Comparing the crystallization and rheological behavior of organogels developed by pure and commercial monoglycerides in vegetable oil.

We investigated the crystallization and rheological behavior of organogels developed with commercial (MSGC) and pure (MSGP) monoglycerides in safflower oil solutions (0.5% to 8% wt/wt). The MSGC was composed of 1-mono-stearoyl-glycerol (1-MSG, 37.7%) and 1-mono-palmitoyl-glycerol (1-MPG, 54.0%), and the MSGP essentially by 1-MSG (93.51%). The elastic (G') and loss (G″) moduli of the MSGC and MSGP-oil solutions were measured from 80°C until achieving 5°C, and then during isothermal conditions. The d(G')/d(time) rheograms, where d(G')/d(time) is the difference in G' between subsequent time-temperature conditions during cooling, followed closely the phase transition observed by the monoglycerides (MG). The d(G')/d(time) profile showed that the formation of the inverse lamellar α mesophase provided a limited structure to the vegetable oil. In contrast, the crystallization of the sub-α phase in the MSGC-oil system, and of the sub-α1 and sub-α2 phases in the MSGP-oil system structured the vegetable oil through the uptake and retention of oil within their microstructure. Additionally, smaller crystals formed the three-dimensional crystal structure in the MSGC organogels. This is in comparison with the larger crystal size observed in MSGP organogels. Nevertheless, for a similar MG concentration the MSGC organogels showed higher G' and solid fat content (SFC) than the MSGP organogels, and the differences were greater as the MG concentration increased. We consider that the mixed sub-α structure developed by 1-MSG and 1-MPG in the MSGC-oil systems favored the incorporation and retention of higher amounts of oil, in comparison with the sub-α1 and sub-α2 structures developed just by 1-MSG in the MSGP-oil systems.