Objective/Hypothesis: In postprandial clinical trials, stable isotope-labeled triacylglycerols (TAGs) as tracers can be added to the ingested fat in order to track its absorption and metabolic fate. Because most TAG tracers contain saturated fatty acids, we tested the hypothesis that such tracer addition may impact fat crystalline properties and lipolysis by digestive lipases.
Methods Used: we monitored the thermal and polymorphic behavior of anhydrous milk fat (AMF) enriched in homogeneous TAGs tracers and compared it with the native AMF using DSC and power XRD. As tracers, we used a mixture of tripalmitin, triolein and tricaprylin at 1.5 and 5.7wt% (concentrations used in clinical trials). We further tested the impact of tracers on the lipolysis of AMF using a static in vitro model of duodenal digestion.
Results: The addition of TAG tracers modified the AMF melting profile, especially at 5.7wt%. Both AMF and AMF enriched with 1.5wt% tracers were completely melted around 37°C (close to the body temperature), while the AMF enriched with 5.7wt% tracers remained partially crystallized at 37°C. Regarding the kinetics of AMF polymorphic transformation, while only β’ form was observed in the native AMF, the β-form was detected in the AMF containing 5.7wt% tracers. Lipolysis of AMF enriched with 5.7wt% tracers was delayed compared with that of AMF and AMF enriched with 1.5wt% tracers.
Conclusions: Low amounts of TAG tracers including tripalmitin do not have a high impact on fat digestion, but one has to be cautious when using higher amounts of these tracers.