Les propriétés de cristallisation et les interactions moléculaires intervenant dans des matières grasses naturelles, en létat ou modifiées, ainsi que dans leurs mélanges ont été caractérisées, et ceci dans le contexte de la mise sur le marché de produits alimentaires gras à teneur réduite en acides gras trans. En plus dune compréhension des propriétés de cristallisation, ce travail propose une modélisation offrant une possibilité de prédiction de propriétés de systèmes ternaires à partir des systèmes binaires correspondants. Enfin, la dernière partie de ce travail concerne une étude plus détaillée de la cinétique du polymorphisme et de lintersolubilité des constituants triglycéridiques dun composé majeur des formulations « low-trans » : lhuile de palme, ainsi que dun grand nombre de ses fractions (stéarines, oléines, superoléines et fractions intermédiaires). Lensemble des résultats démontre lintérêt de réaliser des diagrammes de phases pour létude du comportement dynamique de systèmes lipidiques et la nécessité de combiner plusieurs techniques pour caractériser ces systèmes hautement complexes et instables.

For many years, substitutes for butterfat have been the subject of much controversy. Their acceptance as being nutritionally equal to butterfat has often been question. The importance of this problem lies primarily in its economic and nutritional significance. A recent study of pulic attitudes toward dairy products conducted by Alfred Politz Research, Inc. for the American Dairy Association, shows that 48.4 per cent of the poulation believed that butter is a more nutritions food than oleomargarine. Only 6 per cent thought that oleomargarine is more nutritious while 27.2 per cent believed they are about the same. The remainder, 18.4 per cent, stated that they did not know. Margarine tax laws were in force for some time while vegetable oils were being tested as a human food. In addition to chemical examination, many investigations were conducted with rats, calves, and humans. Although there were still conflicting results, the tax laws were repealed and substitutes wen on the market to compete with butter. Many investigators still question the decision that substitutes are qual to butter, nutritionwise. Many investigations (4, 6, 21, 34) have shown that butter contains one or more growth factors which have not, as yet been identified. Chemical methods have failed to identify any of these factors, and so other methods have been considered. It is a well known fact that interrelationships exist between fat metabolism and the metabolism of other substances. It has been shown (11) that dietary fat affects the metabolism of other nutrients such as calcium and phosphorus. Although not clearly understood, it has been demonstrated (25, 37) that the kidney plays an important role in fat transport and metabolism. The value of urinalysis as a method of indicating the metabolism as a whole is well known, as well as is the high sensitivity of metabolic systems to minute quantities of some substances. The possibility of detecting growth factors or other substances through a study of excreted metabolites seems worthy of consideration in this study. Recent work with paper chromatography at the University of Texas (48) has indicated that each individual has a specific urinary metabolic pattern. Similarities have been found in the patterns of identical twins and schizophrenics. It was also found that the diet changed this pattern to a certain extent, although this was not studied extensively. The problem reported here is a study of urine obtained from highly inbred rats fed animal and vegetable fats analyzed by use of paper chromatography.