Modelling lipase‐catalysed transesterification of fats containing n‐3 fatty acids monitored by their solid fat content

Transesterification of fat blends rich in n‐3 polyunsaturated fatty acids (n‐3 PUFA), catalysed by a commercial immobilised thermostable lipase from Thermomyces lanuginosa, was carried out batch‐wise. Experiments were performed, following central composite rotatable designs (CCRDs) as a function of reaction time, temperature and media formulation. Mixtures of palm stearin, palm kernel oil and a commercial concentrate of triacylglycerols rich in n‐3 PUFA (“EPAX 2050TG” in CCRD‐1 and “EPAX 4510TG” in CCRD‐2) were used. The time‐course of transesterification was indirectly followed by the solid fat content (SFC) values of the blend at 10 °C, 20 °C, 30 °C and 35 °C. A decrease in all SFC values of the blends at 10 °C, 20 °C, 30 °C and 35°C was observed upon transesterification. The SFC_{10 °C} and SFC_{20 °C} of transesterified blends varied between 18 and 48 and SFC_{35 °C} between 6 and 24. These values fulfil the technological requirements for the production of margarines. Under our conditions, lipid oxidation may be neglected. However, the accumulation up to 8.3% free fatty acids in reaction media is a problem to overcome. The development of response surface models, describing both the final SFC value and the SFC decrease, will allow predicting results for novel proportions of fats and oils and/or a novel combination time‐temperature.     

Pattern recognition of lipase‐catalyzed or chemically interesterified fat blends containing n‐3 polyunsaturated fatty acids

The feasibility to discriminate among samples of different fat blends prior and after inorganic or lipase‐catalyzed interesterification, via pattern recognition techniques [principal component analysis (PCA) and discriminant analysis (DA)], was investigated. Blends I and II, consisting of mixtures of palm stearin, palm kernel oil and a concentrate of triacylglycerols (TAG) rich in n‐3 polyunsaturated fatty acids (EPAX 4510TG or EPAX 2050TG) were used. These blends, prior (64 samples) and after interesterification, catalyzed by an immobilized Thermomyces lanuginosa lipase (Lipozyme TL IM, 54 samples) or by sodium methoxide (10 samples), were characterized by their acylglycerol profiles (25 chromatographic peaks) and solid fat content (SFC) at 10, 20, 30 and 35 °C. PCA on the multivariate data (i) showed that the initial samples were characterized by higher SFC and higher contents of high‐melting TAG and (ii) suggested two separate clusters of initial and interesterified samples. DA was performed on the multivariate data to determine which of the 29 variables have discriminative power. When the 124 samples, characterized by their acylglycerols, were grouped into (i) initial and interesterified samples of blends I or II (four groups) or (ii) also by the catalyst used (six groups), 98.4% of the samples were correctly classified.     

Operational stability of immobilised lipase/acyltransferase during interesterification of fat blends

The lipase/acyltransferase from Candida parapsilosis is an unusual enzyme that preferably catalyses alcoholysis over hydrolysis in biphasic aqueous/organic media. The aim of this study was to evaluate the operational stability of an immobilised form of this enzyme during the interesterification of fat blends containing n‐3 polyunsaturated fatty acids, in solvent‐free media, at 60 °C, carried out continuously and batchwise. When the interesterification was performed in a continuous fluidised‐bed reactor, an operational half‐life of 9 h was estimated. The biocatalyst was also reused in consecutive 23‐h batches, in a total of four batches, either using fresh medium with no water addition or adding water to rehydrate the biocatalyst. When no water and extra water was added to the reaction medium, the obtained half‐lives were 10 and 18 h, respectively. Thus, the loss of activity may be explained by a progressive dehydration occurring along the reaction rather than by product or substrate inhibition effects. The interesterification activity was accompanied by changes in the acylglycerol profile. An increase in compounds of low equivalent carbon number (ECN) and in triacylglycerols (TAG) of ECN 42 and 44 was observed. This increase was accompanied by the consumption of TAG of ECN 46, 48 and 50.     

