Physicochemical characterization and in vitro digestibility of β-lactoglobulin/β-Lg f142-148 complexes

The hypotensive peptide beta-lactoglobulin (beta-Lg) f7142-148, known as lactokinin, was shown to bind to bovine beta-lactoglobulin variant A (beta-Lg A). Complexes of beta-Lg A:beta-Lg f142-148 were prepared at pH 6.8 and 40 degrees C in a molar ratio of 1:5, and recovered subsequently by ultrafiltration. Under these conditions 0.9 moles of beta-Lg 17142-148 bound per mole of beta-Lg A. The analysis of the complexes by high performance size exclusion chromatography and laser light scattering revealed that particle size of the complexes was smaller than the beta-Lg A particle size. beta-Lg A formed polydispersed aggregates at pH 6.4, while a single aggregate peak was observed in the case of the complexes. Matrix-assisted laser desorption ionization time-of-flight mass spectrometry confirmed the presence of the peptide beta-Lg f142-148 in the complexes. The in vitro digestibility of beta-Lg A and of the complexes determined using pepsin, trypsin, pancreatin, pepsin/trypsin and pepsin/pancreatin were similar, whereas chymotrypsin and pepsin/chymotrypsin digested the complexes more slowly. The binding of beta-Lg 17142-148 to beta-Lg A could delay the hydrolysis of this peptide by digestive enzymes. (c) 2006 Elsevier Ltd. All rights reserved.