Supercritical fluid extraction of oils from apple seeds: Process optimization, chemical characterization and comparison with a conventional solvent extraction

Oils from apple seeds were extracted with the application of supercritical fluid (SFE) and Soxhlet techniques. The effect of SFE experimental variables such as pressure (10-30 MPa), temperature (40-60 degrees C) and carbon dioxide flow rate (1-8 L/h) on the yield, antioxidant activity and total phenolic content was investigated using a central composite design. The experimental data were fitted with a second-order polynomial equation using regression analysis. The maximum yield, obtained at the optimum processing conditions (24 MPa, 40 degrees C, 1 L/h of carbon dioxide flow rate, 140 min) was 20.5 +/- 1.5% (w/w). For comparison, the yield from Soxhlet extraction was 22.5 +/- 2.5% (w/w). Both techniques produced an oil with a fatty acids profile rich in linoleic acid. However, the extract from SFE was higher in linoleic acid (63.76 +/- 4.96 g/100 g(oil)) than that achieved by Soxhlet (49.03 +/- 3.85 g/100 g(oil)). Despite the higher unsaturated fatty acids content, SFE extracts reported a higher oxidative stability (21.4 +/- 1.2 h) compared to that one extracted by Soxhlet (12.1 +/- 1.1 h). This result was expport addressing the extraction of apple seed oil by supercritical fluid at pressures lower tha The most abundant phenolic compound found in the extract was phloridzin (2.96 +/- 0.046 mu g/gs(eed) in SFE oil and 1.56 +/- 0.026 mu g/gs(eed) in Soxhlet). Instead, amygdalin, one of the antinutrients present in seeds, was not detected in the SFE oil. Industrial relevance: The present study provided results addressing the extraction of apple seed oil by supercritical fluid at pressures lower than 30 MPa. The process allowed extracting an oil that was rich in unsaturated fatty acids, oxidative stable thanks to the high antioxidant activity, and free from anti-nutritional compounds.