Phase separation in soft-serve ice cream mixes: rheology and microstructure

Soft-serve ice cream mixes containing 4% milk protein and 0.14% locust bean gum (LBG) showed extensive visual phase-separation after 21 days at 5 °C, unless κ-carrageenan was added to the formulation. Addition of κ-carrageenan (0-0.02%) did not inhibit microscopic phase separation between protein and polysaccharide. A higher degree of “emulsification” of the protein-enriched phase into the continuous serum phase was observed as the κ-carrageenan concentration increased, which correlated with inhibition of macroscopic serum separation in the mix. After macroscopic separation, the serum phase of mixes with different κ-carrageenan concentrations showed similar microstructural and rheological characteristics, implying no concentration of LBG and no presence of κ-carrageenan in the serum phase. The rheological behaviour of the protein-enriched phases indicated κ-carrageenan/casein interactions. There was no evidence of “weak-gel” formation through the addition of κ-carrageenan as a means for macroscopic stability in the system.