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Investigating the role of food structure and processing in lipid digestion for production of healthier food

Final Report Summary - FOODPRO FORHEALTH (Investigating the role of food structure and processing in lipid digestion for production of healthier food)

FoodPro ForHealth aimed to investigate the role of food structure on the physico-chemical breakdown of emulsified fats during in vitro digestion, in order to develop novel approaches for prolonging satiety and reducing dietary fat intake. A multidisciplinary approach combining fundamental physical and biological sciences was required to better understand the mechanisms underlying fat digestion and the impact of emulsion structure on lipase activity. This proposal involved studies that provided important information about the interaction of food ingredients with digestive enzymes, surfactants and lipids in the gut. Through improved understanding of this effect, we have developed food systems with potential to slow the digestion and sustain the release of fats for uptake in the gut. Bile salts are bio-surfactants secreted by the liver which help breakdown the fats during digestion. FoodPro ForHealth focused on ways of limiting the access of bile salts to the fat, as a potential mechanism of slowing fat digestion, either by designing interfaces that resist displacement by bile salts, or by binding bile salts in the small intestine. Understanding how the bile salts interact with emulsifiers and stabilizers commonly found in processed foods during the digestion process, will help to rationally develop healthier foods, not only capable of promoting satiety but also of reducing blood lipid and cholesterol levels. This will help to address obesity and associated conditions, one of the major challenges currently faced by the EU. At the host institution (Institute of Food Research - IFR), Cristina Fernandez-Fraguas has used, in particular, a range of colloidal and interfacial methodologies to identify the mechanisms by which food ingredients can influence fat digestion through either bulk or interfacial effects. She has also carried out experiments simulating the digestion process, under realistic, physiological conditions, following established IFR protocols. The results demonstrate feasible approaches for modifying both the continuous phase and the interface of emulsions by using specific types of food biopolymers. This will allow the design of food structures able to control bile salt behaviour / transport and hence have a marked impact upon fat digestion and metabolic health.

APPROACH
The project initially looked at the design of the interfaces between the fat and the water that hinder adsorption of bile salts as a potential mechanism to reduce adsorption of fat digesting enzymes, and thus to limit the rate of lipolysis. Model emulsified foods covering a range of responses to digestive conditions were selected; these included systems representative of protein-based ingredients such as (B-lactoglobulin - B-lg, a-lactalbumin - a-la, whey protein isolate - WPI), polysaccharide–protein complexes (sugar beet pectin - SBP) and gels (Hydroxypropyl methylcellulose - HPMC). A relevant mixture of two common bile salts (BS), sodium taurocholate (NaTC) and sodium glycodeoxycholate (NaGDC), was used. These studies were then extended to investigate the implication of the BS binding properties of dietary fibre in the control of fat digestion. Firstly, colloidal methodologies were used in order to characterize the different ingredients and to investigate emulsion stability. A range of interfacial techniques, including particle electrophoresis analysis, tensiometry, interfacial dilatational rheology, interfacial biosensors and atomic force microscopy, were used to determine changes in interfacial behaviour of the adsorbed layers in presence of BS. The impact of the particularly interesting systems on the extent of lipid digestion was investigated by means of a laboratory-based digestion model simulated conditions encountered in the gut.

CONCLUSIONS
FoodPro ForHealth has enabled the use of physico-chemical approaches to investigate the interaction of diverse food structures with digestive enzymes, surfactants and fats in a simulated gut environment representing both the stomach and small intestine. FoodPro ForHealth has shown, firstly, that heat treatment is a successful strategy to enhance the resistance of whey protein interfacial layers to displacement by Tween 20 and bile salts. Secondly, digestion of emulsified fats stabilised with a naturally occurring protein-polysaccharide complex (SBP) and a non-ionic polymer (HPMC) was similar despite their different competitive adsorption behaviour at low BS concentrations. This reflected that BS are very effective at adsorbing and disrupting interfaces, and they appear to be the critical step for the progression of fat digestion in the small intestine. Thirdly, the binding of BS to celluloses in solution can affect displacement by BS in two ways, by changing interfacial properties of the cellulose-BS complexes, and by reducing free BS available to displace cellulose and/or complexes. Dr. Fernandez demonstrated that the potential of cellulose ethers to influence satiety is more related to their ability to bind BS in solution than their ability to disrupt adsorption of BS at the interface. This important finding, together with the challenge of designing interfaces to restrict adsorption of bile salts, led us to focus our attention on how a specific dietary fibre with proven cholesterol reducing properties, would impact fat digestion. From here, FoodPro ForHealth provided new insights into how the binding of either soluble (B-Glucans) and insoluble fibres from oats to bile salts in the bulk, impact the interfacial properties of the emulsions related to access for digestion. In addition, the different adsorption behaviour observed between different bile salts structures supports the necessity of filling the gaps in our understanding of the roles of various essential components in fat digestion. FoodPro ForHealth has given us a better, fundamental understanding of how interfacial and bulk properties, solution conditions, and interactions with bile salts determines the digestibility of food structures, and in particular the availability of fat for uptake. This is generating renewed scientific interest due to the growing social and economic consequences of the obesity crisis in the developed world. The design of healthier foods to control obesity is a top priority in the EU: it is estimated that treating obesity and related diseases (such as type 2 diabetes and cardio-vascular disorders) takes up to 5% of the EU’s total healthcare budget. FoodPro ForHealth has made a significant contribution to bridge the knowledge gaps between the physical sciences and nutrition, to improve our understanding of how the structure of food can influence digestion of carbohydrates, proteins and fats, and how this in turn can influence dietary intake, satiety, and metabolic health. This knowledge can be exploited in tailoring novel food systems able to control bile salt behaviour / transport as a potential route to modulate lipid absorption. Applying physical and materials science principles to understand fundamental processes, such as bile salt adsorption/interaction, and to modulate digestion and interfacial/bulk properties of complex food structures is a novel, emerging area of industry-relevant research, and may be associated with further, emerging health benefits such as fat metabolism and gut health.

An extended final report is included as an attachment