Acceptability and digestibility of emulsions in a rat model: Effects of solid fat content and lipid type

The present study sought to determine if alterations in the chemical nature and form of fat in food would reduce digestibility while maintaining acceptability in rats. Oil-in-water emulsions (d < 1 μm) were prepared with either liquid palm oil, solid hydrogenated palm oil or solid docosane, all stabilized with sodium caseinate. The emulsions were incorporated into a fat-free rodent feed, and each offered over 5 days to separate cohorts of 12 male Sprague-Dawley rats housed in metabolic cages. The feed formulated with solid hydrogenated palm oil was significantly less acceptable than the feeds containing either liquid palm oil or docosane (feed intake 4.9, 26.6 and 32.1 g/animal/day respectively). The proportion of the fat retained (i.e. absorbed) was significantly less in the animals consuming the feed formulated with solid docosane than in the animals consuming either the liquid or solid palm oil (retention 8.7, 99.6, and 97.2%, respectively). The appearance of the feces from the rats fed docosane was different from the rats fed the triacylglycerol samples and thermal analysis revealed many of the solid alkane droplets had not coalesced during passage through the rat's digestive system. These results indicate that indigestible fats can be packaged into food in a manner that does not compromise the acceptability of the product, and does not produce any apparent intestinal distress.