Modification of menhaden oil by enzymatic acidolysis to produce structured lipids: Optimization by response surface design in a packed bed reactor

A comprehensive review of lipase-catalyzed acidolysis as a method for producing structured glycerides

The production of structured lipids is a current trend in food technology in order to enhance the properties of fats and oils. Lipases have been utilized in many instances for this purpose, in most examples in an immobilized form. In this review, after discussing the different strategies to produce artificial lipids using lipases (esterification, transesterification, interesterification), we have focused on acidolysis. The reaction commences with hydrolysis at one position of the triglyceride molecule and is followed by the esterification between the released hydroxyl group and the target fatty acid (although other carboxylic acids can be used, such as phenolic acid derivatives). This means that water plays a double role, as substrate in the first step and as an undesired by-product in the second one. Therefore, the control of water activity becomes critical in these reactions. This review discusses the advantages, possibilities and drawbacks of this strategy to produce tailor-made designed lipids, summarizing many of the papers related to this strategy. The summarized results show the complexity of this reaction that can make the understanding and reproducibility of the reactions complex if there are no strict controls of all parameters determining the final yields.

Positional distribution of DHA in triacylglycerols: natural sources, synthetic routes, and nutritional properties

Docosahexaenoic acid (DHA, 22:6 n-3) is a long-chain polyunsaturated fatty acid (PUFA) present in high quantities in the mammalian brain and is a precursor of several metabolites. Clinical trials have demonstrated the benefits of dietary DHA in infants and adults. Triacylglycerols (TAGs) are the most abundant components of many natural oils, and in specific oils (e.g., fish, algal oils, etc.), they represent the main molecular form of dietary DHA. The positional distribution of DHA in the TAG glycerol backbone (sn-2 vs. sn-1/3) varied among different sources. Recent studies have shown that in human breast milk, DHA is mainly esterified at the sn-2 position (∼50% DHA of the total DHA), thus attracting research interest regarding the nutritional properties of sn-2 DHA. In this review, we summarize the different sources of TAG in natural oils with high amounts of DHA, including fish, algae, and marine mammal oils, with a focus on their positional distribution. Methods for analyzing the distribution of fatty acids in TAG of high-PUFA oils are discussed, and the lipase-catalyzed synthetic routes of specific triacylglycerols with sn-2 DHA are summarized. Furthermore, we discuss the recent research progress on the nutritional properties of DHA associated with its positional distribution on TAGs.

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.

Solvent-free enzymatic preparation of feruloylated monoacylglycerols optimized by response surface methodology

The ability of immobilized lipase B from Candida antarctica (Novozym 435) to catalyze the direct esterification of glyceryl ferulate (FG) and oleic acid for feruloylated monoacylglycerols (FMAG) preparation in a solvent-free system was investigated. Enzyme screening and the effect of glycerol on the initial reaction rate of esterification were also investigated. Response surface methodology (RSM) was used to optimize the effects of the reaction temperature (55-65 degrees C), the enzyme load (8-14%; relative to the weight of total substrates), oleic acid/(FG + glycerol) (6:1-9:1; w/w), and the reaction time (1-2 h) on the conversion of FG and yield of FMAG. Validation of the RSM model was verified by the good agreement between the experimental and the predicted values of FG conversion and FMAG yield. The optimum preparation conditions were as follows: temperature, 60 degrees C; enzyme load, 8.2%; substrate ratio, 8.65:1 (oleic acid/(FG + glycerol), w/w); and reaction time, 1.8 h. Under these conditions, the conversion of FG and yield of FMAG are 96.7 +/- 1.0% and 87.6 +/- 1.2%, respectively.

