Effects of lipid oxidation on fish lipids — amylopectin interactions

The results of studies on fish lipid oxidation effects on lipid‐amylopectin starch interactions are presented. Particular attention is paid to fish lipid availability (extractability from the system) and fatty acid contributions to individual lipid groups after mixing‐provoked interaction and after a 30‐day storage at —18 °C. The study involved model systems containing fish lipids at different levels of oxidation, lipids containing an antioxidant (BHA), and gelatinised amylopectin starch in a 10% aqueous solution. The lipid to starch ratio was 1:1. The test systems were subjected to selective extraction. The extracts were assayed for lipid content, peroxide value, anisidine value, fluorescence, and fatty acid composition. Compared to fresh fish lipids, those lipids, which were oxidised to a higher extent were shown to be more amenable to complexing with amylopectin, but they were also more readily released during frozen storage. On the other hand, addition of BHA stabilised the lipid‐amylopectin starch interaction during storage at —18 °C. In the entire systems tested, polyunsaturated fatty acids, eicosapentaenoic and docosahexaenoic acids in particular, proved to be most susceptible to binding, up to 90% of the latter being complexed.     

Effects of thermal treatment on fish lipids‐amylose interaction

The paper describes a study on effects of thermal treatments (microwave heating and freezing) on fish lipids‐amylose starch interactions. Particular attention was paid to lipid availability (extractability from the system) and contribution of fatty acids to various groups of lipids after interactions produced by mixing, microwave heating and storage. Analyses were made on model systems containing fish lipids at different oxidation levels and gelatinised with 10% aqueous solution of amylose starch. The lipid:starch ratio was 1:1. The systems were assayed before and after mixing, microwave heating (4 min, 90 W), freezing (30 d, –18 °C), and heating followed by freezing. Lipid extractability (selective extraction), peroxide value (PV), anisidine value (AsV), fluorescence, and fatty acid profiles (GC/MS) were determined. Mixing of fish lipids with amylose was shown to result in lipid‐amylose interaction. The thermal treatments applied (microwave heating or freezing at –19 °C for 30 d) were observed to exert different, significant effects on fish lipids‐amylose starch interactions. The effects depended also on the extent of lipid oxidation. Fatty acids of the lipids were bound selectively, PUFA, and particularly DHA, were subjected to stronger binding and higher amounts of those acids were bound.     

Lipids and fatty acids of important finfish: New data for nutrient tables

There is an urgent need for thorough and reliable information on the lipid content and fatty acid composition of food. Data on fish lipids (1960 to the present) have been collected and evaluated for the preparation of nutrient and food composition tables for this important commodity. Some factors affecting these data include the lack of standardization in fish nomenclature, cut of fish, season and location of catch, and variability of methods of analysis. The derivation and use of conversion factors relating wt percent methyl ester data in the literature to g fatty acid/100 g fish are described. Tabulated data are presented for total lipid and 14 fatty acids in 11 important finfish.     

A Method for Analyzing Fatty Acids in Cattle Hair,with Special Emphasis on Lauric Acid and Myristic Acid

This study is aimed at improving a protocol for measuring fatty acids in cattle hair with respect to sensitivity, repeatability, and speed to increase its applicability as a biomarker. For the investigation, 14 hair samples from German Holstein cows are used. Alternative methods for grinding the hair (mortar vs mill), lipid extraction (modified Folch vs kit extraction), and solvent evaporation before injection on a gas chromatograph (evaporated vs unevaporated extracts) are tested. Hair ground with a mill compared to that with a mortar has smaller particles and a higher concentration of total lipids after extraction (p < 0.02). The kit used for lipid extraction is faster, and the amount of extracted total lipids and individual fatty acids, especially C12:0, is increased (p = 0.001). The analysis of unevaporated methyl ester extracts using gas chromatography (GC) analysis yields 5.8 and 1.3 higher amounts of C10:0 and C12:0, respectively, than those of evaporated extracts (p < 0.001). According to the results, the protocol for determining fatty acids in cattle hair can be improved by grinding the hair with a mill, extraction of lipids with a kit, and direct loading of methyl ester extracts in a gas chromatograph. Practical Applications: The fatty acid profile of hair reflects the metabolic status of an animal for the previous 1–3 weeks, as these fatty acids are not influenced by diurnal and short‐term fluctuations. An improved protocol is developed that increases the throughput of fatty acid analysis and improves its applicability for practical use. For breeding and animal welfare, the analysis of cattle hair is possible for more efficient evaluation of the hair fatty acid profile as a robust biomarker in a larger animal population.     

