Thermomechanical Characterization of Oleogels Elaborated with a Low Molecular Weight Ethyl Cellulose and Monoglycerides

Abstract

The interaction between a low molecular weight (i.e., 19 kDa) ethyl cellulose (EC) and a commercial monoglyceride (MGc) in the development of EC-MGc oleogels was evaluated through rheological, DSC, and infrared spectroscopy measurements. The oleogels were developed through cooling (80°C to 2°C, 10°C/min) vegetal oil solutions of EC at concentrations above (10%), below (7%), and at EC’s minimal gelling concentration (8%), and in EC-MGc mixtures using MGc below its minimal gelling concentration (0%, 0.1%, 0.25%, 0.5%, 1%). At 0.10% MGc most of the monoglycerides developed hydrogen bonds with the EC developing oleogels structured through EC-monoglyceride-EC interactions. As the EC concentration increased the EC-0.1% MGc oleogels achieved higher elasticity (G’) than the EC oleogels. Using MGc concentrations ≥ 0.25% the excess of monoglyceride increased the oil’s relative polarity favoring the EC-EC over the EC-monoglyceride-EC interactions. Below 10 °C the monoglycerides in the oil crystallized within the free spaces of the entangled EC fibers acting as active filler. Thus, at the same EC concentration the EC-0.25% MGc, EC-0.50% MGc, and EC-1% MGc oleogels achieved higher G’ than the corresponding EC-0.10% MGc oleogels (P < 0.01). This behavior was more evident as the EC concentration increased. The rheological measurements during cooling showed that below 40 °C the EC went through a structural rearrangement that decreased the oleogels’ elasticity. Since the structural rearrangement was cooling rate, EC and MGc concentration dependent, these factors could be used to tailor the rheological properties of oleogels developed with low molecular weight EC.