Enzymatic synthesis of position-specific low-calorie structured lipids

An immobilized sn-1,3-specific lipase from Rhizomucor miehei (IM 60) was used to catalyze the interesterification of tristearin (C_18:0) and tricaprin (C_10:0) to produce low-calorie structured lipids (SL). Acceptable product yields were obtained from a 1:1 mole ratio of both triacylglycerols with 10% (w/w of reactants) of IM 60 in 3 mL hexane. The SL molecular species, based on total carbon number, were 44.2% C₄₁ and 40.5% C₄₉, with 3.8 and 11.5% unreacted tristearin C₅₇ and tricaprin C₂₇, respectively, remaining in the product mixture. The best yield of C₄₁ species (44.3%) was obtained with zero added water. Tricaprylin (C_8:0) was also successfully interesterified with tristearin in good yields at 1:1 mole ratio. Products were analyzed by reverse-phase high-performance liquid chromatography with an evaporative light-scattering detector. Reaction parameters, such as substrate mole ratio, enzyme load, time course, added water, reaction media, and enzyme reuse, were also investigated. Hydrolysis by pancreatic lipase revealed the specific fatty acids present at the sn-1,3 positions of SL. Biocatalysis Symposium Paper, presented at the AOCS Annual Meeting & Expo, Seattle, Washington. May 11–14, 1997.     

Chemical synthesis of tricaproin, trienantin and tricaprylin

In the present work, we optimised the glycerol + caproic acid/enantic acid/caprylic acid esterification conditions, using chemical routes, in order to get tricaproin, trienantin and tricaprylin in a medium solely composed of reagents. The option for cleaner conditions, without catalyst and solvent was preferred. The best conditions for tricaprylin and trienantin chemical synthesis were 6 h of contact, with a temperature around 160 ± 5 °C, followed by a 20 h of contact using higher temperatures (around 200 ± 5 °C). The volatility of caproic acid impeded the prolonged use of higher temperatures and this limited the yield of tricaproin that could be obtained. The synthesis of these triacylglycerols in the absence of both solvent and catalyst is of importance in consideration of the possible nutritional use of the products so formed.     

Solvent-free enzymatic synthesis of structured lipids containing CLA from coconut oil and tricaprylin

Lipase-catalyzed acidolysis of different TAG with CLA was performed to produce structured lipids (SL) containing CLA. An immobilized lipase from Mucor miehei (Lipozyme IM, Novo Nordisk Inc., Franklinton, NC) was used as the biocatalyst in a solvent-free system. Conconut oil and tricaprylin, which are sources of medium-chain FA, were the starting substrates, and a mixture of FFA (MFFA) containing 73% CLA was the donor of the acyl groups. For each TAG, four different ratios of TAG/MFFA were blended to prepare about 500 g of mixture containing 10, 20, 30, and 40% CLA (w/w). Each blend was reacted with 5% lipase at 65°C for 48 h under nitrogen. Over the range of TAG/MFFA ratios examined, CLA was incorporated effectively by the enzyme. Lipozyme IM exhibited no special preference for any particular FA, since the incorporation of FA was proportional to their concentration in the system. FFA, PV, p-anisidine value (p-AV), iodine value (IV), and saponification number (SN) were evaluated for all the SL. FFA, PV, and p-AV depended on the purification process and showed no significant deterioration of SL with respect to the original TAG, whereas IV and SN depended on the composition of the SL, mainly the CLA content.     

Lipase-catalyzed incorporation of conjugated linoleic acid into tricaprylin

Three commercially available immobilized lipases, Novozym 435 from Candida antarctica, Lipozyme IM from Rhizomucor miehei, and Lipase PS-C from Pseudomonas cepacia, were used as biocatalysts for the interesterification of conjugated linoleic acid (CLA) ethyl ester and tricaprylin. The reactions were carried out in hexane, and the products were analyzed by gas-liquid chromatography. The effects of molar ratio, enzyme load, incubation time, and temperature on CLA incorporation were investigated. Novozym 435, as compared to Lipozyme IM and Lipase PC-C, showed the highest degree of CLA incorporation into tricaprylin. By hydrolysis with pancreatic lipase, it was found that Lipozyme IM and Lipase PS-C exhibited high selectivity for the sn-1,3 position of the triacylglycerol early in the interesterification, with small extents of incorporation of CLA into the sn-2 position, probably due to acyl migration, at later reaction times. A small extent of sn-1,3 selectivity during interesterification by Novozym 435 was observed.     

Heat capacity of the triglycerides: Tricaproin,tricaprylin and tricaprin

Heat capacities of tricaproin, tricaprylin, tricaprin and their binary mixtures were determined between 325 and 423°K. In this temperature range, the heat capacity of tricaproin increased from 174 to 206 cal/mol-K, of tricaprylin from 221 to 281 cal/mol-K and of tricaprin from 276 to 309 cal/mol-K. Mixtures of tricaproin/tricaprin and tricaprylin/tricaprin behave as ideal solutions, while a mixture of tricaproin/tricaprylin did not behave as an ideal solution for this temperature range.     

Density and viscosity of low-molecular weight triglycerides and their mixtures

The viscosities of tributyrin (C4∶0) and binary mixtures of this triglyceride with a diesel fuel, tricaproin (C6∶0), and tricaprylin (C8∶0) were determined for the temperature range −5 to 85°C and for shear rates of 1.62–64.7 s⁻¹. The resulting dynamic viscosities were fit to a power law model to obtain values for the consistency coefficient and the flow behavior index. These results indicated slightly pseudoplastic flow behavior (indices ranged from 0.94 to 0.99) for tributyrin and its mixtures. The calculated consistency coefficients for tributyrin and those previously obtained for tricaproin, tricaprylin and tricaprin were fit by a least-squares method to the three-parameter Vogel model to account for the effect of temperature. An ideal solution relationship and the Kendall-Monroe model were used to predict the density and consistency coefficients, respectively, for binary and quaternary mixtures of these low-molecular weight triglycerides.     

Rapid measurements of boiling point and vapor pressure of short-chain triglycerides by thermogravimetric analysis

Temperature dependence of vapor pressure and the boiling points for tricaproin (Tcap) and tricaprylin (Tcpy) were measured by a new rapid thermogravimetric analysis (TGA) method. Results were in agreement with data from other references. The Clausius/Clapeyron model fitted Tcap and Tcpy vapor pressure data with errors of 6% or less for pressures ranging from ambient down to 20 mmHg. This agreement with the model suggests that the vapor of these compounds has a large degree of ideal gas behavior and that their vaporization enthalpies are nearly constant from 25 to 400°C. Comparable accuracy and precision were obtained with TGA and differential scanning calorimetry methods for the compounds tested; however, TGA plots had significantly straighter baselines, which made vapor pressure determinations more convenient.