Phase behaviour of fats and their mixtures.

The main features of glyceride crystallization are discussed on the basis of earlier known crystal structures of glycerides and the new results, particularly on their structure in the liquid state. An analysis of the methyl end group packing is presented, which enables to predict whether a particular crystal form of a mixed triglyceride exists. It is also demonstrated, how these basic informations can be used in order to obtain the molecular conformation from powder data, and this is illustrated in the case of a 2-oleo-disaturated glyceride.



Molekulare Anordnung der Glyceride



An Hand der fruheren Erkenntnisse uber die Kristallstruktur der Glyceride sowie der neueren Ergebnisse, insbesondere hinsichtlich ihrer Struktur im flussigen Zustand, werden die Hauptmerkmale der Kristallisation von Glyceriden diskutiert. Die beschriebene Analyse der Packung der Methyl-Endgruppe ermoglicht es, vorauszusagen, ob eine bestimmte Kristallform eines gemischten Triglycerids vorliegt. Es wird auch dargestellt, inwiefern diese Grundkenntnisse zur Ermittlung der molekularen Anordnung aus den Daten der Pulver-Diagramme eingesetzt werden konnen; als Beispiel wurde ein 2-Oleo-digesattigtes Glycerid gewahlt.

Molecular Arrangement in Glycerides

Identifying key structural indicators of mechanical strength in networks of fat crystals

The polymorphism and intersolubility of a series of palmitic, stearic and oleic triglycerides have been investigated in order to understand the thermal properties of fractions of natural fats. Results are shown for tripalmitin (PPP), 2-stearo-dipalmitin, (PSP) and 2-oleo-dipalmitin (POP); these molecules differ essentially in the number of carbons (P→S) and the degree of unsaturation of chains (S→O). The different polymorphic forms have been verified by variable temperature X-ray powder diffraction. The organization of the fatty acid carbon chains in the most stable polymorphic form(β′ or β) has been studied by variable temperature NMR spectroscopy by means of the protons relaxation times T1, T2 and T1ϱ. The construction of binary phase diagrams (PPP-PSP and PPP-POP), from the data obtained by differential scanning calorimetry and X-ray powder diffraction, shows the formation of solid solutions or monotectic interactions, according to the nature and the polymorphic form of the triglycerides. The kinetic of the very importantβ′→β transition has been analyzed by variable temperature powder X-ray diffraction for PPP, and [PPP-PSP] or [PPP-POP] blends. The molecular interactions occurring between the mixed crystals have been explained, by applying the model of Avrami and by an empirical isolation method.

Polymorphism and intersolubility of some palmitic, stearic and oleic triglycerides: PPP, PSP and POP

The reasons for the increased world-wide incidence of obesity, type-2 diabetes, and cardiovascular disease include sedentary lifestyles and poor food choices. Regulatory agencies in several countries now require companies to add unattractive front of package labels to their products where salt, sugar and fat (or saturated fat) levels are prominently displayed. After the demise of partially hydrogenated fats, saturated fat has become the new target. Consumption of saturated fat over polyunsaturated oil has been clearly shown to increase cholesterol levels in humans. However, saturated fats provide the functionality required in many food products. To complicate matters, concerns over sustainability, veganism, genetically modified organisms, animal welfare, as well as religious beliefs, severely limit our sources of saturated fat. In this review we will discuss recent advances in our understanding of the nano and mesoscale structure of fats, responsible for their physical functionality and contrast it to that of fat mimetics. Fat mimetics include polymeric networks of ethylcellulose, emulsion-templated networks of proteins and polysaccharides, colloidal and self-assembled fibrillar networks of polar lipid crystals, as well as solid o/w emulsions of oil trapped within crystallized lamellar mesophases. Clean label and economic considerations will also be touched upon.

Advances in our understanding of the structure and functionality of edible fats and fat mimetics

The x-ray structure analysis of a single crystal of the β-@#@ form of 2-11-bromoundecanoyl-l, 1- dicaprin has revealed an arrangement of carbon atom chains within a molecular layer that is identical to that found in the β-form monoacid triglycerides. However the packing of the molec-ular layers within the crystal lattice is sub-stantially different because of the unequal fatty acid chain-lengths in the symmetrical diacid triglyceride of this investigation.

Janice T. Gordon

Papers

The Crystal Structure of a Diacid Triglyceride