- CHOICE, Laundry detergents > Soap nuts 100g tested in front loader review (October 19, 2021) <https://www.choice.com.au/products/home-and-living/laundry-and-cleaning/laundry-detergents/soap-nuts-100g-tested-in-front-loader>.
- CHOICE, Laundry detergents > Water in front loader review (October 19, 2021) <https://www.choice.com.au/products/home-and-living/laundry-and-cleaning/laundry-detergents/water-in-front-loader>.
- CHOICE, Laundry detergents > Soap nuts 100g tested in top loader review (October 19, 2021) <https://www.choice.com.au/products/home-and-living/laundry-and-cleaning/laundry-detergents/soap-nuts-100g-tested-in-top-loader>.
- CHOICE, Laundry detergents > Water in top loader review (October 19, 2021) <https://www.choice.com.au/products/home-and-living/laundry-and-cleaning/laundry-detergents/water-in-top-loader>.