A systematic review on the acyl migration in enzymatic synthesis of structured lipids: Mechanisms, influencing factors, evaluation methods, and future prospects

Structured lipids (SLs) are modified triacylglycerols with specific physicochemical or nutritional properties. Acyl migration is a universal chemical phenomenon observed during interesterification, a critical process in the enzyme-catalyzed synthesis of SLs. Acyl migration causes shifts in the positional composition of lipids that bring changes in function. Recent advances in understanding acyl migration during lipase-catalyzed interesterification reactions were systematically summarized, offering a comprehensive overview of its mechanisms and influencing factors. The current research on acyl migration has been mainly at the level of enzymatic reactions, and the evaluation methods of acyl migration degree need further exploration. It is necessary to investigate the acyl migration throughout the production of SLs. A thorough investigation into the factors influencing rates of interesterification, hydrolysis, and randomization, along with their underlying mechanisms, is imperative for the efficient development of specialized SL products.

Production of Margarine Fat Containing Medium- and Long-Chain Triacylglycerols by Enzymatic Interesterification of Peony Seed Oil, Palm Stearin and Coconut Oil Blends

This paper reports the preparation of margarine fat using Lipozyme TL IM as a catalyst and peony seed oil (PSO), palm stearin (PS) and coconut oil (CO) as raw materials. The results indicate that there were no significant changes in fatty acid composition before or after interesterification of the oil samples. However, the total amount of medium- and long-chain triglycerides (MLCTs) increased from 2.92% to 11.38% in sample E1 after interesterification, mainly including LaLaO, LaMO, LaPM, LaOO, LaPO and LaPP. Moreover, the slip melting point (SMP) of sample E1 decreased from 45.9 °C (B1) to 33.5 °C. The solid fat content (SFC) of all the samples at 20 °C was greater than 10%, indicating that they could effectively prevent oil exudation. After interesterification, the samples exhibited a β' crystal form and could be used to prepare functional margarine.

Spectroscopic Evidence of Thermal Changes in Plant Oils during Deep-Frying—Chemical and Infrared Studies

For this study, the thermal degradation of palm, coconut, rice bran, and rapeseed (canola) oils was studied. Products formed during deep-frying were identified using chemical methods and these results were verified with those derived from FT-IR (Fourier-transform infrared spectroscopy) studies. Mathematically processed spectral data were analyzed in terms of the breaking of double bonds, the decomposition of the carotenoids, and the reduction of the C=O carbonyl group. Clearly visible changes in the position and intensity of some bands were used for explaining the structural changes in the studied oils. These changes prove that during the heating of the oils, decomposition of the plant fat into fatty acids appears, together with the reduction of the number of certain bonds (e.g., C=C, =C-H, and C=O) and cracking of the acylglycerol chains. The iodine values of the heated oils, determined from the FT-IR spectra measurements, show a significant decrease in their degree of unsaturation level. These effects, visible in the FT-IR spectra, confirm the chemical and structural changes derived from the chemical and physicochemical studies of the plant oils. The influence of heating time on the band intensity of proteins was also studied.

Detection and quantification of palmolein and palm kernel oil added as adulterant in coconut oil based on triacylglycerol profile

Economically motivated adulteration of expensive coconut oil with low cost oil, like palm kernel oil and palmolein is difficult to detect and quantify by available methods primarily due to their overlapping physicochemical properties with coconut oil. In the present work, a HPLC method has been developed to detect and quantify the degree of adulteration of coconut oil with palmolein and palm kernel oil based on triglyceride structure. The normalized area percentage of trilaurin (C36) among the three major TAG molecular species dilaurin-monocaprin/myristin-caprylin-laurin (C34), trilaurin (C36) and dilaurin-monomyristin (C38) of coconut oil was chosen as detection index for quantifying degree of adulteration of coconut oil with palm kernel oil, while the area ratio of dipalmitoyl-monoolein: trilaurin was chosen as detection index for quantifying adulteration of coconut oil with palmolein. The RP-HPLC based method developed in the present work is effective with a 2-4% minimum detection limit of adulterant oils and 78-98% detection accuracy depending on the degree of adulteration and types of oil.

