Emulsions - Articles and news items
Issue 5 2015 • 28 October 2015 • Geoff Talbot, The Fat Consultant
An emulsion is a fine dispersion of liquid droplets in another liquid continuous phase in which the droplets are immiscible or insoluble. In food terms, the two phases are generally oils and water. Food emulsions tend to take one of two forms – either oil in water (O/W), e.g. cream and mayonnaise, or water in oil (W/O), e.g. butter and spreads – although more complex duplex emulsions such as water in oil in water (W/O/W) and its opposite oil in water in oil (O/W/O) are also possible. In simplistic terms, water is water but oils can differ in their properties and functionality so what is the best oil to use for a specific food emulsion? In this article, the basic properties of fats that play a role in this choice will be described and how these are important in food emulsions will be discussed…
Issue 3 2012 • 4 July 2012 • Dr Henelyta Ribeiro, Global Project Leader, Unilever
The production of emulsions with very low mechanical stress and a lower energy input than conventional mechanical methods have been developed in recent years and will be presented in this overview, the so-called membrane and microchannel emulsification. They are efficient processes due to their operational flexibility, reproducibility, straightforward upscaling and reduction in the ratio of equipment size to production capacity, which may lead to novel process intensification1.
The literature has reported distinct membrane and microchannel emulsification technologies developed in various laboratories around the world (Japan, Germany, UK, Switzerland, the Netherlands, France and USA). Membrane emulsification methods include cross-flow, dead-end (also called premix), rotating and vibrating processes. Microchannel emulsifica – tion can be performed using T and Y-junctions, and also by multiple microchannels as the grooved and asymmetric straight-through array types2. Both technologies are able to produce monodisperse oil-in-water (O/W) and water-inoil (W/O) emulsions. It depends on the surface hydrophilicity or hydrophobicity of the membrane respectively. Multiple emulsions (W/O/W) with uniform droplet sizes can also be successfully manufactured.
Issue 6 2011 • 4 January 2012 • John Coupland, Professor of Food Science, Penn State University
Very often, the most important ingredients in food are those present in the smallest quantities. Flavours, phytochemicals and micronutrients compounds may only be added at parts per million levels but their presence is essential to determining the functional properties of the food. While these molecules differ in both structure and function, many share common features. First, they are very poorly water-soluble, typically less than a few grams per litre, but are often much more soluble in oils. The partitioning between a lipid phase and water is given by a partition coefficient, the ratio of concentrations in each phase at equilibrium.
For many of the molecules of interest, the partition coefficient is in the order one thousand in favour of the lipid phase. Second, they are readily destroyed by chemical oxidation and/or acid hydrolysis. Interestingly, the metals that catalyse their oxidation and the acids that cause hydrolysis are much more soluble in water but much less soluble in oil. Finally, they are expensive; flavours in particular can be huge contributors to the overall cost of the product. This last point means that there is a commercial pressure to ensure all of the molecules added to the food are active within the food. To begin to solve this problem we need to consider how the molecules are distributed within the food.
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