Data for Early stages of fat crystallisation evaluated by low field NMR and Small-Angle X-ray Scattering

Low field NMR (20 MHz) is commonly used in the studies of fats in the form of solid fat content (SFC) measurements. However, it has the disadvantage of having low sensitivity to low amounts of crystalline material (0.5%), thus often incorrectly determining crystallisation induction times. From spin lattice relaxation rate measurements (R1) during the isothermal crystallisation measurements of cocoa butter between 0.01 and 10 MHz using fast field cycling NMR we learnt previously, that the most sensitive frequency region is below 1 MHz. Thus, we further focused to analyse our 10 kHz data in detail, by observing its time-dependence of R1 and comparing it to standard SFCNMR and SFC determinations from Small Angle X-ray Scattering (SFCSAXS). Although not reflecting directly the SFC, the R1, at this low frequency, is very sensitive to changes in molecular aggregation, particularly to the forming of lamellar assemblies of the triglycerides (main components of cocoa butter), and hence potentially serving as an alternative for determination of crystallisation induction times. Alongside R1, we also show that SFCSAXS is more sensitive to early stages of crystallisation, that is, standard SFCNMR determinations become more relevant when crystal growth starts to dominate the crystallisation process, but fail to pick up earlier crystallisation steps. This paper is a first step towards developing an NMR method for studying the early stages of crystallisation of fats and presenting an alternative method to determine SFC by SAXS. The data for Figure 2: Small and wide-angle X-ray Scattering of CB held isothermally at 22 °C. Every pattern represents a 7 minute measurement. The dashed lines indicates the position of the α-polymorph, the arrow in the SAXS region is signalling the peak position of the β’-polymorph. The arrows in the WAXS region are signalling the positions where the β’-polymorph peaks are usually observed, and where broad peaks are present. The data for Figure 3: Crystallisation of CB at 22 °C. (A) SFCNMR turnover and the corresponding Gompertz fit. (B) SFCSAXS plot and the Gompertz fit of the first crystallisation event, which has not been captured by SFCNMR. (C) R1 values at 10 kHz (circles) and 10 MHz (squares).