Operational stability of Thermomyces lanuginosa lipase during interesterification of fat in continuous packed‐bed reactors

The operational stability of a commercial immobilized lipase from Thermomyces lanuginosa (“Lipozyme TL IM”) during the interesterification of two fat blends, in solvent‐free media, in a continuous packed‐bed reactor, was investigated. Blend A was a mixture of palm stearin (POS), palm kernel oil (PK) and sunflower oil (55 : 25 : 20, wt‐%) and blend B was formed by POS, PK and a concentrate of triacylglycerols rich in n‐3 polyunsaturated fatty acids (PUFA) (55 : 35 : 10, wt‐%). The bioreactor operated continuously at 70 °C, for 580 h (blend A) and 390 h (blend B), at a residence time of 15 min. Biocatalyst activity was evaluated in terms of the decrease of the solid fat content at 35 °C of the blends, which is a key parameter in margarine manufacture. The inactivation profile of the biocatalyst could be well described by the first‐order deactivation model: Half‐lives of 135 h and 77 h were estimated when fat blends A and B, respectively, were used. Higher levels of PUFA in blend B, which are rather prone to oxidation, may explain the lower lipase stability when this mixture was used. The free fatty acid content of the interesterified blends decreased to about 1% during the first day of operation, remaining constant thereafter.     

Application of palm olein in the production of zero‐trans Iranian vanaspati through enzymatic interesterification

The utilization of palm olein in the production of zero‐trans Iranian vanaspati through enzymatic interesterification was studied. Vanaspati fat was made from ternary blends of palm olein (POL), low‐erucic acid rapeseed oil (RSO) and sunflower oil (SFO) through direct interesterification of the blends or by blending interesterified POL with RSO and SFO. The slip melting point (SMP), the solid fat content (SFC) at 10–40 °C, the carbon number (CN) triacylglycerol (TAG) composition, the induction period (IP) of oxidation at 120 °C (IP₁₂₀) and the IP of crystallization at 20 °C of the final products and non‐interesterified blends were evaluated. Results indicated that all the final products had higher SMP, SFC, IP of crystallization and CN 48 TAG (trisaturated TAG), and lower IP₁₂₀, than their non‐interesterified blends. However, SMP, SFC, IP₁₂₀, IP of crystallization and CN 48 TAG were higher for fats prepared by blending interesterified POL with RSO and SFO. A comparison between the SFC at 20–30 °C of the final products and those of a commercial low‐trans Iranian vanaspati showed that the least saturated fatty acid content necessary to achieve a zero‐trans fat suitable for use as Iranian vanaspati was 37.2% for directly interesterified blends and 28.8% for fats prepared by blending interesterified POL with liquid oils.     

Lipase-catalyzed incorporation of n−3 PUFA into palm oil

Two immobilized lipases, IM60 from Rhizomucor miehei and QLM from Alcaligenes sp., were used as biocatalysts for the modification of the FA composition of palm oil by incorporating n−3 PUFA. Acidolysis and interesterification reactions were conducted with hexane as organic solvent, and the products were analyzed by using GLC. After a 24-h incubation in hexane, there was an average incorporation of 20.8% EPA and 15.6% DHA into palm oil, respectively, while the percentages of palmitic and oleic acids in palm oil decreased by 28.8 and 11.8%, respectively. Higher EPA and DHA incorporation was obtained when EPAX (fish oil concentrate high in n−3 PUFA) was used in the ethyl ester form (interesterification reaction) than in the free acid form (acidolysis) in the presence of Lipozyme (IM60 lipase. Lipase QLM was found to discriminate against EPA, and it showed slightly better catalytic activity for DHA in the free acid form than in the ethyl ester form. Generally, as the mole ratio of the acyl donor to TAG increased, the percentage incorporation of EPA and DHA increased; however, reactions catalyzed by Lipozyme IM60 did not show increases in the incorporation beyond a TAG/EPAX mole ratio of 3. When limitations due to mass transfer were not a factor, an increase in the reactant amount also gave an increase in the percentage incorporation of the n−3 PUFA. Palm oil containing EPA and DHA was successfully produced and may be beneficial in certain food and nutritional applications.     

