Enzymatic Interesterification of Cold-Pressed Maqui (Aristotelia chilensis (Mol.) Stuntz) Seed Oil and Belly Oil from Rainbow Trout (Oncorhynchus mykiss) Through Supercritical CO2

Abstract

A new antioxidant lipid (AL) was synthesized from rainbow trout (Oncorhynchus mykiss) belly oil and cold-pressed maqui (CPM) (Aristotelia chilensis (Mol.) Stuntz) seed oil via enzymatic interesterification using Thermomyces lanuginosus in supercritical CO₂ medium. A Box-Behnken design with 15 experiments was employed, with the independent variables being the following: belly oil/CPM oil ratio (10/90, 50/50, and 90/10, w/w), supercritical CO₂ temperature (40.0, 50.0, and 60.0 °C), and supercritical CO₂ pressure (100.0, 200.0, and 300.0 bar) for enzymatic interesterification. A multiple optimization was conducted based on the response variables yield and eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and tocopherol contents. The optimized conditions for the AL synthesis were: 81.4/18.6 (w/w), 40.0 °C and 299.99 bar, respectively. The corresponding responses variables were: 77.10% for yield, 5.12 and 4.95 g·100 g^-1 total fatty acids for EPA and DHA, respectively, and 217.96, 4.28, 3.48, 64.48, and 6.39 mg·kg^-1 oil for α-tocopherol, α-tocotrienol, β-tocopherol, γ-tocopherol, and δ-tocopherol, respectively. A novel AL was successfully synthesized starting from two abundant natural resources commonly considered as by-products during industrial processing. In agreement with the high EPA, DHA, and tocopherol presence, this AL can be recommended to be employed in nutritional and therapeutic supplements, according to its health benefits, particularly concerning antioxidant and anti-inflammatory properties.

Keywords: Aristotelia chilensis (Mol.) Stuntz; DHA content; EPA content; RSM optimization; belly oil; cold-pressed maqui seed oil; enzymatic interesterification; rainbow trout; supercritical CO2; tocopherols.

Figure 1

Effect of independent variables of the interesterification process on yield (%). (a) Standardized Pareto diagram for the response variable yield (%). A higher value than the blue line mark indicates a significant effect, p < 0.05. (b) Estimated response surface. Diagram for the response variable yield (%) of supercritical CO₂ temperature (°C) vs. supercritical CO₂ pressure (bar) at constant belly from rainbow trout/cold-pressed maqui seed oil (w/w) ratio.

Figure 2

Effect of independent variables of the interesterification process on EPA and DHA (mg·kg⁻¹ oil). Panels (a,c): Standardized Pareto diagram for the response variable EPA and DHA (mg·kg⁻¹ oil), respectively. A higher value than the blue line mark indicates a significant effect, p < 0.05. Panels (b,d): Estimated response surface diagram for the response variable EPA and DHA (mg·kg⁻¹ oil). Belly oil from rainbow trout/cold-pressed maqui seed oil (w/w) relation vs. supercritical CO₂ pressure (bar) at constant supercritical CO₂ temperature (°C).

Figure 3

Standardized Pareto diagrams for the response variable tocopherols: (a) α-tocopherol, (b) α-tocotrienol, (c) β-tocopherol, (d) γ-tocopherol, and (e) δ-tocopherol. A higher value than the blue line mark indicates a significant effect, p < 0.05.

Figure 4

Estimated response surface diagrams for the response variable tocopherols: (a) α-tocopherol, (b) α-tocotrienol, (c) β-tocopherol, (d) γ-tocopherol, and (e) δ-tocopherol. Diagrams (a,b,c.3,d.3,e.2) show the effect of supercritical CO₂ temperature (°C) vs. supercritical CO₂ pressure (bar) at constant belly oil from rainbow trout/cold-pressed maqui seed oil (w/w) ratio. Diagrams (c.1,d.1) show the effect of belly oil from rainbow trout/cold-pressed maqui seed oil (w/w) ratio vs. supercritical CO₂ temperature (°C) at supercritical CO₂ pressure (bar). Diagrams (c.2,d.2,e.1) show the effect of belly oil from rainbow trout/cold-pressed maqui seed oil (w/w) ratio vs. supercritical CO₂ pressure (bar) at constant supercritical CO₂ temperature (°C).

Figure 5

RSM graphs for the desirability value based on the belly oil from rainbow trout/cold-pressed maqui seed oil ratio, supercritical CO₂ pressure, and supercritical CO₂ temperature: (a) belly oil from rainbow trout/cold-pressed maqui seed oil vs. supercritical CO₂ temperature, (b) belly oil from rainbow trout/cold-pressed maqui seed oil vs. supercritical CO₂ pressure, and (c) supercritical CO₂ temperature vs. supercritical CO₂ pressure.

Figure 6

Differential scanning calorimetry. (a) Comparison thermogram of cold-pressed maqui seed oil, belly oil from rainbow trout, and antioxidant lipid. (b) Comparison of variation in solid content (%) as a function of temperature (°C) for cold-pressed maqui seed oil, belly oil from rainbow trout, and antioxidant lipid (LA). (1) peak with low-melting point TAG (LMTAG); (2, 3, 4) peaks with medium-melting point (MMTAG).