Dispersion: key to optimizing the functionality of hydrocolloids

Hydrocolloids are macromolecules that are added to food for technological purposes, either to achieve an effect on texture, or to perform one or more functions within the food, such as stabilizing the emulsion, retaining water or keeping particles in suspension. The most common presentation of hydrocolloids is in powder form, i.e. tiny particles composed of several molecules. For these particles to be functional in the food, it is not enough just to add them to the food, but it must be ensured that they are dissolved. Incomplete dissolution of the hydrocolloid can lead to the following problems:

  • Lumps and traces of poorly dissolved product, retained in filters and sieves, can cause them to clog and lead to delays or failures during the manufacturing process.
  • Loss of functionality, that forces to increase the dosage of use, with the consequent increase in the price of the formula.
  • Defects in the texture or behavior of the final product, as well as the presence of lumps in the product.

In order to achieve a good dissolution, it is important to carry out two previous stages: dispersion and hydration. In the following text, we will focus on explaining the importance of the dispersion stage and on giving a series of guidelines to carry it out properly.

Hydrocolloids have an affinity for water and their functionality is based on their ability to dissolve in water and retain it, giving rise to gels with different textures and functional properties. In order to dissolve properly, the molecules need to be hydrated. The further apart these particles are from each other, i.e. the more dispersed they are, the easier hydration will be. This is because the surface area in contact with the water will be larger. If, on the other hand, the particles are very aggregated, what happens is that the water will come into contact with the particles on their surface, which will hydrate and swell, but will not allow the water to access the particles that have remained on the inside. Thus, the particles on the inside will remain unhydrated. When this happens, the inner particles do not dissolve properly and are not 100% functional. A classic example of this phenomenon is the lumps that form when cocoa powder is added to cold milk. The surface of the cocoa lump is hydrated, but when the lump is broken up, its inner part still has the cocoa powdered product intact.

There are hydrocolloids, such as agar, which practically do not hydrate in cold water. In these cases, cold dispersion is easily achieved by simply applying agitation. However, others, such as xanthan gum, have a very high affinity for cold water and begin to hydrate immediately upon contact with it. In this case, once added to the liquid medium, normal agitation will not be sufficient to break up the aggregates and disperse the particles. This will cause a loss of functionality of the particles, which will not be able to dissolve because they are not well hydrated.

Below we will discuss a number of strategies that can be used to facilitate the dispersion of hydrocolloids:

  • PARTICLE SIZE: The larger the particle size, the easier the dispersion will be. The hydration process will be slower as it will take longer to hydrate a larger particle size, but the dispersion will be easier and a higher functionality will be achieved in the end. Thus, it will be easier to disperse an 80 mesh size xanthan gum, than a 200 mesh xanthan gum.
  • PREMIXING: Pre-mixing with other dry ingredients such as sugar and/or salt facilitates dispersion. The other ingredients will be sandwiched between the hydrocolloid particles acting as separators between them. Adding the mixture to the liquid and stirring will make it easier to disperse them and prevent them from clumping together to form lumps.
  • STIRRING: Stir the liquid medium vigorously until a vortex is formed. By adding the hydrocolloid powder slowly over the sides of the vortex, the speed of agitation will allow the particles to be more easily dispersed in the liquid. The product should not be added over the center of the vortex to prevent the powder from sticking to the agitator.
  • PREDISPERSION IN ALCOHOL/ OIL/ CARAMEL: Pre-dispersing the powder in a fluid medium with little free water such as alcohol, oil, caramel or brine allows for pre-dispersion. As there is no free water, the particles cannot hydrate, but they can separate from each other. Thus, when the aqueous medium is added to this pre-dispersion, the particles that are already separated will hydrate gradually and independently.

Once the particles are well dispersed and hydrated, we can move on to their dissolution so then the hydrocolloid will be fully functional in our food.

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