Establishing the biopolymer ratio of whey protein–pectin complexes before and after thermal stabilisation

Fat-replacers can be applied to enhance creaminess as they often possess a high ability to bind water. Especially for mixed biopolymer complexes, such as whey protein–pectin complexes (WPPC), the viscosity measurement can show non-linear behaviour, impairing exact calculations of bound water or elucidating the structure from the intrinsic viscosity. By means of mass balance based on ultra-centrifugation and capillary viscosimetry, an alteration in biopolymer ratio during thermal stabilisation was determined. The initial ratio of 5:1 (w/w) shifted in favour of the protein component in the complex. 98% of the pectin were not incorporated in the complex but remained in the outer phase increasing its viscosity. By considering this alteration, the voluminosity of WPPC was calculated to be 18.3 ±0.5 mL g−1. Supplementary scanning electron micrographs showed a porous complex structure dominated by denatured whey proteins, which were linked by few pectin molecules. A model of the thermally induced complex formation from whey protein isolate and low-methoxyl pectin was postulated in which the unbound pectin plays a catalyst-like role.