The MCT is likely undergoing rancidification
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Is the color of the MCT changing after being sonicated?
Everyone’s joking about adding honey cut but VEA may have a place here
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Although many minor compounds present in oil can act as prooxidants, some can present antioxidant properties. Such is the case of tocopherols, tocotrienols, carotenoids, phenolic compounds and sterols.
via: https://www.sciencedirect.com/science/article/abs/pii/S095671351200641X
Bingo
In case anyone needs a spoon on this at some point in the future, build an enclosure that will fit your sonicator probe and your emulsion vessel and nitrogen flush it OR I think Ace makes a glass sonication reactor that fits some units that you could probably rig a nitrogen line to. or if you’re at a large enough scale, Qsonica makes flow cells that I’m guessing (haven’t tried em) you could rig up to an inert loop.
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Have you done this yourself? I have the Qsonica flowcell and never introduced air into the system and still got the same results of oxidation. 
I’ve used an inert blanket to mitigate the rancidification of MCT when it’s sonicated. Like I said above, I haven’t used a flowcell myself, but I understand the basic mechanics. How are you moving material through the flowcell?
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Peristaltic pump. Primed the entire system with MCT before starting.
FYI, Sonicating cannabinoids in MCT (or any oil) base does nothing… You need a good surfactant system, and your formula should be mostly water if you want to make nano/enhance bioavailability. Look at the company Cannasol Technologies. They have equipment, surfactant, and bitter blockers all available in reasonable quantities.
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can a high shear homogenizer do the same bad things to mct?
I’ve been running into this problem myself recently.
At my employer’s behest I’ve been ultrasonicating tincture blends using just MCT and distillate and immediately ran into this issue myself.
We’re using a QSonica with a 1" sonotrode for creating emulsifications but recently my employer has taken an interest in sonication to guarantee thorough homogeny of suspended cannabinoids in oil-based products.
While this is entirely unnecessary as no surfactants are present I nevertheless conducted the procedure and sure enough the oil picked up a terrible smell. This was using just distillate and MCT. MCT by itself develops the same odor, an acrid and burnt smell like singed cotton or vape coils being fired dry.
A number of tests were conducted and I discovered an interesting trend, the lighter an oil is the worse it smells after the same treatment. A number of tests were conducted using the same sonication parameters and different oils.
All tests were performed using an amplitude of 70 and a runtime of 4 minutes using a QSonica machine and a 1" sonotrode.
- MCT Oil: Clear and colorless: Smell is remarkably bold and offensive, noticeable as a gustatory sense as well.
- Sunflower Oil: Clear with slight color: Nearly as bad as MCT, smell and taste are strong.
- Grapeseed Oil: Clear with slight color: Nearly as bad as MCT and SFO, smell and taste are strong.
- Extra Virgin Olive Oil: Transparent and Yellow-Green: Taste is subdued, possibly by oil’s natural flavor and aroma.
- Hempseed Oil: Non-Transparent and Dark: Foul taste is minimal, subdued to faintness by oil’s natural taste and aroma.
I do not know whether it is the structure (saturated/nonsaturated), molecular weight or other composition of the fatty acids involved but from my preliminary explorations it seems as though the following trend can be safely surmised; the lighter an oil is the worse it reacts to sonication, the darker an oil is the less noticeable this issue becomes.
Hope this helps others though personally I do not see what is to be gained by sonicating basic tincture recipes; there is more harm than good to come of utilizing this technology for simple mixing/homogeny.
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Heat degrades mct
I’m willing to bet the friction of the homogenizer is hot enough to degrade it
I once had to remove mct from disty that was over mixed
It’s nearly impossible to remove by distillation as it codistills
It also leaves a horrific smell once degraded
I believe this is the case as, while the overall temperature of the solution WILL rise appreciably during the sonication process the cavitation phenomenon by which the sonicator functions produces much, much higher localized temperatures on the small scale.
I ran into the same problem when trying to sonicate aqueous solutions whose viscosity had been increased using high molecular weight hydrocolloids. In essence, the watery mixture was too thick and the friction/energy introduced via the sonotrode essentially ‘burnt’ my liquid. The smell was identical between oil-only mixtures and water-gum mixtures.
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It seems to be clearly related to the concentration of unsaturated fatty acids and other anti-oxidants. Your data follow this trend. Those components may delay the occurence of oil degrdation by the probe.
Commercial MCT oil usually contains c8:c10 chains.
C6 are removed because of their unoleasant smell and taste. Could be that ultrasounds rapidely rapidly alter c8/c10 to c6, in absence of anti oxidants.
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C8 acids aren’t that much more pleasant, it’s literally Cow vs Goat 
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Do you mean pure c8 mix ?
MCT is rIch in c8, like 40-60%, and does not smell nor taste much at room temperature. Once heated hot enough, above 160c, one can perceive a coconut smell. Once it cools down, an unpleasant smell persists, a bit like dead fish. But it does not persist for weeks.
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I don’t mean C8 esters but free octanoic acid, sorry for the confusion.
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Still, this may be a more likely explanation.
Caprylic (octanoic, c8) acid is described as rancid. Could be that ultrasounds alter the triglyceride (ester of fatty acids) to the corresponding acids.
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Absolutely, hydrolysis of the esters appears quite plausible given the energy introduced and discharge through cavitation.
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I read through the instruction manual a little more thoroughly recently and found a small excerpt located in the operational section, it outlines the phenomenon of ozone/free radical formation of reactive species during normal operation of the ultrasonicator. Knowing that reactive oxygen is produced by the sonicator it is now much easier to understand what is happening to the oil and how the presence and abundance of unsaturated double bonds could influence differing oils either taking on or resisting fouling during sonication.