Purification of tocopherols and phytosterols by a two-step <Emphasis Type="Italic">in situ</Emphasis> enzymatic reaction

The purification of tocopherols and phytosterols (referred to as sterols) from soybean oil deodorizer distillate (SODD) was attempted. Tocopherols and sterols in the SODD were first recovered by short-path distillation, which was named sODD tocopherol/sterol concentrate (SODDTSC). The SODD-TSC contained MAG, DAG, FFA, and unidentified hydrocarbons in addition to the two substances of interest. It was then treated with Candida rugosa lipase to convert sterols to FA steryl esters, acylglycerols to FFA, and FFA to FAME. Methanol (MeOH), however, inhibited esterification of the sterols. Hence, a two-step in situ reaction was conducted: SODDTSC was stirred with 20 wt% water and 200 U/g mixture of C. rugosa lipase at 30°C, and 2 moles of MeOH per mole of FFA was added to the reaction mixture after 16h. The lipase treatment for 40 h in total achieved 80% conversion of the initial sterols to FA steryl esters, complete hydrolysis of the acylglycerols, and a 78% decrease in the initial FFA content by methyl esterification. Tocopherols did not change throughout the process. To enhance the degree of steryl and methyl esterification, the reaction products, FA steryl esters and FAME, were removed by short-path distillation, and the resulting fraction containing tocopherols, sterols, and FFA was treated with the lipase again. Distillation of the reaction mixture purified tocopherols to 76.4% (recovery, 89.6%) and sterols to 97.2% as FA steryl esters (recovery, 86.3%).     

Isolation of tocopherol and sterol concentrate from sunflower oil deodorizer distillate

The isolation of tocopherols and sterols together as a concentrate from sunflower oil deodorizer distillate was investigated. The sunflower oil deodorizer distillate was composed of 24.9% unsaponifiable matter with 4.8% tocopherols and 9.7% sterols, 28.8% free fatty acid (FFA) and 46.3% neutral glycerides. The isolation technology included process steps such as biohydrolysis, bioesterification and fractional distillation. The neutral glycerides of the deodorizer distillates were hydrolyzed byCandida cylindracea lipase. The total fatty acids (initial FFA plus FFA from neutral glycerides) were converted into butyl esters withMucor miehei lipase. The esterified product was then fractionally distilled in a Claisen-vigreux flask. The first fraction, which was collected at 180–230°C at 1.00 mm of Hg for 45 min, contained mainly butyl esters, hydrocarbons, oxidized products and some amount of free fatty acids. The fraction collected at 230–260°C at 1.00 mm Hg for 15 min was rich in tocopherols (about 30%) and sterols (about 36%). The overall recovery of tocopherols and sterols after hydrolysis, esterification and distillation were around 70% and 42%, respectively, of the original content in sunflower oil deodorizer distillate.     

Recovery of sterols as fatty acid steryl esters from waste material after purification of tocopherols

Tocopherols are purified industrially from soybean oil deodorizer distillate by a process comprising distillation and ethanol fractionation. The waste material after ethanol fractionation (TC waste) contains 75% sterols, but a purification process has not yet been developed. We thus attempted to purify sterols by a process including a lipase-catalyzed reaction. Candida rugosa lipase efficiently esterified sterols in TC waste with oleic acid (OA). After studying several factors affecting esterification, the reaction conditions were determined as follows: ratio of TC waste/OA, 1∶2 (wt/wt); water content, 30%; amount of lipase, 120 U/g-reaction mixture; temperature, 40°C. Under these conditions, the degree of esterification reached 82.7% after 24 h. FA steryl esters (steryl esters) in the oil layer were purified successfully by short-path distillation (purity, 94.9%; recovery, 73.1%). When sterols in TC waste were esterified with FFA originating from olive, soybean, rapeseed, safflower, sunflower, and linseed oils, the FA compositions of the steryl esters differed somewhat from those of the original oils: The content of saturated FA was lower and that of unsaturated FA was higher. The m.p. of the steryl esters synthesized (21.7–36.5°C) were remarkably low compared with those of the steryl esters purified from high-b.p. soybean oil deodorizer distillate substances (56.5°C; JAOCS 80, 341–346, 2003). The low-m.p. steryl esters were soluble in rapeseed oil even at a final concentration of 10%.     

