Designing added-protein yogurts: Relationship between in vitro digestion behavior and structure

Increasing the protein content of a food is an effective way to deliver enhanced satiating signals to the consumer. Protein structures are related to their breakdown properties under gastric conditions and understanding their in vitro proteolysis could provide valuable information on their contribution to satiating ability. Four different yogurts were formulated with double the amount of protein by adding extra skimmed milk powder (MP), whey protein concentrate (WPC), calcium caseinate (CAS) or a blend of whey protein concentrate and calcium caseinate (MIX). Their rheological behavior and light microscopy and SDS-PAGE data were analyzed at different times of oral plus gastric in vitro digestion (0, 30, 60 and 120 min). The yogurts with added whey protein (WPC and MIX) maintained high consistency index values throughout in vitro digestion, which is related to increased gastric distension and to an extended feeling of fullness. In addition, the rapid gastric emptying of whey proteins in a more unaltered form than casein may result in a stronger increase in postprandial plasma amino acid concentration, increasing the satiating signals. Consequently, adding whey protein to the formulation of yogurts can enhance satiety, despite processing steps such as thermal treatment and fermentation. (C) 2017 Elsevier Ltd. All rights reserved.