Digestion of the 1-O-alkyl diacylglycerol ethers of atlantic dogfish liver oils by Atlantic salmon Salmo salar

Dogfish (Squalus acanthias) liver poses a waste disposal problem in Canada because it is not utilized for any commercial purpose. The liver of Atlantic dogfish, which is often up to 20% of the weight of the fish, contains 40–70% oil. The oil contains about 30–40% 1-O-alkyl diacylglycerol ethers (DAGE) which render it unacceptable for human use, and it has also not been considered satisfactory for animal feed use. Polyunsaturated fatty acids (20∶5n−3 and 22∶6n−3) are present in dogfish liver oils at levels comparable to those in herring oil. Dogfish liver oil could be a source of essential fatty acids for Atlantic salmon (Salmo salar), but their ability to hydrolyze DAGE from dogfish oil has not been examined. Experiments were designed to measure the digestibility of fatty acids of DAGE in salmon. The fatty acid moieties were liberated by the digestive enzymes of the fish and made readily available as a source of energy. The 1-O-alkylglycerol ether moiety was absorbed to a small extent but should not constitute a health problem in either the fish or the human fish consumer. The long-chain polyunsaturated fatty acids were particulary well absorbed, with an apparent digestibility in salmon of 87–95% when feeding on dogfish liver oil. The total fatty acids and other lipids were in fact both absorbed to the extent of approximately 85%. Presented in part at the Annual Meeting of the American Oil Chemists’ Society, Atlanta, Georgia, May 1994.     

Digestion and absorption of free and esterified fish oil fatty acids in rats

This study was designed to test the hypotheses that digestibility and post-absorption metabolism of fish oil are influenced by impaired lipolysis and by the stereospecific composition of its triacylglycerols. Male Wistar rats were fed nonpurified diets containing one of the following fat sources: 9% native fish oil (NFO), 9% autorandomized fish oil (RFO), 8.1% fish oil-derived free fatty acids (FO-FFA) plus 0.9% glycerol, or 9% soybean oil (SO) as a reference fat. In a 24-day balance study, apparent digestibility of total dietary fat averaged 93.1% in the SO, NFO and RFO groups, and 90.9% in the FO-FFA group. Randomization of fish oil had no effect on apparent digestibility of individual fatty acids. In rats fed FO-FFA, apparent absorption of saturated and monounsaturated fatty acids was lower when compared to the NFO and RFO groups. Feeding the FO-FFA diet tended to increase plasma triglyceride content. The hypocholesterolemic effect of polyunsaturated n−3 fatty acids was not influenced by the dietary source. Similar effects on fatty acid profiles of plasma and liver phospholipids were caused by the NFO, RFO and the FO-FFA diets. We conclude that once polyunsaturated n−3 fatty acids are absorbed, their effect on lipid metabolism is not determined by the dietary source.     

Composition of wax esters,triglycerides and diacyl glyceryl ethers in the jaw and blubber fats of the Amazon River dolphin (Inia geoffrensis)

The lower jaw fat of the Amazon River dolphinInia geoffrensis contains 52.8% wax ester, 44.7% triglyceride and 2.5% diacyl glyceryl ether, while its dorsal blubber fat is >98% triglyceride. Examination of the intact lipids, the derived fatty acids and the derived fatty alcohols by gas chromatography reveals that the blubber triglycerides show characteristics of freshwater fish fats, but the jaw fat lipids have several distinctive features. Jaw fat wax esters, triglycerides and diacyl glyceryl ethers are all rich in C₁₀, C₁₂ and C₁₄ fatty acids and contain no polyunsaturated acids. The fatty alcohols in the wax esters are over 90% saturated. The major carbon numbers in the jaw fat triglycerides (C₃₈–C₄₆) are considerably lower than those of the blubber triglycerides (C₄₈–C₅₄). The possible adaptation of the jaw lipids for use in the underwater echolocation process of this dolphin is discussed.     

