Dromedary milk fat: thermal and structural properties 1. Crystalline forms 
obtained by slow cooling

Karray, Nadia; Lopez, Christelle; Lesieur, P.; Ollivon, Michel

doi:10.1051/lait:2004014

Cited by 20 publications

(21 citation statements)

References 19 publications

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“…Next to this weak XRD peak, a major diffraction line, at about 20 °C, which increases in intensity upon cooling is also recorded at q = 0.15 Å -1 (42.15 Å) with a weak second order at q = 0.30 Å -1 (about 21 Å). This same crystalline structure has been previously observed at small angles for the slow cooling of the ADMF at 0.1°C·min -1 as a single line [9]. The small peak recorded at about q = 0.2-0.225 Å -1 from the beginning of the experiment at T = 50°C is attributed hypothetically to the presence of waxy lipids in the extracted fat since more polar lipids would be expected to form a bilayer of much larger period, as discussed in [9].…”

Section: Combined Xrdt and Dsc Measurementssupporting

confidence: 86%

“…Surprisingly, in spite of the broad diversity of TG present in ADMF, a single crystalline form, characterized by a single sharp and narrow line by XRD at small angles, was found in the previous study [9]. This specific behavior which was hypothetically related to the fluctuations of day to night and camel body temperatures, again raises the question of the molecular TG packing in such complex fats.…”

Section: Introductionmentioning

confidence: 59%

“…Experiments were conducted using Microcalix (Centre National de la Recherche Scientifique, Châtenay-Malabry, France), an apparatus allowing simultaneous timeresolved synchrotron X-ray diffraction as a function of temperature (XRDT) and high sensitivity differential scanning calorimetry (DSC) to be carried out on the same sample, as reported previously [4,9,15,19,23]. The recording of XRDT patterns and the calibration of the detectors and the calorimeter were conducted as previously reported [4,9,10,19,23].…”

Section: Combined Xrdt and Dsc Measurementsmentioning

confidence: 99%

“…The recording of XRDT patterns and the calibration of the detectors and the calorimeter were conducted as previously reported [4,9,10,19,23]. The analysis of the XRDT patterns was performed as previously described [9,14].…”

Section: Combined Xrdt and Dsc Measurementsmentioning

confidence: 99%

“…ADMF is an essential nutriment in desert areas with a complex fatty acid composition [2,5,8], which has already been discussed in the first article of this series [9]. As observed for other fats and in the previous study [9], the coupling of X-ray diffraction (XRD) as a function of temperature (XRDT) and differential scanning calorimetry (DSC) is the best technique to characterize the structural and thermal behavior of ADMF [14][15][16][17][18][19][20][21]25]. XRD permits the study of the various lamellar structures formed by triacylglycerols (TG).…”

Section: Introductionmentioning

confidence: 97%

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Dromedary milk fat: thermal and structural properties 2. Influence of cooling rate

