Epsilon Open Archive

Abstract

Insulin resistance, high blood glucose and raised total blood cholesterol are major risk factors for cardiovascular disease and type 2 diabetes. Partly they are caused by overweight and obesity. Diet is an important modifiable determinant for these risk factors and understanding how food characteristics, e.g. composition and structure, influence appetite and metabolic responses might aid in the development of healthy foods.

In this thesis I examined how formulation, processing techniques (baking, cooking, extrusion) and process parameters affect rye, oat and wheat food characteristics (including structure and dietary fibre composition) and the implications of this for appetite and metabolic responses in humans. In vitro digestion methods were used to study structural changes, gastric disintegration, digesta viscosity and glucose release. In human trials, the effect of aeration method (fermentation or whipping) in rye crispbread production on appetite and metabolic responses was evaluated.

When inulin was added to rye porridge, available water was reduced, decreasing starch gelatinisation and viscosity, changes with potentially counteracting effects on glucose response in humans. Smaller oat bran particles in bread increased degradation of β-glucan during fermentation, but also increased their solubility, events with opposing effects on digesta viscosity. Increased viscosity is an underlying mechanism for the ability of β-glucans, and certain other dietary fibres, to lower glucose response and total blood cholesterol. In fermented rye crispbread viscous fibres were more degraded and postprandial insulin response higher when compared with unfermented rye crispbread. However, the effect could also be attributed to slower gastric disintegration for the unfermented rye crispbread. Choice of aeration method had no observable impact on appetite. An amylose layer surrounding starch granules was observed only in sourdough-fermented soft rye bread. This seemed to inhibit glucose release, despite degraded viscous dietary fibres and rapid gastric disintegration.

To conclude, processing and formulation were found to generally affect more than one food characteristic, which might be of relevance for a specific metabolic response. The net effect of characteristics associated with a targeted metabolic response should be considered when designing or selecting foods intended to promote health.