Assessment of in Vitro Digestibility of Dietary Carbohydrates Using Rat Small Intestinal Extract

Abstract

There are few studies on the assessment of digestibility of nondigestible carbohydrates, despite their increasingly important role in human health. In vitro digestibility of a range of dietary carbohydrates classified as digestible (maltose, sucrose, and lactose), well-recognized (lactulose, fructooligosaccharides (FOS), and two types of galactooligosaccharides (GOS) differing in the predominant glycosidic linkage), and potential (lactosucrose and GOS from lactulose, OsLu) prebiotics using a rat small intestinal extract (RSIE) under physiological conditions of temperature and pH is described. Recognized and potential prebiotics were highly resistant to RSIE digestion although partial hydrolysis at different extents was observed. FOS and lactulose were the most resistant to digestion, followed closely by OsLu and more distantly by both types of GOS and lactosucrose. In GOS, β(1 → 6) linkages were more resistant to digestion than β(1 → 4) bonds. The reported in vitro digestion model is a useful, simple, and cost-effective tool to evaluate the digestibility of dietary oligosaccharides.

Evaluation of the impact of a rat small intestinal extract on the digestion of four different functional fibers

“…Sucrose was the most digested structure causing important increases in fructose content. A similar trend was observed by Ferreira-Lazarte et al (2017) 14 after the digestion of FOS with RSIE exhibiting the tetrasaccharide structure the highest degradation (40%). The trisaccharide also increased, most likely, due to degradation of the tetrasaccharide.…”

“…These results underline the relevance of the higher M w composition in terms of digestibility. 16,36 Higher hydrolysis in Inulin Orafti GR was observed in the tetrasaccharide fraction after 180 min of digestion, supporting the data obtained in the in vivo and in vitro studies by Ferreira-Lazarte et al (2017) 14 and Molis et al (1996), 37 resulting in 12% and 11% of total digestion, respectively. In the case of Raftilose P95, a not significant decrease of tri-and tetrasaccharides was observed: hydrolysis being higher in the case of the linkage β(2 → 1) between fructose monomers (inulotriose and inulotetraose of Raftilose P95), when glucose is not present in the structure ending compared to sucrose oligosaccharides (kestose and nystose of Inulin Orafti GR) ( Table 2).…”

“…This could suggest the lower resistance of the β(2 → 1) bonds to the action of the digestive enzymes. 14 With respect to oligosaccharides from galactose, chromatographic profiles by GC-FID of AlphaGOS P undigested and after digestion with RSIE are shown in Fig. 2.…”

“…Increases in galactose levels also suggest that linkages between galactose monomers are being broken by digestive enzymes, similar to the degradation of β-GOS derived from lactose and lactulose observed during small intestinal digestion in previous works. 14,16,36,38,39 Beneficial effect of the α-GOS on the modulation of the intestinal microbiota is wellknown. 40,41 Nevertheless, there is not enough information about their digestibility, even the expert scientific panel from the European Food Safety Authority (EFSA) claims that the α-GOS are non-digestible carbohydrates.…”

“…12,13 Recently, a promising in vitro digestibility method of dietary carbohydrates using rat small intestinal extract (RSIE) has questioned the belief that recognized prebiotics oligosaccharides derived from lactose (GOS) and fructooligosaccharides (FOS) reach the distal portions of colon without alterations. [14][15][16] Therefore, with the aim of gain more insight on the benefits of non-digestible carbohydrates, in this work the digestibility of commercial functional fiber, such as α-galactooligosaccharides derived from peas and different types of fructans have been tested using a rat small intestine extract.…”