An Insight into the Solid-State Miscibility of Triacylglycerol Crystals

The crystallization properties of triacylglycerols (TAGs) strongly determine the functional properties of natural lipids. The polymorphic and mixing phase behavior of TAG molecules have long been, and still are, a hot topic of research with special relevance for the cosmetic, pharmaceutical, and food industry. To avoid the difficulties arising from the study of whole real fats, studies at the molecular level on mixtures of a limited number of TAGs has become an indispensable tool to identify the underlying causes of the physical properties in lipid systems. In particular, phase diagrams of binary mixtures of TAGs exhibiting a different degree of heterogeneity (monoacid or mixed fatty acids; molecular symmetry; the presence of cis or trans double bonds) have resulted in a significant breakthrough in our knowledge about structure-interaction-function relationships. The present work aims to provide an overview of the main reports regarding binary and ternary TAG systems, from the early studies to the most recent developments.

Evaluation of enzymatic interesterification in structured triacylglycerols preparation: a concise review and prospect

Enzymatic interesterification (EIE) is one of the emerging technologies in the specialty fats industry. EIE has several advantages over the conventional chemical interesterification method, such that the process has higher flexibility and efficiency, is environmentally friendly and the immobilized enzyme can be recycled besides of the lower requirement for substrate's acid value. The physical properties and nutritional qualities of the fats and oils are modified after EIE, depending on the change in the position of fatty acids on the triacylglycerol (TAG) molecules. Evaluation of the interesterification reaction are important and useful in terms of its technological applications. This paper summarizes the conventional methods and the advancement for evaluating EIE processes, e.g., determination of the change in slip melting points, solid fat contents, TAG with equivalent carbon numbers, and sn-2 fatty acid compositions of the end product. Nonetheless, these methods are not comprehensive because during the EIE process, acyl migration occurs. A novel and convenient evaluation model which is based on the fatty acid distribution on the glycerol-backbone is proposed as a perspective. This model can be employed to monitor the interesterification degree and acyl migration during a regiospecific EIE process, which serves as a reaction rule that can be employed to control and optimize the EIE process, thereby producing structured TAG with desired properties.

Enzyme-assisted three-phase partitioning: An efficient alternative for oil extraction from Sesame (<em>Sesamum indicum</em> L.)

Three-phase partitioning (TPP) was explored for oil extraction from Sesamum indicum L. seeds. The process parameters, namely the salt concentration, slurry/t-butanol ratio and system pH were standardized. The optimum conditions for maximum oil recovery using TPP were an ammonium sulphate concentration of 40% (w/v), slurry/t-butanol ratio of 1:1 (v/v) and system pH of 5.0. The powdered seeds were subjected to enzyme-assisted three-phase partitioning (EATPP) which was pre-treated with pectinase, protease and a mixture of ɑ-amylase and amylo-glucosidase (1:1 ratio) followed by TPP (as standardized conditions) and its efficacy in recovering oil was compared with TPP and solvent extraction (SE). Out of all the enzymes studied, EATPP with pectinase resulted in the highest oil recovery (86.12%), which was higher than that of TPP (78.24%). The free fatty acids, saponification value and peroxide values were observed to be lower in the case of TPP and EATPP when compared to SE, indicating better oil quality.

Liver and serum lipids in Wistar rats fed a novel structured lipid containing conjugated linoleic acid and conjugated linolenic acid

Conjugated linoleic acid (CLA) and conjugated linolenic acid (CLnA) have been known to have several health-promoting effects. The aim of this study was to introduce a novel structured lipid (SL) including both CLA and CLnA (cis9, trans11, cis13-18:3, punicic acid) into one triacylglycerol (TAG) molecule through enzymatic interesterification and investigate its effect on body weight, liver and serum lipids in Wistar rats. CLA oil, pomegranate seed oil (as a rich source of CLnA) and soybean oil (as a negative control) were applied as other experimental oils. The rats were fed the oils at 1500 mg/kg body weight per day via oral gavage for 45 days. Gas chromatography analysis showed that SL included CLnA and CLA in roughly equal concentrations. The in vivo study revealed that SL had the greatest effect on the reduction in liver lipid weight (4.65 g/100g of liver) and liver TAG (13.28 mg/g) compared to soybean oil (8.7 g/100g and 18.8 mg/g, respectively). High density lipoprotein cholesterol (HDL-C) in the serum of rats which were fed CLA oil significantly (p < 0.05) increased (from 0.95 to 1.14 mmol/l). Pomegranate seed oil reduced low density lipoprotein cholesterol (LDL-C) and total cholesterol (about 40% and 24% reduction, respectively). A remarkable TAG reduction (p < 0.05) was observed in all treated rats.

