Application of enzymatic interesterification reactions for the manufacturing of stable food oleogels

In recent years, a growing focus on health and sustainability has driven interest in alternatives to traditional solid fats. Solid fats present a high content of saturated fatty acids, which are linked to health problems. Additionally, their production has strong environmental impacts. Therefore, locally available vegetable oils, known to be more sustainable and healthier, represent a better option. Nevertheless, liquid oils can’t substitute solid fats without chemical or structural modification. Oleogels are a possible solution to structure liquid oils and impart them a gel-like consistency that resemble solid fats. Oleogelation is a process in which high melting molecules with affinity with liquid oil create a network that traps the oil. Physically mixing a gelator and a liquid oil often leads to poor stability and leakage. To improve oleogel stability, the composition of the gelator and the oil might be adjusted using enzymatic interesterification reactions. Enzymatic interesterification uses a lipase to rearrange fatty acid chains on the glycerol backbone of triglycerides. When it is conducted between a mixture of liquid oil and saturated triglycerides, it’s possible to obtain oleogels that are more stable than those obtained via simple mixing. In fact, the enzyme can exchange unsaturated fatty acid chains with saturated ones through a series of hydrolysis and re-esterification reactions. The rearrangement of fatty acid chains leads to a triglycerides mixture with properties that differ from the original one. In this thesis, Thermomyces lanuginosus lipase immobilized on Immobead150 (TLL-Im) was studied to evaluate its effectiveness in obtaining stable oleogels from mixtures of liquid oils and tristearin (SSS). The optimal oil for the reaction was selected by studying the interactions of canola oil, high-oleic sunflower oil and soybean oil (SBO) with SSS. Physical blends of oils and SSS at varying concentrations were produced through an oleogelation process and analysed with Polarized Light Microscopy (PLM). Based on both their macroscopic and microscopic characterization, SBO and SSS physical blends proved the most stable against phase separation among the oils tested. However, their stability was still limited. Interesterification reactions were carried out to improve stability of SBO-SSS blends at 1 %wt, 10 %wt and 15 %wt of SSS. The resulting oleogels were characterized using PLM, Differential Scanning Calorimetry (DSC), synchrotron Small-Angle X-ray Scattering (SAXS) and Wide-Angle X-ray Scattering (WAXS). Their properties were investigated through a comparative analysis of both not interesterified (N_EIE) blends and interesterified (EIE) ones. Compared to their N_EIE counterparts, EIE samples appeared to be more stable against phase separation during storage. The crystal network of the EIE oleogels appeared to be more irregular, with different distribution of crystalline aggregates of smaller size. The thermal properties of the EIE samples were different from the physical mixtures, with lower melting and crystallization enthalpies. Furthermore, a shift towards lower values of on-set and off-set temperatures of crystallization and melting events was evident. The results obtained indicate that TLL-Im effectively catalyzed the interesterification reaction for the formation of oleogels from SBO and SSS. The observed differences between EIE and N_EIE samples demonstrate the method’s efficiency, suggesting potential for future developments in the design of low saturated fat food.