Thesis (Ph. D.)--University of Michigan, 1935. / Cover title. "Reprinted from Industrial and engineering chemistry, vol. 29 ... August, 1937." eContent provider-neutral record in process. Description based on print version record. "Literature cited": p. 910.

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The physicochemical characteristics of seven cold-pressed flaxseed oils sold in New Zealand were investigated for their fatty acid composition, tocopherol composition, moisture and volatile matter, free fatty acids, chlorophyll pigments, unsaponifiable matter, total phenolic acids and flavanoids, and colour. The seven cold-pressed flaxseed oils exhibited significant variations in their physicochemical characteristics. Quality of the oils in terms of oxidative stability was also investigated. Four oils were found to be within the limit of good stability oil indices, measured in terms of peroxide value, p-anisidine value, conjugated dienoic acids, specific extinction in ultraviolet spectrum, acid value and food oil sensor readings (to indicate total polar compounds). The role of minor constituents in the oxidative stability of two selected oils with different levels of fatty acid composition and minor constituents was investigated. Pan heating at 150�C caused loss of tocopherols, plastochromanol-8, phenolic acids, chlorophyll pigments, β-carotene and lutein and changes in the fatty acid composition. The pan-heated oils exceeded the limit of good stability oil indices using the measurement mentioned above except for acid value. The addition of α-tocopherol to the oils did not provide enhanced protection to the oils in accelerated aging of oil tests at 60�C. It was most likely that phenolic acids present in the oils played a dominant role in the oxidative stability of the oils. Lipase-catalyzed transesterification of triolein with cinnamic and ferulic acids using a commercially available immobilized lipase B from Candida antarctica (Novozym 435) was conducted to evaluate the antioxidant activity of the lipophilized products as model systems for enhanced protection of unsaturated oil. The lipophilized products were identified using Electrospray Ionization-Mass Spectroscopy (ESI-MS). Separation and isolation of two classes of lipophilized products was also achieved using a solid phase extraction method developed in this study for further investigation into the structure-free radical scavenging activity. Free radical scavenging activity was determined using the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) method. The polarity of the solvents proved important in determining the free radical scavenging activity of the substrates. Ferulic acid showed much higher free radical scavenging activity than cinnamic acid, which had limited activity. The esterification of cinnamic acid and ferulic acid with triolein resulted in significant increase and decrease in the free radical scavenging activity, respectively. These opposite effects were due to the effect of addition of electron-donating alkyl groups on the predominant mechanism of reaction (hydrogen atom transfer or electron transfer) of a species with DPPH. The effect of esterification of cinnamic acid was confirmed using ethyl cinnamate which greatly enhances the free radical scavenging activity. Although, compared with the lipophilized cinnamic acid product, the activity was lower. The free radical scavenging activity of the main component isolated from lipophilized cinnamic acid product using solid phase extraction, monocinnamoyldioleoylglycerol, was as good as the unseparated mixture of lipophilized product. Based on the ratio of a substrate to DPPH concentration, lipophilized ferulic acid was a much more efficient free radical scavenger than lipophilized cinnamic acid. Lipase-catalyzed transesterification of flaxseed oil with cinnamic and ferulic acids using Novozym 435 was conducted to evaluate whether the lipophilized products provided enhanced antioxidant activity in the oil. The lipophilized products were identified using ESI-MS and were examined for their free radical scavenging activity toward DPPH in ethanol and ethyl acetate. Ferulic acid showed the highest free radical scavenging activity among all substrates tested while cinnamic acid had negligible activity. The effect of esterification of cinnamic acid and ferulic acid with flaxseed oil was similar to that with triolein. Lipophilized ferulic acid was a better free radical scavenger as compared with lipophilized cinnamic acid and extended the naturally-occuring antioxidant capacity of the flaxseed oil. Lipophilized cinnamic acid did not provide much enhanced radical scavenging activity in the flaxseed oil as the presence of natural hydrophilic antioxidants in the oil had much greater radical scavenging activity. It may still be useful for unsaturated oils with a small amount of natural antioxidants in them. Lipophilized cinnamic and ferulic acids showed higher free radical scavenging activity when tested in a less polar solvent (ethyl acetate) whereas ferulic acid showed better activity in a more polar solvent (ethanol). These results indicate that the choice of solvent for the DPPH assay is critical in evaluating the free radical scavenging activity of substrates of differing polarity, and support previous observations by other authors that the solubility of an antioxidant in relation to the site of oxidation is an important factor for consideration in the use of antioxidants.

