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I am trying to break down the starches in a certain variety of oats in the most efficient way possible. I have to break the whole oats down after cooking, so they are fine particles for the amylase to do its work.

However, if I add the amylase at the beginning of the blend, could I be damaging / denaturing the enzyme from the shear forces of the blender (I am using a 600 Watt stick blender)

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    Is there any reason you can't add your amylase with gentler stirring after the main blending stage? – mbjb Jan 20 at 3:04
  • I had initially thought adding it before blending would be giving some kind of mechanical advantage, speeding up the enzyme reaction process. But then I thought it might be too much and denaturing it after getting mixed results, which is why I asked the question. – Amphibio Jan 20 at 8:05
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There are three ways in which a protein can be denatured:

  1. Chemically (for example, the 'cooking' of protein like fish by acid, as in ceviche).
  2. Through heat.
  3. Through mechanical force.

I will assume that in your situation, chemical denaturation does not occur.

From a quick search through some scientific literature, mechanical protein denaturation is a fairly new research topic. I found an MSc thesis that lists three experimental techniques for mechanical denaturation: optical tweezers, magnetic tweezers, and force mode AFM (atomic force microscopy). All these methods act on a single protein molecule, grabbing it at two ends and 'stretching' it, which denatures the protein.

While it is possible that your stick blender denatures some proteins mechanically, but it seems unlikely to have a large effect. It seems much more likely that the blending is causing your mixture to heat up above the denaturation temperature through friction. This could also explain your inconsistent results, if you do not always reach this temperature.

A good test is given in mbjb's comment: blend the oats first, let the mixture cool down if it has warmed up, then gently mix in the amylase. You could measure the mixture's temperature throughout the process if you want more information, potentially comparing it to amylase's denaturation temperature (which I could not quickly find, but you might be able to).

PS. in response to your comment: the enzyme reaction process will be sped up by temperature (where warmer means faster, until you get to the denaturation regime) and proper mixing. I see no other mechanical advantages of blending in the amylase using a stick blender.

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  • Yes, it is interesting - I have kept a note of temperature before, during and after blending, and it does raise the overall temperaure by a few degrees... which I guess means at the point of the blades inside the mixture, the temperature is actually being raised by an even greater amount? – Amphibio Feb 11 at 18:30
  • @Amphibio Possibly. DId you see any differences in temperature between the mixed results you mentioned? – LSchoon Feb 11 at 20:36

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