Production of structured triacylglycerols in an immobilised lipase packed‐bed reactor: batch mode operation

Structured triacylglycerols with caprylic acid at the sn‐1 and sn‐3 positions of the glycerol backbone and eicosapentaenoic acid (EPA) at the position sn‐2 were synthesised by acidolysis of a commercially available EPA‐rich oil (EPAX4510, Pronova Biocare) and caprylic acid catalysed by the 1,3‐specific immobilised lipase Lipozyme IM. The reaction was carried out in an immobilised lipase packed‐bed reactor by recirculating the reaction mixture through the bed. The exchange equilibrium constants between caprylic acid and the native fatty acids of EPAX4510 were determined. The n‐3 polyunsaturated fatty acids (PUFAs), EPA and docosohexaenoic acid (DHA), were the most easily displaced by the caprylic acid. The exchange equilibrium constants were 3.68 and 3.06 for EPA and DHA, respectively. The influence of the flow rate of the reaction mixture through the packed‐bed and the substrate concentration in the reaction rate were studied. For flow rates between 74 and 196 cm³ h^?1 (bed of 6.6 mm internal diameter and 0.46 porosity) and triacylglycerol concentrations between 0.036 and 0.108 M , the data fitted well to an empirical kinetic model which allowed representative values of the apparent kinetic constant to be obtained. Hence, the average reaction rates and kinetic constants of exchange of caprylic acid and native fatty acids of EPAX4510 could be calculated. In the conditions indicated, the parameter (lipase mass × time/triacylglycerol mass, m_Lt/V[TG]₀) constituted the intensive variable of the process for use in predicting the composition of structured triacylglycerols at different reaction times. At equilibrium, the structured triacylglycerol produced had the following composition: caprylic acid 59.5%, EPA 9.6%, DHA 2.2% and oleic acid 11.8%. Copyright © 2004 Society of Chemical Industry     

Physicochemical Properties of Lipase-Catalyzed Interesterified Fat Containing α-Linolenic Acid

Two substrate blends (8:6:6 and 6:6:9, by weight) of anhydrous butterfat (ABF), palm stearin (PS), and flaxseed oil (FSO) were interesterified by immobilized lipases. The reaction was carried out in the absence of solvent at 60 °C for 24 h in a 1-L tank stirred-batch type reactor. In terms of equivalent carbon number (ECN) of triacylglycerol (TAG), the areas of ECN 36-38 (from FSO) and ECN 48-50 (from PS) decreased during the interesterification while ECN 42–46 increased with increasing reaction time. As interesterification time increased, the decreased enthalpy (?H), peak temperature (T _P) and transition range were observed. After short path distillation, interesterified fat (IF) was produced in which α-linolenic acid contents (ALn, mol%) of the 8:6:6 and 6:6:9 IF were 15.7 and 21.7%, respectively. Tocopherol, cholesterol and phytosterol contents in each IF were significantly reduced after short path distillation. In this study, hardness of 6:6:9 IF and 8:6:6 IF were 217 and 800 g/cm², respectively. After interesterification, short spacing at 4.6 Å disappeared or weakened, indicating that the predominant polymorphic form had changed from the β form to the desirable crystalline structure of the β′ form.     

Enzymatic interesterification of structured lipids containing conjugated linoleic acid with palm stearin for possible margarine production

Structured lipids containing conjugated linoleic acid as a functional ingredient were blended with palm stearin in the ratios of 30 : 70, 40 : 60, 50 : 50, 60 : 40 and 70 : 30 (wt/wt). The blends were subjected to enzymatic interesterification by Candida antarctica lipase. After interesterification of the blends, changes in the physical properties of the products, including lower melting points and solid fat contents along with different melting behaviors, were evidenced. Analysis of triacylglycerols (TAG) of the interesterified blends showed a decrease in the concentration of high‐melting TAG. X‐ray diffraction analysis revealed, that all the reacted blends were predominantly in the β' crystal form. The mixture could be used for the formulation of margarines or other, similar products.     