Karray¹,

Lopez

Lesieur

et al. 2005

Lait

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-The crystallization behavior of anhydrous dromedary milk fat (ADMF) was examined using Microcalix (Centre National de la Recherche Scientifique, Châtenay-Malabry, France), an instrument coupling time-resolved synchrotron X-ray diffraction as a function of temperature (XRDT) at both small and wide angles and high-sensitivity differential scanning calorimetry (DSC) at an intermediate (1 °C·min -1 ) and at a fast (5 °C·min -1 ) cooling rate from 60 to -20 °C, together with their subsequent melting at 1 °C·min -1 . Upon cooling at 1 °C·min -1 , the crystallization of ADMF started at about 24 °C with the formation of a lamellar structure with a 46.9 Å period corresponding to a double-chain length molecular stacking and hexagonal chain packing (2L 1 α). From 20 °C, a major crystalline species also with double-chain lengths of 42.5 Å and orthorhombic chain packing (2L 2 β') was observed. The successive crystallizations of varieties 2L 1 and 2L 2 were correlated with the apparition of two large exothermal events recorded simultaneously by thermal analysis (DSC). However, comparison of XRDT and DSC recordings revealed the presence of a third exothermal peak probably related to a transition α → β'. At fast cooling (5 °C·min -1 ) of ADMF, three crystalline varieties were formed: the 2L 1 α (47.6 Å), 2L 2 β' (42.15 Å) and a new crystalline structure with 4 chain lengths: 4L β' of period 84.5 Å, while three endotherms were recorded by DSC. This last crystalline form which had never been characterized until now, likely corresponds to the accumulation of defects in the stable 2L β' form (42.15 Å) resulting from fast cooling and then to a local lack of symmetry in the 4L cell along the c axis of the crystals. This lack of symmetry was released during a transition 4L → 2L observed upon heating. A polymorphic transition α →β' was always observed upon ADMF heating following cooling at either 5 or 1 ° C·min -1 . Compared with the slow cooling at 0.1 °C·min -1 which was studied in the previous paper of this series, ADMF presented different structural and thermal properties. Indeed, the cooling at 1 °C·min -1 and 5 °C·min -1 generated an unstable crystalline form (α) that was not found at slow cooling at 0.1 °C·min -1 . However, the major stable form 2L β' was always observed in the three types of cooling.polymorphism / X-ray diffraction / differential scanning calorimetry / camel's milk * Corresponding author ( ): michel.ollivon@cep.u-psud.frArticle published by EDP Sciences and available at http://www.edpsciences.org/lait or http://dx

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Section: Combined Xrdt and Dsc Measurementssupporting

confidence: 86%

Section: Introductionmentioning

confidence: 59%

Section: Combined Xrdt and Dsc Measurementsmentioning

confidence: 99%

Section: Combined Xrdt and Dsc Measurementsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

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Dromedary milk fat: thermal and structural properties 2. Influence of cooling rate

Karray¹,

Lopez

Lesieur

et al. 2005

Lait

Self Cite

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Crystallisation and melting properties of dromedary milk fat globules studied by X‐ray diffraction and differential scanning calorimetry. Comparison with anhydrous dromedary milk fat

Lopez

Karray²,

Lesieur

et al. 2005

Euro J Lipid Sci & Tech

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Crystallisation and melting properties of triacylglycerols (TG) in dromedary milk fat (DMF) globules are studied by X‐ray diffraction (XRD) as a function of temperature coupled with high‐sensitivity differential scanning calorimetry (DSC), using synchrotron radiation. The crystallisation properties studied on cooling at ∣dT/dt∣ = 1 °C.min−1 from 60 °C to −8 °C show the successive formation of two double‐chain length (2L) lamellar structures: α 2L1 (46.7 Å) from 22 °C and β' 2L2 (41.7 Å) from 9 °C, which coexist until the end of the cooling process. These two types of crystals are related to the two exothermal peaks recorded simultaneously by DSC. The melting properties are studied on subsequent heating of DMF globules at dT/dt = 1 °C.min−1. The detailed analysis of the intensity and position of the XRD peaks recorded as a function of time shows that (i) the α 2L1 structure melts first, (ii) some TG from 2L1 melt and are incorporated again in the 2L2 structure, and (iii) the 2L2 structure melts with a final melting temperature over 44 °C. The influence of the dispersion of TG molecules in individual fat globules, with the presence of an interface with water, was determined by comparing their crystallisation behaviour to that of the same TG extracted from cream (anhydrous DMF) under the same experimental conditions. Results show that the same lamellar structures, α 2L1 and then β' 2L2, are formed on cooling in the dispersed and bulk states. However, crystallisation in the unstable α form is favoured in fat globules.

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Physical Characterization of Milk Fat and Milk Fat-Based Products

McCarthy¹,

Wong²

2020

Advanced Dairy Chemistry, Volume 2

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Dromedary milk fat: thermal and structural properties 1. Crystalline forms obtained by slow cooling

Cited by 20 publications

References 19 publications

Dromedary milk fat: thermal and structural properties 2. Influence of cooling rate

Dromedary milk fat: thermal and structural properties 2. Influence of cooling rate

Crystallisation and melting properties of dromedary milk fat globules studied by X‐ray diffraction and differential scanning calorimetry. Comparison with anhydrous dromedary milk fat

Physical Characterization of Milk Fat and Milk Fat-Based Products

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