Temperature effects on the gelation of ethylcellulose oleogels

The parameters affecting the mechanical properties of ethylcellulose (EC) oleogels have been examined with respect to setting temperatures during gelation, as well as post-gelation storage stability. Gel samples were allowed to set at a variety of different temperatures (-20, 4, 20, 40, 50, 60, 80, 100 degrees C) for 24 h before incubation and mechanical testing at 25 degrees C. An increase in gel strength was observed with increasing setting temperature due to the formation of a more efficient polymer-polymer hydrogen bonding network. The role of intermolecular hydrogen bonds in the formation of the EC network was confirmed using a rheological approach where a decrease in the storage modulus was observed with increasing temperature. Higher gel strength was found when the molten gel is heated above the polymer melting temperature (T-m) or high polymer concentration was used, leading to greater concentration of hydrogen bonding sites. These results further exemplify the role of hydrogen bonds in the formation of the EC gel network. The addition of surfactants (SMS and GMO) increased gel strength, but did not affect the setting temperature effect. However, this behavior was not observed when mixing above Tm or when high polymer concentration were employed. EC oleogels demonstrated the ability to re-arrange with respect to the last setting temperature to which they were subjected. This behavior was referred to as the temperature history memory effect. Time-temperature experiments demonstrated the mechanical stability of EC oleogels over a period of three months at the high temperature setting treatment. (C) 2015 Elsevier Ltd. All rights reserved.