Extraction and Encapsulation of Squalene Rich Cod (Gadus macrocephalus) Liver Oil Using Supercritical CO2 Processes for Oxidative Stability Enhancement

Abstract

Cod liver oil (CLO) was extracted using conventional hexane and pressing methods or ecofriendly supercritical carbon dioxide (SC-CO2). The extraction main parameters including temperature (A), pressure (B), and CO2 flow rate (C) were optimized using response surface methodology. The oil chemical composition, safety, thermostability, and biological properties were characterized. The optimized SC-CO2 extraction conditions were A = 49°C, B = 29.9 MPa, and C = 4.97 mL/min. Time-dependent extraction curves revealed a 68%, 85%, and 89% CLO recovery in 5, 15, and 20 h, respectively. SC-CO2-extracted oil contained the highest squalene (≈150 µg/mL) and vitamins D and K concentrations and the lowest toxic heavy metal levels. Thermogravimetric analysis indicated that SC-CO2-extracted oil was more susceptible to thermal degradation because of its high purity. SC-CO2-extracted CLO exhibited radical scavenging and antimicrobial functions and was cytotoxic for cancer cells suggesting its potential use in the nutraceutical industry and novel functional material designs. Solid-lipid particles(SLPs) were obtained using particle production from gas saturated solutions (PGSS) process, which is a clean process, with the wall matrix poly-ethylene glycol. The yield and encapsulation efficiency were 71.13±0.44%, 35.52±0.22%, respectively under the conditions of 25 MPa, 4:20 (SCO:PEG, w/w); 9-PEG. Bulk density and tapped density were 0.30±0.02 g/cm3, 0.33±0.02 g/cm3, respectively, at the 9-PEG, and Carr’s index value was 9.09 ±0.97. The particle size was 315.83 nm at 9-PEG, and the typical form of powder from PGSS process was confirmed through a scanning electron microscope. The presence of squalene in the CLO and the encapsulation of CLO in the SLPs were confirmed through fourier transform infrared spectroscopy analysis. The crystallinity of SLPs were confirmed using the X-Ray diffractometer analysis and Differential scanning calorimiter analysis. Antioxidant activity evaluation was performed, and 9-PEG was showed the highest activity at ABTS+ 142.60±5.71 mgTE/g, at DPPH 30.38±1.44 mgTE/g, respectively. Oxidation stability evaluation of SLPs was performed, peroxide value of CLO changed 7.46±0.21 meq/kg to 22.50±0.30 meq/kg, whereas SLP did not show a significant change.