In vitro fermentability of a pectin fraction rich in hairy regions

Pectins are widely used in the food industry as gelling agents, and are also recognised to promote human health as dietary fibre. Commercially available pectins are similar in composition, with high uronic acid contents. A pectin rich in hairy regions was extracted under alkaline conditions. This sample contained 56 g neutral sugars but only 15 g uronic acids/100 g and had a very complex molecular structure, with highly branched arabinan side chains. It was subjected to in vitro fermentation with fresh human faecal bacteria and compared to a commercial pectin and a larch arabinogalactan. The two pectins were metabolised completely within 6 h, whereas approximately 20% of the arabinogalactan remained un-degraded after 24 h. Higher amounts of short-chain fatty acids were produced from the pectin hairy regions than from the commercial preparation with propionate being more than doubled. Concomitantly, the pH was lowered to a larger extent. These two features are of interest from a physiological point of view, since they are considered to be beneficial to colon health. Thus, pectin fractions rich in hairy regions might be an interesting dietary fibre with slightly improved physiological properties compared to commercial pectins.