Research has shown that not only the nature of fatty acids (FA) but also their position on the triacylglycerol molecule may play a fundamental role in the extent to which FAs are absorbed. Additionally, fat emulsification may affect the activity of digestive lipases, and thus, may govern the digestion and absorption of FAs.
To better understand this phenomenon, we evaluated the bioavailability of FAs in linseed-oil and palm-stearin blends compared to their interesterified mix, using a sn-1,3 stereospecific lipase. Additionally, we evaluated the FAs absorption of the interesterified mix in o/w emulsions, which were either stabilized using chitosan (3% w/w in water) or sodium-caseinate (10% w/w in water), to understand the effect of size reduction together with the effect of these compounds on lipids absorption. Emulsions were prepared by homogenizing 40% of the interesterified fat with 60% of the emulsifier-solution at 20,000 rpm. Creaming stability, rheology and oil-droplet size distribution were assessed. Test meals (1 g) were fed at 36oC through an intragastric feeding tube on Sprague-Dawley male rats after 18h fasting. In addition, a control group (400 mg fat + 600 mg water feed) and a blank group (physiological serum feed) were considered. Postprandial blood samples were collected after meal administration and the FA profile of plasma lipids was determined.
No significant differences in FAs absorption were found when comparing linseed-oil and palm-stearin blends with their interesterified mix. Thus, interesterification was proved to be instrumental to change fat texture, without altering FA bioavailability. In relation to o/w emulsions, the overall 0–8-h plasma responses given by the areas under the curve showed a significantly higher total FAs absorption in the sodium-caseinate stabilized emulsion, compared to the other two meals, enhancing FAs bioavailability. No differences were found between the chitosan stabilized emulsion and the control meal. This was attributed to the formation of large flocs, which may restrict the access of lipases to the lipids within the droplets, counteracting the effect of droplet size reduction.
Prof. Pedro Bouchon, pbouchon@ing.puc.cl
