Author: Herr Dr. Amoneit
Last saved by: Saritas, Sevim

Tailored Interfacial Rheology for Gastric Stable Adsorption Layers 
Nathalie Scheuble, Andreas Steingötter, Peter Fischer, Institute of Food, Nutrition and Health, ETH Zürich, 8092 Zürich, Switzerland

The use of oil-in-water emulsions as tailored fat delivery systems with defined breakdown pathways is a possible strategy to fight obesity [1]. Fat lead to overconsumption as it involves palatability, what determines dietary preferences [2]. Controversy, its sensory properties implement neuronal responses, which correlate with a short-term control of appetite and satiety [3]. After ingestion of dispersed fat, the rate and activation of lipolysis and associated satiating hormonal responses, is determined by the emulsion stabilisation and the size of the fat droplets [4]. Therefore, by designing interfacial layers, lipase activity and lipid release, may be modified. Hence, we established a model system of a protein-biopolymer adsorption layer with composite material properties, making the interface stable during exposure to the gastric environment (temperature, pH, mechanical stress, enzymes, etc.). Such model layers will be scaled up to lipid emulsions. Their lipid release during digestion will be validated in vivo by magnetic resonance imaging, and thus emulsions can be further optimised. 
Physicochemical changes and enzymatic degradation of interfacial layers at the MCT oil/water interface were monitored online by interfacial shear rheology and pendant drop experiments. We show the weakening of a β-lactoglobulin (β-lg) layer at body temperature and acidification, and its hydrolysis by pepsin. Adding methylated nanocrystalline cellulose (metNCC) to the β-lg layer formed a synergistic, composite layer. This layer thermogelled at body temperature and resisted hydrolysis by pepsin. Interfacial tension measurements indicated a complete resistance to dog gastric lipase activity. Coexistence of β-lg  and metNCC  at the air/water interface was evidenced by neutron reflectometry measurements. The utilised layers and their analysis provide knowledge of physicochemical changes during in vitro digestion of interfaces, which promote functional food formulations.

[1] Norton I. et al.; Obesity Reviews 8 (2007) 83-88.
[2] Gaillard D. et al.; Annal of the NYAS (2008) 1141, 163 -175.
[3] Rolls E. et al.; Journal of Neuroscience 19 (1999) 1532-1540.
[4] Golding M. et al.; Soft Matter 7 (2011) 3513-3523.