Isolation and purification of perfluorodecanoic and perfluorooctanoic acids from rat tissues

A procedure for the extraction, separation, and isolation of perfluorodecanoic and perfluorooctanoic acids from biological samples is described. The use of conventional lipid extraction procedures leads to substantial loss of the perfluorinated fatty acids added to tissue. The presence of sulfuric acid in aqueous saline during phase partitioning is essential for the recovery of perfluorodecanoic and perfluorooctanoic acids in the organic phase following their extraction from tissue. The perfluorinated fatty acids are co-eluted with simple lipids from silica gel columns using diethyl ether/trifluoroacetic acid (100∶1, v/v). Simple lipids are separated by thin layer chromatography. By substituting trifluoroacetic acid for acetic acid in the developing solvents, perfluorodecanoic and perfluorooctanoic acids migrate with other free fatty acids.     

The lipids of human pancreas with special reference to the presence of fatty acid methyl esters

Total lipids were extracted from human pancreas with chloroform-methanol, chloroform-methanol following acidification, and benzene. A similar proportional amount of total lipid was obtained by each procedure. Regardless of the method of extraction (i.e., whether or not methanol was present), a small proportion (about 1%) of the total lipid was found to consist of fatty acid methyl esters. Triglycerides constituted the major fraction (about 80%) of the pancreatic lipids; in addition to methyl esters, the remaining lipids comprised free fatty acids, phospholipids, cholesterol esters, and traces of free cholesterol. In general, each class of lipid had a similar over-all fatty acid composition with palmitic and oleic acids as predominant components. The methyl esters had a relatively high content of linolenic acid, and the free fatty acids contained a notably high proportion of palmitic acid, in each case accompanied by a corresponding decrease in the proportion of oleic acid present.     

Extraction of lipids from cottonseed tissue: III. Cyclopropenoid fatty acids from glanded and glandless seed

Principal storage sites of cyclopropenoid fatty acids in glanded and glandless cottonseed tissues were investigated by measuring the content of cyclopropenoid fatty acids in lipids obtained by a cytoplasmic disruptive solvent (hexane-acetone-water) and a non-disruptive solvent (hexane-acetone). The content of cyclopropenoid fatty acids in lipid obtained by either solvent did not differ quantitatively, indicating that cyclopropenoid fatty acids are not stored preferentially in extraspherosomal cytoplasm. Since this observation was also made with glanded tissue, whose glands are thoroughly disrupted by hexane-acetone-water but not by hexane-acetone, the lipoidal material of glands are also not rich in cyclopropenoid fatty acids. These observations indicate that oil-rich spherosomes are the principal sites of cyclopropenoid fatty acids, as well as the reserve oil of cottonseed, and suggest that the greater content of cyclopropenoid fatty acids in lipid prepared by increased periods of solvent-extraction is from release of binding to tissue components, rather than a thorough extraction of somewhat inaccessible (extraspherosomal) areas of tissue. Previous paper in this series is given in Reference 2. ARS, USDA.     