The high content of monoene fatty acids in the lipids of some midwater fishes: Family myctophidae

The total lipids of eleven species of Myctophids caught at depths between 20 and 700 m in the northern Pacific Ocean were analyzed using silicic acid column chromatography (lipid classes) and capillary gas chromatography (fatty acid and fatty alcohol composition). The major components in the lipid classes were triacylglycerols or wax esters; triacylglycerols were the dominant acyl neutral lipids (68.1–96.1%) in eight species, and wax esters were found as the dominant lipid (85.5–87.9%) in three species. The major fatty acids and alcohols contained in the was esters of the three fishes were 18:1n–9, 20:1n–9, 20:1n–11, and 22:1n–11 for fatty acids, and 16:0, 18:1, 20:1, and 22:1 for fatty alcohols. Fatty acids in the triacylglycerols ranging from C₁₄ to C₂₂ were predominantly of even chain length. The major components were 16:0, 16:1n–7, 18:1n–9, 20:1n–11, 22:1n–11, 20:5n–3 (icosapentaenoic acid), and 22:6n–3 (docosahexaenoic acid). In both the triacylglycerols and the wax esters, the major fatty components were monoenoic acids and alcohols. It is suggested from the lipid chemistry of the Myctophids that they may prey on the same organisms as the certain pelagic fishes such as saury and herring, because the large quantities of monoenoic fatty acids are similar to those of saury, herring, and sprats whose lipids originate from their prey organisms such as zooplanktons which are rich in monoenoic wax esters.     

Variation in fatty acid composition of the different acyl lipids in seed oils from fourSesamum species

Seeds from different collections of cultivatedSesamum indicum Linn. and three related wild species [specifically,S. alatum Thonn.,S. radiatum Schum and Thonn. andS. angustifolium (Oliv.) Engl.] were studied for their oil content and fatty acid composition of the total lipids. The wild seeds contained less oil (ca. 30%) than the cultivated seeds (ca. 50%). Lipids from all four species were comparable in their total fatty acid composition, with palmitic (8.2–12.7%), stearic (5.6–9.1%), oleic (33.4–46.9%) and linoleic acid (33.2–48.4%) as the major acids. The total lipids from selected samples were fractionated by thin-layer chromatography into five fractions: triacylglycerols (TAG; 80.3–88.9%), diacylglycerols (DAG; 6.5–10.4%), free fatty acids (FFA; 1.2–5.1%), polar lipids (PL; 2.3–3.5%) and steryl esters (SE; 0.3–0.6%). Compared to the TAG, the four other fractions (viz, DAG, FFA, PL and SE) were generally characterized by higher percentages of saturated acids, notably palmitic and stearic acids, and lower percentages of linoleic and oleic acids in all species. Slightly higher percentages of long-chain fatty acids (20∶0, 20∶1, 22∶0 and 24∶0) were observed for lipid classes other than TAG in all four species. Based on the fatty acid composition of the total lipids and of the different acyl lipid classes, it seems thatS. radiatum andS. angustifolium are more related to each other than they are to the other two species.     

Evidence that palmitic acid is absorbed assn-2 monoacylglycerol from human milk by breast-fed infants

