Aleurone is the most nutritionally interesting layer of wheat grain due to its high amount of dietary fibres and bioactive compounds. Its dietary fibres (mainly arabinoxylans) pass over the upper part of the digestive tract, and arrive to the colon where they will be fermented into beneficial metabolites, such as short-chain fat acids (SCFA). Phenolic acids are bound to fibre’s structure. Thus they will be carried together with the fibre to the large intestine, and there they might be released by bacterial esterase-enzymes and exert beneficial effects.
The paper of Natalia Rosa et al. 2013 explored the effects of the disintegration of aleurone structure on its fibre fermentability, i.e. the formation of SCFA and the microbial metabolites derived from its co-passenger ferulic acid (FA). This was studied in an in vitro model using human faecal microbiota as an inoculum. The structure of aleurone was modified by mechanical (dry grinding) or enzymatic (xylanase-enzyme with or without feruloyl esterase activity) treatments in order to increase its physical accessibility and degrade its complex cell-wall network.
It was demonstrated that the structure of wheat aleurone strongly affected its microbial metabolism, i.e. the formation of SCFA, gases, and phenolic metabolites. Decrease in particle size and concomitant increase of aleurone’s specific surface area had a tendency to increase the production of total gas and SCFA by enhancing the microbial accessibility.
The higher solubilisation of cell-wall fibres, accompanied or not by the release of its phenolic co-passenger FA did not increase the formation of SCFA in this study. However, the release of FA from fibres by enzymatic treatment promoted colonic metabolites, notably phenylpropionic acids which can have anti-inflammatory properties. This study improved the knowledge of cereal processing on gastrointestinal effects.
Rosa, N.N., Aura, A.-M., Saulnier, L., Holopainen-Mantila, U., Poutanen, K., Micard, V., 2013. Effects of disintegration on in vitro fermentation and conversion patterns of wheat aleurone in a metabolical colon model. Journal of Agricultural and Food Chemistry 61, 5805–5816.