F Xanthan Gum

Posted by gary_admin 13/08/2018 0 Comment(s) Engineering Case,

 

Hydration of Xanthan Gum

Xanthan gum (E415) is a polysaccharide widely used for its thickening and stabilising effect on emulsions and suspensions, especially in sauces and dressings. It is also used to control ice crystal formation in frozen desserts such as ice cream. The product forms a gel structure which is shear thinning and is often used in combination with other rheology modifiers, particularly Guar gum as the two combine to give greatly increased effects.

 

The Process

Xanthan gum can be dispersed into hot or cold systems, and many grades are available, including some designed for easy dispersion. The powder has a strong tendency to form lumps when added to the water and a number of dispersion and hydration methods are used to try to overcome this. These vary according to the scale of production, other ingredients used etc. but include:

  • Slow addition of the powder into the vortex in an agitated vessel. Once dispersed mixing continues to allow the product to hydrate.
  • The gum may be premixed with other powdered ingredients such as sugars which reduces the formation of agglomerates by separating the particles.
  • Similarly the product may be dispersed into non-aqueous phase liquids such as oils. This is then added to the aqueous phase allowing the gum to hydrate.

 

The Problem

Dispersion of gums and thickeners using conventional agitators can give rise to several problems:

  • Agglomerates can easily form, even when the above steps are taken to reduce the risk. Agitators do not produce sufficient shear to rapidly break these down.
  • Potential full yield is difficult to obtain using traditional methods.
  • Many formulations contain unnecessarily high levels of gum to compensate for poor yield, increasing raw material costs.
  • Once viscosity increase has started, agitation of the solution and therefore powder dispersion becomes increasingly difficult.
  • Long mixing times are required to complete dispersion/hydration. This can degrade the gel.
  • Premixing powders or non-aqueous phase liquid with the gum adds to process time and costs.
  • Unhydrated gum can gradually hydrate during storage or subsequent processing, leading to undesired changes in product viscosity.
  • It is not possible to create high percentage gum solutions with traditional methods. Solutions of this type may be required in certain applications where water is limited in the formulation.

 

The Solution

A Silverson High Shear mixer can produce an agglomerate-free dispersion and fully hydrate Xanthan gum in a fraction of the time taken by conventional methods. This is achieved by the mixing/shearing action of the Silverson rotor/stator workhead. Operation is as follows:

Stage 1

The vessel is charged with liquid and the mixer is started. The gum is added to the water as rapidly as possible. The high speed rotation of the rotor blades creates a powerful suction which draws the liquid and powder into the workhead where they are rapidly mixed.

Stage 2

Centrifugal force drives the powder and liquid towards the periphery of the workhead, where they are subjected to intense high shear in the gap between the rotors and stator wall. The product is forced out of the stator and projected radially back into the body of the mix.

Stage 3

Fresh materials are simultaneously drawn into the workhead. In a short mixing cycle all the material passes many times through the workhead, progressively reducing the particle size and exposing an increasing surface area to the surrounding liquid, accelerating hydration.

 

The Advantages

  • Maximised yield/functionality allows products to be formulated with reduced gum content, cutting raw material costs.
  • Agglomerate-free mix.
  • Rapid mixing times.
  • Consistent product quality and repeatability.
  • Premixing of gum with powders or non-aqueous phase is not required.
  • Operator error is effectively eliminated.

The batch size, formulation, type of ingredients and the viscosity of the end product dictates which Silverson model is best suited to processing requirements - see overleaf.

 

Silverson “U” Series

  • Ideal for larger batches
  • Capable of rapidly incorporating large volumes of powders
  • Suitable for higher viscosity mixes
  • Single-piece dynamic mixing head designed for CIP

 

High Shear Batch Mixers

  • Suitable for batches of up to 1000 litres
  • Can be used on mobile floor stands
  • Can easily be moved from vessel to vessel
  • “V” Range mixers (illustrated) available for bulk powder incorporation

 

Silverson Flashblend

  • Ideal for larger batches
  • Capable of rapidly incorporating large volumes of powders
  • Minimised aeration
  • Minimised cleaning requirements
  • Controlled powder addition rate
  • Minimum operator input required
  • Suitable for higher viscosities

 

High Shear In-Line Mixers

  • Ideal for larger batches
  • Easily retro fitted to existing plant
  • Must be used in conjunction with an efficient intank agitator to wet out powder
  • Aeration free
  • Self pumping
  • Can be used to discharge vessel
  • Ultra Hygienic models available

 

High Shear Bottom Entry Mixers

  • Suitable for use on high viscosity products in conjunction with an anchor stirrer/scraper.
  • No immersed shaft - reduces cleaning requirements
  • Two-speed units available.Variable speed can be obtained with an inverter