Supercritical carbon dioxide processing for the extraction and delivery of flax bioactives

• Author / Creator

  Comin, Lauren

• Flax is an oilseed praised for high omega-3 oil, fiber and lignan content. Supercritical carbon dioxide (SCCO2) can be used as a green solvent alternative to process flax bioactives. SCCO2 extraction was used to remove lignan Secoisolariciresinol Diglucoside (SDG) from full fat and defatted whole flax seeds and hulls and hydrolyzed whole seed. Temperature, pressure and addition of ethanol modifier had no effect on CO2 loading of SDG. However, when seed was pre-hydrolyzed, significantly higher loading was obtained compared to other seed treatments, as hydrolysis reduced the size of SDG macromolecules and released free SDG. SCCO2 dried aerogels were formed from β-glucan and flax mucilage. Compared to 10% mucilage, 5% β-glucan aerogels had lower surface area (165.55 m2/g vs 201.13 m2 /g) and maintained less of their hydrogel volume (37.62% vs 56.90%), but had a similar density (0.19 g/cm3 for β-glucan and 0.16 g/cm3 for mucilage). SCCO2-dried aerogels showed significantly less volume shrinkage compared to air-dried gels and had a more uniform structure compared to freeze-dried gels. Pregelatinized corn starch (PGS) and β-glucan aerogels were impregnated with bioactive lipids. The effect of processing conditions, including temperature, pressure and flow mode were dependent on the complexity of the lipid, as well as the partition of the lipid between the matrix and the SCCO2 phase. Oleic acid had higher impregnation efficiency in PGS compared to flax oil because of higher purity and smaller molecular size and weight. For flax oil, its low solubility in SCCO2 limited its impregnation in PGS. For β-glucan aerogels, depending on when oil is incorporated (before, after or during drying), different impregnation efficiencies were achieved. FTIR and SEM results suggest oil has an effect on the gelation of β-glucan. SDG concentrate, Beneflax, was added to β-glucan and mucilage aerogels prior to SCCO2 drying. When Beneflax was added prior to gelation, regardless of technique, SDG concentration was not different. However, when hydrogels were impregnated by soaking in 70% ethanol Beneflax solutions, SDG recovery from aerogels was significantly lower. Overall, results suggest new uses for food-grade polymers using SCCO2 processing,including the formation of aerogels and impregnation of flax bioactives.

• Subjects / Keywords

  • Aerogel
  • Flax
  • Impregnation
  • Supercrtical CO2
  • Lignan

• Graduation date

  Fall 2011

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3SM6G

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.