Effects of extraction and fractionation pressures on supercritical extraction of cholesterol from beef tallow

Edible beef tallow was extracted by supercritical CO2 in a dynamic mode at pressures from 138 to 345 bars and temperatures of 40 and 50°C. The lipid fractions were collected at 34.5 bar/40°C. A retrograde behavior of lipid solubility was observed around 170–175 bar. The ranges of the cholesterol concentration [chol.], were 300–450 mg/100 g and 50–200 mg/100 g lipid for the fractions extracted at 138 bar and 345 bar, respectively. Beef tallow was also extracted with sequentially varied pressures of 138, 345 and 138 bars at 40°C and collected at 34.5 bar/40°C. The results showed that after 20 kg CO2 was used for extracting 100 g of loaded beef tallow the weight of the residual beef tallow remaining in the extractor was 23 g with [chol.] of 49 mg/100 g lipid. The lower [chol.] of the residual beef tallow represents a 60–70% reduction in cholesterol content, when compared with untreated beef tallow where [chol.] ranges from 130 to 160 mg/100 g lipid. To isolate lipid fractions containing higher [chol.], beef tallow was extracted at 345 bar/40°C and then fractionated into three separators connected in series with decreasing pressures of 173 bar, 117 bar, and 34.5 bar at 40°C, respectively. The results showed that the fractions collected from the third separator (34.5 bar) contained concentrated [chol.] ranging from 272 to 433 mg/100 g lipid. The fatty acid analysis revealed that the fractions containing high [chol.] generally consisted of high concentrations of myristic and palmitoleic acids but low concentrations of stearic and oleic acids.