Chapter 20 - The impact of fine particles and their wettability on the coalescence of sunflower oil drops in water

Abstract

The coalescence of sunflower oil (SFO) drops plays an important role in the production of low fat spreads. Typically, as part of the production process, a phase inversion step is required during cooling and agitation and the inversion is strongly dependent on coalescence rates. This chapter describes the process by which coalescence rates of 5% sunflower oil drops in water are measured under agitated conditions with and without fine particles being present. When using polymer particles of less than 10 μm in size, coalescence rates could be increased or reduced, the extent depending on their concentration and wetting characteristics. The greatest enhancement occurs with 1.4g/L PMMA particles wetted by oil and partially wetted by water. With monoglyceride fat crystals, similar results are found with very dramatic increases in coalescence with 1 to 2% fat with respect to sunflower oil while at 5%, coalescence is totally repressed. Monoglyceride fat crystals in the form of the predominantly fully saturated monoglyceride Hymono 7804 produce a similar range of effects following a similar speed reduction. These effects are found over a concentration range up to 5% w/w relative to 5% SFO dispersion in water with a large enhancement of coalescence in the 1 to 2% range. Coalescence is also enhanced at the 1 to 2% w/w concentrations due to a lowering of temperature alone from 60 °C to 20 °C when agitating at 240 rpm just as is required in the production of low fat spreads; but at 5% w/w, coalescence is totally repressed.