Bridging the gap: Capillary suspensions prepared with protein particles

Summary

Especially living in the Netherlands, we are making use of bridges probably few times a day. But there are also very different, microscopically small bridges that are present in our daily life without us noticing: Tiny liquid bridges between particles! In this work, we explored how the flow properties of protein particle suspensions can be adjusted by the formation of such small water bridges. For many products, the product’s flow properties are directly relevant for both their functionality and consumer acceptance. Think for example of food spreads or cosmetic and pharmaceutical creams: If they are too thin, they keep dripping, if they are too thick, they can hardly be spread. The principle of adjusting flow properties of suspensions via water bridges, also referred to as capillary bridge formation, has been mainly investigated for non-absorbing, synthetic particles, while for a range of products, such as foods, pharmaceuticals and cosmetics, biopolymeric particles are preferred. We find that capillary bridge formation provides a rather straightforward manner to also adjust different flow properties of suspensions of water-absorbing biopolymeric particles. A special point of interest is how the water distributes within and between the particles. This water distribution is strongly related to the spreadable nature of the material, but also the brittleness of the product and its behavior upon heating.