Milk fatty acids consist of about 20–25% palmitic acid (16∶0), with about 70% of 16∶0 esterified to thesn-2 position of the milk triacylglycerols. Hydrolysis of dietary triacylglycerols by endogenous lipases producessn-2 monoacylglycerols and free fatty acids, which are absorbed, reesterified, and then secreted into plasma. Unesterified 16∶0 is not well absorbed and readily forms soaps with calcium in the intestine. The positioning of 16∶0 at thesn-2 position of milk triacylglycerols could explain the high coefficient of absorption of milk fat. However, the milk lipase, bile salt-stimulated lipase, has been suggested to complete the hydrolysis of milk fat to free fatty acids and glycerol. These studies determined whether 16∶0 is absorbed from human milk assn-2 monopalmitin by comparison of the plasma triacylglycerol total andsn-2 position fatty acid composition between breast-fed and formula-fed term gestation infants. The human milk and formula had 21.0 and 22.3% of 16∶0, respectively, with 54.2 and 4.8% 16∶0 in the fatty acids esterified to the 2 position. The plasma triacylglycerol total fatty acids had 26.0±0.6 and 26.2±0.6% of 16∶0, and thesn-2 position fatty acids had 23.3±3.3 and 7.4±0.7% of 16∶0 in the three-month-old exclusively breast-fed (n=17) and formula-fed (n=18) infants, respectively. Marked differences were found in the plasma total and the 2 position phospholipid percentage of 20∶4ω6, i.e., 11.6±0.3 and 6.9±0.6 (total), 17.7±1.4 and 9.7±0.6 (sn-2 position) and percentage of 22∶6ω3, 4.6±0.3 and 2.1±0.3 (total), 5.6±0.6 and 2.0±0.2 (sn-2 position) for the breast-fed and formula-fed infants, respectively. These studies provide convincing evidence that 16∶0 is absorbed from human milk assn-2 monoacyl-glycerol. The metabolic significance of the differences in positional distribution of fatty acids in the plasma lipids of breast-fed and formula-fed infants is not known.     

Influence of triacylglycerol structure and fatty acid profile of dietary fats on milk triacylglycerols in the rat. A two-generation study

We investigated the influence of dietary fatty acid profile and triacylglycerol structure on the fatty acid profile and triacylglycerol structure of milk lipids in two generations of rats. Three groups of rats received diets containing 20% fat of which approximately 20% was n-3 fatty acids located in different positions of the triacylglycerol: a fish oil-based diet [docosahexaenoic acid (22:6n-3) predominantly in thesn-2 position], a seal oil-based diet (22:6n-3) predominantly in thesn-1/sn-3 position or a plant oil-based diet [α-linolenic acid (18:3n-3) distributed evenly between the three positions]. This design allowed us to investigate (i) the effect of the triacylglycerol structure of the dietary fat; (ii) the effect of receiving the n-3 fatty acids as long-chain derivatives or as the precursor, 18:3n-3; and (iii) the long-term effects over two generations. The fatty acid profiles of the milk lipids largely reflected the diets, but in the second generation, the level of medium-chain fatty acids was higher (P<0.05) in the milk from rats fed the fish oil diet (24%) compared with the other dietary groups (15 and 18%). This suggests an increased endogenous synthesis of fatty acids in the mammary glands of the fish oil-fed rats. The levels of long-chain n-3 fatty acids in milk were higher (P<0.05) in rats fed maire n-3 fatty acids in milk were higher (P<0.05) in rats fed marie oils (8–12%) compared with rats fed vegetable oil (1%) in both generations. The level of long-chain n-3 fatty acids was significantly higher in the milk from the fish oil-fed rats (12.3%) compared to the seal-oil fed rats (8.0%) in the first generation, but not in the second generation (8.9 vs. 9.1%). The general structure of milk triacylglycerols was maintained in the three experimental groups with 16:0 acylated in thesn-2 position and 18:1 in thesn-1/sn-3 positions. The triacylglycerol structure of mammalian milk appears to be conserved even during extreme dietary manipulation over two generations and an extensive enrichment with long-chain n-3 polyunsaturated fatty acids requires their presence in the diet.     

Comparative study of the molecular species of chloropropanediol diesters and triacylglycerols in milk fat

In an effort to establish the origin of the fatty acid esters of 3-chloropropanediol, which recently have been isolated in small amounts from goat milk, we compared the molecular species composition of the chlorohydrin diesters and of goat milk triacylglycerols. The chloropropanediol diesters were found to be composed of molecular species containing C₁₀−C₁₈ fatty acids and corresponded closely in carbon number to those calculated for the long chain sn-1,2-diacyl-glycerol moieties of goat milk triacylglycerols. The molecular species of goat milk total triacylglycerols contained C₄−C₁₈ fatty acids. It is suggested that triacylglycerols and chloropropanediol diesters are derived from the same pool of long chain fatty acids. A molecular distillate of bovine milk fat did not contain chloropropanediol diesters, while the available samples of human milk fat were shown to contain alkyldiacylglycerols as the major components of a neutral lipid fraction corresponding in polarity to the chloropropanediol diesters.     

