Smooth drinks for winter nights: holiday fun with the MTM!
As we head into the holiday period here at PCS Instruments, we thought it would be fun to investigate the tribological properties of a few of the different drinks options on offer this winter season. This falls into a growing field called Oral Tribology and focuses on how food and drinks feel as you consume them.
There are many examples of the MTM being used to test and evaluate the properties of foods and drinks, including work to investigate the mouthfeel of wines, the creaminess of chocolates and the richness of mayonnaise and these applications just scratch the surface! With the global food and beverage market valued at over $281 billion it’s easy to see why world leaders in academia and industry are using the MTM to gain every advantage possible.
The drinks we chose for our investigation were:
- Mulled Wine
- Advocaat
- Hot Chocolate
- Irish Cream
- Port
These were chosen to give us a range of different mouthfeels to investigate and compare. Irish cream and advocaat having a classic creamy richness, port and mulled wine with a more dry and crisp feel and hot chocolate bringing in a whole new complex factor of suspended particles.
To test the drinks, we created a bespoke profile for the MTM that consisted of multiple Stribeck steps. The instrument was set up with the pot filler fitted and using PDMS specimens.
The aim of our investigation was to see if we could differentiate not only between the drinks with very diverse mouthfeels, but also between the ones that have similar properties and ingredients; the mulled wine and port, and the Irish cream and advocaat.
We succeeded in this aim as you can see below!
The results above from the MTM broadly align with what we would expect. The mulled wine and port can be grouped together, the advocaat and Irish cream together, and the hot chocolate behaving slightly differently to them all.
We aren’t going to analyse the results too closely in this investigation; we will leave that for you to do as you sit down for a drink over the festive period. However, there are a couple of interesting points to pull out for you to ponder during these long winter nights.
First, comparing port to mulled wine. If you happen to have a sip of these drinks, see whether you pick up on the subtle difference in mouthfeel (not just flavour) between them. When we tried both, we noticed that the port had a richer, heavier feel to it; and that it seemed to be slightly higher in viscosity. This could explain the lower initial friction coefficient and the earlier move into the mixed and EHD regimes on the Stribeck curve, which would be consistent with findings on the effect of viscosity.
Second, comparing hot chocolate to the other drink options. As you can see hot chocolate behaves quite differently to both the thick, rich Irish cream, and the thin, crisper mulled wine. There are many possible explanations for this behaviour. One possible reason for this is the makeup of the hot chocolate, its protein filled milk explaining the low boundary friction and then the suspended particles of hot chocolate powder getting entrained into the contacting PDMS surfaces to increase their surface roughness and postpone the transition to the boundary and EHD regimes.
We hope you will try all three at some point over the holidays to develop your own hypotheses and please do let us know! We would love to read your thoughts on it!
Finally, we look at two drinks with very different mouthfeels: mulled wine and Irish cream. With such different viscosities and ingredients it is easy to see why these would differentiate so well. The thicker and richer Irish cream shows consistently better lubricating properties across all the lubrication regimes as well as an earlier transition between them.
So, what do we recommend? Well simply put, our recommendation is to drink whatever brings you joy this holiday period, whether that be any of the options we’ve tested or any other drink for that matter. We won’t draw any conclusions about what drinks are best or worst! However, if you have any thoughts about this work at all please do drop us a line through our contact form or via LinkedIn.
This bit of work is just a bit of fun, but what we hope you take away from it is the power of tribology to provide insight into the world around us in every walk of life. It impacts every day actions in ways that we don’t realise until we stop to think about it.
If you work in the field of biotribology or even just think it might be relevant to your work, whatever the area of specialisation, please do get in touch with us here so we can talk through your needs and help you expand your ability to test, analyse and compare the formulations you work with.
We hope you have a lovely holiday period and we look forward to working with you in the new year!