The effects of partial or total replacement of fish oil with linseed oil or corn oil or both in diets of cobia were valuated. Basal diet was isonitrogenous and isoenergetic and contained 15% crude lipid. Results of the 8-wk feeding trial show that fish fed diet containing only fish oil grew significant better than fish fed other replacement diets (replacement level 33-100%). Fish fed diet containing only plant oil grew the least and had the lowest liver weight, condition factor and body lipid concentration. Oil replacement did not significantly change liver mRNA gene expression of fatty acid desaturase and elongase. As levels of replacement increased, tissue PUFA increased while HUFA decreased. Fish fed all fish oil diet had the highest respiratory burst activities of head kidney phagocytes. Serum of the fish fed the all vegetable oil diets had the lowest lysozyme activities. Fish fed all linseed oil diet had the highest SOD activities. Serum alternative complement pathway activity, aspartate transaminase and alanine transaminase activity did not vary among treatments. The results show that cobia juveniles had relatively high need for fish oil in their diets, and the ability to synthesized HUFA from PUFA was limited. Partial or total replacement (33-100%) of fish oil with linseed oil or corn oil or both were detrimental to fish growth and immune responses.

Lipase-catalyzed esterification and transesterification reactions of selected phenolic acids with lipids were investigated in organic solvent media. The esterification of linoleyl alcohol with dihydrocaffeic acid (DHA) in neat hexane medium resulted in highest esterification yield (EY) of 17% when a Candida antarctica lipase (Novozym 435) was used to catalyze the reaction. The use of co-solvents t-butanol and 2-butanone with hexane resulted in a dramatic increase in EY. The highest EY of 83% was obtained in hexane:2-butanone mixture of 85:15 (v/v) using Novozym 435; however lower EY (40%) was obtained when a lipase from Rhizomucor meihei (Lipozyme IM 20) was used. Increasing the amount of the co-solvent 2-butanone in the hexane:2-butanone mixture to 75:25 (v/v) resulted in a lower EY of 75% with Novozym 435; using the same enzyme, the esterification of a more unsaturated alcohol, linolenyl alcohol, with DHCA in the hexane:2-butanone mixture of 75:25 (v/v) resulted in EY of 76% which was similar to that obtained with linoleyl alcohol as lipid substrate. The esterification of DHCA and ferulic acid with linolenyl alcohol in the hexane:2-butanone mixture of 65:35 (v/v) resulted in an EY of 58 and 16%, respectively. Both linoleyl and linolenyl alcohols demonstrated mass action effects with EY of 99% in DHCA: fatty alcohol ratio of 1:8. Using a molar ratio of 1:2, the transesterification reactions of DHCA with trilinolein (TLA) and trilinolenin (TLNA) in hexane:2-butanone mixture of 75:25 (v/v) resulted in total transesterification yields (TYs) of phenolic lipids of 66 and 62%, respectively. The TYs of phenolic monoacylglycerols was higher than that of phenolic diacylglycerols for both TLA and TLNA transesterification reactions. A lower molar ratio of DHCA to TLA of 1:4 resulted in a lower TY of 53%. Using a molar ratio of 1:2, the TY of TLA and TLNA with ferulic acid in hexane:2-butanone mixture of 65:35 (v/v) was 16 and 14%, respectively. An equal molar transesterification reaction of DHCA with flaxseed oil, in a hexane:2-butanone mixture of 75:25 (v/v), resulted in the production of only phenolic monoacylglycerols (19%); however, decreasing the molar ratio resulted in the production of both phenolic mono and diacylglycerols. A molar ratio of DHCA to flaxseed oil (1:8) resulted in a TY of 76%, with 43 and 33% phenolic mono and diacylglycerols, respectively. Changing the solvent mixture of hexane:2-butanone from 65:35 to 85:15 (v/v) resulted in an increased in the TY of phenolic diacylglycerols from 24 to 55% with no significant effect on the TY of phenolic monoacylglycerols. The transesterification reaction resulted in a change in the composition of the C18:3 FA from 53% in the unmodified oil to 60 and 65% in the phenolic mono and diacylglycerols. Transesterification reaction of DHCA with fish liver oil in the solvent mixtures of hexane:2-butanone of 75:25 and 85:15 (v/v) resulted in TY of 56 and 65%, respectively. Transesterification in solvent: mixture of 75:25 resulted in a 40 and 16% TY of phenolic mono and diacylglycerols, respectively, whereas that in the solvent mixture of 85:15 (v/v) resulted in a 38 and 37% TY of phenolic mono and diacylglycerols, respectively. The structures of phenolic lipids of linoleyl and linolenyl alcohols with DHCA were confirmed by LC/MS analysis likewise for the phenolic mono and diacylglycerols from transesterification of DHCA with TLA and TLNA as well as flaxseed and fish liver oils. The phenolic esters of the fatty alcohols demonstrated radical scavenging properties similar to that of alpha-tocopherol but less than for DHCA; however, the phenolic lipids obtained with the use of TLA and TLNA as substrate as well as flaxseed and fish liver oil, demonstrated significant radical scavenging effects but less than that of alpha-tocopherol and DHCA.