Comparative evaluation of solvent extraction methods for the determination of neutral and polar lipids in beef

Samples of lean (< 5% fat), medium (13–15%) and high-fat (> 20%) ground beef were extracted for total lipid by 4 methods of wet extraction employing chloroform/methanol (CM), n-hexane/iso-propanol (HIP) and ethyl alcohol/ethyl ether (AE), and by 3 methods of soxhlet extraction of freeze-dried material by petroleum ether (PE) or eithyl ether (EE), CM and methylene chloride/ methanol (MM). The purified lipid was fractionated into neutral and polar lipid fractions by silicic acid chromatography and the frac-tions were analyzed for fatty acid distribution by gas liquid chroma-tography (GLC). The soxhlet procedure employing either PE or EE extracted less than 75% of total lipid, 89% of triglycérides and 15% of polar lipids from lean beef as compared to other methods, and as the fat content increased from 3 to 20%, extracted amounts of polar lipid which increased to 40% of that extracted by other methods. The fatty acid distribution of the fractionated triglycerides and polar lipids was generally within experimental error for each frac-tion, irrespective of the method of extraction. The percentages of 16:0 and 18:1 were significantly less in polar lipids than in trigly-cerides. In addition to significantly higher percentage of 18:2, the polar lipids contained up to 20% of long-chain fatty acids not detected in triglycerides. The soxhlet procedures with CM or MM were as effective as wet extraction procedures in extracting neutral and polar lipids. Presented at the 73rd AOCS annual meeting, Toronto, 1982. Contribution No. 512, Food Research Institute, Agriculture Canada.     

Effect of freezing on quality of sea bass and gilthead sea bream

Freezing is an efficient method of fish preservation. The aim of the present work was to examine the impact of freezing in fatty acid composition and in the in vitro inhibitory activity of sea bass (Dicentrarchus labrax) and gilthead sea bream (Sparus aurata) fillet lipids against platelet activating factor (PAF). The Bligh and Dyer extraction method and the counter‐current distribution method were used to obtain total, polar and neutral lipids. The fatty acid analysis conducted using the internal standard method and the biological assay on washed rabbit platelets took place calculating the in vitro inhibitory activity of fish lipids against 2.5 × 10^?11 M of PAF. No statistical changes (p<0.05) occurred in fatty acid content of fresh and thawed gilthead sea bream, while fatty acid amount in thawed sea bass was significantly higher (p<0.05) compared to fresh fish. Total lipids of both thawed fish species exhibited stronger anti‐thrombotic activity compared to fresh fish. Freezing preserved fish quality and reinforced the anti‐thrombotic properties of fish oils, since even after 6 months of freezing, fish oils preserve their nutritional value in terms of protecting against cardiovascular diseases. Practical applications: Fish fillets contain high amount of unsaturated lipids that may easily undergo lipid oxidation. Freezing and frozen storage prevent such oxidative changes so fish quality is retained. Fatty acids and PAF‐antagonists in fish are of major importance since they contribute to the nutritional value of fish. The practical application of this work lies on the evaluation of the nutritional value of fish in terms of cardio protection by examining the impact of freezing on the levels of fatty acids and PAF‐antagonists in aquacultured fish fillets.     

Oolichan Grease: A Unique Marine Lipid and Dietary Staple of the North Pacific Coast

Oolichan grease, a dietary fat prepared from smelt-like fish, is highly prized by north Pacific coast aboriginal cultures. The composition of oolichan grease is unclear, with one report indicating a high 22:6n-3 content consistent with cold-water marine oils, but another reporting a much lower value. We noted that oolichan grease remains solid up to 15 degrees C, suggesting a low polyunsaturate content. After extracting total lipids from four fresh oolichan fish and four samples of grease, fatty acids were quantitated by high resolution gas chromatography (GC), as were additional samples of fish lipid and grease that were fractionated into triglyceride (TG), phospholipid (PL), and free fatty acids by thin-layer chromatography. In contradistinction to one prior report, we found EPA and DHA in fresh fish total lipids to be 0.9 and 2.2 wt%, respectively, while in the extracted grease, both were reduced to 0.5 wt%. Only the fresh fish PL fraction contained appreciable DHA. The bulk of the grease consisted of saturated fatty acids (30.3 wt%) and mono-unsaturates (55.0 wt%), explaining its high melting point. Excepting its very low omega-6 content (<2 wt%), oolichan grease is quite similar in composition to human adipose TG. Its solid state at environmental temperatures and low peroxidizability index made it suitable for storage and transport, explaining its status as a preferred trade item among regional aboriginal groups.     

