Symmetry, chirality and crystalline tendency: the polymorphism of triacylglycerols
Bibliographic record
Abstract
The physical properties of foods containing fat are often dependent on the polymorphism of the constituent triacylglycerols (TAG). This is illustrated by the favourable physical and sensory properties associated with the β' form for margarine and butter and the β(V) form for chocolate. Recent investigations have revealed that the stereochemistry of TAG molecules has a profound influence on their polymorphism. For instance, a pure enantiomer of TAG (sn-10:0-10:0-16:0) was β'-tending while the corresponding racemic mixture (rac-10:0-10:0-16:0) was β-tending. In addition, the binary phase diagram for mixtures of the two enantiomers, sn-10:0-10:0-16:0 and sn-16:0-10:0-10:0, showed the formation of a eutectic (metastable β'-form conglomerate) and a molecular compound (stable β-form racemic compound). At heart, these differences in polymorph and crystalline tendency stem from differences in the stereochemistry of the unit cell -i.e. both enantiomers in the β unit cell, one enantiomer in the β' unit cell. Information on the relative stereochemical arrangement of molecules within the unit cell is also available from the crystallographic space group. This information (determined by X-ray diffraction) is available for a number of β- and β'-tending, chiral and achiral TAG systems. Like crystalline tendency (discussed previously), space group data indicates that the unit cell for TAG in the β' polymorph contains only one stereoisomer whereas the unit cell for TAG in the β polymorph contains both stereoisomers (conformers in achiral and enantiomers in chiral systems). Therefore, based on the current data, the stereochemical arrangement of TAG molecules in the unit cell is associated with the polymorphic form of the solid - both stereoisomers in the β form and one stereoisomer in the β' form. This perspective clearly explains the observed differences in polymorphic behavior for enantiopure and racemic TAG including the β'-stability of enantiopure systems. As a result, the current descriptive mechanism for TAG polymorphism is vastly improved when the stereochemical orientation of the constituent TAG molecules is considered.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".