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Starch Test: How to test for starch in your mushroom supplements

Updated: Feb 15, 2022

You may not know this, but most mushroom supplements do not contain any mushrooms at all. The majority of the products on the market are made with the spindly “roots” of mushrooms called mycelium rather than the fruiting body. Supplements made from mycelium contain starch, indicating that the supplement does not have verifiable levels of beneficial beta-glucans.

Mycelium vs. Fruiting Body

If you’re not familiar with terms like “mycelium” or “fruiting body,” you’re not alone. Mushrooms are mysterious to the western world, and how they are grown commercially is not common knowledge. Here's a brief breakdown of some of the steps many growers utilize to grow mushrooms.

One of the first steps is inoculating sterilized bags of grain or woodchips with mushroom spores for a specific species. Under the right conditions, originating from the spores, the mycelium, appearing as a network of white threadlike strands, will spread throughout the bag covering all of the grain, creating a solid block.

mycelium colonizing on grain
Mycelium colonizing on grain

After a few days or weeks, when the mycelium has colonized all of the grain, the grower will increase humidity, fresh air exchange, adjust the temperature, lighting and other environmental controls to create optimal conditions for fruiting body formation.

Oyster Fruiting Body
Oyster mushrooms fruiting from mycelium

Once the fruiting body has fully formed it will be cut from the mycelium. The fruiting body is the part of the mushroom that is generally most recognizable, and if the mushroom is edible, then you might enjoy eating it!

Why do the test?

When it comes to mushroom supplements, it’s essential that it’s made from the fruiting body because this part contains significant amounts of healthy beta-glucans.

Supplements made from the mycelium and grain blocks do not have much in the way of beta-glucans; they are mostly grain filler.

This simple test will determine the type of mushroom supplement you have by detecting the presence of starch through a chemical reaction with iodine.

Follow these steps to find out if your mushroom supplements contain starch:

Supplies to gather:

  • Iodine disinfectant: Povidone-iodine, iodine-potassium mixtures, or an iodine tincture - Any of these will work, and you should be able to find one at your local pharmacy. We used Betadine in our test, which is a povidone-iodine solution.

  • Mushroom supplement powder sample

  • Small glass jar

  • Dropper

  • Nitrile gloves

  • Paper Towels


Iodine can stain clothing, skin, and equipment so take care while handling and don’t consume.


  1. Protect your counter top with a newspaper and put on nitrile gloves.

  2. Add about 1/4 cup of water to glass.

  3. Add mushroom sample to water.

  4. Use the dropper to add a few drops of iodine to the sample.

  5. Mix solution to evaluate results:

    1. The solution becomes light orange/yellowish color when starch is not present.

    2. The solution becomes dark blue-black when starch is present.

  6. After testing, wash your hands and dump samples down the drain.

Evaluating the Results

A color change will determine if there is starch present or not:

  • Starch not present: Liquid will remain yellowish/orange

  • Starch present: Liquid will turn dark blue or black

Starch in your mushroom supplements means you’re not consuming a whole fruiting body product and not receiving the most significant wellness value mushrooms have to offer. We recommend trying one of Zenspora’s pure whole fruiting body mushroom supplements for the best mushroom wellness experience.

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