The physicochemical characteristics of seven cold-pressed flaxseed oils sold in New Zealand were investigated for their fatty acid composition, tocopherol composition, moisture and volatile matter, free fatty acids, chlorophyll pigments, unsaponifiable matter, total phenolic acids and flavanoids, and colour. The seven cold-pressed flaxseed oils exhibited significant variations in their physicochemical characteristics. Quality of the oils in terms of oxidative stability was also investigated. Four oils were found to be within the limit of good stability oil indices, measured in terms of peroxide value, p-anisidine value, conjugated dienoic acids, specific extinction in ultraviolet spectrum, acid value and food oil sensor readings (to indicate total polar compounds). The role of minor constituents in the oxidative stability of two selected oils with different levels of fatty acid composition and minor constituents was investigated. Pan heating at 150�C caused loss of tocopherols, plastochromanol-8, phenolic acids, chlorophyll pigments, β-carotene and lutein and changes in the fatty acid composition. The pan-heated oils exceeded the limit of good stability oil indices using the measurement mentioned above except for acid value. The addition of α-tocopherol to the oils did not provide enhanced protection to the oils in accelerated aging of oil tests at 60�C. It was most likely that phenolic acids present in the oils played a dominant role in the oxidative stability of the oils. Lipase-catalyzed transesterification of triolein with cinnamic and ferulic acids using a commercially available immobilized lipase B from Candida antarctica (Novozym 435) was conducted to evaluate the antioxidant activity of the lipophilized products as model systems for enhanced protection of unsaturated oil. The lipophilized products were identified using Electrospray Ionization-Mass Spectroscopy (ESI-MS). Separation and isolation of two classes of lipophilized products was also achieved using a solid phase extraction method developed in this study for further investigation into the structure-free radical scavenging activity. Free radical scavenging activity was determined using the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) method. The polarity of the solvents proved important in determining the free radical scavenging activity of the substrates. Ferulic acid showed much higher free radical scavenging activity than cinnamic acid, which had limited activity. The esterification of cinnamic acid and ferulic acid with triolein resulted in significant increase and decrease in the free radical scavenging activity, respectively. These opposite effects were due to the effect of addition of electron-donating alkyl groups on the predominant mechanism of reaction (hydrogen atom transfer or electron transfer) of a species with DPPH. The effect of esterification of cinnamic acid was confirmed using ethyl cinnamate which greatly enhances the free radical scavenging activity. Although, compared with the lipophilized cinnamic acid product, the activity was lower. The free radical scavenging activity of the main component isolated from lipophilized cinnamic acid product using solid phase extraction, monocinnamoyldioleoylglycerol, was as good as the unseparated mixture of lipophilized product. Based on the ratio of a substrate to DPPH concentration, lipophilized ferulic acid was a much more efficient free radical scavenger than lipophilized cinnamic acid. Lipase-catalyzed transesterification of flaxseed oil with cinnamic and ferulic acids using Novozym 435 was conducted to evaluate whether the lipophilized products provided enhanced antioxidant activity in the oil. The lipophilized products were identified using ESI-MS and were examined for their free radical scavenging activity toward DPPH in ethanol and ethyl acetate. Ferulic acid showed the highest free radical scavenging activity among all substrates tested while cinnamic acid had negligible activity. The effect of esterification of cinnamic acid and ferulic acid with flaxseed oil was similar to that with triolein. Lipophilized ferulic acid was a better free radical scavenger as compared with lipophilized cinnamic acid and extended the naturally-occuring antioxidant capacity of the flaxseed oil. Lipophilized cinnamic acid did not provide much enhanced radical scavenging activity in the flaxseed oil as the presence of natural hydrophilic antioxidants in the oil had much greater radical scavenging activity. It may still be useful for unsaturated oils with a small amount of natural antioxidants in them. Lipophilized cinnamic and ferulic acids showed higher free radical scavenging activity when tested in a less polar solvent (ethyl acetate) whereas ferulic acid showed better activity in a more polar solvent (ethanol). These results indicate that the choice of solvent for the DPPH assay is critical in evaluating the free radical scavenging activity of substrates of differing polarity, and support previous observations by other authors that the solubility of an antioxidant in relation to the site of oxidation is an important factor for consideration in the use of antioxidants.

