Sustainable alcoholysis of soybean oil in supercritical carbon dioxide and analysis of the structured lipids with nuclear magnetic resonance spectroscopy
Date
2019-09
Authors
Vafaei, Nazanin
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Abstract
Producing structured lipids (SLs) from oils that contain high levels of unsaturated fatty acids (UFAs) can be one of the keys to solving issues associated with trans and saturated fats in the food industry. Due to various nutritional and functional properties of SLs, they fulfill different applications in the food and pharmaceutical industries. This thesis has focused on production of two SLs - a high monoester mixture of soybean oil (HHMS) and a soybean oil-based DAG oil (SDO). HMMS can be used as an emulsifier mixture due to its rich composition of monoglycerides (MGs), diglycerides (DGs) and propylene glycol esters (PGEs). SDO can be used as a low caloric oil due to having a higher amount of 1,3-DGs compared to conventional oils. The main objective was producing and analyzing SLs in an environmentally-friendly manner. Enzymatic alcoholysis under supercritical CO2 (SCCO2) was chosen for production of both HMMS and SDO. Nuclear Magnetic Resonance (NMR) using 1H, 13C, and 31P spectroscopy was utilized for analysis of SLs. In the production of HMMS, enzyme and time significantly influenced the level of 1-MGs, 2-MGs and 1,2-DGs. The 31P-NMR quantification of HMMS demonstrated that out of the total amount of MGs produced, they are composed of 212.9% of 2-MG and 40.3% of 1-MG at a pressure of 276 bar, at 70 °C, and an enzyme load of 10% (w/w) following 4h of enzymatic alcoholysis. Among the three methods, 31P-NMR proved to be a practical methodology with high-reproducibility for the precise detection and quantification of partially esterified glycerols and free fatty acids in the SLs. After an 8h enzymatic alcoholysis in SCCO2, the percentage change of total DGs in SDO increased dramatically (1700%) compared to the same reaction at atmospheric pressure. A total DG content of 44% (w/w), containing 60% of the healthier 1,3-DG isomer versus 40% 1,2-DG, was obtained at a pressure of 80 bar, at 60 °C, and an enzyme load of 10% (w/w) following 8h of enzymatic alcoholysis. Integration of greener alternative processes of production and practical analysis of SLs contributes to the development of complex lipid mixtures that have functional and nutraceutical properties.
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Keywords
Enzymatic reactions, Soybean oil, Supercritical carbon dioxide, Structured lipids, NMR