Extraction of lignans, proteins and carbohydrates from flaxseed meal with pressurized low polarity water.

This study examined the application of pressurized low polarity water (PLPW) extraction of lignans, proteins and carbohydrates from defatted flaxseed meal. Key processing conditions included temperature (130, 160, 190 C), solvent pH (4, 6.5 and 9), solvent to solid ratio (90, 150 and 210 mL/g) and introduction of co-packing material (0 and 3 g glass beads). The addition of 3 g glass beads increased the yields for all target compounds. The maximum yield of lignans (21 mg/g meal) was obtained at 170 C with solvent to solid ratio of 100 mL/g meal at pH 9. Optimal conditions for protein extraction were pH 9, solvent to solid ratio of 210 mL/g meal and 160 1C. Total carbohydrates recovery was maximized at 215 mg/g meal (50percent recovery) at pH 4 and 150 1C with solvent to solid ratio of 210 mL/g meal. The increase of temperature accelerated extraction, thus reducing solvent volume and time to reach equilibrium. For the extraction of proteins and carbohydrates, however, a temperature of 130 to 160 C is recommended, as proteins and carbohydrates are vulnerable to  thermal degradation. (Authors abstract)

Dietary sources of phenolics are beneficial for disease prevention. Flaxseed is one dietary source which contains considerable amount of phenolics namely lignans that have beneficial health effects. Therefore, incorporation of flaxseed lignans into foods is particularly attractive from the perspective of development of functional foods with specific health advantages.
Flaxseed lignans have traditionally been extracted using organic solvents particularly ethanol and acetone and proteins and carbohydrates have been extracted with NaCl solutions and water, respectively. Water can be used to replace organic solvents. It can be treated as a multi-polarity solvent by manipulating its temperature and pressure. Pressurized low polarity water (PLPW) is a promising extraction and fractionation technique that uses hot liquid water under pressure. The objective of the present study was to optimize the extraction of lignans from flaxseed meal using PLPW. The selectivity and recovery of PLPW were tested at several different temperatures, pHs, amount of co-extraction packing materials and solvent to solid ratio. The effects of extraction conditions on total soluble proteins and total carbohydrates were also investigated by measuring their concentrations in the extracts.

The amount of SDG extracted increased with temperature. The highest yield (21 mg/g meal) of SDG was obtained at 160 to 190 C giving a total SDG amount of 21mg per g of flaxseed meal.
Extraction yield of SDG increased from 30percent at 130 C to approximately 97percent at 190 C at 120 min. In general, the extraction of SDG was more efficient at temperatures in range of 160 to 190 C.  Protein yields reached a maximum value (225 mg/g meal) at 160 C, pH 9 and 400 min extraction. The increase in extraction temperature from 130 to 160 1C resulted in higher protein yield but the overall gain in percentage recovery was less than 20percent.

Drawback of low temperature extractions were longer extraction time and the need for more water which would have to be removed in the preparation of dry extracts. The optimal temperature was about 160 C which gave a yield of 210 mg per g of flaxseed meal. A rise in extraction temperature from 130 to 160 C at S/S 100mL/g enhanced the total carbohydrate yield by about 40percent. However, there was a decline in carbohydrate content when the temperature was further increased from 160 to 190 C.

Lignans, proteins and carbohydrates were successfully extracted from flaxseed meal with PLPW. Yields of lignans, proteins and carbohydrates were improved with 1 to 1.5 ratio of meal to co packing glass beads. Optimal conditions for extraction of lignans were pH 9 buffered water at 170 C and 5.2 MPa, and 100 mL/g solvent to solid ratio. Protein optimal yield was obtained at pH 9, 160 C and 210 mL/g S/S. For carbohydrates, a temperature of 150 1C, 210 mL/g S/S and pH 4 or 6.5 is recommended. Protein degradation and carbohydrate hydrolysis were lower at 160 than at 190 C. Based on the results of this study, PLPW has the potential to develop into a commercially viable technology for the extraction of lignans, proteins and carbohydrates from flaxseed meal. (Editors comments)