ORIGINAL PAPER A Novel Cryo-SEM Technique for Imaging Vegetable Oil Based Organogels Michael A. Rogers Æ Alexandra K. Smith Æ Amanda J. Wright Æ Alejandro G. Marangoni Received: 29 June 2007 / Revised: 8 August 2007 / Accepted: 10 August 2007 / Published online: 6 September 2007 Ó AOCS 2007 Abstract Gels were prepared by cooling dilute solutions (2% wt/wt) of 12-hydroxystearic acid (12-HSA) in canola oil and storing them at 30 °C for 24 h. The gel’s in-situ supramolecular network structure was imaged using four techniques: polarized light microscopy (PLM), 3-dimen- sional deconvolution polarized light microscopy (3DPLM), and cryo-scanning electron microscopy (cryo-SEM) of the xerogel and of an osmium tetroxide vapor fixed gel washed with isobutanol. Most of the canola oil was immobilized in the gel by fixation with osmium tetroxide therefore very little of the canola oil was removed during washing unlike the xerogel where all of the canola oil has been displaced. The in-situ supramolecular network structure as observed by PLM, was comparable to that seen through the new cryo-SEM method for fixed organogel. Cryo-SEM images of the xerogel did not show similar length scales or strand thickness as compared to the PLM images. The lengths of the network strands were much shorter for the xerogel as compared to the osmium tetroxide treated sample and the structures visualized by PLM. Furthermore, the thickness of the strands observed using PLM or cryo-SEM were in the size range of 3–10 lm while the xerogels had strands in the range of 0.01–0.1 lm thick. Therefore, the removal of canola oil from the gel using 80/20% v/v hexane/acetone with no fixation disrupted the supramolecular network. Introduction Organogel formation and its application has attracted a great deal of research attention over the past 15 years. Recently, the rate of publication focusing on organogels has increased steadily [1]. Interest in these complex systems stems from their abundant applications in foods, pharma- ceuticals, cosmetics and petrochemicals. However, the interest in ‘‘self-assembled fibrillar networks’’ (SAFINs) extends beyond food and pharmaceutical research. Many SAFINs are present in nature and include materials such as fibrous actin [2], clathrin [3], tubulin [4], keratin [5], insulin [6], collagen [7], silk [8], and amyloid fibrils which are associated with Alzheimer’s and other neurodegenerative diseases [9]. In these systems, as the gelator is cooled in solution it forms a super-saturated solution and microscopic phase separation occurs rather than crystallization events which entail macroscopic phase separation. These gelator molecules self-assemble in stochastic nucleation events with highly specific interactions promoting one-dimensional growth [1]. Molecular gels require small molecular weight gelators to self-assemble prior to supramolecular aggregation of these structures. The formation of SAFINs occurs when the solution or sol is cooled below its gelation temperature. In terms of a molecular gel, the sol is defined as a dispersion of solid particles in a colloidal solution. Generally, the concentration of the gelator molecule is below 2 wt% which represents the percolation concentration threshold for fibrillar species under quiescent conditions [1]. As the solution is cooled below the melting point of the 12HSA gelator molecule it forms a super-saturated solution causing the gelator molecules to self-assemble via sto- chastic nucleation [1]. This one-dimensional growth results in fiber formation which may be described as ‘crystal-like’ M. A. Rogers Á A. K. Smith Á A. G. Marangoni (&) Department of Food Science, University of Guelph, Guelph, ON, Canada N1G2W1 e-mail: amarango@uoguelph.ca A. J. Wright Department of Human Health & Nutritional Science, University of Guelph, Guelph, ON, Canada N1G2W1 123 J Am Oil Chem Soc (2007) 84:899–906 DOI 10.1007/s11746-007-1122-9