Effect of processing conditions on the structure of mono stearin-oil-water gels

The effect of processing conditions on the formation and stability of a gel comprised of oil, water, monostearin and stearic acid was studied. Processing conditions (homogenization rate (10,000-30,000 rpm), cooling rate (0.05-20 degrees C/min), homogenization temperature (70-95 degrees C)) had no effect on the initial storage modulus and melting temperature of the gel. Salt (NaCl) addition to the aqueous phase in the range 0-0.25% did not affect these parameters either; however, 0.5% salt addition lead to a similar to 2 degrees C decrease in melting temperature and a doubling of the storage modulus. Optimal preparation conditions for the gel were mainly determined from its microstructure by polarized light microscopy - a smaller globule size and a more homogenous size distribution were considered a desirable feature. Optimum conditions included homogenization rates greater than 20,000 rpm, cooling rates above 6 degrees C/min, homogenization temperatures above, but close to, the Krafft temperature of monostearin (72 degrees C), and 0% salt concentration. The gelation temperature decreased by 2 degrees C with each 1 degrees C/min increase in cooling rate, from 1 degrees C/min to 5 degrees C/min. (c) 2007 Elsevier Ltd. All rights reserved.