Milk fat structure of a patient with type 1 hyperlipidemia

Structural analyses were performed on milk fat samples obtained 3–10 days postpartum from a lactating patient with primary Type 1 hyperlipidemia. The milk triacylglycerols contained 3–7% C₁₀, 14–21% C₁₂, 20–30% C₁₄, 22–26% C₁₆ and 20–30% C₁₈ (largely oleic) acids. Gas liquid chromatographic (GLC) analyses of the X-1,3- and X-1,2-diacylglycerols on polar siloxane columns showed a markedly non-random association of acyl chains. Stereospecific analyses indicated that the short chain length fatty acids were confined essentially to the sn-3-position of the triacylglycerol molecule. Furthermore, these acids were largely absent from the phosphatidylcholines and the endogenous sn-1,2-diacylglycerols of the milk fat. It is concluded that the short chain fatty acids are incorporated into the milk triacylglycerols during the final stage of biosynthesis via the phosphatidic acid pathway, and that the overall fatty acid distribution is consistent with the 1-random 2-random 3-random hypothesis.     

Positional distribution on n−3 fatty acids in triacylglycerols from rat adipose tissue during fish oil feeding

The present study was designed to investigate the metabolism of the n−3 olyunsaturated fatty acids (PUFA) in adipose tissue and its dependence upon dietary factors. Changes in the positional distribution of the fatty acids in triacylglycerols from retroperitoneal adipose tissue were studied as a function of time on rats fed for 4 wk a diet enriched with fish oil. The stereospecific analysis of triacylglycerols was based on random formation ofrac-1,2-diacylglycerols by Grignard degradation. This was followed by synthesis ofrac-phosphatidic acids and treatment with phospholipase A₂. In the triacylglycerols of the fish oil diet, 57% of the total n−3 fatty acids were in position 3,i.e., two-thirds of 22∶5n−3 and 22∶5n−3 were esterified insn-3 position, whereas 22∶6n−3 was equally distributed in positions 2 and 3. After 4 wk of feeding fish oil, the fatty acid composition of adipose tissue triacylglycerols reached a steady state. Half of the n−3 fatty acids were found in position 3, namely 75% of 22∶5n−3, 50% of 20∶5n−3 and 18∶4n−3 and 45% of 22∶6n−3, the latter being equally distributed in positions 2 and 3. This pattern of distribution resembled that found in triacylglycerols of the fish oil diet, except for a higher proportion of 20∶5n−3 in adipose tissue in position 1 at the expense of position 3. Throughout the 4-wk period of fish oil feeding, the distribution pattern of minor n−3 fatty acids (18∶4n−3 and 22∶5n−3) in adipose tissue triacylglycerols remained unchanged. On the other hand, at the onset of fish oil feeding, 20∶5n−3 and 22∶6n−3 became concentrated in position 3, but thereafter 20∶5n−3 was progressively incorporated into position 1 and 22∶6n−3 into position 2. We thus conclude that n−3 fatty acids are differentially esterified in triacylglycerols of white adipose tissue. Despite the complex sequence of hydrolysis and acylation steps involved, the positional distribution of n−3 fatty acids was found to be similar in both the fish oil diet and the stored fat, in contrast to what was observed for nonessential fatty acids.     

A cross-species comparison of neutral lipid composition of milk fat of prosimian primates