Analytical Strategies Involved in the Detailed Componential Characterization of Biooil Produced from Lignocellulosic Biomass

Elucidation of chemical composition of biooil is essentially important to evaluate the process of lignocellulosic biomass (LCBM) conversion and its upgrading and suggest proper value-added utilization like producing fuel and feedstock for fine chemicals. Although the main components of LCBM are cellulose, hemicelluloses, and lignin, the chemicals derived from LCBM differ significantly due to the various feedstock and methods used for the decomposition. Biooil, produced from pyrolysis of LCBM, contains hundreds of organic chemicals with various classes. This review covers the methodologies used for the componential analysis of biooil, including pretreatments and instrumental analysis techniques. The use of chromatographic and spectrometric methods was highlighted, covering the conventional techniques such as gas chromatography, high performance liquid chromatography, Fourier transform infrared spectroscopy, nuclear magnetic resonance, and mass spectrometry. The combination of preseparation methods and instrumental technologies is a robust pathway for the detailed componential characterization of biooil. The organic species in biooils can be classified into alkanes, alkenes, alkynes, benzene-ring containing hydrocarbons, ethers, alcohols, phenols, aldehydes, ketones, esters, carboxylic acids, and other heteroatomic organic compounds. The recent development of high resolution mass spectrometry and multidimensional hyphenated chromatographic and spectrometric techniques has considerably elucidated the composition of biooils.

Trans-free Shortenings through the Interesterification of Rice Bran Stearin, Fully Hydrogenated Soybean Oil and Coconut Oil

Trans-free interesterified fat was prepared from binary blends of rice bran stearin (RBS) and fully hydrogenated soybean oil (FHSBO) with RBS/FHSBO mass ratio of 50:50, 60:40 and 70:30. Commercial lipozyme RM IM (10 wt% of total substrate) was used to catalyze the reaction. Coconut oil (CO, 20 wt% of RBS/FHSBO) was also added to increase the medium-chain fatty acids content. The enzymatic interesterified fats EIEF were evaluated for their physical properties (i.e., solid fat content (SFC), polymorphism and crystal morphology) and the bioactive phytochemical contents. The SFC curves after interesterification were flattened, indicating a wide plastic range. SFC of the EIEF with different ratio (RBS/FHSBO=50:50, 60:40 and 70:30) at 25 °C were 34.2, 25.7 and 17.8%, respectively, while the physical blends at the same ratio showed 41.4, 35.7 and 27.7%. From X-ray diffraction (XRD), β polymorphic form was observed in physical blends, whereas only β’ crystal form was discovered in EIEF, which is most desired for shortenings and margarines preparation. EIEF contained 416.7–602.4 mg/100 g oryzanol, 25.4–36.5 mg/100 g total tocopherols and 319.3–431.8 mg/100 g total phytosterols, which could confer health benefits. The results indicated that EIEF may have a potential use in shortenings and margarines preparation.

Lipase catalyzed interesterification of rice bran oil with hydrogenated cottonseed oil to produce trans free fat

Lipase catalyzed interesterification of rice bran oil (RBO) with hydrogenated cottonseed oil (HCSO) was carried out for producing a low trans free fat. The interesterification reaction was performed by varying parameters such as weight proportions of RBO and HCSO, reaction temperatures, time period and lipase concentration. Both non specific and specific lipases namely Novozym 435 and Lipozyme TL IM were employed for this study. Based on the data generated, the optimum reaction conditions were found to be: weight proportion of RBO and HCSO, 80:20; lipase concentration, 5 % (w/w) of substrates; reaction temperature, 60 °C; reaction time, 4 h for Lipozyme TL IM and 5 h for Novozym 435. The degree of interesterification, calculated based on the results of solid fat characteristics was used for comparing the catalytic activity of Novozym 435 and Lipozyme TL IM. It was observed that the degree of interesterification (DI) reached a near 100 % at the 4th hour for reaction employing Lipozyme TL IM with a rate constant of 0.191 h(-1) while Novozym 435 catalyzed reaction reached a near 100 % degree of interesterification at the 5th hour with a rate constant of 0.187 h(-1), suggesting that Lipozyme TL IM has a faster catalytic activity.