Chemical and enzymatic interesterification of a beef tallow and rapeseed oil equal‐weight blend

A mixture of beef tallow and rapeseed oil (1:1, wt/wt) was interesterified using sodium methoxide or immobilized lipases from Rhizomucor miehei (Lipozyme IM) and Candida antarctica (Novozym 435) as catalysts. Chemical interesterifications were carried out at 60 and 90 °C for 0.5 and 1.5 h using 0.4, 0.6 and 1.0 wt‐% CH₃ONa. Enzymatic interesterifications were carried out at 60 °C for 8 h with Lipozyme IM or at 80 °C for 4 h with Novozym 435. The biocatalyst doses were kept constant (8 wt‐%), but the water content was varied from 2 to 10 wt‐%. The starting mixture and the interesterified products were separated by column chromatography into a pure triacylglycerol fraction and a nontriacylglycerol fraction, which contained free fatty acids, mono‐, and diacylglycerols. It was found that the concentration of free fatty acids and partial acylglycerols increased after interesterification. The slip melting points and solid fat contents of the triacylglycerol fractions isolated from interesterified fats were lower compared with the nonesterified blends. The sn‐2 and sn‐1,3 distribution of fatty acids in the TAG fractions before and after interesterification were determined. These distributions were random after chemical interesterification and near random when Novozym 435 was used. When Lipozyme IM was used, the fatty acid composition at the sn‐2 position remained practically unchanged, compared with the starting blend. The interesterified fats and isolated triacylglycerols had reduced oxidative stabilities, as assessed by Rancimat induction times. Addition of 0.02% BHA and BHT to the interesterified fats improved their stabilities.     

Trans‐free fats through interesterification of canola oil/palm olein or fully hydrogenated soybean oil blends

Binary blends of canola oil (CO) and palm olein (POo) or fully hydrogenated soybean oil (FHSBO) were interesterified using commercial lipase, Lypozyme TL IM, or sodium methoxide. Free fatty acids (FFA) and soap content increased and peroxide value (PV) decreased after enzymatic or chemical interesterification. No difference was observed between the PV of enzymatically and chemically interesterified blends. Enzymatically interesterified fats contained higher FFA and lower soap content than chemically prepared fats. Slip melting point (SMP) and solid‐fat content (SFC) of CO and POo blends increased, whereas those of CO and FHSBO blends decreased after chemical or enzymatic interesterification. Enzymatically interesterified CO and POo blends had lower SMP and SFC (at some temperatures) than chemically interesterified blends. The status was reverse when comparing chemically and enzymatically interesterified CO and FHSBO blends. The induction period for oxidation at 120°C of blends decreased after interesterification. However, chemically interesterified blends were more oxidatively stable than enzymatically interesterified blends. Interesterified blends of CO and POo or FHSBO displayed characteristics suited to application as trans‐free soft tub, stick, roll‐in and baker's margarine, cake shortening and vanaspati fat.     

Preparation and Characterization of Human Milk Fat Substitutes Based on Triacylglycerol Profiles

Human milk fat substitutes (HMFS) having similarity in (TAG) composition to human milk fat (HMF) were prepared by Lipozyme RM IM‐catalyzed interesterification of lard blending with selected oils in a packed bed reactor. Four oil blends with high similarity in fatty acid profiles to HMF were first obtained based on the blending model and then the blending ratios were screened based on TAG composition similarity by enzymatic interesterification in a batch reactor. The optimal ratio was determined as lard:sunflower oil:canola oil:palm kernel oil:palm oil:algal oil:microbial oil = 1.00:0.10:0.50:0.13:0.12:0.02:0.02. This blending ratio was used for a packed bed reactor and the conditions were then optimized as residence time, 1.5 h; reaction temperature, 50 °C. Under these conditions, the obtained product showed high degrees of similarity in fatty acid profile with 39.2 % palmitic acid at the sn‐2 position, 0.5 % arachidonic acid (n‐6) and 0.3 % docosahexaenoic acid (n‐3) and the scores for the degree of similarity in TAG composition was increased from 58.4 (the oil blend) to 72.3 (the final product). The packed bed reactor could be operated for 7 days without significant decrease in activity. The final product presented similar melting and crystallization profiles to those of HMF. However, due to the loss of tocopherols during deacidification process, the oxidative stability was lower than that of the oil blend. This process for the preparation of HMFS from lard with high similarity in TAG composition by physical blending and enzymatic interesterification, as optimized by mathematical models in a packed bed reactor, has a great potential for industrialization.     

