Winkle of Knowledge: Concentration measurement protein

This knowledge wink is dedicated to measuring the concentration of protein in water using the physical parameters of density and viscosity. Commercially available whey protein was used as an example, the concentration of which we were able to determine in the range of ±0.07 %w using a VLO-M2. Our shake is now perfect, and we are also happy to help you optimize your protein solutions!

Why this test?

Have you ever wondered why the gains don’t materialise despite hard training in the gym? Have you ever suspected the protein shake? Who knows how much protein is really in there, especially if you don’t meticulously weigh everything… With a VLO-M2 density and viscosity sensor, we set out in search of answers. In the spirit of ‘Dry January’, this wink of knowledge is not dedicated to alcoholic drinks for once, but to whey protein.

But quite apart from the fun factor involved in mixing, measuring and drinking protein shakes: Aqueous protein solutions are not only used in the production of whey products, e.g. for the fitness industry, but are also important pillars of the modern biotech and pharmaceutical industries. Whey protein is a cost-effective way to enter the diverse world of proteins.

What is a Wink of Knowledge? 

Do you need to quickly measure, draw or do/build something? The speed with which the result may be achieved counts more than the perfect (scientific) approach. For this reason, we have introduced the Wink of Knowledge. Science in the wink of an eye, so to speak. We don’t want to prove anything scientifically. We simply want to quickly demonstrate something pragmatically. If you are interested, we would be happy to discuss these results in more detail with you and your project. 

Results 

Mixtures with different concentrations of commercially available whey protein isolate in water were prepared using a balance. The concentrations were chosen to cover the range close to the manufacturer’s recommendation. The recommendation is to dissolve 25g of powder (which corresponds to approx. 3 level tablespoons) in 300 ml of water. Assuming a density of approx. 1kg/l for water, this corresponds to a concentration of approx. 8.3 %w. Our mixtures ranged accordingly from 4.5 %w to 12.5 %w. The density and viscosity of these mixtures were measured with a VLO-M2 at ambient conditions (approx. 24°C, atmospheric pressure) and yielded the following concentration dependencies (blue dots):

 
 
 
Both graphs show a very good dependence of the measured values on the protein concentration. For density, the relationship is almost linear, and for viscosity it can be approximated very well as a square (dashed lines). Taking into account the measuring accuracies of the VLO-M2 for the two physical quantities, which are ±0.2 kg/m³ for density and ±0.2 mPas for viscosity, density is clearly the best choice for calculating the concentration under the conditions investigated. However, viscosity as an additional parameter can be very interesting if an additional component such as sugar or alcohol/solvent is added. Even at higher concentrations, the viscosity should then react very strongly to changes in concentration due to the quadratic dependence.
 
The linear fit for the density dependence shows a gradient of 2.74 kg/m³ per weight per cent. With the high measurement accuracy of ±0.2 kg/m³ of the VLO-M2, it would therefore be possible to determine the concentration of whey protein in water with an accuracy of approx. ±0.07 %w (after field adjustment/repeatability even half of this).
 
Of course, with this knowledge we had to directly check the preparation recommendation of 3 level tablespoons in 300 ml of water and ended up at the orange dot in the graphs above. The expected concentration would be 8.3 %w, but the measured density would correspond to a much lower concentration of approx. 5.5 %w. An increase in the amount of protein by approx. 50% would therefore be necessary in our case in order to fulfil the consumption recommendation. As a side note, the water used for the ‘real’ protein shake was slightly cooler (approx. 22°C), which is why the viscosity in this example was also higher. The effect on the water density is relatively small at approx. 0.4 kg/m³ for the 2°C difference and would correspond to approx. 0.15 %w whey protein in this calculation.

Conclusion

Mixtures of whey protein and water in the range of 4.5 %w to 12.5 %w were measured for density and viscosity, and a clear concentration dependence was found. Assuming a linear fit for the density data, we would expect a concentration measurement with approx. ±0.07 %w accuracy for the VLO-M2. It would be interesting to measure other proteins that are found in relevant concentrations in the medical or pharmaceutical sector, for example.

In addition, we were able to optimize our protein shake recipe by using, measuring and comparing the preparation recommendation: TrueDyne Sensors AG now recommends increasing the dose by 50% to 4.5 tablespoons of protein powder per 300 ml of water when using the non-calibrated measuring device “tablespoon from the TrueDyne drawer”.

Which sensors were used? 

viscosity sensor VLO-M2

  • Click here to learn more about our sensor

Sensors that might interest you

Gases

Density sensor DGF-I1

Fluids

Density sensor DLO-M2
Density sensor DLO-M2_ex
Viscosity sensor VLO-M2

Density

Density sensor DGF-I1
Density sensor DLO-M2
Density sensor DLO-M2_ex
Viscosity sensor VLO-M2

Viscosity

Viscosity sensor VLO-M2

Applications that might interest you

Monitoring fuel concentrations

From volume (l)
to mass (kg)

Monitoring of welding gas mixtures

Monitoring of gas mixtures used in food packaging

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