The present study delineates the effect of the addition of non- ionic hydrophilic and hydrophobic food grade surfactants on the properties of the stearic acid and soybean oil oleogel. The oleogel was thoroughly analyzed by bright field microscopy, FTIR spectroscope, x- ray diffractometer, differential scanning calorimeter and mechanical tester. It was observed that the surfactants significantly altered the microstructure of the oleogels, which can be explained by the intermolecular interactions amongst the oleogel components. The alteration in the intermolecular interactions and the microstructures also resulted in the significant alterations in the thermal and the mechanical properties. It can be concluded that the properties of the stearic acid oleogels can be modulated just by adding surfactants in varied proportions so as achieve definite textural properties.
TopIntroduction
Stearic acid is a long-chain saturated fatty acid and has been used in many industrial applications (Piantoni, 2014; Sato & Boistelle, 1984). Stearic acid undergoes a polymorphic transformation during crystallization from crystallization solutions (Canselier, 1993; Maher, Croker, Seaton, Rasmuson, & Hodnett, 2014; Severino, Pinho, Souto, & Santana, 2011). There are 4 polymorphic forms of stearic acid, namely, A, B, C and E (Beckmann, Kämmer, Meier, & Boistelle, 1986; Sato & Boistelle, 1984). The polymorphs A and B are the commonly occurring polymorphs while crystallizing stearic acid from apolar solutions (Nissim Garti & Sato, 1986; N Garti, Wellner, & Sarig, 1980). Polymorph B of stearic acid appears as a leaf-like structure, whereas, polymorph A appears as a fiber-like structure. The crystallization process of stearic acid can be altered by adding food emulsifiers (e.g. Span 80, Span 60, Span 40, Tween 80, Tween 60 and Tween 20) in the crystallization solutions (N Garti, Wellner, & Sarig, 1981). Though the food emulsifiers have been used successfully to prevent fat bloom in chocolates by modifying the crystal structure of the fats (MENG, et al., 2013), our group has recently reported that Span 60 and Tween 20 promote the precipitation of stearic acid in oleogels as fiber-like and leaf-like structures, respectively (Uvanesh, Sagiri, Senthilguru, et al., 2016; Uvanesh, Sagiri, Banerjee, et al., 2016).