Effect of emulsifiers and fat crystals on shear induced droplet break-up, coalescence and phase inversion

We have investigated the breakup and coalescence of food grade emulsions under dynamic conditions with a range of emulsifiers. Not unexpectedly, breakup of the emulsions varied with applied shear. The coalescence rate for an emulsifier free system with purified sunflower oil after the imposed shear was reduced, was measured at 1.2 × 10−2 s−1, which is similar to reported values for non-food systems but could be totally arrested by the use of Tween 80, other surfactants such as gelatin and Tween 20 were also used. Phase inversion of 40% tripalmatin with either Tween 20 or monopalmatin, which is an important industrial process, was shown not to occur in the absence of crystals. By adjusting the emulsifier concentration and hence the movement of the crystals we have shown that the crystallisation of triglycerides controls the process dynamics and ultimately the phase inversion temperature. Both of the former effects also help describe the need for an excessive amount of emulsifier when forming food grade nano-emulsions. Thus, we show that with a myritol emulsion with either Tween 20 or Tween 80, it is the back reaction of nano-emulsion coalescence that determines the final droplet size and not the initial energy input from the emulsification process.