Comparison of experimental techniques used in lipid crystallization studies

Four methods were used to monitor the crystallization behavior of anhydrous milk fat (AMF), milk fat triacylglycerols (MF-TAG), and MF-TAG plus diacyl glycerols (MF-DAG). The crystallization process was monitored by measuring the solid fat content, turbidity, and scattering intensity of the crystalli zing material, as well as by imaging using polarized light microscopy combi ned with digital image processing. In general, induction times followed the order MF-DAG > AMF > MF-TAG for all techniques. However, the absolute valu e for the induction times differed substantially; on average 3 min by micro scopy, 7 min by light-scattering spectroscopy, 13 min by turbidimetry, and 25 min by pulsed nuclear magnetic resonance. Microscopic imaging coupled to image processing proved to be the most sensitive method, suitable for the study of early events in the crystallization of fats.