Purification of steryl esters from soybean oil deodorizer distillate

Soybean oil deodorizer distillate (SODD) contains steryl esters in addition to tocopherols and sterols. Tocopherols and sterols have been industrially purified from SODD but no purification process for steryl esters has been developed. SODD was efficiently separated to low b.p. substances (including tocopherols and sterols) and high b.p. substances (including 11.2 wt% DAG, 32.1 wt% TAG, and 45.4 wt% steryl esters) by molecular distillation. The high b.p. fraction is referred to as soybean oil deodorizer distillate steryl ester concentrate (SODDSEC). We attempted to purify steryl esters after a lipase-catalyzed hydrolysis of acylglycerols in SODDSEC. Screening of industrially available lipases indicated that Candida rugosa lipase was most effective. Based on the study of several factors affecting hydrolysis, the reaction conditions were determined as follows: ratio of SODDSEC/water, 1∶1 (w/w); lipase amount, 15 U/g reaction mixture; temperature, 30°C. When SODDSEC was agitated for 24 h under these conditions, acylglycerols were almost completely hydrolyzed and the content of steryl esters did not change. However, study with a mixture of steryl oleate/trilinolein (1∶1, w/w) indicated that about 20% of constituent FA in steryl esters were exchanged with constituent FA in acylglycerols. Steryl esters in the oil layer obtained by the SODDSEC treatment with lipase were successfully purified by molecular distillation (purity, 97.3%; recovery, 87.7%).     

Enzymatic pretreatment of deodorizer distillate for concentration of sterols and tocopherols

Separation of sterols and tocopherols from fatty acids in deodorizer distillate was facilitated through lipase-catalyzed modification of fatty acids in canola, mixed and soya deodorizer distillates. The fatty acid esterification with methanol catalyzed by SP-382 (an immobilized nonspecific lipase) proceeded rapidly, with conversion of fatty acid to methyl ester in 5 h being 96.5, 83.5 and 89.4%, respectively. A model mixture of pure oleic acid and dl-α-tocopherol was used to study any potential side reactions that may lower the tocopherol content during the esterification reaction. Under the conditions employed, the loss of tocopherol was less than 5%. Simple vacuum distillation (1–2 mm Hg) was employed to remove the volatile fraction (methyl esters of fatty acids, some fatty acids and other volatiles) of the esterified deodorizer distillate, leaving behind sterols, sterol esters and tocopherols. Sterols and tocopherols were almost completely retained in the residue fraction with recoveries in the range of 95%. Overall recoveries of sterols and tocopherols after esterification and distillation were over 90% for all the deodorizer distillate samples.     

Large-scale purification of γ-linolenic acid by selective esterification using Rhizopus delemar lipase

γ-Linolenic acid (GLA) is a physiologically valuable fatty acid, and is desired as a medicine, but a useful method available for industrial purification has not been established. Thus, large-scale purification was attempted by a combination of enzymatic reactions and distillation. An oil containing 45% GLA (GLA45 oil) produced by selective hydrolysis of borage oil was used as a starting material. GLA45 oil was hydrolyzed at 35°C in a mixture containing 33% water and 250 U/g-reaction mixture of Pseudomonas sp. lipase; 91.5% hydrolysis was attained after 24 h. Film distillation of the dehydrated reaction mixture separated free fatty acids (FFA; acid value 199) with a recovery of 94.5%. The FFA were selectively esterified at 30°C for 16 h with two molar equivalents of lauryl alcohol and 50 U/g of Rhizopus delemar lipase in a mixture containing 20% water. The esterification extent was 52%, and the GLA content in the FFA fraction was raised to 89.5%. FFA and lauryl esters were not separated by film distillation, but the FFA-rich fraction contaminated with 18% lauryl esters was recovered by simple distillation. To further increase the GLA content, the FFA-rich fraction was selectively esterified again under similar conditions. As a result, the GLA content in the FFA fraction was raised to 97.3% at 15.2% esterification. After simple distillation of the reaction mixture, lauryl esters contaminating the FFA-rich fraction were completely eliminated by urea adduct fractionation. When 10 kg of GLA45 oil was used as a starting material, 2.07 kg of FFA with 98.6% GLA was obtained with a recovery of 49.4% of the initial content.     