Synthesis of regioisomerically pure triacylglycerols containing n‐3 very long‐chain polyunsaturated fatty acids

There is growing scientific evidence that consumption of n‐3 very long‐chain polyunsaturated fatty acids (n‐3 VLC‐PUFA) helps in brain and eye development, and protects against a range of common degenerative diseases. This has provided the impetus to the scientists to develop new and renewable sources for these important fatty acids so that the food industry is able to produce and market products fortified with n‐3 VLC‐PUFA. The bioactive efficacy and stability of food products containing n‐3 VLC‐PUFA may be determined not only by the amount of n‐3 VLC‐PUFA present but also by the positional distribution of these acids within the triacylglycerol (TAG) molecules (regiopurity). Studies of the effects of positional distribution on the functionality of n‐3 VLC‐PUFA containing oils have been hampered by a general lack of pure TAG regioisomers for experimentation. This paper reviews methods that have been used for the synthesis of TAG regioisomers containing n‐3 VLC‐PUFA, with special reference to those in which one n‐3 VLC‐PUFA occurs in combination with two long‐chain saturated acids.     

Oxidative Stabilities of Enzymatically Interesterified Fats Containing Conjugated Linoleic Acid

Interesterified fat was produced from soybean oil (SBO) and palm stearin (PS) using two different weight ratios of substrates. Conjugated linoleic acid (CLA; 10?wt% on the weight of SBO and PS) was used as a functional fatty acid. Interesterification and acidolysis was simultaneously carried out to exchange fatty acids and incorporate CLA in the triacylglycerol (TAG) backbone, respectively, using immobilized lipase. Comparative study was carried out between interesterified fats and blends (before interesterification) for the quantification of physical properties (i.e., solid fat content, melting and crystallization behavior) and oxidative stability. In the interesterified fat 5.2–6.1?% CLA was incorporated in the TAG backbone. Blends showed higher solid fat content (SFC) and melting point than interesterified fat at each measured temperature. The Rancimat test was performed for the oxidative stability where the interesterified fat showed significantly lower induction time than physical blends. After the addition of antioxidants such as butylated hydroxytoluene (BHT), rosemary extract, tertiary butylhydroquinone (TBHQ), propyl gallate (PG), etc. into the interesterified fat, the induction time was significantly increased. On the other hand, different deacidification methods (alkaline, batch deodorized and short path distillation) were performed after interesterification to remove the free fatty acids. After deacidification, oxidative stability of alkaline deacidified sample showed significantly (P?≤?0.05) longer induction time compared to short path distillation (SPD) and physically deacidified samples. In this study, interesterified functional fat that may have a potential functionality for the margarines and shortenings were produced and their oxidative stability was observed.     

Domain structure and miscibility studies of blends of styrene–butadiene–styrene block copolymers (SBS) and styrene–glycidyl methacrylate statistical copolymers (PS‐GMA) using SAXS and DMTA

