The Role of Food Structure in the Biophysics of Digestion: The Remarkable Coevolution of the Casein Micelle

There is more to nutrition than food composition, and the biophysics of food structures, from the nanoscale to microscale, regulates and controls the release of macro- and micro-nutrients, bioactives and phytochemicals. As diets shift from whole foods to including more ultra-processed foods (UPFs) or UPFs designed to mimic whole foods (plant-based milk, cheese and cellular meat), research must focus not only on the sensory and organoleptic appeal but also on the postprandial responses, satiety and on satiation. For example, plant-based milk and cheese are visually similar to their dairy equivalent, yet they lack highly phosphorylated casein micelle calcium nanoclusters. The coevolution of the casein micelle highlights the role structure plays in digestion as chymosin preferentially cleaves κ-casein at the 105-106 phe-met bond, which destabilizes the micelle surface and curdles milk into solid cheese, altering subsequent digestive kinetics, postprandial response and satiety. Food structures designed to slow digestion and their postprandial response are reinventing ingredient isolate, emphasizing the inclusion of intact plant cells in UPFs. With every intended trait imparted to the food, unintended consequences may alter satiety, food choice and postprandial responses and must constantly be reevaluated.