An experiment was conducted to determine the effect of addition of antioxidants or encapsulation of linseed oil on the oxidative stability of linseed oil and the effect on growth and fatty acid composition of rainbow trout fed these products. Four diets differing only in their lipid sources were prepared by cold extrusion: 1) fish oil (FO), 2) linseed oil (LO), 3) linseed oil (980 g/kg) stabilized with vitamin E (7.5 g/kg) and butylated hydroxytoluene (BHT) (12.5 g/kg) (stabilized linseed oil; SLO) and 4) linseed oil (350 g/kg) containing vitamin E (7.5 g/kg), BHT (12.5 g/kg) and encapsulated in a coating material primarily consisting of hydrogenated palm oil (630 g/kg) (encapsulated linseed oil; ELO). Diets were fed twice daily to rainbow trout to apparent satiation (n=22 / replicate; 7 replicates per treatment) during a 168 day growth trial. Following the growth trial, the fish were humanely euthanized by a sharp blow to the cranium and analyzed for fatty acid composition, thiobarbituraric reactive substances (TBARS), fillet colour and sensory attributes (trained and consumer panels). There were no significant differences between treatments on any of the growth parameters investigated or TBARS levels of fish fillets. Omega-3 polyunsaturated fatty acids of trout fed LO were significantly higher than those fed FO (35.5% of total fatty acids vs. 27.6%) and ELO (28.9%) (P < 0.05). EPA and DHA levels were not significantly different between treatments. Diet samples were stored for 168 days at room temperature in sealed plastic containers. Following storage, the oxidative stability index (OSI) of the FO and LO diets were reduced to 0.00 hours while that of the SLO diet 9.20 hours and the ELO diet was 11.40 hours. Trained panelists determined fish fed FO had a significantly higher aroma intensity and significantly lower aroma desirability and overall acceptability than those fed SLO. The rancid aroma and flavour of the FO-fed fish was significantly higher than fish fed the other treatments (P < 0.05). Consumer panelists found no significant differences between the sensory attributes of fish fed the four experimental diets and exhibited no preference between treatments (P > 0.05). Fillets from fish fed FO had significantly higher values than the other three treatments for redness (3.59 vs values between 1.86 and 2.07) and yellowness (25.35 vs values between 20.51 and 21.22) (P < 0.05). Addition of antioxidants to linseed oil improves its oxidative stability during storage and processing and results in fish fillets with fatty acid composition and consumer acceptance equal or superior to fish fed fish oil.