The fatty acid composition of milk fat is known to be affected by dietary and genetic differences, while the milk triacylglycerol structure is believed to be attuned to the needs of the subsequent lipolysis during gastrointestinal passage. The availability of milk samples from eight species of prosimian primates, whose milk triacylglycerol structure had not been analyzed, offered an opportunity to further assess these ideas. The milk samples were collected by manual expression and the lipids extracted with chloroform/methanol (2∶1, vol/vol). The lipid classes were resolved by thin-layer chromatography, and the neutral lipids subjected to detailed analyses by capillary gas-liquid chromatography of fatty acids and molecular species of triacylglycerols using nonpolar and polarizable liquid phases. The milk samples were found to differ greatly in total fat content (4–73%) and in the composition of the neutral liqid classes and molecular species. The concentration of triacylglycerols ranged from 88–95%, free fatty acids from 0.5–10%, alkyldiacylglycerols from 0.5–5.0%, and diacylglycerols, monoacylglycerols and free and esterified cholesterol made up the remainder. The fatty acid chain length ranged from C₈−C₂₄, with palmitic (16–31%) and oleic (13–40%) acids being the major components in most of the species. In all instances, the molecular association of the fatty acids differed from random distribution by a higher proportion of the monoacid (trioleoyl) and diacid (dipalmitoyloleoyl) glycerols. The phylogenetic influences on neutral milk lipid composition, however, remained unclear, as some of the differences between closely related species were greater than those between more distantly related ones. Triacylglycerol structures are abbreviated by listing their three constituent fatty acids in sequence, e.g., PPP, LaOL.     

Effects of different medium-chain fatty acids on intestinal absorption of structured triacylglycerols

To study the effect of the chain length of medium-chain fatty acids on the intestinal absorption of long-chain fatty acids, we examined the lymphatic transport of fat following administration of five purified structured triacylglycerols (STAG) containing different medium-chain fatty acids in the sn-1, 3 positions and long-chain fatty acids in the sn-2 position in a rat model. Significant amounts of medium-chain fatty acids were found in lymph samples after intragastric administration of 1,3-dioctanoyl-2-linoleyl-sn-glycerol (8∶0/18∶2/8∶0), 1,3-didecanoyl-2-linoleyl-sn-glycerol, and 1,3-didodecanoyl-2-linoleyl-sn-glycerol. The accumulated lymphatic transport of medium-chain fatty acids increased with increasing carbon chain length. The recoveries of caprylic acid (8∶0), capric acid (10∶0), and lauric acid (12∶0) were 7.3±0.9, 26.3±2.4, and 81.7±6.9%, respectively. No significant differences were observed for the maximal intestinal absorption of linoleic acid (18∶2n−6) when the chain length of medium-chain fatty acids at the primary positions was varied, and the absorption of 18∶2 and oleic acid (18∶1) from 8∶0/18∶2/8∶0 and 1,3-dioctanoyl-2-oleyl-sn-glycerol was similar. We conclude that the chain length of the medium-chain fatty acids in the primary positions of STAG does not affect the maximal intestinal absorption of long-chain fatty acids in the sn-2 position in the applied rat model, whereas the distribution of fatty acids between the lymphatics and the portal vein reflects the chain length of the fatty acids. Presented in part at the 3rd ISSFAL Conference, Lyon, France, June 1–5, 1998.     

Positional analyses of triacylglycerol fatty acids in the milk fat of the antarctic fur seal (Arctocephalus gazella)

The positional distribution of fatty acids has been determined for the milk triacylglycerols of the Antarctic fur seal,Arctocephalus gazella. Of particular interest was the positional distribution of the polyunsaturated n−3 fatty acids in milk triacylglycerols (TG). In adipocytes of pinnipeds, TG are synthesized with the n−3 fatty acids primarily in thesn-1,3 positions. To determine the positional distribution, extracts of enzymatically digested lipids were separated by thin-layer chromatography, and the constituent fatty acids were separated and quantified by gas-liquid chromatography. Monoenoic and saturated fatty acids comprised over 75% of the total, the ratio of monoenoic to saturated fatty acids being 2∶1. The percent content of the long-chain n−3 fatty acids, 20∶5, 22∶5 and 22∶6, ranged between 15–20%. The positional analyses revealed that at thesn-2 position of milk TG, saturated fatty acids were in excess (57%), and the content of n−3 fatty acids was less than 5%. More than 80% of the n−3 fatty acids in milk were located in thesn-1,3 positions. The data indicate that in pinnipeds TG are synthesized in the mammary gland and adipose tissue with fatty acids having similar positional distributions.     

