Selective enrichment of symmetric monounsaturated triacylglycerols from palm stearin by double solvent fractionation

The aim of this study was to produce a fractionated palm stearin enriched in symmetric monounsaturated triacylglycerols (SMUT), such as 1,3-dipalmitoyl-2-oleoyl-glycerol (POP), 1-palmitoyl-2-oleoyl-3-stearoyl- rac-glycerol (POS), and 1,3-distearoyl-2-oleoyl-glycerol (SOS) using two-stage acetone fractionation. Palm stearin, containing 27.2 g/100 g total SMUT and 33.8 g/100 g tripalmitin was used as the starting material for the fractionation. A liquid fraction produced from palm stearin under the best conditions (temperature, 17 °C; volume-to-weight ratio of acetone to palm stearin, 8; crystallization time, 8 h) established in this study was free of tripalmitin (<0.5 g/100 g) and contained 44.5 g/100 g total SMUT (∼37.3 g/100 g POP, ∼6.4 g/100 g POS, and ∼0.8 g/100 g SOS). The yield of the liquid fraction was 61.3 g/100 g of the initial palm stearin weight. The liquid fraction was crystallized to further increase SMUT concentration. After fractionation at 4 °C for 24 h, a solid fraction with total SMUT content of 63.2 g/100 g (∼53.0 g/100 g POP, ∼9.1 g/100 g POS, and ∼1.1 g/100 g SOS) was obtained and its yield was 30.8 g/100 g of initial palm stearin weight. The resulting fractionated palm stearin would be suitable for use in preparing cocoa butter equivalents due to the high SMUT content.