Extraction of tocopherols from the deodorized distillate of soybean oil with liquefied petroleum gas

Deodorizer distillate, produced during the last processing step of edible oil refinement, is a mixture of tocopherols, sterols, fatty acids, glycerides, hydrocarbons, water and other materials. The amount of tocopherols in deodorizer distillate is large enough to be considered as raw material for vitamin E preparation. In this work, separation of tocopherols from sterols has been achieved using liquefied petroleum gas (LPG) extraction. LPG was chosen as extraction solvent in order to improve extract recovery and prevent tocopherol degradation.     

Separation of squalene from olive oil deodorizer distillate using short-path molecular distillation

Squalene was recovered from an olive oil deodorizer distillate (OODD) containing 40% of squalene by a two-step process. The first step was to esterify the free fatty acids (FFAs) to make them less volatile. The second step was to separate the squalene by molecular distillation. The best esterification conditions were found to be 190°C and 360 min, where FFA content of the reaction mixture was reduced from 49.3% to 7.9%, however, an inevitable squalene loss (30%) was also observed due to a discontinuous operation. The remaining squalene (28%) in the esterified mixture was then distilled using a molecular distillation unit at elevated temperatures (190–230°C) and pressures (0.05–5 mmHg). When the temperature and vacuum during distillation increased, FFA content in the distillate reduced while distillate yield and squalene purity increased. The highest distillate yield (27.7%) and squalene purity (98.1%) were obtained at the highest applied temperature (230°C) under the lowest absolute pressure (0.05 mmHg), where FFA content of distillate was measured as 1.8%. High percentage of squalene (95%–98%) could be distilled at 230°C between 0.05 and 0.5 mmHg absolute pressures. The overall squalene recovery after all treatments was calculated as 68%.     

Application of short path distillation for recovery of polyphenols from deodorizer distillate

During physical refining of oil derived from ‘high temperature short time’ (HTST) pretreated rapeseeds, polyphenols are separated from the oil during deodorization and accumulate together with other high‐value minor compounds in the so‐called deodorizer distillate. For recovery of these compounds single‐stage and multistage short path distillations were carried out in a laboratory scale apparatus at evaporation temperatures between 110 and 170°C and pressures between 0.006 and 0.01 mbar. In addition, the removal of traces of pesticides from rapeseed deodorizer distillate was investigated. It was observed that these compounds can be separated from deodorizer distillate by means of short path distillation very effectively. On the basis of these experiments, a recovery process for polyphenols was proposed involving short path distillation, acid catalyzed esterification with methanol, solvent crystallization and solvent extraction processes. The final product was a polyphenol enriched extract containing about 14% of polyphenols. A polyphenol recovery of 50% is considered to be reachable and fractions rich in tocopherols and sterols may be obtained as by‐products.     

Purification of docosahexaenoic acid from tuna oil by a two-step enzymatic method: Hydrolysis and selective esterification

Purification of docosahexaenoic acid (DHA) was attempted by a two-step enzymatic method that consisted of hydrolysis of tuna oil and selective esterification of the resulting free fatty acids (FFA). When more than 60% of tuna oil was hydrolyzed with Pseudomonas sp. lipase (Lipase-AK), the DHA content in the FFA fraction coincided with its content in the original tuna oil. This lipase showed stronger activity on the DHA ester than on the eicosapentaenoic acid ester and was suitable for preparation of FFA rich in DHA. When a mixture of 2.5 g tuna oil, 2.5 g water, and 500 units (U) of Lipase-AK per 1 g of the reaction mixture was stirred at 40°C for 48 h, 83% of DHA in tuna oil was recovered in the FFA fraction at 79% hydrolysis. These fatty acids were named tuna-FFA-Ps. Selective esterification was then conducted at 30°C for 20 h by stirring a mixture of 4.0 g of tuna-FFA-Ps/lauryl alcohol (1:2, mol/mol), 1.0 g water, and 1,000 U of Rhizopus delemar lipase. As a result, the DHA content in the unesterified FFA fraction could be raised from 24 to 72 wt% in an 83% yield. To elevate the DHA content further, the FFA were extracted from the reaction mixture with n-hexane and esterified again under the same conditions. The DHA content was raised to 91 wt% in 88% yield by the repeated esterification. Because selective esterification of fatty acids with lauryl alcohol proceeded most efficiently in a mixture that contained 20% water, simultaneous reactions during the esterification were analyzed qualitatively. The fatty acid lauryl esters (L-FA) generated by the esterification were not hydrolyzed. In addition, L-FA were acidolyzed with linoleic acid, but not with DHA. These results suggest that lauryl DHA was generated only by esterification.     

