Food Structure and Health
Imaging Food in the Gut
Primary Objective
- Determine the impact of food structure on food phase behaviour and gastric emptying using in vivo magnetic resonance imaging (MRI) approaches in collaboration with the Norfolk & Norwich University Hospital (N&NUH).
Our knowledge of food structure behaviour in vivo is very limited. In some instances studies have focussed on biological responses, with changes in structure during the digestive process either being simply inferred or defined by characterisation of gastric and duodenal aspirates. Whilst offering insight into digestion, such in vivo studies are highly invasive in nature and will only ever be carried out on a limited number of healthy volunteers and allow only certain types of liquid foods to be studied. The advent of high resolution MRI imaging offers an unprecedented opportunity to study the behaviour of foods in the GI tract but only a limited number of studies have been reported on this topic. Consequently, almost nothing is known about any new structures that might be formed in the GI tract in vivo after eating, either as a result of the change in environment on entering the stomach, or as a result formation of degradation products. The phase behaviour of foods in the gastric compartment, which determines the nature of food-derived material entering the duodenum, will plays a key role in rates of nutrient uptake. We are therefore attempting to broaden our knowledge of food behaviour in vivo, linking it with in vitro studies undertaken in other research areas within this programme.
It is also apparent that both the composition and physical properties of food structures, and their breakdown products, may affect gastrointestinal function. Gastric emptying rates are generally faster for liquid compared to solid foods, with particulates larger than 1-2mm being retained in the stomach for longer. Changes in emulsion structure (such as flocculation) which lead to changes in bulk viscosity may also impact on subsequent gastric processing In addition factors such as viscosity and particulate density can affect gastric emptying rates. We are studying the way in which colloidal structures either interact or rearrange in the stomach in vivo and thus affect gastric function and phase behaviour.
Figure 4.1: MR transverse image slice of the upper abdomen of a prone subject showing layering of a mousse-style dessert 20 minutes after consumption (gastric secretions in light grey) (Alan Mackie & Paul Malcolm, unpublished data)
Collaboration with the Norfolk & Norwich University Hospital's (N&NUH) Radiology Academy has enabled us to undertake some preliminary comparative studies looking at the differences in rates of gastric emptying for two meal types, a dark chocolate and a chocolate mousse style dessert. Figure 4.1 shows the clear layering that was visible in both these food types. These types of measurements can be enhanced by optimising the pulse sequences used in advance of undertaking human studies. The research is fully supported by the N&NUH Radiology Academy (one of only three in the country) and their expertise enables us to measure gastric volumes and therefore rates of emptying and phase behaviour.
We will be using model emulsion based food structures including a mousse stabilised with starch, which we have developed as a matrix for diagnosis of food allergies, and model emulsified food systems developed and studied elsewhere in the programme.
We are also using our expertise in NMR and micro-imaging facilities to develop and design the pulse sequences that will optimise contrast between the various components (such as lipid or starch) of the model meals to maximise the visibility of the various phases in the sample and gain further information regarding dynamic changes in the food structure and composition.
Fax: +44(0)1603 507723 
