Protein products and sprouts from flaxseed (Linum usitatissimum L.)

Wanasundara, Janitha Priyakanthi Deepani (1995) Protein products and sprouts from flaxseed (Linum usitatissimum L.). Doctoral (PhD) thesis, Memorial University of Newfoundland.

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    Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission.
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Abstract

Polysaccharides of flaxseed coat (flax mucilage) were removed by soaking of whole seeds in water or sodium bicarbonate solution or treatment with commercially- available carbohydrases. The extent of polysaccharide removal was determined by monitoring the concentration of total sugars and pentoses as well as viscosity values of the aqueous polysaccharide extracts prepared from treated flaxseed. A direct relationship existed between the amount of seeds dispersed in the extraction medium and the total contents of sugars and pentoses or viscosity values (correlation coefficients of 0.957, 0.974 and 0.921, respectively). These indicators served well in quantitating the content of polysaccharides in aqueous extracts. Soaking in a 0.10 M sodium bicarbonate solution for 12 h removed most of the mucilage from seed coats. Treatment of seeds with Viscozyme® L (22.5 mg protein/100 g seeds) for 12 h removed more polysaccharides from seed coat than Pectinex™ Ultra SP or Celluclast® 1.5L under similar conditions. Scanning electron microscopy provided evidence that polysaccharides were removed from seed coats by pre-treatments employed. Nitrogen solubility and protein recovery from meals of mucilage-reduced seeds was improved since there was less interference from seed coat polysaccharides which were co-extracted with proteins. Sodium hexametaphosphate-assisted protein isolation from mucilage-reduced seeds was optimized under laboratory conditions for pH, meal-to- solvent ratio and concentration of sodium hexametaphosphate using response surface methodology with a central composite rotatable design. Maximum nitrogen solubility and protein recovery were obtained at pH 8.89 and 9.04, meal-to-solvent ratio of 1:33.5 and 1:33 and sodium hexametaphosphate concentration of 2.75 and 2.85%, respectively. The prepared flax protein isolate contained 78% protein. Lysine was the first limiting amino acid of the protein isolate. The computed protein efficiency ratio and biological value indicated a reasonably good quality of protein in the isolate. The isolate contained elevated levels of phytic acid and total phosphorus. Electrophoretic results showed that the isolate was composed of total proteins of flaxseed. -- The isolated flax proteins were acylated with acetic or succinic anhydride. Approximately 84.5 and 56.9% of the free amino groups of protein isolates were acylated when 0.2 g anhydride/g protein was used. The colour and solubility of the protein isolate were improved due to acylation. Emulsifying activity and stability were enhanced by succinylation, but acetylation had a negative influence. Furthermore, foaming ability and fat binding capacity of succinylated products were less than those of their acetylated counterparts. Acylation reduced the in vitro digestibility of flax proteins. -- In another study flaxseeds were germinated for 8 days. Germinated seeds had lowered content of dry matter due to the use of their reserve components as an energy source for the developing seedlings. The crude protein content did not show a significant (p<0.05) change but the content of non-protein nitrogen compounds including free amino acids as well as agmatine and spermidine increased during the germination period. The in vitro digestibility was lowered but the calculated values for protein efficiency ratio and biological value of seeds did not change upon germination. Lipid content of seeds was reduced by 58% during germination but their fatty acid composition did not change. The content of neutral lipids, accounting for 96% of total flax lipids, was significantly (p<0.05) decreased while those of glyco and phospholipids increased. There was also a decrease in the content of triacylglycerols and an increase in the diacylglycerols, monoacylglycerols and free fatty acids of the neutral lipid fraction. The content of phosphatidylcholine, phosphatidyiserine and phosphatidylethanolamine in the phospholipid fraction was decreased while that of phosphatide acid and lysophosphatidylethanolamine increased significantly (p<0.05) due to germination. The quantities of raffinose and sucrose in the seeds were reduced while those of fructose and glucose increased after germination. The mineral composition of the seeds was not affected by germination. The content of known antinutrients of seeds namely, cyanogenic glycosides, phytic acid and trypsin inhibitors were lower in the germinated seeds as compared to those in their ungerminated counterparts.

Item Type: Thesis (Doctoral (PhD))
URI: http://research.library.mun.ca/id/eprint/1627
Item ID: 1627
Additional Information: Bibliography: leaves [228]-256
Department(s): Science, Faculty of > Biochemistry
Date: 1995
Date Type: Submission
Library of Congress Subject Heading: Flaxseed; Flaxseed in human nutrition; Oilseed products; Sprouts

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