Document Type : Research Article
Authors
Department of Food Science and Technology, Faculty of Agriculture, University of Tabriz, Tabriz, Iran
Abstract
Introduction
Growing public awareness regarding the link between diet and chronic diseases is driving a significant demand for healthier food formulations. The high content of saturated and trans fatty acids in many bakery products is a major cause of cardiovascular disease, type 2 diabetes, and obesity. Consequently, the World Health Organization (WHO) recommends replacing fats like butter and shortening with vegetable oils rich in unsaturated fatty acids. This presents a major challenge for the food industry, as solid fats play a key role in creating desirable sensory properties like texture and mouthfeel, and their direct replacement with liquid oils leads to a significant decline in product quality.
Oleogels, formed by creating a three-dimensional network of oleogelators within vegetable oils, have been proposed as a structured alternative to solid fats. Numerous studies have successfully demonstrated the potential of oleogels as fat replacers in various bakery products. For instance, beeswax-based oleogels have been shown to improve the nutritional profile of cakes without compromising quality attributes. However, most research has focused on wax-based oleogels. There is a scarcity of studies that systematically investigate and compare the performance of low-HLB emulsifiers (such as monoglyceride, polyglycerol ester, and Span 60) used alone for the complete replacement of butter in a cake formulation. Furthermore, butter has technological limitations, including a poor ability to trap and stabilize air bubbles, which can affect cake volume and texture. Therefore, this study aimed to investigate oleogels using monoglyceride, polyglycerol ester, and Span 60 emulsifiers in cold-pressed peanut oil (an oil chosen for its excellent nutritional profile) and evaluate their potential as a functional and healthy butter replacement in butter cake.
Materials and Methods
In this research, peanut oil was first extracted using a cold-press machine. Oleogels were then prepared by adding 12% (w/w) of monoglyceride (MG), polyglycerol ester (PG), and Span 60 (SG) to the oil, followed by placing it in a 75°C water bath. The physicochemical properties of the oleogels including crystal morphology (light microscopy), oil holding capacity (OHC) via centrifugation, thermal behavior (Differential Scanning Calorimetry - DSC), firmness (back extrusion test), molecular structure (Fourier Transform Infrared Spectroscopy - FTIR), and oxidative stability (peroxide value) were evaluated. Finally, butter cakes were prepared with complete replacement of butter by the selected oleogels (MG and PG). The cakes were then analyzed for firmness and sensory evaluation (color, taste, texture, and overall acceptability).
Results and Discussion
The type of oleogelator significantly impacted the oleogel properties, an effect dictated by the underlying crystal microstructure. Microscopic images revealed that the MG formed a dense, uniform network with fine, needle-like crystals. In contrast, PG also formed needle-like crystals, but they were larger and less dense, while SG created a weak network containing large, rosette-like crystals and significant spaces. This structural difference was directly reflected in the macroscopic properties. The dense network of MG was highly effective at trapping oil, resulting in the highest Oil Holding Capacity (100%) and the greatest firmness. Conversely, the sparse network of SG resulted in poor oil retention and minimal firmness, demonstrating a clear structure-function relationship. Thermal analysis by DSC further supported these findings. MG showed the highest thermal stability, evidenced by its high melting enthalpy, which corresponds to the energy required to disrupt its well-ordered crystalline network. FTIR analysis confirmed that the network was stabilized by non-covalent interactions, such as hydrogen bonds and van der Waals forces. Furthermore, the oleogels demonstrated improved oxidative stability. The strong physical barrier provided by MG and PG networks showed that the rate of peroxide value increased over 30 days compared to pure oil.
In the cake evaluation, samples formulated with MG and PG had significantly softer texture than the control cake made with butter. This is attributed to the enhanced air-holding capacity of the firmer oleogels and the inherent emulsifying properties of the gelators. Crucially, the sensory analysis revealed that the cakes containing oleogel scored higher texture and taste value, and their overall acceptability score was equal to or even higher than that the control sample.
Conclusion
The findings demonstrated that the oleogelator type dictated the physicochemical and structural properties of oleogels. The monoglyceride-based oleogel exhibited superior performance, showing the highest oil holding capacity, thermal stability, and firmness, followed by the polyglycerol ester-based oleogel. Microstructural analysis confirmed that these properties were linked to the crystal morphology, .FTIR analysis verified that gelation was driven by non-covalent interactions. Most importantly, when monoglyceride and polyglycerol ester oleogels used as a complete butter substitute in butter cakes, produced cakes with a softer texture and received overall acceptability scores equal to or higher than the control. Therefore, this study confirms the high potential of monoglyceride and polyglycerol ester-based oleogels to develop healthier bakery products. Despite promising results, the study had limitations, including the use of a single oil type and one oleogelator concentration. Textural and sensory analyses could also be more comprehensive. Further research need to focus on evaluating these oleogels in other bakery products, investigating long-term stability, and optimizing the production process.
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