Effect of Tween 20 on structure, phase-transition behavior and mechanical properties of monoglyceride oleogels

The aim of this study was to investigate the impact of the addition of a non-gelling non-ionic surfactant, Tween 20 (Tw20), at varying weight ratios with monoglycerides, MGs (0 – 20 g Tw20 to 10 g of MGs as structurant /100 g olive oil) in the crystalline network of the MGs-based oleogels. Several analytical methods such as differential scanning calorimetry (DSC), confocal and polarized optical microscopy, rheometry, and infrared spectroscopy were employed for the characterization of the oleogel structures. The DSC and FT-IR provided evidence that Tween 20 affects the MGs network structure in the oleogels. With addition of Tween 20 the crystal size and the melting/crystallization temperatures of the MGs crystal polymorphs were altered, along with a strengthening of the oleogel structure. Moreover, the presence of Tween 20 in the MGs oleogels accelerated the transformation of the higher free energy crystal forms (α-crystals) to the more thermodynamically stable β-polymorph of the MGs. Apparently, an oil-in-oil emulsion gel is being formed with the MG crystalline entities acting as Pickering particles around the oil/Tween 20 droplets in the oleogel structure. These findings provide valuable information on the synergistic effect of a non-ionic surfactant on monoglyceride-based oleogels, which could be beneficial in constructing multi-component lipid-phases for potential food or cosmetic applications.