Relationship between oxidative stability of vitamin E and production of fatty acids in oils during microwave heating

Effects of microwave heating on the oxidative stability ofd-tocopherols were studied in relation to the production of fatty acids in oils. During microwave heating, the stability of tocopherols decreased in the orderδ>β>γ>α. This order did not depend on the types of ethyl esters of fatty acids or oils present. But, the shorter the chainlength and the lower the degree of unsaturation of the fatty acid ethyl esters, the greater was the reduction in amount of individual tocopherols. A similar tendency was observed when tocopherol-stripped vegetable oils, with equimolar mixtures of tocopherols added, were treated under the same conditions. The reduction in tocopherols became greater with increasing levels of free fatty acids.     

The absorption of fish oils and concentrates

Both preventive and curative therapies have created a considerable demand for eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids. The most common sources for ω3 fatty acids are fish oil. The concentrations of EPA and DHA in commercial oils, after modest enrichment, reach about 300 mg/g; alternative technologies can produce reasonably priced fish oils containing 400 or even 500 mg/g of ω3 acids. When the acids are liberated from the glycerides, concentrates of ethyl esters or free acids with 65 to 70% total ω3 fatty acids (at least 50% EPA+DHA) are readily prepared. Difficulties have arisen because most clinical trials have used fish oils of unspecified composition, and some trials are now based on either ethyl esters or free acids. There are at least three different, but not mutually exclusive, absorption routes in humans, namely the preduodenal route, the lymphatic routevia chylomicrons, and the routevia the portal vein to the liver. This makes it difficult to compare results. The difficulty in obtaining dose-related clinical data may in part be due to the form in which the ω3 acids are offered and due in part to the natural presence of these fatty acids in the body. The nontriglyceride forms, especially the free acids, have been advocated for standardization of trials to facilitate interlaboratory comparisons. Based on a paper presented at the Symposium on Milk Lipids held at the AOCS Annual Meeting, Baltimore, MD, April 1990.     

A Comprehensive Evaluation of the Melting Points of Fatty Acids and Esters Determined by Differential Scanning Calorimetry

The melting point is one of the most important physical properties of a chemical compound and it plays a significant role in determining possible applications. For fatty acid esters the melting point is essential for a variety of food and non-food applications, the latter including biodiesel and its cold-flow properties. In this work, the melting points of fatty acids and esters (methyl, ethyl, propyl, butyl) in the C₈–C₂₄ range were determined by differential scanning calorimetry (DSC), many of which for the first time. Data for triacylglycerols as well as ricinoleic acid and its methyl and ethyl esters were also acquired. For some compounds whose melting points have been previously reported, data discrepancies exist and a comprehensive determination by DSC has not been available. Variations in the present data up to several °C compared to data in prior literature were observed. The melting points of some methyl-branched iso- and anteiso-acids and esters were also determined. Previously unreported systematic effects of compound structure on melting point are presented, including those for ω-9 monounsaturated fatty acids and esters as well as for methyl-branched iso and anteiso fatty acids and esters. The melting point of a pure fatty acid or ester as determined by DSC can vary up to approximately 1 °C. Other thermal data, including heat flow and melting onset temperatures are briefly discussed. Product names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by USDA implies no approval of the product to the exclusion of others that may also be suitable.     

Esterified lipids of the freshwater dinoflagellatePeridinium lomnickii

Steryl esters, phytyl esters and triacylglycerols of a naturally occurring freshwater dinoflagellate,Peridinium lomnickii, were identified using capillary gas chromatography-mass spectrometry (GC-MS). Steryl esters differing in degree of unsaturation were separated, prior to analysis, by argentation thin layer chromatography. 5α(H)-Cholestanol was more dominant, relative to 4α-methylstanols, in steryl esters than in the free sterols, but the same sterol moieties occurred in both fractions. Monoenoic fatty acids were enriched in the steryl esters relative to the free fatty acids. Major acyl groups in steryl esters were 16∶0 or 20∶1, with smaller amounts of 14∶0 and 18∶1. In triacylglycerols the acyl moieties were 14∶0, 16∶0, 18∶1, 16∶1 and 12∶0, in order of decreasing abundance. Phytyl esters, previously inferred to occur in a marine dinoflagellate only by analysis of transesterified products, were identified by GC-MS comparison with authentic compounds. Direct analysis of these esterified lipids has not been reported for freshwater phytoplankton. The 4α-methylstanyl esters, 5α(H)-cholestan-3β-yl esters and phytyl esters occurring inP. lomnickii are further features in common with marine dinoflagellates, additional to the 4α-methylsterols reported previously.     

