Modification of carbohydrate quality in cereals and its consequences for digestion and metabolism

Starches from different botanical origins and genetic backgrounds, subjected to different processing conditions in different matrices are digested at different rates in the small intestine. Subsequently different amounts of this starch, with differing structural properties, will reach the large intestine, termed resistant starch (RS). The structure and amount of starch that reaches the large intestine may have a significant effect on rates of microbial fermentation, and on the microbial community composition, resulting in differing fermentation end-points. Pathways of starch fermentation in vivo in the large intestine, and the influence of different physical forms of starch, are not fully understood. I aim to explore how differences in cereal starch molecular structure can influence digestion and fermentation.
In collaboration with JIC we will use wheat and/or barley with mutations in starch biosynthetic pathway giving rise to alterations in starch structure in plants with defined genetic backgrounds. The molecular and physical structure of these starches will be characterised using a range of physical methods, and in vitro digestion kinetics will be determined using the latest kinetic models. Mutations in the biosynthetic pathway of starches may alter the amylose/amylopectin ratio, as well as more subtle effects on branching patterns and chain length distributions. The effects of mutations on starch structure during processing will be characterised to determine their influence on digestion and microbial fermentation.
Using foods made from these substrates, which have had their physical structure and in vitro digestibility highly characterised, we will carry out in vitro fermentation and in vivo human feeding studies. Microbial samples from these studies will be subjected to metagenomic and metatranscriptomic analysis allowing a detailed exploration of the changes in microbial communities and starch degradation pathways in response to different starch structures.