Co-gels of whey protein isolate with crosslinked waxy maize starch: Analysis of solvent partition and phase structure by polymer blending laws

The only variable in this analysis was the “solvent avidity parameter”, p, defined as the ratio of water to polymer in the (continuous) WPI phase divided by the corresponding ratio for the (dispersed) PCS phase. The best fit was obtained with p≈3.3. This high relative affinity of WPI for water implies restricted swelling of PCS except at low concentrations of either or both components of the mixtures. The changes in G′ observed on heating indicated that at high concentrations of WPI separation into a dispersed starch phase in a continuous protein matrix occurred prior to gelatinisation of PCS. At lower concentrations of WPI, however, gelatinisation of PCS was accompanied by large increases in G′, indicating formation of a starch network which was then fragmented by gelation of WPI. Fragments of starch network (on the length scale of ∼10-100 μm) embedded in a WPI gel matrix were visualised directly by light microscopy.