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Influence of Minor Oil Components on Sunflower, Rice Bran, Candelilla, and Beeswax Oleogels

Scharfe, Maria; Niksch, Jonas; Flöter, Eckhard

The impact of the solvent composition on wax oleogels is addressed by (1) increasing polar components (PC) in sunflower and canola oil through thermal treatment and (2) removing minor components from untreated oils by column chromatography. Subsequently, oleogels are produced at 0.05 and 10 °C min−1 using 4% or 10% w/w of either sunflower, rice bran, candelilla, or beeswax. Oleogels firmness, break‐up behavior during amplitude sweeps, and gelation and dissolution are studied using penetration tests, rheology, and differential scanning calorimetry (DSC), respectively. Moreover, the crystal morphology of 4% w/w samples, gelled at 10 and 0.05 °C min−1, is studied using bright field microscopy. Distinct effects caused by the presence or absence of PCs on the characteristics mentioned above are observed, depending on the wax type. The formation of highly ordered wax crystal structures is favored in oils without PCs and low cooling rates. Data on gel formation and dissolution reveal a decrease in wax solubility in the absence of PCs. In contrast, the critical gelation concentration (CGC) decreases when PCs are present, independent of their concentration, indicating that PCs aid network formation. Moreover, the break‐up behavior during oscillatory stress is significantly different, leading to more network fragments and higher energy dissipation with increasing strain. Practical applications: It is found that the oil composition, in particular, the fatty acid composition of TAGs and dissolved minor polar oil components, profoundly affect wax oleogel properties. Although not all mechanisms leading to these changes can be unraveled within this study, a fundamental understanding of solvent composition's role on oleogel formation, dissolution, and network properties is vital in the light of product applications. Moreover, trustworthy and comparable oleogel research can only be achieved if the impact of solvent composition is considered in experiments. That way, the capability of oleogels for industrial applications might be maximized. For that, a detailed characterization of oil quality, particularly the fatty acid composition and presence of minor polar components, is required to conduct reliable scientific work in oleogel research.
Published in: European Journal of Lipid Science and Technology, 10.1002/ejlt.202100068, Wiley