Particle Interactions Immobilise the Suspension

Video Transcript

So I was dining alone in a restaurant in Vancouver a little while ago and I was served up a bowl of miso soup and managed to capture and film two interesting behaviours in that bowl.

I had just stirred the bowl of soup and then I started filming and the first thing we see is tectonic plate formation! What’s happening here is that the plumes of particles of soybean paste are working their way up in convection cells from the bottom of the bowl getting to the top and then where those plumes spread out and meet each other, you’re getting the formation of these fault lines and effectively subduction zones.

It’s a very similar process to what goes on in the formation of tectonic plates on the crust of the earth. The next thing that happens is that those particles start to assemble themselves into a structure. We see this aggregation, flocculation process occurring, and we can see the graininess appearing as that structure forms.

Now as incredibly delicate as this structure is, you can see that it’s strong enough to have arrested the motion in the soup that I put into it when I initially stirred it. Structures that are formed by particle interactions or emulsified droplet interactions are incredibly important from a point of view of stability.

We study those structures in my lab using oscillatory testing techniques and controlled stress rheometry. Our customers then take that information and they use that for understanding the influence of, for example, formulation variables, temperature and aging on ultimately stability of those structures. They then use this information for formulating anything from paints to beverages, pharmaceutical suspensions to cosmetic emulsions.

I hope this has been useful for you! If you have any questions regarding measuring the structure in your own products, then please get in touch. Please hit the subscribe button and look forward to seeing you at the next video!