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Pressing Dried Mealworms For Oil

I was wondering if anyone has tried using oil presses to extract the high oil content of mealworms. I raise mealworms and superworms for composting purposes and was thinking I could press them for oil to cook with. The remaining mealworm cake could then be incorported into baked goods for extra protein. Anyone see any problems with this idea?


  • @BugCatcher5 - check through some of the existing forum threads on mealworms, one of our contributors (@gringojay) has a fairly detailed exploration of pressing oil from mealworms.

  • Even though @Gringojay made a good suggestion about pressing oil in insects, I can tell you from my personal experience that this doesn't work. I used a 'Piteba' (the same one mentioned by Gringojay) to press oil out of mealworms and BSF larvae and neither gave anything but a whole lot of mess, unfortunately.

    Apparently, pressing animal fat is not the way to go here.

  • Hi EntoJesse, - Sorry to hear the Piteba manual seed oil expeller didn't work. Did you dry the insects at all? If the insects still had most of their water content then that would make a messy mass.

  • Don't worry, it was indeed our best bet to a cheap DIY solution. I tried dried mealworms destined for human consumption in the Netherlands, probably at very low moisture (I thought it might've been too low), I also tried dried BSF larvae in Ghana, probably at higher moisture rates because of the ambient high humidity rates. I had better hopes for the BSFL in Ghana as the dry product needs a little bit of moisture (like 10-20% I believe) to work well. But neither worked at all; not a drop of fat unfortunately.

  • So EntoJesse - Hydo-phobic (water shy) solvents are probably the way to extract the oil without getting rid of all the insect's moisture; food industry non-polar solvents (not alcohol) are hydro-phobic. Hexane is probably the most commonly used & then removed from the end-product; if you used soybean oil for cooking it was probably partially processed with hexane.

    The set-up used for this is called a soxhlet extraction; which is basically passing hexane through bio-mass with a design feature that allows removal of the hexane. Although hexane smells/seems problematic it is actually not very toxic. Just make sure when working with it that there is very good ventilation or big enough extraction fans on; don't let anyone smoke or light match where working. Humans can detect hexane down to a low 30 ppm & we'd need long term exposure to ~ 250 ppm for neurologically toxic kind of damage to occur (OSHA, occupational regulators, say 8 hours breathing hexane at 500 ppm is the workplace maximum for neurological safety).

    I think (?) for low tech work you could soak the insects that are cleaned & matted dry to the touch euthanized insects (ideally broken/sheared/chopped open) immersed to their top layer with hexane in a covered bucket (hexane fumes can give you a headache, be noxious to the respiratory tract, significant contact on skin be absorbed - so wear goggles/gloves). Keep it at moderate temperature ("room temperature) & periodically swill around the contents (or stir with a through fitting using something like an electric drill or motor to turn a shaft with a paddle on the end, like a paint stirrer, sunk down into the bucket interior). To release any interior pressure that might build up in a closed vessel "burp" some air out every now & then. A day of 24 hours should be enough for the hexane to draw the oil out. Then filter out the solids leaving the hexane pass through a filter set-up with it's load of oil (& probably some pigments); squeezing the solid residue in some kind of a press will bring some more out if strong fan to push fumes away .

    The real problem with this (instead of investing in a soxhlet apparatus) is to make it so you don't have to get more than brief exposure to the hexane fumes which can depress the central nervous system in acute over-exposure; don't keep deliberately sniffing the project (stuff smell similar to gasoline) to see if you can tell how much hexane is in play. Once you feel vertigo (as if dizzy or might fall) then that is an indication you are getting too much exposure - it (vertigo) will go away in time (depending on exposure figure a couple of hours) once you remove yourself to fresh air ; just don't make the same mistake the next day when pick up where left off (when sense vertigo/dizzy just close everything (bucket/jars/bowls) back up good, it won't become contaminated with microbes or go bad.

    Since hexane boils at a lower temperature (69 celsius = 156 fahrenheit) than alcohol (173 fahrenheit) then , once you have got rid of the solids through filtration, you can dilute the hexane extracted solution with alcohol; & then bring the blend to the hexane boiling point (but less than the alcohol's boiling point) so that it (the hexane) will evaporate leaving the oil behind in the alcohol. A double-boiler type of set up on an electric heat source is a good way to keep the boiling temperature regulated.

    You'd definitely want to have good ventilation & NO open flames when creating vaporized hexane.; it is not explosive but is flammable. When boiling the alcohol & hexane blend put some clean rough (not smooth) surfaced stones into the same boiling vessels for the 2 compounds to roil around in there if you boiling in a closed vessel (for example in a still) these "boiling stones" are to keep the internal dynamics of the 2 solvents from creating any potentially problematic spots. Also hexane expands >3 fold when heated so leave head room in your boiling vessel; if just using an open pot a continual stirring is a good technique.

    If are not using a soxhlet type of extraction (which allows the re-capture, & thus re-use of hexane condensed after it rises as vapor inside the closed system loop) then the boiling off of hexane from the alcohol will release the hexane vapor into the open air. There must be excellent air circulation to carry the hexane vapor away from humans (& animals). Unfortunately the laboratory quality "n-hexane" (HPLC reagen grade) that would be best to use is expensive compared to industrial hexane; industrial hexane is cheap because it is not as pure & usually blended with some other solvents.

    So, if you measure the fluid volume of hexane extracted oil & add to it a bit more fluid volume of alcohol then you know when over 1/2 of that total volume has been evaporated off (no open flame!) you have removed the hexane portion. The evaporation of the hexane could also be done passively; just set everything in a shallow container & the hexane will evaporate off 1st. Now, if you do not have "pure" alcohol to add & must use human beverage alcohol (ex: vodka) then don't forget to calculate how much water is in that "proof" alcohol when measuring out the actual alcohol volume you need.

    Anyway using a low tech (non-soxhlet) technique may require a series of alcohol additions to fully get rid of the hexane via boiling off/evaporation. In other words stir in more alcohol & evaporate off residual hexane again - And then when have evaporated/distilled off the hexane you must remove the alcohol; which (the alcohol) can also be evaporated or simmered off. And if you had to use beverage alcohol don't the "boiling stones" if used a hot plate for heat; because you will have a more conflicted interaction of heated molecules . Plus, after getting get rid of all the hexane & (most of) alcohol you will need to decant away that residual water (from the vodka). Chilling/freezing the water/insect oil or alcohol/insect oil for a few days in the refrigerator should cause enough of a separation so that you can see an oil layer to skim/collect.

  • edit: last paragraph 4th sentence should read "... don't FORGET the boiling stones ..." (ie: if not just letting the alcohol evaporate without boiling)

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