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microwave-assisted extraction, etc. In some cases, in order to achieve a better extraction effect, these methods are adopted cooperatively. The solvent extraction method
generally uses hot water, acid, alkali, ethanol, etc., as solvents, and mostly use hot
water. The water extraction method is safe, nontoxic, but time-consuming and inefficient, and acid-alkali extraction is inclined to destroy the spatial structure and the
activity of the flaxseed gum. A main principle of the enzymatic hydrolysis method is
to use an enzyme capable of degrading the components of the plant’s cytoderm, and
therefore the active ingredient could be sufficiently released. The enzymatic extraction method asks for mild extracting conditions. It is energy-saving, the obtained
dietary fiber has a high purity rate, but the price of the enzyme itself is high, thus
the extraction cost is relatively high. Microwave-assisted extraction can significantly
shorten the extracting duration by water extraction method, the extraction rate is
obviously increased, but the energy consumption is high, which is not conducive
to industrialization and expansion of production. At present, the most promising
method for preparing soluble dietary fiber is membrane separation, but this method
cannot produce insoluble dietary fiber flax gum as the dietary fiber.
10.6.3 Extraction and Utilization of Lignin from Processed
Flaxseed Oil Residues
Lignin is a phytoestrogen, a natural phenolic compound synthesized from bimolecular phenylpropanoid. Lignin is widely distributed in many plants and in a variety
of foods, especially among the whole grains and beans, with the highest content in
flaxseed (0.7–2%), which is 75–800 times higher than other foods. The main lignans
in flaxseed are secoisolariciresinol (SECO) and its secoisolariciresinol diglucoside
(SDG). In recent years, researchers in Canada, Australia, the United Kingdom, and
the United States have done a lot of work on the research and development of the
medicinal efficacy of flaxseed cake dregs. High-purified, standardized lignan extracts
that conform to the curative requirements have been developed and adopted in various foods. Unilever Co., Ltd. and Elcom Biotech Co., Ltd. have applied for patents
on the utilization of lignan in food, medicine, and cosmetics. Take another example, Golden Flax 4U and Natunola of Canada have developed lignan products in
the form of natural flaxseed husk; a variety of products such as nutritionally functional super-emulsions and whole milk beverages containing lignans also have been
appearing in the market. In addition, some components for health care contained in
lignans have particular utility in the production of functional foods with properties
of anti-inflammatory or anti-aging.
At present, the main methods for the extraction of lignin from flaxseed cake dregs
are the following: traditional ethanol-water extraction, microwave-assisted extraction, enzymatic extraction, high-pressure, and low-polarity water extraction. Traditional ethanol extraction has the disadvantages of long time-consumption, low recovery rate, and environmental pollution. Enzymatic extraction has advantages of good
J. Ma et al.
microwave-assisted extraction, etc. In some cases, in order to achieve a better extraction effect, these methods are adopted cooperatively. The solvent extraction method
generally uses hot water, acid, alkali, ethanol, etc., as solvents, and mostly use hot
water. The water extraction method is safe, nontoxic, but time-consuming and inefficient, and acid-alkali extraction is inclined to destroy the spatial structure and the
activity of the flaxseed gum. A main principle of the enzymatic hydrolysis method is
to use an enzyme capable of degrading the components of the plant’s cytoderm, and
therefore the active ingredient could be sufficiently released. The enzymatic extraction method asks for mild extracting conditions. It is energy-saving, the obtained
dietary fiber has a high purity rate, but the price of the enzyme itself is high, thus
the extraction cost is relatively high. Microwave-assisted extraction can significantly
shorten the extracting duration by water extraction method, the extraction rate is
obviously increased, but the energy consumption is high, which is not conducive
to industrialization and expansion of production. At present, the most promising
method for preparing soluble dietary fiber is membrane separation, but this method
cannot produce insoluble dietary fiber flax gum as the dietary fiber.
10.6.3 Extraction and Utilization of Lignin from Processed
Flaxseed Oil Residues
Lignin is a phytoestrogen, a natural phenolic compound synthesized from bimolecular phenylpropanoid. Lignin is widely distributed in many plants and in a variety
of foods, especially among the whole grains and beans, with the highest content in
flaxseed (0.7–2%), which is 75–800 times higher than other foods. The main lignans
in flaxseed are secoisolariciresinol (SECO) and its secoisolariciresinol diglucoside
(SDG). In recent years, researchers in Canada, Australia, the United Kingdom, and
the United States have done a lot of work on the research and development of the
medicinal efficacy of flaxseed cake dregs. High-purified, standardized lignan extracts
that conform to the curative requirements have been developed and adopted in various foods. Unilever Co., Ltd. and Elcom Biotech Co., Ltd. have applied for patents
on the utilization of lignan in food, medicine, and cosmetics. Take another example, Golden Flax 4U and Natunola of Canada have developed lignan products in
the form of natural flaxseed husk; a variety of products such as nutritionally functional super-emulsions and whole milk beverages containing lignans also have been
appearing in the market. In addition, some components for health care contained in
lignans have particular utility in the production of functional foods with properties
of anti-inflammatory or anti-aging.
At present, the main methods for the extraction of lignin from flaxseed cake dregs
are the following: traditional ethanol-water extraction, microwave-assisted extraction, enzymatic extraction, high-pressure, and low-polarity water extraction. Traditional ethanol extraction has the disadvantages of long time-consumption, low recovery rate, and environmental pollution. Enzymatic extraction has advantages of good