Acylglycerols Containing Trihydroxy Fatty Acids in Castor Oil and the Regiospecific Quantification of Triacylglycerols

Ricinoleate, a monohydroxy fatty acid in castor oil, has many industrial uses. Dihydroxy and trihydroxy fatty acids can also be used in industry. We report here the identification of diacylglycerols (DAG) and triacylglycerols (TAG) containing trihydroxy fatty acids in castor oil. The C₁₈ HPLC fractions of castor oil were used for mass spectrometry of the lithium adducts of acylglycerols to identify trihydroxy fatty acids and the acylglycerols containing trihydroxy fatty acids. Two DAG identified were triOH18:1–diOH18:1 and triOH18:0–OH18:1. Four TAG identified were triOH18:1–OH18:1–OH18:1, triOH18:0–OH18:1–OH18:1, triOH18:1–OH18:1–diOH18:1 and triOH18:0–OH18:1–diOH18:1. The structures of these two newly identified trihydroxy fatty acids were proposed as 11,12,13-trihydroxy-9-octadecenoic acid and 11,12,13-trihydroxyoctadecanoic acid. The locations of these trihydroxy fatty acids on the glycerol backbone were almost 100% at the sn-1,3 positions or at trace levels at the sn-2 position. The content of these acylglycerols containing trihydroxy fatty acids was at the level of about 1% or less in castor oil.     

Modification of butterfat by selective hydrolysis and interesterification by lipase: Process and product characterization

Butterfat was chemically modified via combined hydrolysis and interesterification, catalyzed by a commercial lipase immobilized onto a bundle of hydrophobic hollow fibers. The main goal of this research effort was to engineer butterfat with improved nutritional properties by taking advantage of the sn-1,3 specificity and fatty acid specificity of a lipase in hydrolysis and ester interchange reactions, and concomitantly decrease its level of long-chain saturated fatty acid residues (viz., lauric, myristic, and palmitic acids) and change its melting properties. All reactions were carried out at 40°C in a solvent-free system under controlled water activity, and their extent was monitored via chromatographic assays for free fatty acids, esterified fatty acid moieties, and triacylglycerols; the thermal behavior of the modified butterfat was also assessed via calorimetry. Lipase-modified butterfat possesses a wider melting temperature range than regular butterfat. The total saturated triacylglycerols decreased by 2.2%, whereas triacylglycerols with 28–46 acyl carbons (which contained two or three lauric, myristic, or palmitic acid moieties) decreased by 13%. The total monoene triacylglycerols increased by 5.4%, whereas polyene triacylglycerols decreased by 2.9%. The triacylglycerols of interesterified butterfat had ca. 10.9% less lauric, 10.7% less myristic, and 13.6% less palmitic acid residues than those of the original butterfat.     

Lipase-catalyzed synthesis of hydroxy stearates and their properties

Hydroxy fatty acid (HFA) esters of long-chain alcohols, such as hydroxy stearates, have potential applications from lubricants to cosmetics. These esters were synthesized enzymatically to overcome the problems associated with chemical processes. An immobilized lipase, Rhizomucor miehei, was employed as catalyst in the esterification reaction between hydroxy-stearic acid as a source of HFA and monohydric fatty alcohols (C₈–C₁₈). The yields of esters were in the range of 82–90% by conducting the reactions at 65±2°C, 2–5 mm Hg pressure, and 10% lipase concentration. The products were analyzed by infrared spectroscopy, and some of their analytical characteristics were determined.