No abstract

In an effort to improve the physical and/or thermal characteristics of solid fats, the enzymatic interesterification of tallow and butterfat with high-oleic sunflower oil and soybean oil was investigated. The two simultaneously occurring reactions, interesterification and hydrolysis, were followed by high-performance Hquid chromatography of altered glycerides and by gas-liquid chromatography of liberated free fatty acids. The enzymes used in these studies were immobilized lipases that included either a 1,3-acyl-selective lipase or a c/s-9~Cls-selective lipase. The degree of hydrolysis of the fat/oil mixtures was dependent upon the initial water content of the reaction medium. The extent of the interesterification reaction was dependent on the amount of enzyme employed but not on the reaction temperature over the range of 50-70°C. Changes in melting characteristics of the interesterified glyceride mixtures were followed by differential scanning calorimetry of the residual mixed glycerides after removal of free fatty acids. Interesterification of the glyceride mixes with the two types of enzymes allowed for either a decrease or increase in the solid fat content of the initial glyceride mix.

An energy minimized three-dimensional structure of a collagen microfibril template was constructed based on the five-stranded model of Smith (1968), using molecular modeling methods and Kollman force fields (Weiner and Kollman, 1981). For this model, individual molecules were constructed with three identical polypeptide chains [Gly-Pro-Pro)n, (Gly-Prop-Hyp)n, or (Gly-Ala-Ala)n, where n = 4, 12, and 16) coiled into a right-handed triple-helical structure. The axial distance between adjacent amino acid residues is about 0.29 nm per polypeptide chain, and the pitch of each chain is approximately 3.3 residues. The microfibril model consists of five parallel triple helices packed so that a left-handed superhelical twist exists. The structural characteristics of the computed microfibril are consistent with those obtained for collagen by X-ray diffraction and electron microscopy. The energy minimized Smith microfibril model for (Gly-Pro-Pro)12 has an axial length of about 10.2 nm (for a 36 amino acid residue chain), which gives an estimated D-spacing (234 amino acids per chain) of approximately 66.2 nm. Studies of the microfibril models (Gly-Pro-Pro)12, (Gly-Pro-Hyp)12, and (Gly-Ala-Ala)12 show that nonbonded van der Waals interactions are important for microfibril formation, while electrostatic interactions contribute to the stability of the microfibril structure and determine the specificity by which collagen molecules pack within the microfibril.

A low‐temperature synthesis of fatty alkanolamides, fatty diamides and fatty aralkylamides directly from triglycerides and primary amines provides essentially quantitative yields of the various products. The reactions run to completion in 3–12 h at temperatures of 50–60°C, approximately 100°C lower than employed in present conventional practice. The amines are used in excess and serve as solvent, reagent and, perhaps, as catalyst. The amides were characterized by melting point and spectroscopic (infrared and nuclear magnetic resonance) methods. If the mixed amides produced from the various natural triglyceride mixtures of fats and oils are acceptable products, this synthetic method provides these products in satisfactory quality while conserving energy and avoiding the intermediate production of free fatty acids or their esters.

A technique for the synthesis of monosubstituted fatty amides at low temperature and ambient pressure was developed. This method involved the condensation of an amine with a triacylglycerol. The primary amine (ethyl, n-butyl, n-hexyl and n-octyl were tested) acted as reagent and solvent for the fatty substrates. No additional o~ ganic solvent or catalyst was added. Tallow, vegetable oils and fish oil all served well as substrates, as did pure tripalmitin. The rate of amidation was dependent upon temperature and the ratio of fat to amine. In a series of experiments conducted with tallow and n-butylamine at a fatmmine molar ratio of 1:16, amidation could be carded out at 20°C, producing n-butyltallowamide in 83% yield in 24 hr. When the fatmmine molar ratio was reduced to 1:8, and the temperature raised to 45°C, the amide yield was 87.6% in 24 hr. When the reaction was carried out at the boiling point of n-butylamine {78°C) and at a fat: amine ratio of 1:8, the amide yield was 93.2% in 4 hr. The reaction progressed more rapidly with higher molecular weight amines. The identity and purity of the amides was assessed by thin-layer chromatography and confirmed by elemental analyses and infrared and C 1~ nuclear magnetic resonance spectroscopy.