Physical and chemical transformations of cereal food during oral digestionin human subjects

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 spaghett i for a physiologically-determined time, and the levels of particle degrada tion and starch digestion before swallowing were compared for each food. Th e amounts of saliva moistening bread and spaghetti before swallowing were, respectively, 220 (SEM 12) v. 39 (SEM 6) g/kg fresh matter. particle size r eduction also differed since bread particles were highly degraded, showing a loss of structure, whereas spaghetti retained its physical structure, wit h rough and incomplete reduction of particle size. Starch hydrolysis was tw ice as high for bread as for spaghetti, mainly because of the release of hi gh-molecular-mass alpha-glucans. The production of oligosaccharides was sim ilar after mastication of the two foods, respectively 125 (SEM 8) and 92 (S EM 7) g/kg total starch. Starch hydrolysis, which clearly began in the mout h, depended on the initial structure of the food, as in the breakdown of so lid food. These significant physical and chemical degradations of solid foo ds during oral digestion may influence the entire digestive process.