Application of DSC analysis to study oil gelation

Over the last decades, overweight and obesity have reached critical levels all over the world, increasing risks of life-threatening diseases, such as cardiovascular disease and cancer. This has been mainly attributed to eating habits including a high consumption of palm oil or hydrogenated fats rich in saturated and trans fatty acids. The EU is asking for actions and strategies to improve the nutritional value of lipid-containing foods, thus assuring healthier and more sustainable diets, ultimately reducing health-related costs. One of the most innovative and promising ways to face these issues is oil gelation (oleogelation). This is a relatively novel strategy by which liquid oils are structured into semi- solid materials, called oleogels, by exploiting the structuring ability of defined molecules in oil. The interest in oleogels has increased dramatically in the last decade due to their potential as replacers of hard stock fats in different foods, such as bakery products, ice-cream, chocolate-based products. Beside their potential use as fat-replacers, oleogels have been recently proposed as functional components able to modulate lipolysis as well as the delivery of bioactive lipophilic molecules. This aspect could open new horizons for their use as a tool to improve food health functionality as well as energy management deriving from lipid ingestion. Based on these considerations, the present research studied the effect of gelator molecules on the structural properties of oleogels obtained by using sunflower oil (SO) or extra virgin olive oil (EVOO). To this aim, a selection of gelators, i.e., rice wax (RW), monoglycerides (MG), ethyl-cellulose (EC) and γ-oryzanol and β-sitosterol (PS) were considered at 10% w/w concentration. In this context, differential scanning calorimetry (DSC) analysis was applied to characterize the oleogelators and oleogels thermal properties as well as to study their destructuring behavior upon heating. Beside thermal properties, to better study system structure, macro- and microscopic appearance as well as oil absorbing capacity, and rheological properties were evaluated. Both SO and EVOO were efficiently gelled by the selected molecules, showing self-standing appearance and good capacity to bind oil. However, the gelator type definitively affected the gel macro and micro characteristics. Considering thermal properties, all oleogels revealed a broad endothermic peak with lower Tpeak as compared to neat gelators. This behavior was expected and is attributable to the initial disaggregation of the network in oil followed by the melting of crystals. Beside other analytical methodologies needed to characterized oleogel structure, DSC analysis resulted fundamental to understand the susceptibility of oleogel structure to temperature changes. This information is crucial in the attempt to use oleogel in food applications, being foods subjected to different temperature changes during food processing.