Effects of emulsifier addition on the crystallization and melting behavior of palm olein and coconut oil

Two commercial emulsifiers (EM1 and EM2), containing predominantly monoacylglycerols (MAGs), were added in proportiond of 1.0 and 3.0% (w/w) to coconut oil and palm olein. EM1 consisted of approximately 90% MAGs, whereas EM2 consisted of approximately 50% MAGs. The crystallization behavior of these systems was evaluated by differential scanning calorimetry (DSC) and microscopy under polarized light. On the basis of DSC results, it was clear that the addition of EM2 accelerated the crystallization of coconut oil and delayed the crystallization of palm olein. In both oils EM2 addition led to the formation of smaller spherulites, and these effects improved the possibilities for using these fats as ingredients. In coconut oil the spherulites were maintained even at higher temperatures (20 °C). The addition of EM1 to coconut oil changed the crystallization pattern. In palm olein, the addition of 3.0% (w/w) of this emulsifier altered the pattern of crystallization of this fat.

Chemical interesterification of blends of palm stearin, coconut oil, and canola oil: physicochemical properties

trans-Free interesterified fat was produced for possible usage as a margarine. Palm stearin, coconut oil, and canola oil were used as substrates for chemical interesterification. The main aim of the present study was to evaluate the physicochemical properties of blends of palm stearin, coconut oil, and canola oil submitted to chemical interesterification using sodium methoxide as the catalyst. The original and interesterified blends were examined for fatty acid composition, softening and melting points, solid fat content, and consistency. Chemical interesterification reduced softening and melting points, consistency, and solid fat content. The interesterified fats showed desirable physicochemical properties for possible use as a margarine. Therefore, our result suggested that the interesterified fat without trans-fatty acids could be used as an alternative to partially hydrogenated fat.

Enhanced hypocholesterolemic effects of interesterified oils are mediated by upregulating LDL receptor and cholesterol 7-α- hydroxylase gene expression in rats

The concentration of LDL cholesterol in plasma is strongly influenced by the amount and type of lipid in the diet. Our studies have shown that positional changes in the fatty acids in blended oil introduced using lipase-catalyzed interesterification differentially modulate circulating LDL levels in rats compared with those observed in rats given a physical blend of oils. To investigate the molecular basis of these differences, transcriptional profiling of genes involved in cholesterol homeostasis was studied after feeding rats with a semipurified diet containing 10% fat from native oils; coconut oil (CNO), rice bran oil (RBO), or sesame oil (SESO); blended (B); CNO+RBO(B) or CNO+SESO(B) and interesterified oil (I); CNO+RBO(I) or CNO+SESO(I) for 60 d. Hepatic LDL receptor (LDL-R) expression significantly increased in rats fed interesterified oils by 100-200% compared with rats fed blended oils and by 400-500% compared with rats fed CNO. Positional alteration in fatty acids of oils used in the diet induced changes in LDL-R expression, which was accompanied by parallel changes in cholesterol-7α-hydroxylase (CYP7A1) and SREBP-2 genes. This suggested that not only the fatty acid type but also its position in the TG of dietary lipids play an important role in maintaining plasma cholesterol levels by suitably modulating gene expression for LDL-R in rat liver.

Lowering of platelet aggregation and serum eicosanoid levels in rats fed with a diet containing coconut oil blends with rice bran oil or sesame oil

The present investigation was undertaken to study the effects of feeding a diet containing blended and interesterified fat to rats on thrombotic parameters such as platelet aggregation and eicosanoid levels in blood serum. Male Wistar rats were fed with a diet containing 10% fat from native; coconut oil (CNO), rice bran oil (RBO), sesame oil (SESO), blended; (CNO+RBO blend (B), CNO+SESO(B), or interesterified oils; CNO+RBO interesterified (I), CNO+SESO(I) for a period of 60 days. Rats given a diet containing blended oil of CNO+RBO(B) or CNO+SESO(B) showed a decrease in rate of ADP induced aggregation of platelets by 34% and 30%, respectively, compared to those fed with CNO. Aggregation induced by collagen was also reduced similarly in rats given blended or interesterified oils of CNO with RBO or SESO. Feeding interesterified oil CNO+RBO(I), and CNO+SESO(I) to rats also resulted in decrease in rate of ADP induced platelet aggregation by 37% and 34%, respectively, compared to rats fed with CNO. The prostacyclin/thromboxane ratio in serum was increased in rats fed with blended and interesterified oil compared to those fed with CNO. These results indicated that CNO when blended or interesterified with RBO or SESO exhibit antithrombotic effects as compared to the effect observed by feeding rats with CNO.