Production of FAME from acid oil model using immobilized <Emphasis Type="Italic">Candida antarctica</Emphasis> lipase

Acid oil is a by-product in the neutralization step of vegetable oil refining and is an alternative source of biodiesel fuel. A model substrate of acid oil, which is composed of TAG and FFA, was used in experiments on the conversion to FAME by immobilized Candida antarctica lipase. FFA in the mixture of TAG/FFA were efficiently esterified with methanol (MeOH), but the water generated by the esterification significantly inhibited methanolysis of TAG. We thus attempted to convert a mixture of TAG/FFA to FAME by a two-step process comprising methyl esterification of FFA and methanolysis of TAG by immobilized C. antarctica lipase. The first reaction was conducted at 30°C in a mixture of TAG/FFA (1∶1, wt/wt) and 10 wt% MeOH using 0.5 wt% immobilized lipase, resulting in efficient esterification of FFA. The reaction mixture after 24 h was composed of 49.1 wt% TAG, 1.3 wt% FFA, 49.1 wt% FAME, and negligible amounts of DAG and MAG (<0.5 wt%). The reaction mixture was then dehydrated and used as a substrate for the second reaction, which was conducted at 30°C in a solution of the dehydrated mixture and 5.5 wt% MeOH using 6 wt% immobilized lipase. The activity of the lipase increased gradually when the reaction was repeated by transferring the enzyme to a fresh substrate mixture. The activity reached a maximum after 6 cycles, and the content of FAME achieved was >98.5 wt% after a 24-h reaction. The immobilized lipase was very stable in the first-and second-step reactions and could be used for >100 d without significant loss of activity.     

Simulation of continuous deodorizers: Effects on product streams

This work deals with the simulation of deodorization, one important process in the edible oil industry related to the removal of odoriferous compounds. The deodorizer was modeled as a multicomponent stripping-column in cross-flow and countercurrent flow. The impact of processing parameters on the quality of the product streams was analyzed. The deodorization of soybean and canola oils (plant scale) and wheat germ oil (lab-scale) was studied under typical ranges of temperature, stripping steam rate, and pressure. Their entire compositions were considered within the simulations, including acylglycerols, FFA, and other key components such as tocopherols and sterols. The deodorization results were analyzed in terms of retention of tocopherol and sitosterol and of neutral oil loss to the distillate. The deodorizer modeling considered Murphree efficiencies and entrainment for each plate. A case study, i.e., the deodorization of soybean oil, illustrated the applicability of our modeling.     

Enzymatic Production of Fatty Acid Methyl Esters by Hydrolysis of Acid Oil Followed by Esterification

Acid oil, a by-product of vegetable oil refining, was enzymatically converted to fatty acid methyl esters (FAME). Acid oil contained free fatty acids (FFA), acylglycerols, and lipophilic compounds. First, acylglycerols (11 wt%) were hydrolyzed at 30 °C by 20 units Candida rugosa lipase/g-mixture with 40 wt% water. The resulting oil layer containing 92 wt% FFA was used for the next reaction, methyl esterification of FFA to FAME by immobilized Candida antarctica lipase. A mixture of 66 wt% oil layer and 34 wt% methanol (5 mol for FFA) were shaken at 30 °C with 1.0 wt% lipase. The degree of esterification reached 96% after 24 h. The resulting reaction mixture was then dehydrated and subjected to the second esterification that was conducted with 2.2 wt% methanol (5 mol for residual FFA) and 1.0 wt% immobilized lipase. The degree of esterification of residual FFA reached 44%. The degree increased successfully to 72% (total degree of esterification 99%) by conducting the reaction in the presence of 10 wt% glycerol, because water in the oil layer was attracted to the glycerol layer. Over 98% of total esterification was maintained, even though the first and the second esterification reactions were repeated every 24 h for 40 days. The enzymatic process comprising hydrolysis and methyl esterification produced an oil containing 91 wt% FAME, 1 wt% FFA, 1 wt% acylglycerols, and 7 wt% lipophilic compounds.     

