From food to physiology characterization and in vitro digestion of milk products and investigation of postprandial metabolism and inflammation after a high-fat meal intake in a human nutrition intervention study

According to the World Health Organization worldwide obesity has more than doubled since 1980. The World health statistics 2012 report shows that one in six adults is obese, one in ten diabetic and one in three has a raised blood pressure. Overweight and obesity are major risk factors for cardiovascular diseases,According to the World Health Organization worldwide obesity has more than doubled since 1980. The World health statistics 2012 report shows that one in six adults is obese, one in ten diabetic and one in three has a raised blood pressure. Overweight and obesity are major risk factors for cardiovascular diseases, diabetes and some cancers. The causes of overweight and obesity are mainly a decrease in physical activity and an increased intake of energy-dense foods leading to a positive energy balance. Not only dietary patterns play a major role in the development of obesity. Food composition also directly impacts on postprandial metabolism and inflammation and, in long term, may contribute to systemic low-grade inflammation, a characteristic associated with the obese state. Thus it is not surprising that there is a growing interest in better understanding the effect of different foods and food compounds on human metabolism and health. The aim of the NutriChip project is to develop a microfluidic chip device to screen foods and their compounds for health promoting, e.g. immune-modulatory, properties. Milk products have been chosen as a food model because their consumption has been shown to be associated with decreased levels of inflammatory markers (1), and also because technological and microbiological transformations allow the realization of various products, such as yoghurt and cheese, having potentially different physiological effects. This thesis covers the biochemical (products characterization and in vitro digestion) and physiological (human nutrition study) aspects of the NutriChip project. Initially, differently heat-treated and fermented milk products were characterized by a proteomic approach. Various fractionation methods were used for selectively enriching minor milk and bacterial proteins in different dairy products. Proteins were separated and identified by two dimensional (2D) gel-electrophoresis and liquid chromatography coupled to mass spectrometry (LC-MS/MS) analysis. All data are collected in an interactive platform, called protein atlas, which is now publicly available on http://www.foodle.ch/de/proteinstart. Currently, the database contains more than 200 different milk proteins and about 250 bacterial proteins. For a better in depth characterization of fermented products, a method for the enrichment of living bacterial cells has been developed. This method allows the investigation of bacterial proteomes under different fermentation conditions. The method was used to monitor the adaption of the yoghurt bacteria Lactobacillus bulgaricus and Streptococcus thermophilus during milk fermentation. Some well-known stress respo