Optimization of solid fat content and crystal properties of a trans-free structured lipid by blending with palm midfraction.

The optimization of solid fat content (SFC) and crystal properties of trans-free structured lipids (SL) synthesized by incorporating stearic acid into canola oil was investigated. The SLs were blended with varying amounts of palm midfraction (PMF). The SFC and crystal polymorphism were improved. The addition of sucrose stearate (S-170), sorbitan tristearate (STS), and distilled monoglycerides (DMG) to one of the blends, SL40:PMF (70:30, w/w), did not improve crystal polymorphism but had significant effects on crystal morphology. The emulsifiers significantly delayed crystal growth, resulting in smaller crystal sizes as compared to the control. They were unable to inhibit the formation of granular crystals (30-140 microm), which are undesirable in margarine, after 4 weeks of storage at 0 degrees C. Blends treated with S-170 and STS showed many small evenly distributed crystals interspersed with large crystal aggregates (after 4 weeks of storage), whereas the blend treated with DMG and the control showed irregularly shaped globular crystals, also interspersed with large crystal aggregates. However, these crystal aggregates were not observed upon visual and physical examination and may therefore not impart the sensory properties of the finished products negatively.