The impact of dose-dependent caloric salvage by microbial fermentation processes in the lower gut and the extent of renal excretion for the overall energetic availability of the alternative bulk
sweetener Palatinit were investigated in rats. To evaluate the extent of dose-dependent fermentation a conventional and a germ-free rat model were used and fecal excretions of
Palatinit after intragastric application were compared. Because of the lack of bacterial colonization in the gastrointestinal tract in germ-free rat the difference in fecal excretion of
Palatinit between germ-free and conventional rat is mainly due to bacterial fermentation. To determine the amount of renal excretion of
Palatinit the urine was collected. The experiments were conducted using different amounts of
Palatinit (300 and 1,200 mg/kg
body weight = mg/kg b.w.). Fecal excretions of
Palatinit and its monomers (
sorbitol and
mannitol) were measured by high-performance liquid chromatography (HPLC) and for the determination of renal excretions a gas chromatography system was used. After the application of 300 mg/kg b.w.
Palatinit only the breakdown product
sorbitol could be recovered in the feces of germ-free rats (29% of the applied dose). No intact
Palatinit could be found. In contrast, neither
Palatinit nor the breakdown products
sorbitol or
mannitol could be detected in the feces of conventional rats after application of the same dose. After the application of the higher dose only small amounts of intact
Palatinit were found in the feces of germ-free rats (average 12%). There was no intact measurable
Palatinit in the feces of conventional rats. The fecal excretions of
sorbitol and
mannitol in the feces of the germ-free rats were 55% and 39%; in conventional rats only 21%
sorbitol was excreted. Only traces of
Palatinit,
sorbitol or
mannitol were found in the urine of conventional and germ-free rats after application of the low as well as the high dose. In conclusion, this study clearly shows the dose dependency of fermentation and therefore the dose dependency of the energetic (i.e., caloric) availability of this
disaccharide sugar alcohol. In the calculation of the energy value of
Palatinit the renal excretion of
Palatinit and its monomers can be neglected.