Phase behavior of mixed systems of SOS and OSO

Abstract

Iyoda, T.; Ohtani, A,; Shimidzu, T.; Honda, K. Chem. L r r . 1986,687. (c) Yoneyama, H.; Hirai, T.; Kuwabata, S.; Ikcda, 0. Chem. Leu. 1986,1243. (d) Shimidzu, T.; Ohtani, A.; Iyoda, T.; Honda, K.The phase behavior of mixed systems of SOS (sn-1,3-distearoyl-sn-2-oleoylglycerol) and OS0 (sn-1.3-dioleoyl-sn-2stearoylglycerol) was studied with X-ray diffractometry and thermal analysis by using pure samples (>98.0%). A molecular compound was formed at the mixture of equal weight ratio, giving rise to two monotectic phases of SOS/compound and compound/OSO in a juxtapositional way. The stable form of the compound, &, has an interlamellar distance of 44.72 A of double chain length structure, which is in contrast to the triple chain length structure of the stable forms of SOS and OS0 having the same interlamellar distance of 65 A. &was formed through specific molecular interactions between stearoyl and oleoyl chains connected to glycerol groups: stearoyl chains at the 1,3-positions of SOS and at the 2-pition of OS0 are packed together in one leaflet of the double chain length lamellae, whereas another leaflet contains oleoyl chains of the two molecules. In the monotoctic region of SOS/compound, two crystals are present below the melting point of Be, 36 O C . Above that temperature, the stable crystals of SOS equilibrated with mixed liquid are present. In the monotectic region of compound/OSO, 8, is present with mixed liquid above the melting point of the stable form of OSO, 25 OC, below which two crystal fractions of the compound and OS0 are present. 8, was expected to have a congruent melting point, according to its unique melting and crystallizing behavior. The compound formation having the double chain length structure was also observed in the mixtures of pOP/OSO and POS/OSO, in which P is a palmitoy1 chain. A molecular model of the compound crystal is proposed, based on the molecular structures of SOS, OSO, and principal monounsaturated fatty acids. IaboductionMolecular packings in fats and lipids have important implications for their physical Properties in crystalline, liquid crystalline, and membrane states.' Biologically important fats and lipids are usually composed not only of different chain lengths but of saturated as well as unsaturated chains. These chains are attached to the same backbones, such as glycerol groups, exhibiting close structural proximity. Aliphatic chain-chain interactions in these 0022-3654/92/2096-105 14$03.00/0 fats and lipids are critical in terms of the structurtfunction relationship.2In the case of acylglycerols, the packing conditions are dependent on the chemical natures of fatty acid moieties: chain length, parity (odd or even), unsaturation (cis or trans), etcq2 are remarkably dependent on whether the acyl chains contain cis unsaturation or not. This is due to the fact that the aliphatic Particularly, the moiecular struchves and t h e r " i c behavior

Thermal and structural properties of sn‐1,3‐dipalmitoyl‐2‐oleoylglycerol and sn‐1,3‐dioleoyl‐2‐palmitoylglycerol binary mixtures examined with synchrotron radiation X‐ray diffraction

“…In all the mixtures, the compound formation was observed at the 1:1 (w/w) concentration ratio, indicating specific molecular interactions through the acyl chain moieties. It is worth noting that oleoyl chains are commonly present in all the component TAG of the mixture systems as saturated-oleoyl mixed acid TAG (15)(16)(17).From a technological implication, the occurrence of crystallization and transformation of TAG in the metastable forms is the important process leading to the growth of hard and brittle crystals. Therefore, it is interesting to elucidate the molecular structures and kinetic properties of the mixture systems.…”

Physical properties of fats in food

“…The formation of a molecular compound may be viewed as a special case of eutectic mixing systems that occurs as a result of specific molecular interactions between the component TAGs. Two examples are shown in Table 1.3: for an SOS/OSO mixture (Koyano et al, 1992) and for a POP/PPO mixture …”

Binary Phase Behavior of Saturated-Unsaturated Mixed-Acid Triacylglycerols—A Review

“…For simplicity, multiple β and β forms (β 2 , β 1 , β 2 , β 1 ) are represented by β and β. Polymorphic forms with double or triple chain-length structure are presented as α-2, γ-3, β -2. a P: palmitoyl, S: stearoyl, O: oleoyl, R: ricinoleoyl, L: linoleoyl, E: elaidoyl (data based on previous research) 1,[13][14][15][16][17][18][19][20][21][22][23][24][25] arate leaflets, with stabilized aliphatic chain-chain interactions. With regard to POP/OOP, in case 1, it causes destabilization due to the coexistence of oleoyl and palmitoyl chains in both the leaflets.…”

“…1 a and b . In each mixture, the MC was formed at a concentration ratio of 1:1 13,14 . The most stable form of MC was the β form, The formation of MCs was also observed in some binary mixtures between symmetric and asymmetric saturatedoleic diacid TAGs, such as SOS/SSO 15 and POP/PPO 16 SSO: 1,2-distearoyl-3-oleoyl-rac-glycerol; PPO: 1,2-dipalmitoyl-3-oleoyl-rac-glycerol .…”