Effect of type of emulsifier and co‐solvent on the morphology, thermal, and mechanical properties of γ‐oryzanol and β‐sitosterol organogels

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AbstractThe objective of this study is to investigate the effect of addition of various types of emulsifiers on the morph/ology and thermal and mechanical and properties of organogels. For the preparation of the organogels, γ‐oryzanol and β‐sitosterol mixed at 60:40 w/w ratio were dissolved in decane containing various types of emulsifiers, including Span 80, PGPR, and lecithin, and co‐solvents (butanol and pentanone). The firmness, morphology, and thermal properties of the organogels were studied. SEM micrographs showed branched and twisted strands of the tubular network within the gels prepared in decane. Addition of emulsifiers and co‐solvents increased the polarity of the continuous oil phase and noticeably changed the alignment of the tubules. More linear tubular structures that resemble ribbons with elongated tubules were observed. The firmness of the organogels dropped with addition of emulsifiers and co‐solvents, except for Span‐80, where the firmness is initially increased up to 10% w/w and then decreased. The firmness of the gels prepared with PGPR, lecithin, pentanone, and butanol decreased linearly on increasing the respective emulsifier or co‐solvent concentration between 1% and 20% (w/w). The organogels prepared with Span‐80 were stronger than those prepared with PGPR and lecithin. Moreover, the gels prepared with pentanone were stronger than those prepared with butanol. In addition, the gel‐solution transition temperature of the organogels decreased with increasing emulsifier and co‐solvent concentration. The addition of the emulsifiers seems to interfere with the self‐assembly of the tubular structure and disturb the organization of the hydrophobic tail of oryzanol‐sitosterol in the continuous decane phase. This prevents the formation of a complex branched tubular network resulting in weaker gels.