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Early stages of fat crystallisation evaluated by low‐field NMR and small‐angle X‐ray scattering
Author(s) -
Ladd Parada Marjorie,
Povey Megan J.,
Vieira Josélio,
Rappolt Michael,
Ries Michael E.
Publication year - 2019
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.4860
Subject(s) - small angle x ray scattering , crystallization , chemistry , scattering , analytical chemistry (journal) , free induction decay , relaxation (psychology) , nuclear magnetic resonance spectroscopy , crystallography , chemical physics , spin echo , chromatography , optics , organic chemistry , physics , medicine , psychology , social psychology , magnetic resonance imaging , radiology
Low‐field time‐domain nuclear magnetic resonance (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 low sensitivity to small amounts of crystalline material (0.5%), thus often incorrectly determining crystallisation induction times. From spin–lattice relaxation rate measurements ( R 1 ) 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 focused on analysing our 10‐kHz data in detail, by observing the time dependence of R 1 and comparing it with standard SFC NMR and SFC determinations from small‐angle X‐ray scattering (SFC SAXS ). Although not reflecting directly the SFC, the R 1 at this low frequency is very sensitive to changes in molecular aggregation and hence potentially serving as an alternative for determination of crystallisation induction times. Alongside R 1 , we also show that SFC SAXS is more sensitive to early stages of crystallisation, that is, standard SFC NMR determinations become more relevant when crystal growth starts to dominate the crystallisation process but fail to pick up earlier crystallisation steps. This paper thus demonstrates the potential of studying triacylglycerols at frequencies below 1 MHz for obtaining further understanding of the early crystallisation stages of fats and presents an alternative and complementary method to estimate SFC by SAXS.