Physico-chemical and structural modifications of caseins in micellar casein isolate induced by pulsed electric field

The potential of pulsed electric field (PEF) to modify the structure of caseins in micellar casein isolate (MCI) was investigated. MCI was PEF-treated at room (RT, 23 degrees C) and cold (CT, 4 degrees C) temperatures, using an electric field strength of 16 kV cm-1 for 6 or 31 mu s. Conditions simulating elderly digestion, such as the peptide profile released after gastric digestion and bioactivity, were studied. Unfolding of the protein structure was observed in PEF-treated MCI at RT, which led to cleavage points that were more accessible to enzymes. By contrast, fluorescence emission of tyrosine and tryptophan and Raman spectra indicated a reorganization in the configuration of the micelle in PEF-processed at CT. Under these conditions was observed an increase in the number of peptides generated from gastric digestion compared with untreated MCI, especially the bioactive peptides FSDKIAK f(31-45) and MPFPKYPVEP f(124-133), despite a lower overall uptake of bioactive peptides by Caco-2 cells. Industrial relevance: Micellar casein isolate (MCI) is widely utilized for protein fortification (e.g., in fresh dairy products, smoothies, meat products, and clinical nutrition) and for the adjustment of functional properties in food (e.g., viscosity, foaming). The findings of this work provide valuable information about the potential of PEF processing to modify the properties of MCI.