Structural Study on Fat Crystallization Process Heterogeneously Induced by Graphite Surfaces

Abstract

Some inorganic and organic crystals have been recently found to promote fat crystallization in thermodynamically stable polymorphs, though they lack long hydrocarbon chains. The novel promoters are talc, carbon nanotube, graphite, theobromine, ellagic acid dihydrate, and terephthalic acid, among which graphite surpasses the others in the promotion effect. To elucidate the mechanism, we investigated the influence of graphite surfaces on the crystallization manner of trilaurin in terms of crystal morphology, molecular orientation, and crystallographic features. Polarized optical microscopy, cryo-scanning electron microscopy, synchrotron X-ray diffractometry, and polarized Fourier-transform infrared spectroscopy combined with the attenuated total reflection sampling method were employed for the analyses. All the results suggested that the carbon hexagonal network plane of graphite surfaces have a high potential to facilitate the clustering of fat molecules against high thermal fluctuations in fat melt, the fat molecules form a layer structure parallel to the graphite surface, and the clusters tend to grow into thin plate crystals of the β phase at the temperatures corresponding to low supercooling. The β′ phase also has a larger chance to grow on the graphite surface as supercooling increases.

Heterogeneous Nucleation Effects of Talc Particles on Polymorphic Crystallization of Cocoa Butter

“…By analyzing the relative intensity between small-and wide-angle X-ray diffraction (XRD) peaks, different models were proposed for the adsorption of TAG molecules on both talc and graphite surfaces. 20 A very recent study, 23 using polarized Fouriertransform infrared spectroscopy combined with the attenuated total reflection sampling method, has offered the revised model that LLL molecules adsorb on graphite surfaces to make double-chain length layers parallel to the surfaces.…”

Binary Phase Behavior of 1,3-Distearoyl-2-oleoyl-sn-glycerol (SOS) and Trilaurin (LLL)

“…Meanwhile, the latter two peaks weaken temporarily, and a new small peak occurs at | s | = 2.79 nm −1 ( d = 0.358 nm). These changes indicate the rearrangement of the acyl chains in the sub-cell structure of the LLL β-2 crystals; the characteristic short spacings before and after the changes have recently been reported for pure LLL [ 48 ]. Therefore, we attribute these changes to the polymorphic transformation of LLL crystals from the less stable β-2 (β 2 -2) to the more stable β-2 (β 1 -2).…”

Interactive Polymorphic Crystallization Behavior in Eutectic Triacylglycerol Mixtures Containing Molecular Compound Crystals

“…This transformation from β 2 -2 to β 1 -2 has been previously reported. 43,44 With further heating, all the SAXD and WAXD peaks attenuated beginning at 48 °C and disappeared completely by 57 °C due to the melting of β 1 -2.…”

“…In the meantime, the SAXD peak at 3.16 nm increased in intensity and shifted slightly to a 3.15 nm position. This transformation from β 2 -2 to β 1 -2 has been previously reported. , With further heating, all the SAXD and WAXD peaks attenuated beginning at 48 °C and disappeared completely by 57 °C due to the melting of β 1 -2.…”