Chemical and physical transformations of solid food begin in the mouth, but the oral phase of digestion has rarely been studied. In the present study, twelve healthy volunteers masticated mouthfuls of either bread or spaghetti for a physiologically-determined time, and the levels of particle degradation and starch digestion before swallowing were compared for each food. The amounts of saliva moistening bread and spaghetti before swallowing were, respectively, 220 (SEM 12) v. 39 (SEM 6) g/kg fresh matter. Particle size reduction also differed since bread particles were highly degraded, showing a loss of structure, whereas spaghetti retained its physical structure, with rough and incomplete reduction of particle size. Starch hydrolysis was twice as high for bread as for spaghetti, mainly because of the release of high-molecular-mass a-glucans. The production of oligosaccharides was similar after mastication of the two foods, respectively 125 (SEM 8) and 92 (SEM 7) g/kg total starch. Starch hydrolysis, which clearly began in the mouth, depended on the initial structure of the food, as in the breakdown of solid food. These significant physical and chemical degradations of solid foods during oral digestion may influence the entire digestive process.

Durum wheat aleurone, thanks to its nutrient-rich composition, might be of potential use as a functional ingredient in cereal-based foods provided nutrients can be made available for absorption. We evaluated the in vitro bioaccessibility of thiamine, niacin, and phenolic acids in different aleurone fractions obtained with an industrial processing aimed to obtain material of different composition and particle size. Results indicate that the main phenolic compounds and vitamins investigated have a higher bioaccessibility when present in the inner part of the aleurone layer compared to the outer part of aleurone or the unfractionated bran. Moreover, an ultramicronization treatment employed to reduce particle size does not further improve the bioaccessibility of these compounds. We conclude that aleurone fractions from durum wheat bran could represent a nutritionally relevant ingredient, bringing together a high fiber content and an excellent bioaccessibility of vitamins and phytochemicals generally associated with nutritional benefits.

The study shows that low amounts of aleurone-enriched bread resulted in equivalent plasma levels of ferulic acid as wholegrain bread. This could suggest that, if the absorbed phenolic metabolites after wholegrain product intake exert health benefits, equal levels could be reached through the consumption of lower doses of refined products enriched in aleurone fraction.

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Wheat aleurone, due to its potentially higher bioaccessibility and bioavailability of micronutrients and phenolic acids, could represent a useful ingredient in the production of commonly consumed cereal-based food. The aim of the present study was to investigate the in vitro bioaccessibility of phenolic acids both from an aleurone-enriched bread and from a whole grain bread. The two bread samples were firstly characterized for the phenolic acid content. An in vitro digestion was then performed in order to evaluate the release of phenolic acids. The results obtained suggest that the bioaccessibility of the phenolic acids in the aleurone-enriched bread is higher than in the whole grain bread. These in vitro results suggest the potential use of aleurone in the production of foods, and this may represent an attractive possibility to vehicle nutritionally interesting components to consumers.