Award details

Perception of flavour in fat emulsions: interactions in mouth gut and brain

Reference	BB/D522862/1
Principal Investigator / Supervisor	Professor Robin Spiller
Co-Investigators / Co-Supervisors	Professor Susan Francis, Professor Penny Gowland, Ms Tracey Hollowood, Dr Joanne Hort, Dr Luca Marciani, Professor Andrew Taylor
Institution	University of Nottingham
Department	Nottingham Digestive Diseases Centre
Funding type	Research
Value (£)	319,282
Status	Completed
Type	Research Grant
Start date	01/10/2005
End date	30/09/2008
Duration	36 months

Abstract

High-fat foods lead to calorie overconsumption, because of both their enhanced palatability and high energy density. This study, which involves a multidisciplinary group of scientists from the University of Nottingham and Unilever, aims to use novel emulsion systems, sensory and fMRI techniques to study how oro-nasal and gastrointestinal exposure to fat alter flavour perception (multimodal responses and sensory specific satiety) in humans. Our previous experience with aroma, taste and viscosity suggests that fat can alter flavour (taste and aroma) perception in two ways: 1) by changing the delivery of tastants and volatiles to the taste buds and olfactory receptor cells and 2) interactions between the sensory pathways at a higher, cortical level. Recent fMRI studies using simple chemical stimuli applied to the mouth have identified regions of the brain that are activated by taste, aroma and texture. However there have been few studies of flavour interactions, and no studies using flavoured fat-emulsions. Furthermore, previous studies of flavour perception have largely ignored the importance of swallowing in delivering aroma to the olfactory organ, even when aromas have been presented retro-nasally through the mouth. In the project we will develop a model emulsion system in which tastant and volatile release can be independently controlled. We will then investigate the effect of emulsion microstructure on tastant and volatile release, perceived flavour intensity and hedonic ratings. Using this model system we will study the cortical response to emulsions in the mouth, and how the fat content and viscosity of an emulsion alter the cortical response to flavour. Finally we will determine how this response to flavour in a fat emulsion is influenced by prior oro-nasal and gastrointestinal exposure to the same emulsion. Methods: We will initially use in-vivo techniques such as Apcl-MS and a trained sensory panel to define how fat alters the delivery of volatiles (eg. Strawberry) and tastants (eg. Sucrose) to the retro-nasal space and taste buds, and how this alters flavour perception. We will also examine the impact of emulsion microstructure (such as gelled particle systems and duplex emulsions developed by the industrial partner Unilever Foods Research Centre) on perceived flavour intensity and hedonic rating. We will study the brain¿s response to these well-characterised emulsion stimuli using optimised fMRI sequences at 3T. A novel spray system, designed for use within the confines of an MRI scanner, will be used to deliver stimuli of controlled tastant and volatile release across the surface of the oral cavity. We will assess the brain¿s response to a range of emulsions of varying flavours and viscosities in both primary and secondary sensory cortices, to distinguish the effects of changes in sensory input from those due to higher-order interactions. Finally, we will examine how the brain¿s response to a flavoured emulsion is altered by a high-fat meal, given either by mouth or directly into the stomach via a nasogastric tube. This will allow us to separate changes in brain activation due to oro-nasal sensory stimulation from those due to gastric distension and post-prandial secretion of gut signalling peptides, which we will measure by blood sampling. Outcomes: A model system with controlled tastant and volatile release, and viscosity characteristics, will be developed. We will then use this system to understand the effects of emulsion microstructure on volatile and tastant release, flavour perception and hedonic ratings. This system will allow us to map the cortical representation of oral fat in an emulsion and to separate cortical effects of oral fat from those due to viscosity. We will also determine the cortical basis for how fat in an emulsion alters the response to taste and aroma, both separately and combined, and for the altered perception of flavour by fat and viscosity. Since satiation with a certain food leads to a decline in the specific desire for that food, we will assess the change in the brain¿s response to a flavoured fat emulsion following prior ingestion of a similar emulsion. We expect this change to arise from both sensory specific satiety and gastrointestinal effects, so we will assess the relative importance of oro-nasal and gastrointestinal effects. This project will further our understanding of how fat influences flavour, and thus will provide important new data for the UK food industry as it seeks to develop satisfying low-fat foods.

Summary

Fat makes many foods very tasty, but people who eat a lot of high-fat food often become overweight or even obese. Just why high-fat foods are so tasty is not clear. The taste and aroma of food (which make up its flavour) are due to special chemicals that are present in it. These chemicals send signals via the mouth and the nose to the brain, allowing us to sense (perceive) the food. They way in which these chemicals are sensed may be altered by the presence of fat. However the mouth is also very sensitive to the texture of food, for instance the smoothness of an ice cream, and people seem to like the texture of fat very much. The signals that the mouth and the nose send to the brain interact with each other, and may alter how our brain responds to fat, taste, texture and aroma. We have shown that swallowing a food increases the delivery of the food¿s aroma to the nose, and that the thickness of food in the mouth alters taste, but we still do not know why fat has such a strong effect on improving the flavour of food. We now have a new way of looking at which parts of the brain respond to food called `functional magnetic resonance imaging¿ or fMRI for short. fMRI is a safe way of making a picture of the brain and using fMRI researchers have started to show which parts of the brain respond to fat, taste, texture and aroma. We want to study this interesting problem and: 1) find out how fat changes the amount of the chemicals (responsible for a food¿s flavour) that reach the tongue and the nose, 2) study how combining these chemicals alter the flavour of food containing fat, and how this changes the brain¿s response to food, 3) find out how the brain¿s response to the flavour of food is altered after a person has eaten a large, fatty meal. What will we do? We will create some test foods, which are like milk shakes, that will contain different amounts of fat. We will ask groups or people to taste these, to find out how fat alters their perception of the flavour and how much they like them. We expect that fat will alter the flavour intensity and increase the pleasantness of a food with a sweet taste and fruity aroma. Once we know how thickness, taste, aroma and fat act together to alter flavour intensity and pleasantness, we will then take pictures of the brain using fMRI to help us understand this. These pictures will show us which parts of the brain respond to food flavour. Finally we will take pictures of the brain¿s response to a flavoured high-fat test meat either after drinking it or after putting it directly into the stomach using a tube. We expect that these procedures will alter the flavour and pleasantness of the high-fat test meals, and using fMRI we will be able to separate the effects of a meal in the mouth from those of a meal in the stomach. Who will benefit? These studies will help us to understand why high-fat food is so tasty. If we can understand this then we might be able to design tasty, low-fat foods which are less likely to make people overweight. This will help people who are trying to lose weight and food manufacturers who want to design healthy foods.

Committee	Closed Committee - Agri-food (AF)
Research Topics	Diet and Health, Neuroscience and Behaviour
Research Priority	X – Research Priority information not available
Research Initiative	X - not in an Initiative
Funding Scheme	Industrial Partnership Award (IPA)

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