Isopropyl alcohol extraction of oil and lipids in the production of fish protein concentrate from herring

The extraction of lipid from fatty fish (herring) by the Halifax process for producing fish protein concentrate, using isopropyl alcohol (IPA), is virtually complete. The largest portion of the lipid is found in the first extract and high quality triglyceride oil is readily recovered by cooling this extract; under certain circum-stances it can also be recovered from the second extract. The phospholipids are extracted without obvious degradation and together with free fatty acids are found mostly in the IPA-rich phase from the first extraction. Residual lipid in fish protein concentrate resembles the starting lipid of the fish. Detailed fatty acid compositions are given for various materials.     

Biosynthesis of fatty acids by the carp,Cyprinus carpio L., in relation to environmental temperature

Incorporation in vivo of sodium 1-¹⁴C-acetate into different lipid classes and fatty acids of total lipids and phospholipids of warm adapted and cold adapted carp livers was studied at 5 C and 22 C, respectively. The fatty acid composition of total lipids and phospholipids was also determined. The level of long chain polyunsaturated fatty acids in both total lipid and phospholipid fractions was higher in cold adapted fish than in warm adapted ones. The distribution of radioactivity among different lipid classes depended only on the actual incorporation temperature and was independent of the temperature history of the animals. Livers of fish incorporated a higher percentage of radioactivity into long chain polyunsaturated fatty acids of total lipids and phospholipids in 5 C than in 22 C. The distribution of radioactivity among different fatty acids was dependent on the experimental temperature rather than on the temperature to which the fish were adapted. The results suggest that fish are able to adjust the pattern of the biosynthesis of fatty acids very rapidly to the prevailing temperature and to assure by this way the proper physicochemical properties of their membranes. The possible mechanisms involved in this rapid response are discussed.     

Composition of muscle tissue lipids of silver carp and bighead carp

Lipids have a complex role in the nutritional value of food. Some polyunsaturated fatty acids, characterized as essential, are extremely important for human health. This is primarily related to α-linolenic acid (18:3n-3), eicosapentaenoic acid (20:5n-3) and docosahexaenoic acid (22:6n-3). Content of polyunsaturated n-3 fatty acids is usually much higher in lipids of marine fish than in freshwater fish. Previous investigations have shown that muscle tissue of silver carp and bighead carp from fish farms may be a rich source of essential fatty acids. Because of that, the objective of this work was to examine contents and composition of fatty acids and total lipids in the muscle tissue of silver and bighead carp, with the aim to find out whether there are significant differences in this respect between the two species and to what extent the harvest season can influence the composition of lipids in these freshwater fish. This study showed that there is no significant difference either in the content of polyunsaturated n-3 and n-6 fatty acids, or in the n-6/n-3 fatty acid ratio in these two fish species. The lipids of both the silver and bighead carp from the spring harvest have significantly higher contents of the n-3 acids and a significantly lower n-6/n-3 ratio than fish from the autumn harvest.     