An experiment was conducted to determine the effect of addition of antioxidants or encapsulation of linseed oil on the oxidative stability of linseed oil and the effect on growth and fatty acid composition of rainbow trout fed these products. Four diets differing only in their lipid sources were prepared by cold extrusion: 1) fish oil (FO), 2) linseed oil (LO), 3) linseed oil (980 g/kg) stabilized with vitamin E (7.5 g/kg) and butylated hydroxytoluene (BHT) (12.5 g/kg) (stabilized linseed oil; SLO) and 4) linseed oil (350 g/kg) containing vitamin E (7.5 g/kg), BHT (12.5 g/kg) and encapsulated in a coating material primarily consisting of hydrogenated palm oil (630 g/kg) (encapsulated linseed oil; ELO). Diets were fed twice daily to rainbow trout to apparent satiation (n=22 / replicate; 7 replicates per treatment) during a 168 day growth trial. Following the growth trial, the fish were humanely euthanized by a sharp blow to the cranium and analyzed for fatty acid composition, thiobarbituraric reactive substances (TBARS), fillet colour and sensory attributes (trained and consumer panels). There were no significant differences between treatments on any of the growth parameters investigated or TBARS levels of fish fillets. Omega-3 polyunsaturated fatty acids of trout fed LO were significantly higher than those fed FO (35.5% of total fatty acids vs. 27.6%) and ELO (28.9%) (P < 0.05). EPA and DHA levels were not significantly different between treatments. Diet samples were stored for 168 days at room temperature in sealed plastic containers. Following storage, the oxidative stability index (OSI) of the FO and LO diets were reduced to 0.00 hours while that of the SLO diet 9.20 hours and the ELO diet was 11.40 hours. Trained panelists determined fish fed FO had a significantly higher aroma intensity and significantly lower aroma desirability and overall acceptability than those fed SLO. The rancid aroma and flavour of the FO-fed fish was significantly higher than fish fed the other treatments (P < 0.05). Consumer panelists found no significant differences between the sensory attributes of fish fed the four experimental diets and exhibited no preference between treatments (P > 0.05). Fillets from fish fed FO had significantly higher values than the other three treatments for redness (3.59 vs values between 1.86 and 2.07) and yellowness (25.35 vs values between 20.51 and 21.22) (P < 0.05). Addition of antioxidants to linseed oil improves its oxidative stability during storage and processing and results in fish fillets with fatty acid composition and consumer acceptance equal or superior to fish fed fish oil.

An experiment was conducted to determine the effect of addition of antioxidants or encapsulation of linseed oil on the oxidative stability of linseed oil and the effect on growth and fatty acid composition of rainbow trout fed these products. Four diets differing only in their lipid sources were prepared by cold extrusion: 1) fish oil (FO), 2) linseed oil (LO), 3) linseed oil (980 g/kg) stabilized with vitamin E (7.5 g/kg) and butylated hydroxytoluene (BHT) (12.5 g/kg) (stabilized linseed oil; SLO) and 4) linseed oil (350 g/kg) containing vitamin E (7.5 g/kg), BHT (12.5 g/kg) and encapsulated in a coating material primarily consisting of hydrogenated palm oil (630 g/kg) (encapsulated linseed oil; ELO). Diets were fed twice daily to rainbow trout to apparent satiation (n=22 / replicate; 7 replicates per treatment) during a 168 day growth trial. Following the growth trial, the fish were humanely euthanized by a sharp blow to the cranium and analyzed for fatty acid composition, thiobarbituraric reactive substances (TBARS), fillet colour and sensory attributes (trained and consumer panels). There were no significant differences between treatments on any of the growth parameters investigated or TBARS levels of fish fillets. Omega-3 polyunsaturated fatty acids of trout fed LO were significantly higher than those fed FO (35.5% of total fatty acids vs. 27.6%) and ELO (28.9%) (P < 0.05). EPA and DHA levels were not significantly different between treatments. Diet samples were stored for 168 days at room temperature in sealed plastic containers. Following storage, the oxidative stability index (OSI) of the FO and LO diets were reduced to 0.00 hours while that of the SLO diet 9.20 hours and the ELO diet was 11.40 hours. Trained panelists determined fish fed FO had a significantly higher aroma intensity and significantly lower aroma desirability and overall acceptability than those fed SLO. The rancid aroma and flavour of the FO-fed fish was significantly higher than fish fed the other treatments (P < 0.05). Consumer panelists found no significant differences between the sensory attributes of fish fed the four experimental diets and exhibited no preference between treatments (P > 0.05). Fillets from fish fed FO had significantly higher values than the other three treatments for redness (3.59 vs values between 1.86 and 2.07) and yellowness (25.35 vs values between 20.51 and 21.22) (P < 0.05). Addition of antioxidants to linseed oil improves its oxidative stability during storage and processing and results in fish fillets with fatty acid composition and consumer acceptance equal or superior to fish fed fish oil.