Abstract #193

# 193
Fat globules in milk and their structural modifications during gastro-intestinal digestion.
Harjinder Singh*1, 1Riddet Institute, Palmerston North, New Zealand, 2Massey University, Palmerston North, New Zealand.

The fat globules in milk are unique oil droplets that are stabilized by a specific and structurally-complex membrane, the milk fat globule membrane (MFGM). In the last decade, good progress has been made in on the structure of the milk fat globules and MFGM, and how common processing treatments affect these structures to deliver dairy products with improved functional properties. However, the repackaging or structural alteration of fat globules may also affect the way they are digested, absorbed and metabolized. In addition, the surrounding structures may also play a role in the bioaccessiblity of raw or processed milk fat globules, which may affect the access of the gastrointestinal enzymes to the globules and, therefore, influence the bioavailability of lipids. Our recent work on understanding the structural changes in milk fat globules during gastro-intestinal digestion has revealed that the native fat globules remain stable under gastric conditions, although pepsin is able to hydrolyze most of the MFGM proteins. In contrast, homogenized milk fat globules, coated with caseins, aggregate readily under gastric conditions. Interestingly, it has been discovered recently that the surrounding curd structures formed by coagulation of casein in the gastric environment have a profound effect on the rate of emptying of fat globules and hence the kinetics of lipid digestion. Fat globules in natural milk show longer residence time in the stomach, as they remain entrapped in a cohesive casein network clot. The curds formed by homogenized and heat-treated milk have a more crumbled and porous structure and the fat globule are released faster into the small intestine. Under the intestinal conditions, the lipolytic products, released from the hydrolysis of the triglyceride core of the globules by the action of pancreatic lipase, lead to destabilization and coalescence of the globules. These droplets are surrounded by a liquid-crystalline lamellar phases which are then solubilized as multilamellar vesicles involving bile salts. This talk will focus on recent advances in understanding the milk globules during gastro-intestinal digestion, including the effects of processing on bioavailability of milk fat globules, and the kinetics lipid digestion.

Key Words: fat globules, digestion, milk fat globule membrane (MFGM)

Speaker Bio
Harjinder Singh is the director of the Riddet Institute (Centre of Research Excellence), Massey University in New Zealand. He is a Fellow of the Royal Society of New Zealand, International Academy of Food Science and Technology and Institute of Food Technologists, and has received a number of international awards, including Marschall Rhodia International Dairy Science Award, William C. Haines Dairy Science Award, and the Prime Minister’s Science Prize. His present research is in dairy science and technology, functional foods, food structures and nutrition. He has published over 300 papers and has presented over 100 keynote addresses at international conferences.