Authors:G. Keller, F. Lavigne, C. Loisel, M. Ollivon, and C. Bourgaux
The thermal behavior of three ural fats (displaying very different composition), cocoa butter (CB)2, lard, and a stearin obtained from anhydrous milk-fat (AMF) fractionation, were studied by both DSC and X-ray diffraction as a function of temperature (XRDT). To perform temperature explorations between −30‡C and +80‡C, at rates identical to those used for DSC and ranging from 0.1 K min−1 to 10 K min−1, a new set of X-ray sample-holders, temperature-controlled by Peltier effect, has been developed. It is shown that the three more stable polymorphic forms of CB were easily characterized by either X-ray diffraction or DSC, and existence of two Β-3L forms was confirmed. On the contrary, the more complex polymorphism of lard and AMF required combined examination by DSC and XRDT and the brightness of the synchrotron source for studies at the highest heating rates. Quantitative analysis of the long spacings of XRDT recordings is invaluable for interpretation of thermal events. For instance, it was found that the simultaneous formation of two polymorphic forms, of apparent long spacing of 34 and 42 å, at the onset of lard crystallization might explain the difficulty of its fractionation.
Authors:C. Allais, G. Keller, P Lesieur, M. Ollivon, and F. Artzner
Polymorphism of trilaurin mixed with 4% of cholesterol was studied with a setup coupling calorimetry and phase characterisation
by in-situ X-ray diffraction (Microcalix). Four polymorphic forms were identified. Monotropic and enantiotropic transitions
were identified from the reconstruction of Gibbs free energy diagram which allows the control of trilaurin polymorphism.
Authors:M. Ollivon, G. Keller, C. Bourgaux, D. Kalnin, P. Villeneuve, and P. Lesieur
Coupling of time-resolved synchrotron X-ray diffraction
at both small and wide angles with differential scanning calorimetry is a
new technique that allows simultaneous characterization of thermal and structural
properties of a sample. The apparatus, called Microcalix, works between –30
and +230C at scanning rates comprised between 0.01 and 20C min–1
with a high sensitivity in both measurements using a single sample of small
volume (from about 1 to 20 μL). The last version of the instrument is
designed for laboratory bench and conventional source but preferably with
rotating anode or multilayered mirrors. Measurements under low pressure or
under shear as well as recordings of isothermal evolution are also possible.
The example of the study of polymorphism of a monounsaturated triglyceride
(PPO) will be presented as an application.
Authors:D. Lőrinczy, G. Regdon Jr., B. Keller, S. Szakály, and B. Schäffer
research of near past decades had established the real nutritional value of
fats and oils. In the former theory the nutritional value of fats and oils
is influenced mainly by the rate of saturated/unsaturated fats. It was ruled
out, and positive, inert or risk physiological effect of every single fatty
acid had been established. The health-care effect of omega-3 fatty acid mainly
by the favourable (<3:1) rate of omega-6/omega-3 was established, as inert
was concerned the saturated C16 fatty acid and the
maximal amount of trans-fatty acids carrying health risk in fats was legally
regulated in some countries. These nutritional-physiological requirements
were mainly fulfilled by margarine producers and the elementary fats were
selected in such a way that they should meet these requirements.
method helps to the producers to quickly determine the amount of the liquid
and solid fat at certain temperature and/or to adjust the technological temperature
parameters. The main steps of our method are: a./ determination of cooling
rate (K min–1) of the crystallizer device;
b./ determination of the rate of liquid/solid fat at 10°C temperature.
This value is used for the determination of the rate of fats and oils as a
function of technology and required consistency firmness (spread ability);
c./ determination of the temperature from the cooling curve where the crystallization
of most part of the fat has finished. This value is used for the determination
of outlet temperature parameter of product coming out from the crystallizer
device for margarines or mixed-fat spreads with water-in-oil system.