Synthesis of novel triglycerides from mackerel by-products and vegetable oils

• Main Author: Zuta, Charles Prince
• Other Authors: Simpson, B. K. (advisor)
• Format: Thesis
• Language: English
• Published: McGill University 2003
• Subjects: Functional foods; Mackerels; Fishery processing industries > By-products; Unsaturated fatty acids; Omega-3 fatty acids; Linoleic acid; Fid; antartic*
• Online Access: http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=84863

The study was designed to develop a nutraceutical product from by-products of fish processing. Fish oil was extracted from mackerel tissues (skin, viscera and muscle) using hexane-isopropanol (3:2 v/v) and chloroform-methanol (2:1 v/v) solvent systems. An oxidative study was carried out to determine the best processing and storage conditions to minimize autooxidation of mackerel oil. Urea complexation was used to concentrate polyunsaturated fatty acids (PUFA) from the extracted fish oil. The urea complexation process was optimized to determine the best reaction conditions for high yield of the omega-3 fatty acids in particular, and total PUFA. Conjugated linoleic acid (CLA) was synthesized from four vegetable oils (sunflower, canola, soybean and corn) by alkaline isomerization. The CLA isomers and PUFA concentrated from mackerel tissues were used to synthesize triglycerides by lipase-catalyzed esterification. The effect of temperature, reaction medium, enzyme, moisture removal system and glycerol to fatty acid ratio on extent of synthesis were investigated. The synthesis process was also optimized using central composite design to determine the best conditions for high synthesis yield. The fatty acid composition and positional analyses were determined by GC-FID and electrospray ionization mass spectrometry (EI-MS) The results showed that mackerel skins were most suitable for concentrating PUFA. The eicosapentaenoic acid (EPA) and -docosahexaenoic acid (DHA) content of fish oil from the tissues examined ranged between 6.3--9.7 (wt%) with an iodine value of 134 +/- 5.0. The baseline total PUFA content was increased from ca 21.0 to ca 83.0 (wt%) with an associated iodine value of 296 +/- 7.0 using urea complexation. Low (50 ppm and 100 ppm) levels of alpha-tocopherol in combination with low storage temperature (-40°C) showed lowest oxidation after 66 days of storage. High levels (250 and 500 ppm) of alpha-tocopherol were observed to be prooxidant based on TBARS, peroxide and conjugated diene measurements. Urea to fatty acid ratio and temperature were predominant effectors influencing the amounts of individual omega-3 fatty acids and total PUFA concentrated by urea complexation. The model developed for the optimized urea complexation process were capable of predicting the yields of EPA, DHA, total PUFA and Iodine values to a high degree of accuracy at R2 = 0.87, 0.96, 0.95, and 0.92 respectively. Sunflower oil was most suitable for synthesizing conjugated linoleic acid by alkaline isomerization, compared with soybean, canola and corn oil. Two CLA isomers, c9,t11 and t10, c12 were most abundant and occurred in approximately equal proportions irrespective of vegetable oil used. Total CLA synthesized from sunflower oil was 93.5 +/- 3.5 (wt%) with the two major isomers making up 89 +/- 3.5 (wt%). Candida antartica lipase showed more synthesis activity than Mucor meihie in both organic and solvent-free systems. Analysis of isolated synthesized triglycerides by GC-FID and mass spectrometry showed that DHA, EPA, CLA and linolenic acid were the main fatty acids incorporated into the triglycerides. DHA and EPA were mostly esterified at the sn-2 position.