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Updated: Nov 3, 2023


Q: I’ve noticed on the inside of every soap nut that there is white fuzz that kind of looks like mold. Is this mold? Do I need to throw my soap nuts away? photo by Russ Kleinman, A: What you’re looking at isn’t mold at all, it’s a bunch of vascular bundles that connect the seed to the rest of the fruit to give it nutrients and water as it grows, and it’s the plant’s version of an umbilical cord. The part that looks very fuzzy is also known to winemakers as the “brush” in grapes. This is a natural normal part of the soap nut and most other fruits with seeds. It happens to be particularly noticeable in soap nuts on the inside when they dry, and even with the seed removed, some of this fuzz will remain.

Illustration from Australian Viticulture from the text: “Ripening berries — a critical issue” by Dr. Bryan Coombe, and Tony Clancy, March/April 2001. Illustrations prepared by Jordan Koutroumanidis.

Remember that a soap nut is actually a berry and not a nut, though the terms “soap berry” and “soap nut” are used interchangeably and refer to the same thing. The pericarp (fruit) contains the soap and it hardens into a shell that resembles an acorn. Part of this drying process helps to keep them preserved for a long time. Eco Nuts brand soap nuts (soap berries) are hollow on the inside because we remove that cannon-ball looking seed which doesn’t do much of anything. To help illustrate this further is a diagram of a grape (another kind of berry) which may give you a better idea of all the neat things going on inside a fruit. Can soap nuts grow mold? Indeed, they can just like any other fruit! Mold spores are in the air everywhere and under the right conditions it can sprout up. If you keep soap nuts in a place where they are moist all the time or they get wet and do not dry out, they can grow mold, but this will usually present itself as a gray or green fuzz covering the ENTIRE outside of the berry and will smell moldy. To keep your soap nuts from growing mold, store them in a cool dry place away from moisture. If your household environment is particularly damp, store in an airtight container, and hang your bag to dry in between laundry days. Soap nuts tend to be resistant to mold but things can happen if they are kept constantly moist over a period of days to weeks under the right conditions.


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