Interaction between added whey protein ingredients and native milk components in non-fat acidified model systems

Non-fat acidified milk model systems were constructed from frozen casein and whey protein concentrates produced from skim milk using membrane filtration, and combined with commercial whey protein ingredients, i.e. nano-particulated whey protein (NWP), micro-particulated whey protein (MWP), and whey protein concentrate (WPC). Model systems were characterised in terms of particle size distribution and fractionation, surface hydrophobicity and accessible thiol groups, rheological behaviour, water holding capacity and graininess. Samples containing NWP exhibited higher surface hydrophobicity and increase in accessible thiol groups, shorter gelation time, higher gelation pH and G′, but increasing particle size and number of grains, when compared with addition of MWP and WPC. Addition of MWP resulted in weak gels with a less connected protein network and decreased number of grains. Mixtures of NWP and MWP (1:1) had rheological properties closer to those seen for MWP. Systems with WPC differentiated themselves with a large quantity of small aggregates.