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safe water content in dried bugs to avoid spoiling

How do you measure "safe" water content in dried insects and what is the safe level for it not to spoil? I am new to this. So far I've found that the thing to measure is water activity, but haven't found a level safe for insects. Also, anyone know of a way to measure water activity at home or a proxy for that? I only found some really expensive devices.

Thank you


  • edited March 22

    @slupik - it is fairly easy and reasonably affordable to send samples you've dried to a commercial lab to test moisture content and water activity. You can also test samples of commercially available products (roasted/fried/powdered insects) to figure out the target range that others have established. If you don't want to pay for a lab, you can easily test moisture content and moisture reduction during drying at home using weight:

    Initial Moisture content (MCi) of a sample is measured simply by drying a sample (e.g. 5 grams) at low temperature (105 °C) until constant weight is obtained. Subtract the final weight of the sample from the initial weight (e.g. 5 grams) to determine the weight of moisture that was in the sample and divide by the initial weight of the sample to find the % moisture content (%MC).

    If you are drying a larger batch to a target %MC, you can pre-determine the final target weight to know that you have reached the target %MC. In this case, determine MCi for raw insects using the above method to plug into the formula below in order to determine your final target weight.

    Target %MC (MCf) is determined by weight, so we determine the target final weight (Wf) of the insects by using the initial weight (Wi) of the insects before drying and plugging it into the conversion formula for moisture weight loss during drying:

    Wf = Wi * (100 – MCi) / (100 – MCf)

    We've tested a number of products and generally found that they fall within 3-5% moisture content and at that level have low water activity (<= 0.6). Bacteria usually require at least 0.91, and fungi at least 0.7 (Rockland, L.B.; Beuchat, L.R. (1987). Water Activity:Theory and Applications to Food (2nd ed.). New York: Marcel Dekker.). For reference honey, which is notoriously shelf stable, has a water activity ~0.6

  • Just what I needed, thank you very much @andrew

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