Lipase catalyzed synthesis of neutral glycerides rich in micronutrients from rice bran oil fatty acid distillate

Neutral glycerides with micronutrients like sterols, tocopherols and squalene may be prepared from cheap raw material like rice bran oil fatty acid distillate (RBO FAD). RBO FAD is an important byproduct of vegetable oil refining industries in the physical refining process. Glycerides like triacylglycerols (TAG), diacylglycerols (DAG) and monoacylglycerols (MAG) containing significant amounts of unsaponifiable matter like sterols, tocopherols and hydrocarbons (mainly squalene) may certainly be considered as novel functional food ingredients. Fatty acids present in RBO FAD were esterified with glycerol of varying amount (1:0.33, 1:0.5, 1:1 and 1:1.5 of FAD : glycerol ratio) for 8 h using non-specific enzyme NS 40013 (Candida antartica). After esterification the product mixture containing mono, di- and triglycerides was purified by molecular distillation to remove excess free fatty acids and also other volatile undesirable components. The purified product containing sterols, tocopherols and squalene can be utilized in various food formulations.     

Enzymatic synthesis of steryl esters of polyunsaturated fatty acids

Steryl esters of long-chain fatty acids have water-holding properties, and polyunsaturated fatty acids (PUFA) have various physiological functions. Because steryl ester of PUFA can be expected to have both features, we attempted to synthesize steryl esters of PUFA by enzymatic methods. Among lipases used, Pseudomonas lipase was the most effective for the synthesis of cholesteryl docosahexaenoate. When a mixture of cholesterol/docosahexaenoic acid (3:1, mol/mol), 30% water, and 3000 units/g of lipase was stirred at 40°C for 24 h, the esterification extent attained 89.5%. Under the same reaction conditions, cholesterol, cholestanol, and sitosterol were also esterified efficiently with docosahexaenoic, eicosapentaenoic, arachidonic, and γ-linolenic acids.     

Influence of the vegetable oil refining process on free and esterified sterols

The influence of the refining process on the distribution of free and esterified phytosterols in corn, palm, and soybean oil was studied. Water degumming did not affect the phytosterol content or its composition. A slight increase in the content of free sterols was observed during acid degumming and bleaching due to acid-catalyzed hydrolysis of steryl esters. A significant reduction in the content of total sterols during neutralization was observed, which was attributed to a reduction in the free sterol fraction. Free sterols probably form micelles with soaps and are transferred into the soapstock. The steryl ester content remained constant during all neutralization experiments, indicating that hydrolysis of steryl esters did not take place during neutralization. During deodorization, free sterols are distilled from the oil, resulting in a gradual reduction in the total sterol content as a function of the deodorization temperature (220–260°C). A considerable increase in the steryl ester fraction was found during physical refining, probably owing to a heat-promoted esterification reaction between free sterols and FA.     

The concentration of tocols from rice bran oil deodorizer distillate using solvent

Tocols (tocopherols + tocotrienols) have been concentrated efficiently from rice bran oil (RBO) deodorizer distillate using solvent at low temperature. The levels of total tocols, total tocopherols, and total tocotrienols in RBO deodorizer distillate (starting material) were 31.5, 14.9, and 16.6 mg/g, respectively. Nine different solvents were tested, and acetonitrile was selected as the optimal solvent for concentrating tocols from the RBO deodorizer distillate. There was a significant (p <0.05) increase in the tocol level of the liquid fractions with decreasing temperature, for incubation temperatures up to –20 °C. In addition, significant differences (p <0.05) were observed in the relative percentages of α‐tocopherol, γ‐tocopherol, α‐tocotrienol, and γ‐tocotrienol between the raw sample and liquid fractions obtained at different temperatures using acetonitrile as the solvent. The concentration of the tocols from the RBO deodorizer distillate was temperature dependent, and a maximum of 89.9 mg/g was attained in the liquid fraction at – 40 °C. The relative percentage of tocotrienol homologs in the liquid fraction obtained at – 40 °C was approximately 80%. With acetonitrile as the solvent, the optimal temperature for concentrating the tocols from RBO deodorizer distillate was –20 °C when yield was considered.     

