In vitro colonic fermentation of orange peel fibres: Effect on microbial modulation, SCFAs production and carotenoid degradation

Abstract

Orange peel by-products are valuable for their content of dietary fibre and bioactive compounds that offer health benefits, such as the production of short-chain fatty acids (SCFAs) and modulation of gut microbiota. The aim of this study is to evaluate the prebiotic effect of three fibre-rich fractions of orange peel (orange peel extract, OP; insoluble fibre fraction, IFF; and water-soluble extract, WSE) by means of in vitro fermentation. Degradation of carotenoids during fermentation was examined to explore their interaction with the microbiota. The results indicate that in vitro fermentation of fibre-rich ingredients increased Lactobacillus and Bifidobacterium populations. WSE, rich in bioactive compounds, increased Bifidobacterium by 2.5 times compared with the other fractions, and gave a 1.5-fold higher total SCFAs production and a noteworthy evolution of butyrate. Moreover, although carotenoids decreased during fermentation, they remained detectable at the end of the process, suggesting that they are not efficiently metabolized by microbiota and could persist in the colon for a longer period. These findings open up new avenues of research in the use of by-products to develop novel ingredients. In addition, future research should focus on investigating the behaviour of carotenoids during digestion, as well as their antioxidant, anti-inflammatory, and microbiota-modulating effects.