The article reviews recent studies of crystallization processes of polymorphic modifications of lipid molecules, particularly proncipal saturated and mono-cis-unsaturated fatty acids and mixed acid triacylglycerols. Themodynamic and Kinetic aspects of the polymorphic crystallization are discussed in relation to molecular structures, thermal properties with X-ray diffractometry, differential scanning calorimetry and vibrational spectroscopy.

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We examined the fecal fat excretion of mildly hypertriacylglycerolemic subjects who ingested soft cookies containing 1(3)-behenoyl-2,3(1)-dioleoyl-rac-glycerol (BOO) for 7 days. The subjects included 14 healthy men (average age; 44.9 ± 1.7) whose fasting plasma triacylglycerol level ranged from 150 to 250 mg/dL. Every day for 7 days, the subjects ate 5 soft cookies containing margarine with the BOO-rich experimental oil (BOO intake, 2.46 g/day). The placebo group ate soft cookies containing margarine without BOO. This study was a randomized double-blind, placebo-controlled, crossover study. Feces were collected for 3 days prior to the end of the treatment period, and fecal fat and fatty acid composition were determined. The fecal wet weight was significantly increased in BOO group compared with that in the placebo group. Moreover, fecal fat and fatty acid level were significantly higher in the BOO group than in the placebo group. There were no significant differences in the fecal fatty acid composition of the BOO and placebo groups. These results suggest that dietary BOO increases fecal excretion of dietary fat in humans. However, BOO does not increase the excretion of specific fatty acids; it increases the excretion of all fatty acids of dietary origin, which may lead to lower and delay intestinal absorption of dietary fat.

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The density of liquid and polymorphic crystalline forms of 2-oleoyl-1, 3-dipalmitoylglycerol (POP), 2-oleoyl-1, 3-rac-palmitoyl-stearoylglycerol (POS), and 2-oleoyl-1, 3- distearoylglycerol (SOS) were measured by gas pycnometer. An 0.18 nm³ decrease in molecular volume was observed in all triacylglycerols, corresponding to structural changes in the most stable form of β₁ of the three triacylglycerols. More precisely, the saturated and unsaturated fatty acyl moieties in the triacylglycerols showed no monotonous change in volume.
In sample preparation, density of each polymorphic forms was observed to be highest by symple melt cooling. For melt mediated transformation, and solid state transformation, the values of this parameter were less.

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Triacylglycerols have specific properties which are useful for processing and/or modification of food systems according to their polymorphism, hydrophobic/hydrophilic balance, digestibility, and so on. These phenomena are mainly governed by the structure. Interfacial properties of 3-butyryl-1, 2-dipalmitoylglycerol at O/W emulsion, specific anti-bloom effect of 2-oleoy1-1, 3 dibehenylglycerol and restriction of absorption for 2-stearoyl-1, 3-dihexanoylglycerol are good examples. In the present study, we intend to summarize the relation between the structure and their specific properties.

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The positional distributions of fatty acids (FAs) in fats and oils are principally analyzed by selectively transesterifying the target triacylglycerols (TAGs) at the 1(3) position using Pseudozyma (Candida) antarctica lipase, followed by recovering the resulting 2-monoacylglycerols (MAGs) by chromatography. FA compositions were measured by gas chromatography (GC) after methylating target TAGs and 2-MAGs. The method was collaboratively evaluated by 12 laboratories by analyzing the positional FA distributions in soybean, palm, and sardine oils. The maximum reproducibility relative standard deviations for the major FAs and those at the sn-2 positions of soybean, palm, and sardine oils were 4.41% and 3.92% (18:3n-3), 4.48% and 3.82% (18:0), and 8.93 and 8.24% (14:0), respectively. The values at the sn-2 position were always low. Therefore, these results indicated that the variations were mainly caused by the FA analysis procedure, i.e., the methylation and GC analyses, rather than the enzymatic transesterification and chromatography utilized to prepare 2-MAGs from the target oil.

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