Purification of γ-linolenic acid from borage oil by a two-step enzymatic method

γ-Linolenic acid (GLA) was purified from borage oil by a two-step enzymatic method. The first step involved hydrolysis of borage oil (GLA content, 22.2 wt%) with lipase, Pseudomonas sp. enzyme (LIPOSAM). A mixture of 3 g borage oil, 2 g water, and 5000 units (U) LIPOSAM was incubated at 35°C with stirring at 500 rpm. The reaction was 91.5% complete after 24 h. The resulting free fatty acids (FFA) were extracted from the reaction mixture with n-hexane (GLA content, 22.5 wt%; recovery of GLA, 92.7%). The second step involved selective esterification of borage-FFA with lauryl alcohol by using Rhizopus delemar lipase. A mixture containing 4 g borage-FFA/lauryl alcohol (1:2, mol/mol), 1 g water, and 1000 U lipase was incubated at 30°C for 20 h with stirring at 500 rpm. Under these conditions, 74.4% of borage-FFA was esterified, and the GLA content in the FFA fraction was enriched from 22.5 to 70.2 wt% with a recovery of 75.1% of the initial content. To further elevate the GLA content, unesterified fatty acids were extracted, and esterified again in the same manner. By this repeated esterification, GLA was purified to 93.7 wt% with a recovery of 67.5% of its initial content.     

Supercritical fluid extraction of minor lipids from pretreated sunflower oil deodorizer distillates

The recovery of minor lipid compounds (tocopherols and phytosterols) from sunflower oil deodorizer distillates using countercurrent supercritical carbon dioxide extraction has been studied. Since the raw material employed contains large amounts of triacylglycerols and free fatty acids, chemical transformation of these compounds into their corresponding fatty acid ethyl esters was previously carried out, in order to favor the concentration of minor lipids in the raffinate product. Extractions of the original and pretreated raw material were carried out in a pilot‐scale plant at 65 °C, with pressures ranging from 15 to 23 MPa and solvent‐to‐feed ratios from 15 to 30. The influence of the feed composition in the extraction process was analyzed by comparison of the tocopherol and phytosterol yields and enrichment factors obtained in each case. The chemical transformation of the deodorizer distillate composition significantly enhances the concentration of minor lipids in the raffinate product. Additionally, the reaction step produced a solid phase, mainly consisting of sterols, which was isolated from the liquid product.     

Preparation of highly purified concentrates of eicosapentaenoic acid and docosahexaenoic acid

Because of the complexity of marine lipids, polyunsaturated fatty acid (PUFA) derivatives in highly purified form are not easily prepared by any single fractionation technique. The products are usually prepared as the ethyl esters by esterification of the body oil of fat fish species and subsequent physicochemical purification processes, including short-path distillation, urea fractionation, and preparative chromatography. Lipase-catalyzed transesterification has been shown to be an excellent alternative to traditional esterification and short-path distillation for concentrating the combined PUFA-content in fish oils. At room temperature in the presence of Pseudomonas sp. lipase and a stoichiometric amount of ethanol without any solvent, efficient transesterification of fish oil was obtained. At 52% conversion, a concentrate of 46% eicosapentaenoic acid (EPA) plus docosahexaenoic acid (DHA) was obtained in excellent recovery as a mixture of mono-, di-, and triacylglycerols. The latter can be easily separated from the saturated and monounsaturated ethyl esters and converted into ethyl esters either by conventional chemical means or enzymatically by immobilized Candida antarctica lipase. Urea-fractionation of such an intermediary product can give an EPA+DHA content of approximately 85%.