Effect of extraction methods on lipid yield and fatty acid composition of lipid classes containing γ-linolenic acid extracted from fungi

The effect of extraction procedures on the lipid yield and fatty acid composition of total lipid and main lipid structures (phospholipids, diacylglycerols, triacylglycerols, free fatty acids, and sterol esters) of fungal biomass (Mucor mucedo CCF-1384) containing γ-linolenic acid (GLA) was investigated. Seventeen extraction methods, divided into three groups, were tested: six with chloroform/methanol, five with hexane/alcohols, and six with common solvents or mixtures. The chloroform/methanol procedure (2∶1) was selected as standard, where lipid yield (TL/DCW, total lipid per dry cell weight) was 17.8%, considered to be 100% of lipids present. All chloroform/methanol extractions yielded more than 83% recorvey of lipids. Use of hexane/isopropanol solvent systems led to a maximum of 75% recovery. The best lipid yield was achieved by a two-step extraction with ethanol and hexane (120%). Extraction efficiency of the other solvent systems reached a maximum of 73%. Triacylglycerols were the main structures of lipid isolated; only methanol-extracted lipid contained 58.5% phospholipids. The fatty acid content of total recovered lipid was variable and depended on both the lipid class composition and the solvent system. GLA concentrations in total lipids isolated by hexane/alcohol procedures (7.3–10.7%) are comparable with classical chloroform/methanol systems (6.5–10.0%). The maximal GLA yield was obtained with chloroform/methanol/n-butanol/water/0.1 M ethylenediaminetetraacetic acid (EDTA) (2∶1∶1∶1∶0.1, by vol) and after two-step extraction with ethanol and hexane (14.3 and 13.7 g GLA/kg DCW, respectively). The highest GLA content was analyzed in the phospholipid fraction (16.1%) after using chloroform/methanol/n-butanol/water/0.1 M EDTA (2∶1∶1∶1∶0.1, by vol). Remarkably low concentrations of polyunsaturated fatty acids were determined in the free fatty acid fraction.     

Supercritical carbon dioxide fractionation of fish oil fatty acid ethyl esters

Fractionation of fish oil fatty acid ethyl esters was investigated with the aim of obtaining a lipid fraction enriched in ω-3 fatty acids and with a suitable EPA/DHA ratio. The results obtained highlight the possibility of modifying the original fatty acid ethyl esters concentration by optimizing the extraction conditions in terms of pressure, temperature, and supercritical carbon dioxide flow rate. Supercritical fluid fractionation (SFF) appears to be a useful processing technique for changing the composition of lipids in order to obtain high value functional products. The use of proper fractionation temperatures and pressures along the column influenced the solvent-to-feed ratio to obtain fractions with suitable composition for market requirements.     

Lipids of the Antarctic sei whale,Balaenoptera borealis

The blubber, liver, and muscle of the Antarctic sei whale were analyzed for total lipid content, composition of lipid by classes and positional distribution of fatty acids in individual lipids. The major glycerolipids (triglycerides, phosphatidylcholine, and phosphatidylethanolamine) were fractionated by silver nitrate thin layer chromatography. The phospholipid fractions were analyzed for fatty acid positional distribution. The whale stomach contained almost exclusively the amphipodParathemisto gaudichaudi. Its lipids were also studied and compared with the lipids of the body tissues. The results indicate that the stomach content lipids are subjected to modifications before being deposited in the blubber, liver, and muscle. According to the silver nitrate thin layer chromatographic studies, liver and blubber triglycerides resemble each other in their patterns of positional distribution of fatty acids and in molecular species composition. The phospholipids of liver and blubber also exhibited closely related fatty acid distribution patterns. In general, while the proportions of lipid classes and their predominant fatty acids varied from tissue to tissue, the patterns according to which the lipids had been synthesized seemed to be common. “...And beneath the effulgent Antarctic skies I have boarded the Argo-Navis, and joined the chase against the starry Cetus far beyond the utmost stretch of Hydrus and the Flying Fish.” (1).     