The domain structure and miscibility in the solid state of a series of blends of styrene‐butadiene‐styrene (SBS) block copolymers and styrene‐glycidyl methacrylate (PS‐GMA) statistical copolymers with varying molecular weights and compositions were studied using small angle X‐ray scattering and dynamic mechanical thermal analysis. Depending on the molecular characteristics of each component, different types and degrees of solubilization of PS‐GMA in SBS were found which, in addition to the initially SBS phase morphology, lead to materials with multiphase domain morphologies with differences in size and structure. The degree of solubilization of PS‐GMA into the PS domains of SBS was found to be higher for blends containing PS‐GMA with lower molecular weight (M_w = 18 100 g mol^?1) and lower GMA content (1 wt%) and/or for SBS with higher PS content (39 wt%) and longer PS blocks (M_w = 19 600 g mol^?1). Localized solubilization of PS‐GMA in the middle of PS domains of SBS was found to be the most probable to occur for the systems under study, causing swelling of PS domains. However, uniform solubilization was also observed for SBS/PS‐GMA blends containing SBS with composition in the range of a morphological transition (PS block M_w = 19 600 g mol^?1 and 39 wt% of PS) causing a morphological transition in the SBS copolymer (cylinder to lamella). Copyright © 2006 Crown in the right of Canada. Published by John Wiley & Sons, Ltd     

Enzymatic interesterification of olive oil with fully hydrogenated palm oil: Characterization of fats

Seven different reaction products were prepared via enzymatic interesterification of extra‐virgin olive oil (EVOO) and fully hydrogenated palm oil (FHPO), by varying the initial weight ratio of EVOO to FHPO from 80 : 20 to 20 : 80. The chemical, physical and functional properties of both the semi‐solid reaction products and the corresponding physical blends of the precursor starting materials were characterized. Fats prepared using large proportions of FHPO contained high levels of TAG species containing only saturated fatty acid residues. By contrast, high levels of TAG species containing both saturated and unsaturated fatty acid residues were found in fat products obtained with the lowest proportions of FHPO. Independently of the initial weight ratio of EVOO to FHPO, the interesterified products were characterized by a higher molar ratio of unsaturated to saturated fatty acid residues at the sn‐2 position, were softer over a wide temperature range, exhibited lower oxidative stabilities and were completely melted at lower temperatures than the corresponding physical blends. Potential applications of the reaction products range from margarines (highest weight ratios of EVOO to FHPO) to frying fats (lowest weight ratios of EVOO to FHPO).     

Nitroxide‐mediated synthesis of styrenic‐based segmented and tapered block copolymers using poly(lactide)‐functionalized TEMPO macromediators

Poly(styrene)‐poly(lactide) (PS‐PLA), poly (tert‐butyl styrene)‐poly(lactide) (PtBuS‐PLA) diblocks, and poly(tert‐butyl styrene)‐poly(styrene)‐poly(lactide) (PtBuS‐PS‐PLA) segmented and tapered triblocks of controlled segment lengths were synthesized using nitroxide‐mediated controlled radical polymerization. Well‐defined PLA‐functionalized macromediators derived from hydroxyl terminated TEMPO (PLA_T) of various molecular weights mediated polymerizations of the styrenic monomers in bulk and in dimethylformamide (DMF) solution at 120–130°C. PS‐PLA and PtBuS‐PLA diblocks were characterized by narrow molecular weight distributions (polydispersity index (M_w/M_n) < 1.3) when using the PLA_T mediator with the lowest number average molecular weight M_n= 6.1 kg/mol while broader molecular weight distributions were exhibited (M_w/M_n = 1.47‐1.65) when using higher molecular weight mediators (M_n = 7.4 kg/mol and 11.3 kg/mol). Segmented PtBuS‐PS‐PLA triblocks were initiated cleanly from PtBuS‐PLA diblocks although polymerizations were very rapid with PS segments ～ 5–10 kg/mol added within 3–10 min of polymerization at 130°C in 50 wt % DMF solution. Tapering from the PtBuS to the PS segment in semibatch mode at a lower temperature of 120°C and in 50 wt % DMF solution was effective in incorporating a short random segment of PtBuS‐ran‐PS while maintaining a relatively narrow monomodal molecular weight distribution (M_w/M_n ≈ 1.5). © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Enhancement of mechanical and optical performance of commercial polystyrenes by blending with siloxane‐based copolymers

