How does cereal food structure influence digestion and satiety: In vitro and in vivo approaches: Dissertation

The current study explored the impact of cereal food structure on digestion and satiety. Food structure is important for acceptability, functionality and health effects. Cereal foods contribute significantly to energy and nutrient intakes in the diets worldwide. The benefits of consuming a diet rich in whole grain and dietary fibre (DF) are evident, and cereal DF complex is most likely behind the beneficial effects. The first part of the study investigated the effect of bread structure on masticationinduced structure disintegration, starch hydrolysis and dissolution of compounds from bread matrices. Despite the structural differences among the studied rye and wheat breads, there were only small differences in mastication processes. However, rye breads disintegrated to smaller particles than wheat bread and starch tended to hydrolyse at a slower rate by salivary -amylase. A large array of compounds was dissolved from masticated breads to saliva. Specifically, peptidesand amino acids were dissolved from rye breads and sugars from wheat bread. The relevance of food structure to satiety was explored in the second part of the study. Among rye products with different structures and similar chemical compositions, portions of wholemeal rye bread or extruded wholemeal rye puffs and juice were more effective than the portion of extruded wholemeal rye flakes and juice to maintain some aspects of satiety. Intense oral processing did not relate to satiety response but perceived pleasantness and satiety expectations did. Less pleasant food portions resulted in enhanced satiety as well as those that were anticipated already prior to ingestion to be satiating. Oat bran added to juicewas more effective in maintaining the feelings of satiety and fullness compared tooat bran incorporated in biscuit matrix. The results showed that disintegration of bread structure and the release of compounds differed between bread types already in mastication. The current study was the first to explore the dissolution of compounds from food, namelybread, after mastication using non-targeted metabolomics approach. The significance of the released compounds warrants further research. The study also showed that food structure is of importance for the postprandial satiety responses of high fibre cereal foods. Perceptions of food, such as liking and expectations, as well as interactions of solid and liquid components (hydration and dissolution) of meal in stomach, are suggested to explain the observed differences in satiety responses.