The structure of dairy products, as modified by processing, drives the kinetics of proteolysis and lipolysis in the GI tract and the bioavailability of nutrients

Milk is a great raw material that allows to build a wide variety of structures. It and can be really seen as a “Lego box” from which all the constituents can be separated (cracking) and re-assembled into different products. Recent findings have clearly shown that the structure of dairy products is one of the key drivers to control the kinetics of protein and lipid digestion and consequently the kinetics of nutrient release. The comparison of the fate in the digestive tract of milk protein matrices of identical composition but different micro and macrostructures (liquids and gels) was investigated in vivo using multi-canulated and catheterized mini-pigs (1). Effluents from the duodenum and mid-jejunum as well as plasma samples were collected over 7h. Structure was shown to drive the time of residence of food in the stomach and the liquid-gel transition led to a significant increase in the gastric emptying time. Liquid matrices generated a fast and intense peak of proteins in the intestine and amino acids in the bloodstream. Peptidomic analysis showed different patterns between intestinal samples (2). Finally, rennet gels had a different behaviour than the acid ones forming a compact coagulum in the stomach that slowed down the gastric emptying and delayed the release of amino acids. A mathematical model of digestion was built from these data (3). Then, the influence of the thermal and homogenization treatments used during emulsion manufacture on proteolysis and lipolysis during digestion was assessed. Data showed that homogenization, by increasing the specific surface of the lipid droplets, was accelerating lipid digestion (4). The effect of heat treatment on protein digestion was dependent on the type of protein considered. Finally, the composition and structure of infant formula was shown to modulate protein digestion and affect the immune system maturation and structure of the gut microbiota (5). Structure of dairy products can be seen as a tool to design food of various rates of nutrient release that could be adapted to the nutritional needs of specific population e.g. infant or elderly