Synthesis and characterization of canola oil-stearic acid-based trans-free structured lipids for possible margarine application

Incorporation of stearic acid into canola oil to produce trans-free structured lipid (SL) as a healthy alternative to partially hydrogenated fats for margarine formulation was investigated. Response surface methodology was used to study the effects of lipozyme RM IM from Rhizomucor miehei and Candida rugosa lipase isoform 1 (LIP1) and two acyl donors, stearic acid and ethyl stearate, on the incorporation. Lipozyme RM IM and ethyl stearate gave the best result. Gram quantities of SLs were synthesized using lipozyme RM IM, and the products were compared to SL made by chemical catalysis and fat from commercial margarines. After short-path distillation, the products were characterized by GC and RPHPLC-MS to obtain fatty acid and triacylglycerol profiles, 13C NMR spectrometry for regiospecific analysis, X-ray diffraction for crystal forms, and DSC for melting profile. Stearic acid was incorporated into canola oil, mainly at the sn-1,3 positions, for the lipase reaction, and no new trans fatty acids formed. Most SL products did not have adequate solid fat content or beta' crystal forms for tub margarine, although these may be suitable for light margarine formulation.

Enzymatic Production of Infant Milk Fat Analogs Containing Palmitic Acid: Optimization of Reactions by Response Surface Methodology

Infant milk fat analogs resembling human milk fat were synthesized by an enzymatic interesterification between tripalmitin, coconut oil, safflower oil, and soybean oil in hexane. A commercially immobilized 1,3-specific lipase, Lipozyme RM IM, obtained from Rhizomucor miehei was used as a biocatalyst. The effects of substrate molar ratio, reaction time, and incubation temperature on the incorporation of palmitic acid at the sn-2 position of the triacylglycerols were investigated. A central composite design with 5 levels and 3 factors consisting of substrate ratio, reaction temperature, and incubation time was used to model and optimize the reaction conditions using response surface methodology. A quadratic model using multiple regressions was then obtained for the incorporation of palmitic acid at the sn-2 positions of glycerols as the response. The coefficient of determination (R2) value for the model was 0.845. The incorporation of palmitic acid appeared to increase with the decrease in substrate molar ratio and increase in reaction temperature, and optimum incubation time occurred at 18 h. The optimal conditions generated from the model for the targeted 40% palmitic acid incorporation at the sn-2 position were 3 mol/mol, 14.4 h, and 55 degrees C; and 2.8 mol/mol, 19.6 h, and 55 degrees C for substrate ratio (moles of total fatty acid/moles of tripalmitin), time, and temperature, respectively. Infant milk fat containing fatty acid composition and sn-2 fatty acid profile similar to human milk fat was successfully produced. The fat analogs produced under optimal conditions had total and sn-2 positional palmitic acid levels comparable to that of human milk fat.

TG containing stearic acid, synthesized from coconut oil, exhibit lipidemic effects in rats similar to those of cocoa butter

Lipase-catalyzed interesterification was used to prepare structured TG from coconut oil TG by partially replacing some of the atherogenic saturated FA with stearic acid, which is known to have a neutral effect on lipid levels in the body. The level of stearic acid was increased from 4% in the native coconut oil to 40% in the structured lipids, with most of the stearic acid being incorporated into the sn-1 and sn-3 positions of TG. When structured lipids were fed to rats at a 10% level for a period of 60 d, a 15% decrease in total cholesterol and a 23% decrease in LDL cholesterol levels in the serum were observed when compared to those fed coconut oil. Similarly, the total and free cholesterol levels in the livers of the rats fed structured lipids were lowered by 31 and 36%, respectively, when compared to those fed coconut oil. The TG levels in the serum and in the liver showed decreases of 14 and 30%, respectively, in animals fed structured lipids. Rats fed cocoa butter and structured lipids having a similar amount of stearic acid had similar lipid levels in the serum and liver. These studies indicated that the atherogenic potential of coconut oil lipids can be reduced significantly by enriching them with stearic acid. This also changed the physical properties of coconut oil closer to those of cocoa butter as determined by DSC.

Structured Lipids-Novel Fats with Medical, Nutraceutical, and Food Applications

Generally, structured lipids (SLs) are triacylglycerols (TAGs) that have been modified to change the fatty acid composition and/or their positional distribution in glycerol backbone by chemically and/or enzymatically catalyzed reactions and/or genetic engineering. More specifically, SLs are modified TAGs with improved nutritional or functional properties. SLs provide an effective means for producing tailor-made lipids with desired physical characteristics, chemical properties, and/or nutritional benefits. The production, commercialization outlook, medical, and food applications of SLs are reviewed here. Physical property measurements for SL in food systems and future research needs for increased industrial acceptance are also included in this review.