Well‐defined poly(styrene‐block ‐dimethylsiloxane) copolymers (PS‐b ‐PDMS) with low polydispersity index (M_w /M_n ) and different compositions were synthesized by sequential anionic polymerization of styrene (S) and hexamethyl(ciclotrisiloxane) (D₃) monomers. Synthesized PS‐b ‐PDMS copolymers were characterized by ¹H‐nuclear magnetic resonance, size exclusion chromatography, Fourier transform infrared spectroscopy, and transmission electron microscopy. The physicochemical characterization determined that block copolymers have molar mass values close to ～135,000 g mol^?1, narrow M_w /M_n < 1.3, and chemical composition ranging from low to intermediate PDMS content. Blends of these copolymers with a commercial polystyrene (PS) were obtained by melt mixing and subsequently injection. Films obtained were flexible, and showed lower transparency than the original PS matrix. On the other hand, a 10 wt % incorporation of PS‐b ‐PDMS copolymers leads to better mechanical performance by enhancing elongation at break (～8.8 times higher) and opacity values (～18 times higher). In addition, UV–Vis barrier capacity of the resulting blends is also increased (up to 400% higher). © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45122.     

Interesterification of sesame oil and a fully hydrogenated fat using an immobilized lipase catalyst in both batch and continuous‐flow processes

Lipase‐mediated interesterification of sesame oil and a fully hydrogenated soybean oil was studied at 70 °C in both a batch reactor (BR) and a continuous‐flow packed‐bed reactor (PBR) using four different initial weight ratios of substrates (90 : 10, 80 : 20, 70 : 30 and 60 : 40) with Lipozyme TL IM (Thermomyces lanuginosa) as the biocatalyst. Reaction rates were determined by following the dependence of the profile of the product triacylglycerols (TAG) on the reaction time (BR) or the space time (PBR) via RP‐HPLC‐ELSD. Product TAG identities were confirmed by HPLC‐APCI‐MS. Primary differences between the performances of the two reactors were the maximum level of net hydrolysis (ca. 3 and 10 wt‐% lower acylglycerols at equilibrium for the PBR and BR, respectively), the time or space time required to approach quasi‐equilibrium conditions, and less migration of acyl groups in the PBR trials. For the BR trials, quasi‐equilibrium conditions were approached in 4–6 h, while for the PBR trials short space times (15 min to 2 h) were sufficient to produce effluent compositions similar to equilibrium BR compositions. The predominant TAG families formed by interesterification were LLS, PSO, PSL, SSL, and SSO (L = linoleic; S = stearic; P = palmitic; O = oleic). Oxidative stabilities, melting profiles and solid fat contents were determined for selected reaction products.     

Effect of Interesterification of Palmitic Acid-rich Triacylglycerol on Postprandial Lipid and Factor VII Response

The process of interesterification results in changes in triacylglycerol (TAG) structure and is used to increase the melting point of dietary fats. The acute health effects of this process on palmitic acid-rich fats are uncertain with regard to postprandial lipemia, insulin and factor VII activated (FVIIa) concentrations. Two randomized crossover trials in healthy male subjects compared the effects of meals containing 50 g fat [interesterified palm oil (IPO) versus native palm oil (NPO); n = 20, and IPO versus high-oleic sunflower oil (HOS); n = 18], on postprandial changes in lipids, glucose, insulin, chylomicron composition and FVIIa. Compared with NPO, IPO decreased postprandial TAG and insulin concentrations. Both NPO and IPO increased FVIIa concentrations postprandially; mean increases at 6 h were 21 and 19%, respectively. Compared with HOS, IPO decreased postprandial TAG (47% lower incremental area under the curve) and reduced the postprandial increase in FVIIa concentration by 64% at 6 h; no significant differences in hepatic and total lipase activities or insulin concentrations were noted. All three test meals increased postprandial leukocyte counts (average 26% at 6 h). The fatty acid composition of the chylomicron TAG was similar to the test fats following all test meals. It is concluded that interesterification of palm oil does not result in adverse changes in postprandial lipids, insulin or FVIIa compared to high oleate and native palm oils. George J. Miller: Deceased August 2006.