Lipid Content and Fatty Acid Composition of 15 Marine Fish Species from the Southeast Coast of Brazil

Lipid content and fatty acid composition were determined in edible meat of fifteen marine fish species caught on the Southeast Brazilian coast and two from East Antarctic. Most of the fish had lipid amounts lower than 10% of their total weight. Palmitic acid (C16:0) predominated, accounting for 54–63% of the total amount of saturated fatty acids. Oleic acid (C18:1n-9) was the most abundant (49–69%) monounsaturated fatty acid, and docosahexaenoic acid (DHA) was the predominant polyunsaturated fatty acid (PUFA), accounting for 31–84% of n-3 PUFA. n-3 PUFA level were highest in Antarctic fish meat, comprising 45% of the total fatty acid content, which consisted of mainly EPA (16.1 ± 1.5 g/100 g lipids) and DHA (24.8 ± 2.4 g/100 g lipids). The amounts of EPA + DHA in g/100 g of lipids on the Southeast Brazilian coast and Antarctic fish species investigated were found to be similar: 42.0 ± 1.7 for Bonito cachorro, 41.0 ± 2.3 for Atum, and 39.4 ± 1.8 for peixe porco, respectively. All the studied species exhibited an n-3/n-6 ratio higher than 3, which confirms the great importance of Southeast Brazilian coast fish as a significant dietary source of n-3 PUFA.     

Fatty alcohols in capelin,herring and mackerel oils and muscle lipids: II. A comparison of fatty acids from wax esters with those of triglycerides

The fatty acids recovered from the triglycerides and wax esters of common northwest Atlantic copepods are compared with the fatty acids of wax esters recovered intact from certain fish skin and body lipid, and from commercial fish oils. The fish species, herring, capelin and mackerel, all feed on copepods, and many resemblances of the copepod lipid fatty acids to those of a previous analysis of similar copepods suggest that the basic dietary fat input for these fish may be quite constant. The two copepod fatty acid analyses differed quantitatively in triglyceride 20∶1 and 22∶1 and also in 20∶5ω3 and 22∶6ω3, confirming the primary role of the wax esters in copepods. Selectivity factors are discussed in comparing the copepod wax ester fatty acids with the fatty acids of the wax esters recovered intact from the fish lipids and oils. The basic role of copepods in supplying all types of fatty acids to fish depot fats is considered to be strongly supported by these findings.     

The lipids of corn germ and endosperm

Mature kernels of an inbred corn were hand dissected into germ and endosperm fractions. Among various solvents tested, boiling, water-saturatedn-butanol extracted the most lipid from endosperm, and it was used as t h e extracting solvent for both germ and endosperm. The germ contained 78% of the total lipids and the endosperm 17%. The most striking differences in the fatty acid compositions of the triglycerides and polar lipids were higher levels of stearic and linolenic acids in the endosperm lipids. Although precautions were taken during extraction to inactivate lipases, immediately after harvest the free fatty acid level of the total lipids of the whole kernel was 6.5%. Ninety-five percent of the free fatty acids was in the endosperm fraction where the free fatty acids made up 36.5% of the total lipids. In germ, free fatty acids represented only 0.6% of the total lipids. The individual phospholipid and glycolipid classes of the endosperm and germ lipids were similar except for high levels of lyso compounds in the endosperm lipids. The higher levels of linolenic acid, free fatty acids and lyso lipids in endosperm may affect the keeping quality of the corn grain and of fractions milled from the endosperm. Presented at the AOCS meeting, St. Louis, May 1978.     

Veränderungen im Lipidmuster von Rotbarsch (Sebastes marinus L.) bei der Gefrierlagerung, 1. Mitteilung: Untersuchungen an homogenisiertem Filet mittels Hochleistungsflüssigchromatographie (HPLC)

Changes in Lipid Class Composition of Homogenized Redfish Fillet (Sebastes marinus L.) During Frozen Storage at ?12° C as Monitored by HPLC Redfish (Sebastes marinus L.) was caught in the North Atlantic and the fish muscle was minced immediately after hauling. Samples of mince were stored at ?12° C and subjected to lipid extraction at different time intervals. HPLC analysis showed a very low level of free fatty acids in fresh fish and an increase during storage at ?12° C. Polar lipids decreased on storage, the neutral lipids were almost unchanged.